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Meningitis is an
acute Acute may refer to: Science and technology * Acute angle ** Acute triangle ** Acute, a leaf shape in the glossary of leaf morphology#acute, glossary of leaf morphology * Acute (medicine), a disease that it is of short duration and of recent onset. ...
inflammation Inflammation (from la, wikt:en:inflammatio#Latin, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or Irritation, irritants, and is a protective response involving imm ...
of the protective membranes covering the
brain A brain is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's tiss ...

brain
and
spinal cord The spinal cord is a long, thin, tubular structure made up of , which extends from the in the to the region of the . It encloses the of the spinal cord, which contains . The and spinal cord together make up the (CNS). In s, the spinal cord ...

spinal cord
, known collectively as the
meninges In anatomy Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology concerned with the study of the structure of organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any i ...

meninges
. The most common symptoms are
fever Fever, also referred to as pyrexia, is defined as having a above the due to an increase in the body's temperature . There is not a single agreed-upon upper limit for normal temperature with sources using values between in humans. The increa ...

fever
,
headache Headache is the symptom of pain in the face, head, or neck. It can occur as a migraine, tension-type headache, or cluster headache. There is an increased risk of Depression (mood), depression in those with severe headaches. Headaches can occur ...

headache
, and
neck stiffness Neck stiffness, stiff neck and nuchal rigidity are terms often used interchangeably to describe the medical condition when one experiences discomfort or pain when trying to turn, move, or flex the neck. Possible causes include muscle strain or sp ...

neck stiffness
. Other symptoms include
confusion In medicine, confusion is the quality or state of being bewildered or unclear. The term "acute mental confusion"
or altered
consciousness Consciousness, at its simplest, is or of internal and external existence. Despite millennia of analyses, definitions, explanations and debates by philosophers and scientists, consciousness remains puzzling and controversial, being "at once t ...

consciousness
, vomiting, and an inability to tolerate light or loud noises. Young children often exhibit only nonspecific symptoms, such as irritability, drowsiness, or poor feeding. If a
rash A rash is a change of the which affects its color, appearance, or texture. A rash may be localized in one part of the body, or affect all the skin. Rashes may cause the skin to change color, , become warm, bumpy, , dry, cracked or ed, swell, an ...

rash
is present, it may indicate a particular cause of meningitis; for instance, meningitis caused by meningococcal bacteria may be accompanied by a characteristic rash. The inflammation may be caused by infection with
virus A virus is a that only inside the living of an . Viruses infect all , from animals and plants to s, including and . Since 's 1892 article describing a non-bacterial infecting tobacco plants and the discovery of the by in 1898, more ...

virus
es,
bacteria Bacteria (; common noun bacteria, singular bacterium) are a type of biological cell The cell (from Latin ''cella'', meaning "small room") is the basic structural, functional, and biological unit of all known organisms. Cells are the sm ...

bacteria
or other
microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms ar ...
s, and less commonly by certain
drugs Uncoated tablets, consisting of about 90% acetylsalicylic acid, along with a minor amount of inert fillers and binders. Aspirin is a pharmaceutical drug often used to treat pain, fever, and inflammation. A drug is any chemical substance that ...

drugs
. Meningitis can be life-threatening because of the inflammation's proximity to the brain and spinal cord; therefore, the condition is classified as a
medical emergency A medical emergency is an acute Acute may refer to: Science and technology * Acute angle ** Acute triangle ** Acute, a leaf shape in the glossary of leaf morphology#acute, glossary of leaf morphology * Acute (medicine), a disease that it is o ...

medical emergency
. A
lumbar puncture Lumbar puncture (LP), also known as a spinal tap, is a medical procedure in which a needle is inserted into the spinal canal The spinal canal (or vertebral canal or spinal cavity) is the canal that contains the spinal cord within the vertebral c ...
, in which a needle is inserted into the
spinal canal The spinal canal (or vertebral canal or spinal cavity) is the canal that contains the spinal cord within the vertebral column. The spinal canal is formed by the vertebrae through which the spinal cord passes. It is a process of the dorsal body cavi ...
to collect a sample of
cerebrospinal fluid Cerebrospinal fluid (CSF) is a clear, colorless found within the that surrounds the and of all . CSF is produced by specialised in the of the of the brain, and absorbed in the s. There is about 125 mL of CSF at any one time, and a ...
(CSF), can diagnose or exclude meningitis. Some forms of meningitis are preventable by
immunization Immunization, or immunisation, is the process by which an individual's immune system becomes fortified against an infectious agent (known as the antigen, immunogen). When this system is exposed to molecules that are foreign to the body, called ' ...

immunization
with the
meningococcal ''Neisseria meningitidis'', often referred to as meningococcus, is a Gram-negative bacterium that can cause meningitis Meningitis is an Acute (medical), acute inflammation of the protective membranes covering the brain and spinal cord, known ...
,
mumps Mumps is a viral disease A viral disease (or viral infection) occurs when an organism's body is invaded by pathogenic viruses, and infection, infectious virus particles (virions) attach to and enter susceptible cells. Structural characterist ...
, pneumococcal, and
Hib vaccine The ''Haemophilus influenzae'' type B vaccine, also known as Hib vaccine, is a vaccine A vaccine is a biological preparation that provides active acquired immunity The adaptive immune system, also referred as the acquired immune system, is ...
s. Giving
antibiotic An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting pathogenic bacteria, bacterial infections, and antibiotic medications are widely used in the therapy, ...
s to people with significant exposure to certain types of meningitis may also be useful. The first treatment in acute meningitis consists of promptly giving antibiotics and sometimes
antiviral drug Antiviral drugs are a class of medication used for treating viral infections. Most antivirals target specific viruses, while a broad-spectrum antiviral is effective against a wide range of viruses. Unlike most antibiotics, antiviral drugs do not ...
s.
Corticosteroid Corticosteroids are a class of steroid hormone A steroid hormone is a steroid , hypothetical a steroid with 32 carbon atoms. Its core ring system (ABCD), composed of 17 carbon atoms, is shown with IUPAC The International Union of Pure a ...
s can also be used to prevent complications from excessive inflammation. Meningitis can lead to serious long-term consequences such as
deafness Deafness has varying definitions in cultural and medical contexts. In medical contexts, the meaning of deafness is hearing loss Hearing loss is a partial or total inability to Hearing, hear. Hearing loss may be present at birth or acquired ...
,
epilepsy Epilepsy is a group of non-communicable neurological disorders characterized by recurrent Seizure, epileptic seizures. Epileptic seizures can vary from brief and nearly undetectable periods to long periods of vigorous shaking due to abnormal el ...

epilepsy
,
hydrocephalus :''This article concerns the medical condition. For the hydrocephalus creature in American folklore that bares this condition as a part of its legend, see melon heads.'' Hydrocephalus is a condition in which an accumulation of cerebrospinal flu ...

hydrocephalus
, or
cognitive deficit Cognitive deficit is an inclusive term to describe any characteristic that acts as a barrier to the cognition process. The term may describe * deficits in overall intelligence Intelligence has been defined in many ways: the capacity for logic ...
s, especially if not treated quickly. In 2017, meningitis occurred in about 10.6 million people worldwide. This resulted in 288,000 deaths—down from 464,000 deaths in 1990. With appropriate treatment, the risk of death in bacterial meningitis is less than 15%. Outbreaks of bacterial meningitis occur between December and June each year in an area of
sub-Saharan Africa Sub-Saharan Africa (commonly called Black Africa) is, geographically, the area of the continent of Africa that lies south of the Sahara. According to the United Nations, it consists of all list of sovereign states and dependent territories in ...

sub-Saharan Africa
known as the meningitis belt. Smaller outbreaks may also occur in other areas of the world. The word meningitis comes from the
Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 million as of ...
μῆνιγξ ''meninx'', "membrane", and the medical suffix ''-itis'', "inflammation".


Signs and symptoms


Clinical features

In adults, the most common symptom of meningitis is a severe
headache Headache is the symptom of pain in the face, head, or neck. It can occur as a migraine, tension-type headache, or cluster headache. There is an increased risk of Depression (mood), depression in those with severe headaches. Headaches can occur ...

headache
, occurring in almost 90% of cases of bacterial meningitis, followed by
neck stiffness Neck stiffness, stiff neck and nuchal rigidity are terms often used interchangeably to describe the medical condition when one experiences discomfort or pain when trying to turn, move, or flex the neck. Possible causes include muscle strain or sp ...

neck stiffness
(the inability to flex the neck forward passively due to increased neck
muscle tone In physiology Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology Biology is the natural science that studies life and living organisms, including their anatomy, physi ...
and stiffness). The classic triad of diagnostic signs consists of
neck stiffness Neck stiffness, stiff neck and nuchal rigidity are terms often used interchangeably to describe the medical condition when one experiences discomfort or pain when trying to turn, move, or flex the neck. Possible causes include muscle strain or sp ...

neck stiffness
, sudden , and
altered mental status Altered may refer to: * ''Altered'' (film), a 2006 film * Altered (drag racing), a former drag racing class * Altered scale See also

* Alter (disambiguation) {{Disambiguation ...
; however, all three features are present in only 44–46% of bacterial meningitis cases. If none of the three signs are present, acute meningitis is extremely unlikely. Other signs commonly associated with meningitis include
photophobia Photophobia is a medical symptom Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or condition. A sign for example may be a higher or lower temperature than normal, raised or lowered bl ...
(intolerance to bright light) and
phonophobia Phonophobia, also called ligyrophobia or sonophobia, is a fear Fear is an emotion induced by perceived danger or threat, which causes physiological changes and ultimately behavioral changes, such as mounting an aggressive response or fleeing t ...
(intolerance to loud noises). Small children often do not exhibit the aforementioned symptoms, and may only be irritable and look unwell. The
fontanelle A fontanelle (or fontanel) (colloquially, soft spot) is an anatomical Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, ...

fontanelle
(the soft spot on the top of a baby's head) can bulge in infants aged up to 6 months. Other features that distinguish meningitis from less severe illnesses in young children are leg pain, cold extremities, and an abnormal
skin color Afghan children with fair skin Human skin color ranges from the darkest brown to the lightest hues. Differences in skin color among individuals is caused by variation in pigment A pigment is a colored material that is completely or nearly i ...
.
Nuchal rigidity Neck stiffness, stiff neck and nuchal rigidity are terms often used interchangeably to describe the medical condition when one experiences discomfort or pain when trying to turn, move, or flex the neck. Possible causes include muscle strain or sprai ...

Nuchal rigidity
occurs in 70% of bacterial meningitis in adults. Other signs include the presence of positive
Kernig's sign Kernig's sign (after Woldemar Kernig, Waldemar Kernig (1840–1917), a Russian neurologist) is positive when the thigh is flexed at the hip and knee at 90 degree angles, and subsequent extension in the knee is painful (leading to resistance). This ...
or Brudziński sign. Kernig's sign is assessed with the person lying
supine In grammar In linguistics Linguistics is the scientific study of language, meaning that it is a comprehensive, systematic, objective, and precise study of language. Linguistics encompasses the analysis of every aspect of language, a ...

supine
, with the hip and knee flexed to 90 degrees. In a person with a positive Kernig's sign, pain limits passive extension of the knee. A positive Brudzinski's sign occurs when flexion of the neck causes involuntary flexion of the knee and hip. Although Kernig's sign and Brudzinski's sign are both commonly used to screen for meningitis, the of these tests is limited. They do, however, have very good for meningitis: the signs rarely occur in other diseases. Another test, known as the "jolt accentuation maneuver" helps determine whether meningitis is present in those reporting fever and headache. A person is asked to rapidly rotate the head horizontally; if this does not make the headache worse, meningitis is unlikely. Other problems can produce symptoms similar to those above, but from non-meningitic causes. This is called
meningism Meningism is a set of symptom Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or condition. A sign for example may be a higher or lower temperature than normal, raised or lowered blood ...
or pseudomeningitis. Meningitis caused by the bacterium ''
Neisseria meningitidis ''Neisseria meningitidis'', often referred to as meningococcus, is a Gram-negative bacterium Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram stain, gram-staining method of bacterial differentiatio ...

Neisseria meningitidis
'' (known as "meningococcal meningitis") can be differentiated from meningitis with other causes by a rapidly spreading petechial rash, which may precede other symptoms. The rash consists of numerous small, irregular purple or red spots ("petechiae") on the trunk, lower extremities, mucous membranes, conjunctiva, and (occasionally) the palms of the hands or soles of the feet. The rash is typically non-blanching; the redness does not disappear when pressed with a finger or a glass tumbler. Although this rash is not necessarily present in meningococcal meningitis, it is relatively specific for the disease; it does, however, occasionally occur in meningitis due to other bacteria. Other clues on the cause of meningitis may be the skin signs of
hand, foot and mouth disease Hand, foot, and mouth disease (HFMD) is a common infection caused by a group of virus A virus is a submicroscopic infectious agent that Viral replication, replicates only inside the living Cell (biology), cells of an organism. Viruses ...
and
genital herpes Genital herpes is an Viral disease, infection by the herpes simplex virus (HSV) of the Sex organ, genitals. Most people either have no or mild symptoms and thus do not know they are infected. When symptoms do occur, they typically include small ...

genital herpes
, both of which are associated with various forms of viral meningitis.


Early complications

Additional problems may occur in the early stage of the illness. These may require specific treatment, and sometimes indicate severe illness or worse prognosis. The infection may trigger
sepsis Sepsis is a life-threatening condition that arises when the body's response to infection An infection is the invasion of an organism's body Tissue (biology), tissues by Pathogen, disease-causing agents, their multiplication, and the reaction ...
, a
systemic inflammatory response syndrome Systemic inflammatory response syndrome (SIRS), is an inflammatory state affecting the whole body. It is the body's response to an infectious or noninfectious insult. Although the definition of SIRS refers to it as an "inflammatory" response, i ...

systemic inflammatory response syndrome
of falling
blood pressure Blood pressure (BP) is the pressure Pressure (symbol: ''p'' or ''P'') is the force In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motio ...

blood pressure
,
fast heart rate Tachycardia, also called tachyarrhythmia, is a heart rateHeart rate is the speed of the heartbeat measured by the number of contractions (beats) of the heart The heart is a muscle, muscular Organ (anatomy), organ in most animals, which pu ...
, high or abnormally low temperature, and
rapid breathing Tachypnea, also spelt tackypnoea, is a respiratory rate The respiratory system (also respiratory apparatus, ventilatory system) is a biological system A biological system is a complex network which connects several biologically relevant entiti ...
. Very low blood pressure may occur at an early stage, especially but not exclusively in meningococcal meningitis; this may lead to insufficient blood supply to other organs.
Disseminated intravascular coagulation Disseminated intravascular coagulation (DIC) is a condition in which blood clots form throughout the body, blocking Microvessel, small blood vessels. Symptoms may include chest pain, shortness of breath, leg pain, problems speaking, or problems mov ...
, the excessive activation of
blood clotting Coagulation, also known as clotting, is the process by which blood Blood is a body fluid Body fluids, bodily fluids, or biofluids are liquid A liquid is a nearly incompressible fluid In physics, a fluid is a substance that continu ...
, may obstruct
blood flow Hemodynamics American and British English spelling differences#ae and oe, or haemodynamics are the Fluid dynamics, dynamics of blood flow. The circulatory system is controlled by homeostasis, homeostatic mechanisms of autoregulation, just as hydraul ...

blood flow
to organs and paradoxically increase the bleeding risk.
Gangrene Gangrene is a type of tissue death Necrosis (from Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roug ...
of limbs can occur in meningococcal disease. Severe meningococcal and pneumococcal infections may result in hemorrhaging of the
adrenal gland The adrenal glands (also known as suprarenal glands) are endocrine gland Endocrine glands are ductless glands of the endocrine system The endocrine system is a messenger system comprising feedback loops of the hormones released by interna ...

adrenal gland
s, leading to Waterhouse-Friderichsen syndrome, which is often fatal. The brain tissue may swell, pressure inside the skull may increase and the swollen brain may through the skull base. This may be noticed by a decreasing
level of consciousness Level or levels may refer to: Engineering *Level (instrument), a device used to measure true horizontal or relative heights *Canal pound or level *Regrading or levelling, the process of raising and/or lowering the levels of land *Storey or level, ...
, loss of the
pupillary light reflex The pupillary light reflex (PLR) or photopupillary reflex is a reflex In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular ...
, and abnormal posturing. The inflammation of the brain tissue may also obstruct the normal flow of CSF around the brain (
hydrocephalus :''This article concerns the medical condition. For the hydrocephalus creature in American folklore that bares this condition as a part of its legend, see melon heads.'' Hydrocephalus is a condition in which an accumulation of cerebrospinal flu ...

hydrocephalus
).
Seizure An epileptic seizure, formally known as a seizure, is a period of symptom Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or condition. A sign for example may be a higher or lower tem ...
s may occur for various reasons; in children, seizures are common in the early stages of meningitis (in 30% of cases) and do not necessarily indicate an underlying cause. Seizures may result from increased pressure and from areas of inflammation in the brain tissue.
Focal seizures Focal seizures (also called partial seizures and localized seizures) are seizures which affect initially only one hemisphere of the brain. The brain is divided into two hemispheres, each consisting of four lobes – the frontal, temporal, parie ...
(seizures that involve one limb or part of the body), persistent seizures, late-onset seizures and those that are difficult to control with medication indicate a poorer long-term outcome. Inflammation of the meninges may lead to abnormalities of the
cranial nerves Cranial nerves are the nerves that emerge directly from the brain (including the brainstem), of which there are conventionally considered twelve pairs. Cranial nerves relay information between the brain and parts of the body, primarily to and f ...
, a group of nerves arising from the
brain stem The brainstem (or brain stem) is the posterior stalk-like part of the brain A brain is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and anima ...
that supply the head and neck area and which control, among other functions, eye movement, facial muscles, and hearing. Visual symptoms and
hearing loss Hearing loss is a partial or total inability to hear Hearing, or auditory perception, is the ability to perceive Sound, sounds by detecting Vibration, vibrations, changes in the pressure of the surrounding medium through time, through a ...
may persist after an episode of meningitis. Inflammation of the brain (
encephalitis Encephalitis is inflammation Inflammation (from la, wikt:en:inflammatio#Latin, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or Irritation, irritants, and is a p ...
) or its
blood vessel The blood vessels are the components of the circulatory system The circulatory system, also called the cardiovascular system or the vascular system, is an organ system An organ system is a biological system A biological system is a comp ...
s ( cerebral vasculitis), as well as the formation of
blood clots A thrombus, colloquially called a blood clot, is the final product of the blood coagulation Coagulation, also known as clotting, is the process by which blood Blood is a body fluid in humans and other animals that delivers necessary sub ...

blood clots
in the veins ( cerebral venous thrombosis), may all lead to weakness, loss of sensation, or abnormal movement or function of the part of the body supplied by the affected area of the brain.


Causes

Meningitis is typically caused by an
infection An infection is the invasion of an organism's body tissues by disease-causing agents, their multiplication, and the reaction of host A host is a person responsible for guests at an event or for providing hospitality during it. Host may ...

infection
with
microorganisms A microorganism, or microbe,, ''mikros'', "small") and ''organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes ...

microorganisms
. Most infections are due to viruses, with
bacteria Bacteria (; common noun bacteria, singular bacterium) are a type of biological cell The cell (from Latin ''cella'', meaning "small room") is the basic structural, functional, and biological unit of all known organisms. Cells are the sm ...

bacteria
,
fungi A fungus (plural The plural (sometimes abbreviated An abbreviation (from Latin ''brevis'', meaning ''short'') is a shortened form of a word or phrase, by any method. It may consist of a group of letters, or words taken from the full ...

fungi
, and
protozoa Protozoa (singular protozoon or protozoan, plural protozoa or protozoans) is an informal term for a group of single-celled eukaryote Eukaryotes () are organism In biology, an organism () is any organic, life, living system that ...

protozoa
being the next most common causes. It may also result from various non-infectious causes. The term ''
aseptic meningitis Aseptic meningitis is the inflammation of the meninges, a membrane covering the brain A brain is an organ (anatomy), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head ...
'' refers to cases of meningitis in which no bacterial infection can be demonstrated. This type of meningitis is usually caused by viruses but it may be due to bacterial infection that has already been partially treated, when bacteria disappear from the meninges, or pathogens infect a space adjacent to the meninges (e.g.
sinusitis Sinusitis, also known as rhinosinusitis, is inflammation Inflammation (from la, wikt:en:inflammatio#Latin, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or Irrit ...

sinusitis
).
Endocarditis Endocarditis is an inflammation Inflammation (from la, wikt:en:inflammatio#Latin, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or Irritation, irritants, and is a p ...

Endocarditis
(an infection of the
heart valve A heart valve is a one-way valve check valve Image:Check Valve.svg, 140px, Check valve symbol on piping and instrumentation diagrams. The arrow shows the flow direction. A check valve, non-return valve, reflux valve, retention valve, foot valv ...
s which spreads small clusters of bacteria through the bloodstream) may cause aseptic meningitis. Aseptic meningitis may also result from infection with
spirochete A spirochaete () or spirochete is a member of the phylum In biology, a phylum (; plural The plural (sometimes list of glossing abbreviations, abbreviated ), in many languages, is one of the values of the grammatical number, grammatical ...
s, a group of bacteria that includes ''
Treponema pallidum ''Treponema pallidum'' is a spirochaete bacterium with various subspecies that cause the diseases syphilis, bejel, and yaws. It is transmitted only amongst humans. It is a helically coiled microorganism usually 6–15 μm long and 0.1–0.2 ...

Treponema pallidum
'' (the cause of
syphilis Syphilis is a sexually transmitted infection Sexually transmitted infections (STIs), also referred to as sexually transmitted diseases (STDs) and the older term venereal disease, are infection An infection is the invasion of an orga ...
) and ''
Borrelia burgdorferi ''Borrelia burgdorferi'' is a bacterial Bacteria (; common noun bacteria, singular bacterium) are a type of biological cell. They constitute a large domain of prokaryotic microorganism A microorganism, or microbe,, ''mikros'', " ...
'' (known for causing
Lyme disease Lyme disease, also known as Lyme borreliosis, is a vector-borne disease caused by the ''Borrelia'' bacterium which is spread by ticks in the genus ''Ixodes''. The most common sign of infection is an expanding red rash, known as erythema migrans ...
). Meningitis may be encountered in
cerebral malaria Malaria is a Mosquito-borne disease, mosquito-borne infectious disease that affects humans and other animals. Malaria causes symptoms that typically include fever, fatigue (medical), tiredness, vomiting, and headaches. In severe cases, it can c ...
(malaria infecting the brain) or amoebic meningitis, meningitis due to infection with
amoebae An amoeba (; less commonly spelt ameba or amœba; plural ''am(o)ebas'' or ''am(o)ebae'' ), often called an amoeboid, is a type of cell or unicellular organism A unicellular organism, also known as a single-celled organism, is an organism ...
such as ''
Naegleria fowleri ''Naegleria fowleri'', colloquially known as a "brain-eating amoeba", is a species of the genus ''Naegleria'', belonging to the phylum Percolozoa, which is technically not classified as true amoeba, but a shapeshifting amoeboflagellate Excavata ...
'', contracted from freshwater sources.


Bacterial

The types of
bacteria Bacteria (; common noun bacteria, singular bacterium) are a type of biological cell The cell (from Latin ''cella'', meaning "small room") is the basic structural, functional, and biological unit of all known organisms. Cells are the sm ...

bacteria
that cause bacterial meningitis vary according to the infected individual's age group. * In and
newborns 222x222px, Eight-month-old Fraternal twin, sororal twin sisters An infant (from the Latin word ''infans'', meaning 'unable to speak' or 'speechless') is the more formal or specialised synonym for the common term ''baby'', meaning the juve ...

newborns
up to three months old, common causes are '' group B streptococci'' (subtypes III which normally inhabit the
vagina In mammal Mammals (from Latin language, Latin , 'breast') are a group of vertebrate animals constituting the class (biology), class Mammalia (), and characterized by the presence of mammary glands which in Female#Mammalian female, femal ...

vagina
and are mainly a cause during the first week of life) and bacteria that normally inhabit the
digestive tract The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organ (biology), organs of the digestive syst ...
such as ''
Escherichia coli ''Escherichia coli'' (),Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. also known as ''E. coli'' (), is a Gram-negative bacteria, Gram-negative, Facultative anaerobic organism, facultative anaer ...

Escherichia coli
'' (carrying the K1 antigen). ''
Listeria monocytogenes ''Listeria monocytogenes'' is the species of pathogenic bacteria Pathogenic bacteria are bacteria Bacteria (; common noun bacteria, singular bacterium) are a type of Cell (biology), biological cell. They constitute a large domain (biolog ...
'' (serotype IVb) can be contracted when consuming improperly prepared food such as dairy products, produce and deli meats, and may cause meningitis in the newborn. * Older children are more commonly affected by ''
Neisseria meningitidis ''Neisseria meningitidis'', often referred to as meningococcus, is a Gram-negative bacterium Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram stain, gram-staining method of bacterial differentiatio ...

Neisseria meningitidis
'' (meningococcus) and ''
Streptococcus pneumoniae ''Streptococcus'' is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology Biology is the natural science that studies life and living organisms, including ...

Streptococcus pneumoniae
'' (serotypes 6, 9, 14, 18 and 23) and those under five by (in countries that do not offer vaccination). * In adults, ''Neisseria meningitidis'' and ''Streptococcus pneumoniae'' together cause 80% of bacterial meningitis cases. Risk of infection with ''Listeria monocytogenes'' is increased in persons over 50 years old. The introduction of pneumococcal vaccine has lowered rates of pneumococcal meningitis in both children and adults. Recent skull
trauma Trauma most often refers to: *Major trauma, in physical medicine, severe physical injury caused by an external source *Psychological trauma, a type of damage to the psyche that occurs as a result of a severely distressing event *Traumatic injur ...
potentially allows nasal cavity bacteria to enter the meningeal space. Similarly, devices in the brain and meninges, such as cerebral shunts, extraventricular drains or Ommaya reservoirs, carry an increased risk of meningitis. In these cases, the persons are more likely to be infected with Staphylococci, Pseudomonas, and other Gram-negative bacteria. These pathogens are also associated with meningitis in people with Immunodeficiency, an impaired immune system. An infection in the head and neck area, such as otitis media or mastoiditis, can lead to meningitis in a small proportion of people. Recipients of cochlear implants for hearing loss are more at risk for pneumococcal meningitis. Tuberculous meningitis, which is meningitis caused by ''Mycobacterium tuberculosis'', is more common in people from countries in which tuberculosis is endemic, but is also encountered in persons with immune problems, such as AIDS. Recurrent bacterial meningitis may be caused by persisting anatomical defects, either congenital or acquired, or by disorders of the immune system. Anatomical defects allow continuity between the external environment and the nervous system. The most common cause of recurrent meningitis is a skull fracture, particularly fractures that affect the base of the skull or extend towards the paranasal sinuses, sinuses and petrous pyramids. Approximately 59% of recurrent meningitis cases are due to such anatomical abnormalities, 36% are due to immune deficiencies (such as complement deficiency, which predisposes especially to recurrent meningococcal meningitis), and 5% are due to ongoing infections in areas adjacent to the meninges.


Viral

Viruses that cause meningitis include enteroviruses, herpes simplex virus (generally type 2, which produces most genital sores; less commonly type 1), varicella zoster virus (known for causing chickenpox and Herpes zoster, shingles), mumps, mumps virus, HIV, lymphocytic choriomeningitis, LCMV, Arboviruses (acquired from a mosquito or other insect), and the Influenza virus. Mollaret's meningitis is a chronic recurrent form of herpes meningitis; it is thought to be caused by herpes simplex virus, herpes simplex virus type 2.


Fungal

There are a number of risk factors for fungal meningitis, including the use of immunosuppressants (such as after organ transplantation), HIV/AIDS, and the loss of immunity associated with aging. It is uncommon in those with a normal immune system but has occurred with New England Compounding Center meningitis outbreak, medication contamination. Symptom onset is typically more gradual, with headaches and fever being present for at least a couple of weeks before diagnosis. The most common fungal meningitis is cryptococcal meningitis due to ''Cryptococcus neoformans''. In Africa, cryptococcal meningitis is now the most common cause of meningitis in multiple studies, and it accounts for 20–25% of AIDS-related deaths in Africa. Other less common fungal pathogens which can cause meningitis include: ''Coccidioides immitis'', ''Histoplasma capsulatum'', ''Blastomyces dermatitidis'', and ''Candida (fungus), Candida'' species.


Parasitic

A parasitic cause is often assumed when there is a predominance of eosinophil granulocyte, eosinophils (a type of white blood cell) in the CSF. The most common parasites implicated are ''Angiostrongylus cantonensis'', ''Gnathostoma spinigerum'', ''Schistosoma'', as well as the conditions cysticercosis, toxocariasis, Baylisascaris procyonis, baylisascariasis, paragonimiasis, and a number of rarer infections and noninfective conditions.


Non-infectious

Meningitis may occur as the result of several non-infectious causes: spread of cancer to the meninges (''neoplastic meningitis, malignant or neoplastic meningitis'') and certain drugs (mainly non-steroidal anti-inflammatory drugs,
antibiotic An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting pathogenic bacteria, bacterial infections, and antibiotic medications are widely used in the therapy, ...
s and intravenous immunoglobulins). It may also be caused by several inflammatory conditions, such as sarcoidosis (which is then called neurosarcoidosis), connective tissue disorders such as systemic lupus erythematosus, and certain forms of vasculitis (inflammatory conditions of the blood vessel wall), such as Behçet's disease. Epidermoid cysts and dermoid cysts may cause meningitis by releasing irritant matter into the subarachnoid space. Rarely, migraine may cause meningitis, but this diagnosis is usually only made when other causes have been eliminated.


Mechanism

The meninges comprise three membranes that, together with the
cerebrospinal fluid Cerebrospinal fluid (CSF) is a clear, colorless found within the that surrounds the and of all . CSF is produced by specialised in the of the of the brain, and absorbed in the s. There is about 125 mL of CSF at any one time, and a ...
, enclose and protect the
brain A brain is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's tiss ...

brain
and
spinal cord The spinal cord is a long, thin, tubular structure made up of , which extends from the in the to the region of the . It encloses the of the spinal cord, which contains . The and spinal cord together make up the (CNS). In s, the spinal cord ...

spinal cord
(the central nervous system). The pia mater is a delicate impermeable membrane that firmly adheres to the surface of the brain, following all the minor contours. The arachnoid mater (so named because of its spider-web-like appearance) is a loosely fitting sac on top of the pia mater. The subarachnoid space separates the arachnoid and pia mater membranes and is filled with cerebrospinal fluid. The outermost membrane, the dura mater, is a thick durable membrane, which is attached to both the arachnoid membrane and the skull. In bacterial meningitis, bacteria reach the meninges by one of two main routes: through the bloodstream (hematogenous spread) or through direct contact between the meninges and either the nasal cavity or the skin. In most cases, meningitis follows invasion of the bloodstream by organisms that live on mucous membrane, mucosal surfaces such as the nasal cavity. This is often in turn preceded by viral infections, which break down the normal barrier provided by the mucosal surfaces. Once bacteria have entered the bloodstream, they enter the subarachnoid space in places where the blood–brain barrier is vulnerable – such as the choroid plexus. Meningitis occurs in 25% of newborns with bloodstream infections due to group B streptococci; this phenomenon is much less common in adults. Direct contamination of the cerebrospinal fluid may arise from indwelling devices, skull fractures, or infections of the nasopharynx or the nasal sinuses that have formed a tract with the subarachnoid space (see above); occasionally, Congenital disorder, congenital defects of the dura mater can be identified. The large-scale
inflammation Inflammation (from la, wikt:en:inflammatio#Latin, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or Irritation, irritants, and is a protective response involving imm ...
that occurs in the subarachnoid space during meningitis is not a direct result of bacterial infection but can rather largely be attributed to the response of the immune system to the entry of bacteria into the central nervous system. When components of the bacterial cell membrane are identified by the immune cells of the brain (astrocytes and microglia), they respond by releasing large amounts of cytokines, hormone-like mediators that recruit other immune cells and stimulate other tissues to participate in an immune response. The blood–brain barrier becomes more permeable, leading to Cerebral edema#Vasogenic Cerebral Edema, "vasogenic" cerebral edema (swelling of the brain due to fluid leakage from blood vessels). Large numbers of white blood cells enter the CSF, causing inflammation of the meninges and leading to Cerebral edema#Interstitial Cerebral Edema, "interstitial" edema (swelling due to fluid between the cells). In addition, the walls of the blood vessels themselves become inflamed (cerebral vasculitis), which leads to decreased blood flow and a third type of edema, Cerebral edema#Cytotoxic Cerebral Edema, "cytotoxic" edema. The three forms of cerebral edema all lead to increased intracranial pressure; together with the lowered blood pressure often encountered in
sepsis Sepsis is a life-threatening condition that arises when the body's response to infection An infection is the invasion of an organism's body Tissue (biology), tissues by Pathogen, disease-causing agents, their multiplication, and the reaction ...
, this means that it is harder for blood to enter the brain; consequently brain cells are deprived of oxygen and undergo apoptosis (programmed cell death). It is recognized that administration of antibiotics may initially worsen the process outlined above, by increasing the amount of bacterial cell membrane products released through the destruction of bacteria. Particular treatments, such as the use of glucocorticoid, corticosteroids, are aimed at dampening the immune system's response to this phenomenon.


Diagnosis

Diagnosing meningitis as promptly as possible can improve outcomes. There is no specific sign or symptom that can diagnose meningitis and a
lumbar puncture Lumbar puncture (LP), also known as a spinal tap, is a medical procedure in which a needle is inserted into the spinal canal The spinal canal (or vertebral canal or spinal cavity) is the canal that contains the spinal cord within the vertebral c ...
(spinal tap) to examine the cerebrospinal fluid is recommended for diagnosis. Lumbar puncture is contraindicated if there is a mass in the brain (tumor or abscess) or the intracranial pressure (ICP) is elevated, as it may lead to brain herniation. If someone is at risk for either a mass or raised ICP (recent head injury, a known immune system problem, localizing neurological signs, or evidence on examination of a raised ICP), a Computed tomography, CT or Magnetic resonance imaging, MRI scan is recommended prior to the lumbar puncture. – formal guideline at This applies in 45% of all adult cases. There are no physical tests that can rule out or determine if a person has meningitis. The jolt accentuation test is not specific or sensitive enough to completely rule out meningitis. If someone is suspected of having meningitis, blood tests are performed for markers of inflammation (e.g. C-reactive protein, complete blood count), as well as blood cultures. If a CT or MRI is required before LP, or if LP proves difficult, professional guidelines suggest that antibiotics should be administered first to prevent delay in treatment, especially if this may be longer than 30 minutes. Often, CT or MRI scans are performed at a later stage to assess for complications of meningitis. In severe forms of meningitis, monitoring of blood electrolytes may be important; for example, hyponatremia is common in bacterial meningitis. The cause of hyponatremia, however, is controversial and may include dehydration, the Syndrome of inappropriate antidiuretic hormone hypersecretion, inappropriate secretion of the antidiuretic hormone (SIADH), or overly aggressive Intravenous therapy, intravenous fluid administration.


Lumbar puncture

A lumbar puncture is done by positioning the person, usually lying on the side, applying local anesthetic, and inserting a needle into the dural sac (a sac around the spinal cord) to collect cerebrospinal fluid (CSF). When this has been achieved, the "opening pressure" of the CSF is measured using a manometer. The pressure is normally between 6 and 18 cm water (cmH2O); in bacterial meningitis the pressure is usually elevated. In cryptococcal meningitis, intracranial pressure is markedly elevated. The initial appearance of the fluid may prove an indication of the nature of the infection: cloudy CSF indicates higher levels of protein, white and red blood cells and/or bacteria, and therefore may suggest bacterial meningitis. The CSF sample is examined for presence and types of white blood cells, red blood cells, protein content and glucose level. Gram staining of the sample may demonstrate bacteria in bacterial meningitis, but absence of bacteria does not exclude bacterial meningitis as they are only seen in 60% of cases; this figure is reduced by a further 20% if antibiotics were administered before the sample was taken. Gram staining is also less reliable in particular infections such as listeriosis. Microbiological culture of the sample is more sensitive (it identifies the organism in 70–85% of cases) but results can take up to 48 hours to become available. The type of white blood cell predominantly present (see table) indicates whether meningitis is bacterial (usually neutrophil-predominant) or viral (usually lymphocyte-predominant), although at the beginning of the disease this is not always a reliable indicator. Less commonly, eosinophils predominate, suggesting parasitic or fungal etiology, among others. The concentration of glucose in CSF is normally above 40% of that in blood. In bacterial meningitis it is typically lower; the CSF glucose level is therefore divided by the Blood sugar, blood glucose (CSF glucose to serum glucose ratio). A ratio ≤0.4 is indicative of bacterial meningitis; in the newborn, glucose levels in CSF are normally higher, and a ratio below 0.6 (60%) is therefore considered abnormal. High levels of lactic acid, lactate in CSF indicate a higher likelihood of bacterial meningitis, as does a higher white blood cell count. If lactate levels are less than 35 mg/dl and the person has not previously received antibiotics then this may rule out bacterial meningitis. Various other specialized tests may be used to distinguish between different types of meningitis. A latex agglutination test may be positive in meningitis caused by ''
Streptococcus pneumoniae ''Streptococcus'' is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology Biology is the natural science that studies life and living organisms, including ...

Streptococcus pneumoniae
'', ''
Neisseria meningitidis ''Neisseria meningitidis'', often referred to as meningococcus, is a Gram-negative bacterium Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram stain, gram-staining method of bacterial differentiatio ...

Neisseria meningitidis
'', ''Haemophilus influenzae'', ''
Escherichia coli ''Escherichia coli'' (),Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. also known as ''E. coli'' (), is a Gram-negative bacteria, Gram-negative, Facultative anaerobic organism, facultative anaer ...

Escherichia coli
'' and ''Streptococcus agalactiae, group B streptococci''; its routine use is not encouraged as it rarely leads to changes in treatment, but it may be used if other tests are not diagnostic. Similarly, the Limulus amebocyte lysate, limulus lysate test may be positive in meningitis caused by Gram-negative bacteria, but it is of limited use unless other tests have been unhelpful. Polymerase chain reaction (PCR) is a technique used to amplify small traces of bacterial DNA in order to detect the presence of bacterial or viral DNA in cerebrospinal fluid; it is a highly sensitive and specific test since only trace amounts of the infecting agent's DNA is required. It may identify bacteria in bacterial meningitis and may assist in distinguishing the various causes of viral meningitis (enterovirus, herpes simplex virus, herpes simplex virus 2 and mumps in those not vaccinated for this). Serology (identification of antibodies to viruses) may be useful in viral meningitis. If tuberculous meningitis is suspected, the sample is processed for Ziehl–Neelsen stain, which has a low sensitivity, and tuberculosis culture, which takes a long time to process; PCR is being used increasingly. Diagnosis of cryptococcal meningitis can be made at low cost using an India ink stain of the CSF; however, testing for cryptococcal antigen in blood or CSF is more sensitive. A diagnostic and therapeutic difficulty is "partially treated meningitis", where there are meningitis symptoms after receiving antibiotics (such as for presumptive
sinusitis Sinusitis, also known as rhinosinusitis, is inflammation Inflammation (from la, wikt:en:inflammatio#Latin, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or Irrit ...

sinusitis
). When this happens, CSF findings may resemble those of viral meningitis, but antibiotic treatment may need to be continued until there is definitive positive evidence of a viral cause (e.g. a positive enterovirus PCR).


Postmortem

Meningitis can be diagnosed after death has occurred. The findings from a post mortem are usually a widespread inflammation of the pia mater and arachnoid mater, arachnoid layers of the meninges. Neutrophil granulocytes tend to have migrated to the cerebrospinal fluid and the base of the brain, along with cranial nerves and the
spinal cord The spinal cord is a long, thin, tubular structure made up of , which extends from the in the to the region of the . It encloses the of the spinal cord, which contains . The and spinal cord together make up the (CNS). In s, the spinal cord ...

spinal cord
, may be surrounded with pus – as may the meningeal vessels.


Prevention

For some causes of meningitis, protection can be provided in the long term through vaccination, or in the short term with
antibiotic An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting pathogenic bacteria, bacterial infections, and antibiotic medications are widely used in the therapy, ...
s. Some behavioral measures may also be effective.


Behavioral

Bacterial and viral meningitis are contagious, but neither is as contagious as the common cold or flu. Both can be transmitted through droplets of respiratory secretions during close contact such as kissing, sneezing or coughing on someone, but bacterial meningitis cannot be spread by only breathing the air where a person with meningitis has been. Viral meningitis is typically caused by enteroviruses, and is most commonly spread through fecal contamination. The risk of infection can be decreased by changing the behavior that led to transmission.


Vaccination

Since the 1980s, many countries have included Hib vaccine, immunization against ''Haemophilus influenzae'' type B in their routine childhood vaccination schemes. This has practically Eradication of infectious diseases, eliminated this pathogen as a cause of meningitis in young children in those countries. In the countries in which the disease burden is highest, however, the vaccine is still too expensive. Similarly, immunization against mumps has led to a sharp fall in the number of cases of mumps meningitis, which prior to vaccination occurred in 15% of all cases of mumps. Meningococcal vaccine, Meningococcus vaccines exist against groups A, B, C, W135 and Y. In countries where the vaccine for meningococcus group C was introduced, cases caused by this pathogen have decreased substantially. A quadrivalent vaccine now exists, which combines four vaccines with the exception of B; immunization with this ACW135Y vaccine is now a visa requirement for taking part in Hajj. Development of a vaccine against group B meningococci has proved much more difficult, as its surface proteins (which would normally be used to make a vaccine) only elicit a weak Immunogenicity, response from the immune system, or cross-react with normal human proteins. Still, some countries (New Zealand, Cuba, Norway and Chile) have developed vaccines against local strains of group B meningococci; some have shown good results and are used in local immunization schedules. Two new vaccines, both approved in 2014, are effective against a wider range of group B meningococci strains. In Africa, until recently, the approach for prevention and control of meningococcal epidemics was based on early detection of the disease and emergency reactive mass vaccination of the at-risk population with bivalent A/C or trivalent A/C/W135 polysaccharide vaccines, though the introduction of MenAfriVac (meningococcus group A vaccine) has demonstrated effectiveness in young people and has been described as a model for product development partnerships in resource-limited settings. Routine vaccination against ''Streptococcus pneumoniae'' with the pneumococcal conjugate vaccine (PCV), which is active against seven common serotypes of this pathogen, significantly reduces the incidence of pneumococcal meningitis. The pneumococcal polysaccharide vaccine, which covers 23 strains, is only administered to certain groups (e.g. those who have had a splenectomy, the surgical removal of the spleen); it does not elicit a significant immune response in all recipients, e.g. small children. Childhood vaccination with Bacillus Calmette-Guérin has been reported to significantly reduce the rate of tuberculous meningitis, but its waning effectiveness in adulthood has prompted a search for a better vaccine.


Antibiotics

Short-term antibiotic prophylaxis is another method of prevention, particularly of meningococcal meningitis. In cases of meningococcal meningitis, preventative treatment in close contacts with antibiotics (e.g. rifampicin, ciprofloxacin or ceftriaxone) can reduce their risk of contracting the condition, but does not protect against future infections. Resistance to rifampicin has been noted to increase after use, which has caused some to recommend considering other agents. While antibiotics are frequently used in an attempt to prevent meningitis in those with a basilar skull fracture there is not enough evidence to determine whether this is beneficial or harmful. This applies to those with or without a CSF leak.


Management

Meningitis is potentially life-threatening and has a high mortality rate if untreated; delay in treatment has been associated with a poorer outcome. Thus, treatment with wide-spectrum antibiotics should not be delayed while confirmatory tests are being conducted. If meningococcal disease is suspected in primary care, guidelines recommend that benzylpenicillin be administered before transfer to hospital. Intravenous fluid, Intravenous fluids should be administered if hypotension (low blood pressure) or shock (circulatory), shock are present. It is not clear whether intravenous fluid should be given routinely or whether this should be restricted. Given that meningitis can cause a number of early severe complications, regular medical review is recommended to identify these complications early and to admit the person to an intensive care unit if deemed necessary. Mechanical ventilation may be needed if the level of consciousness is very low, or if there is evidence of respiratory failure. If there are signs of raised intracranial pressure, measures to monitor the pressure may be taken; this would allow the optimization of the cerebral perfusion pressure and various treatments to decrease the intracranial pressure with medication (e.g. mannitol). Seizures are treated with anticonvulsants. Hydrocephalus (obstructed flow of CSF) may require insertion of a temporary or long-term drainage device, such as a cerebral shunt. The osmotic therapy, glycerol, has an unclear effect on mortality but may decrease hearing problems.


Bacterial meningitis


Antibiotics

Empiric antibiotics (treatment without exact diagnosis) should be started immediately, even before the results of the lumbar puncture and CSF analysis are known. The choice of initial treatment depends largely on the kind of bacteria that cause meningitis in a particular place and population. For instance, in the United Kingdom, empirical treatment consists of a third-generation cefalosporin such as cefotaxime or ceftriaxone. In the US, where resistance to cefalosporins is increasingly found in streptococci, addition of vancomycin to the initial treatment is recommended. Chloramphenicol, either alone or in combination with ampicillin, however, appears to work equally well. Empirical therapy may be chosen on the basis of the person's age, whether the infection was preceded by a head injury, whether the person has undergone recent neurosurgery and whether or not a cerebral shunt is present. In young children and those over 50 years of age, as well as those who are immunocompromised, the addition of ampicillin is recommended to cover ''
Listeria monocytogenes ''Listeria monocytogenes'' is the species of pathogenic bacteria Pathogenic bacteria are bacteria Bacteria (; common noun bacteria, singular bacterium) are a type of Cell (biology), biological cell. They constitute a large domain (biolog ...
''. Once the Gram stain results become available, and the broad type of bacterial cause is known, it may be possible to change the antibiotics to those likely to deal with the presumed group of pathogens. The results of the CSF microbiological culture, culture generally take longer to become available (24–48 hours). Once they do, empiric therapy may be switched to specific antibiotic therapy targeted to the specific causative organism and its sensitivities to antibiotics. For an antibiotic to be effective in meningitis it must not only be active against the pathogenic bacterium but also reach the meninges in adequate quantities; some antibiotics have inadequate penetrance and therefore have little use in meningitis. Most of the antibiotics used in meningitis have not been tested directly on people with meningitis in clinical trials. Rather, the relevant knowledge has mostly derived from laboratory studies in rabbits. Tuberculous meningitis requires prolonged treatment with antibiotics. While tuberculosis of the lungs is typically treated for six months, those with tuberculous meningitis are typically treated for a year or longer.


Fluid Therapy

Fluid given intravenously are an essential part of treatment of bacterial meningitis. There is no difference in terms of mortality or acute severe neurological complications in children given a maintenance regimen over restricted-fluid regimen, but evidence is in favor of the maintenance regimen in terms of emergence of chronic severe neurological complications.


Steroids

Additional treatment with corticosteroids (usually dexamethasone) has shown some benefits, such as a reduction of
hearing loss Hearing loss is a partial or total inability to hear Hearing, or auditory perception, is the ability to perceive Sound, sounds by detecting Vibration, vibrations, changes in the pressure of the surrounding medium through time, through a ...
, and better short term neurological outcomes in adolescents and adults from World Bank high-income economy, high-income countries with low rates of HIV. Some research has found reduced rates of death while other research has not. They also appear to be beneficial in those with tuberculosis meningitis, at least in those who are HIV negative. Professional guidelines therefore recommend the commencement of dexamethasone or a similar corticosteroid just before the first dose of antibiotics is given, and continued for four days. Given that most of the benefit of the treatment is confined to those with pneumococcal meningitis, some guidelines suggest that dexamethasone be discontinued if another cause for meningitis is identified. The likely mechanism is suppression of overactive inflammation. Additional treatment with corticosteroids have a different role in children than in adults. Though the benefit of corticosteroids has been demonstrated in adults as well as in children from high-income countries, their use in children from Poverty, low-income countries is not supported by the evidence; the reason for this discrepancy is not clear. Even in high-income countries, the benefit of corticosteroids is only seen when they are given prior to the first dose of antibiotics, and is greatest in cases of ''H. influenzae'' meningitis, the incidence of which has decreased dramatically since the introduction of the
Hib vaccine The ''Haemophilus influenzae'' type B vaccine, also known as Hib vaccine, is a vaccine A vaccine is a biological preparation that provides active acquired immunity The adaptive immune system, also referred as the acquired immune system, is ...
. Thus, corticosteroids are recommended in the treatment of pediatric meningitis if the cause is ''H. influenzae'', and only if given prior to the first dose of antibiotics; other uses are controversial.


Viral meningitis

Viral meningitis typically only requires supportive therapy; most viruses responsible for causing meningitis are not amenable to specific treatment. Viral meningitis tends to run a more benign course than bacterial meningitis. Herpes simplex virus and varicella zoster virus may respond to treatment with antiviral drugs such as aciclovir, but there are no clinical trials that have specifically addressed whether this treatment is effective. Mild cases of viral meningitis can be treated at home with conservative measures such as fluid, bedrest, and analgesics.


Fungal meningitis

Fungal meningitis, such as cryptococcal meningitis, is treated with long courses of high dose Antifungal drug, antifungals, such as amphotericin B and flucytosine. Raised intracranial pressure is common in fungal meningitis, and frequent (ideally daily) lumbar punctures to relieve the pressure are recommended, or alternatively a lumbar drain.


Prognosis

Untreated, bacterial meningitis is almost always fatal. Viral meningitis, in contrast, tends to resolve spontaneously and is rarely fatal. With treatment, Mortality rate, mortality (risk of death) from bacterial meningitis depends on the age of the person and the underlying cause. Of newborns, 20–30% may die from an episode of bacterial meningitis. This risk is much lower in older children, whose mortality is about 2%, but rises again to about 19–37% in adults. Risk of death is predicted by various factors apart from age, such as the pathogen and the time it takes for the pathogen to be cleared from the cerebrospinal fluid, the severity of the generalized illness, a decreased level of consciousness or an abnormally low count of white blood cells in the CSF. Meningitis caused by ''H. influenzae'' and meningococci has a better prognosis than cases caused by group B streptococci, coliforms and ''S. pneumoniae''. In adults, too, meningococcal meningitis has a lower mortality (3–7%) than pneumococcal disease. In children there are several potential disabilities which may result from damage to the nervous system, including sensorineural hearing loss,
epilepsy Epilepsy is a group of non-communicable neurological disorders characterized by recurrent Seizure, epileptic seizures. Epileptic seizures can vary from brief and nearly undetectable periods to long periods of vigorous shaking due to abnormal el ...

epilepsy
, Learning disability, learning and behavioral difficulties, as well as Intellectual disability, decreased intelligence. These occur in about 15% of survivors. Some of the hearing loss may be reversible. In adults, 66% of all cases emerge without disability. The main problems are
deafness Deafness has varying definitions in cultural and medical contexts. In medical contexts, the meaning of deafness is hearing loss Hearing loss is a partial or total inability to Hearing, hear. Hearing loss may be present at birth or acquired ...
(in 14%) and Developmental disability, cognitive impairment (in 10%). Tuberculous meningitis in children continues to be associated with a significant risk of death even with treatment (19%), and a significant proportion of the surviving children have ongoing neurological problems. Just over a third of all cases survives with no problems.


Epidemiology

Although meningitis is a notifiable disease in many countries, the exact incidence (epidemiology), incidence rate is unknown. In 2013 meningitis resulted in 303,000 deaths – down from 464,000 deaths in 1990. In 2010 it was estimated that meningitis resulted in 420,000 deaths, excluding cryptococcal meningitis. Bacterial meningitis occurs in about 3 people per 100,000 annually in Western world, Western countries. Population-wide studies have shown that viral meningitis is more common, at 10.9 per 100,000, and occurs more often in the summer. In Brazil, the rate of bacterial meningitis is higher, at 45.8 per 100,000 annually. Sub-Saharan Africa has been plagued by large epidemics of meningococcal meningitis for over a century, leading to it being labeled the "meningitis belt". Epidemics typically occur in the dry season (December to June), and an epidemic wave can last two to three years, dying out during the intervening rainy seasons. Attack rates of 100–800 cases per 100,000 are encountered in this area, which is poorly served by Health care, medical care. These cases are predominantly caused by meningococci. The largest epidemic ever recorded in history swept across the entire region in 1996–1997, causing over 250,000 cases and 25,000 deaths. Meningococcal disease occurs in epidemics in areas where many people live together for the first time, such as army barracks during mobilization, university and college campuses and the annual Hajj pilgrimage. Although the pattern of epidemic cycles in Africa is not well understood, several factors have been associated with the development of epidemics in the meningitis belt. They include: medical conditions (immunological susceptibility of the population), demographic conditions (travel and large population displacements), socioeconomic conditions (overcrowding and poor living conditions), climatic conditions (drought and dust storms), and concurrent infections (acute respiratory infections). There are significant differences in the local distribution of causes for bacterial meningitis. For instance, while ''N. meningitides'' groups B and C cause most disease episodes in Europe, group A is found in Asia and continues to predominate in Africa, where it causes most of the major epidemics in the meningitis belt, accounting for about 80% to 85% of documented meningococcal meningitis cases.


History

Some suggest that Hippocrates may have realized the existence of meningitis, and it seems that
meningism Meningism is a set of symptom Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or condition. A sign for example may be a higher or lower temperature than normal, raised or lowered blood ...
was known to pre-Renaissance physicians such as Avicenna. The description of tuberculous meningitis, then called "dropsy in the brain", is often attributed to Edinburgh physician Robert Whytt, Sir Robert Whytt in a posthumous report that appeared in 1768, although the link with tuberculosis and its pathogen was not made until the next century. It appears that epidemic meningitis is a relatively recent phenomenon. The first recorded major outbreak occurred in Geneva in 1805. Several other epidemics in Europe and the United States were described shortly afterward, and the first report of an epidemic in Africa appeared in 1840. African epidemics became much more common in the 20th century, starting with a major epidemic sweeping Nigeria and Ghana in 1905–1908. The first report of bacterial infection underlying meningitis was by the Austrian bacteriologist Anton Weichselbaum, who in 1887 described the ''meningococcus''. Mortality from meningitis was very high (over 90%) in early reports. In 1906, antiserum was produced in horses; this was developed further by the American scientist Simon Flexner and markedly decreased mortality from meningococcal disease. In 1944, penicillin was first reported to be effective in meningitis. The introduction in the late 20th century of ''Haemophilus'' vaccines led to a marked fall in cases of meningitis associated with this pathogen, and in 2002, evidence emerged that treatment with steroids could improve the prognosis of bacterial meningitis. World Meningitis Day is observed on 24 April each year.


References


External links

*
Meningitis
Centers for Disease Control and Prevention (CDC) {{Authority control Meningitis, Disorders causing seizures Medical emergencies Acute pain Wikipedia medicine articles ready to translate (full) Medical triads Wikipedia infectious disease articles ready to translate