Arachnoid cysts are

cerebrospinal fluid Cerebrospinal fluid (CSF) is a clear, colorless body fluid found within the tissue that surrounds the brain and spinal cord of all vertebrates. CSF is produced by specialised ependymal cells in the choroid plexus of the ventricles of the bra ...

covered by arachnoidal cells and

collagen Collagen () is the main structural protein in the extracellular matrix found in the body's various connective tissues. As the main component of connective tissue, it is the most abundant protein in mammals, making up from 25% to 35% of the whole ...

that may develop between the surface of the

brain A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a v ...

and the cranial base or on the

arachnoid membrane The arachnoid mater (or simply arachnoid) is one of the three meninges, the protective membranes that cover the brain and spinal cord. It is so named because of its resemblance to a spider web. The arachnoid mater is a derivative of the neural cr ...

, one of the three

meningeal layers In anatomy, the meninges (, ''singular:'' meninx ( or ), ) are the three membranes that envelop the brain and spinal cord. In mammals, the meninges are the dura mater, the arachnoid mater, and the pia mater. Cerebrospinal fluid is located in ...

that cover the brain and the

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the spi ...

. Primary arachnoid cysts are a

congenital disorder A birth defect, also known as a congenital disorder, is an abnormal condition that is present at birth regardless of its cause. Birth defects may result in disabilities that may be physical, intellectual, or developmental. The disabilities can ...

whereas secondary arachnoid cysts are the result of head injury or trauma. Most cases of primary cysts begin during infancy; however, onset may be delayed until adolescence.

Signs and symptoms

Patients with arachnoid cysts may never show symptoms, even in some cases where the cyst is large. Therefore, while the presence of symptoms may provoke further clinical investigation, symptoms independent of further data cannot—and should not—be interpreted as evidence of a cyst's existence, size, location, or potential functional impact on the patient. Symptoms vary by the size and location of the cyst(s), though small cysts usually have no symptoms and are discovered only incidentally. On the other hand, a number of symptoms may result from large cysts: * Cranial deformation or

macrocephaly Macrocephaly is a condition in which circumference of the human head is abnormally large. It may be pathological or harmless, and can be a familial genetic characteristic. People diagnosed with macrocephaly will receive further medical tests to ...

(enlargement of the head), particularly in childrenBarker RA, Scolding N, Rowe D, Larner AJ. ''The A-Z of Neurological Practice: A Guide to Clinical Neurology''

Cambridge University Press Cambridge University Press is the university press of the University of Cambridge. Granted letters patent by Henry VIII of England, King Henry VIII in 1534, it is the oldest university press A university press is an academic publishing hou ...

2005 Jan 10, p61. () * Cysts in the suprasellar region in children have presented as bobbing and nodding of the head called

bobble-head doll syndrome Bobble-head doll syndrome is a rare neurological movement disorder in which patients, usually children around age 3, begin to bob their head and shoulders forward and back, or sometimes side-to-side, involuntarily, in a manner reminiscent of a bob ...

. * Cysts in the left middle cranial fossa have been associated with

ADHD Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterised by excessive amounts of inattention, hyperactivity, and impulsivity that are pervasive, impairing in multiple contexts, and otherwise age-inapp ...

in a study on affected children. *

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 in those with severe headaches. Headaches can occur as a result ...

s. A patient experiencing a headache does not necessarily have an arachnoid cyst. ** In a 2002 study involving 78 patients with a migraine or tension-type headache, CT scans showed abnormalities in over a third of the patients, though arachnoid cysts only accounted for 2.6% of patients in this study. ** A study found 18% of patients with intracranial arachnoid cysts had non-specific headaches. The cyst was in the temporal location in 75% of these cases.Cameron AD. "Psychotic phenomena with migraine and an arachnoid cyst", ''Progress in Neurology and Psychiatry'' 2002 Mar-Apr 6(2
http://www.escriber.com/Progress/Features.asp? Action=View&Archive=True&ID=67&GroupID=&Page=11
*

Seizure An epileptic seizure, informally known as a seizure, is a period of symptoms due to abnormally excessive or synchronous neuronal activity in the brain. Outward effects vary from uncontrolled shaking movements involving much of the body with los ...

s *

Hydrocephalus Hydrocephalus is a condition in which an accumulation of cerebrospinal fluid (CSF) occurs within the brain. This typically causes increased intracranial pressure, pressure inside the skull. Older people may have headaches, double vision, poor ...

(excessive accumulation of cerebrospinal fluid) * Increased

intracranial pressure Intracranial pressure (ICP) is the pressure exerted by fluids such as cerebrospinal fluid (CSF) inside the skull and on the brain tissue. ICP is measured in millimeters of mercury (mmHg) and at rest, is normally 7–15 Millimeter of mercury, mmHg ...

Developmental delay Global developmental delay is an umbrella term used when children are significantly delayed in their cognitive and physical development. It can be diagnosed when a child is delayed in one or more milestones, categorised into motor skills, speech, c ...

* Behavioral changes * Nausea * Dysdiadokinesis *

Hemiparesis Hemiparesis, or unilateral paresis, is weakness of one entire side of the body (''wikt:hemi-#Prefix, hemi-'' means "half"). Hemiplegia is, in its most severe form, complete paralysis of half of the body. Hemiparesis and hemiplegia can be caused ...

(weakness or paralysis on one side of the body) *

Ataxia Ataxia is a neurological sign consisting of lack of voluntary coordination of muscle movements that can include gait abnormality, speech changes, and abnormalities in eye movements. Ataxia is a clinical manifestation indicating dysfunction of ...

(lack of muscle control) * Musical

hallucination A hallucination is a perception in the absence of an external stimulus that has the qualities of a real perception. Hallucinations are vivid, substantial, and are perceived to be located in external objective space. Hallucination is a combinatio ...

* Pre-senile

dementia Dementia is a disorder which manifests as a set of related symptoms, which usually surfaces when the brain is damaged by injury or disease. The symptoms involve progressive impairments in memory, thinking, and behavior, which negatively affe ...

,Richards G, Lusznat RM. "An arachnoid cyst in a patient with pre-senile dementia", ''Progress in Neurology and Psychiatry'', 2001 May–June;5(3
http://www.escriber.com/Progress/Features.asp? Action=View&Archive=True&ID=29&GroupID=&Page=18
a condition often associated with

Alzheimer's disease Alzheimer's disease (AD) is a neurodegeneration, neurodegenerative disease that usually starts slowly and progressively worsens. It is the cause of 60–70% of cases of dementia. The most common early symptom is difficulty in short-term me ...

* In elderly patients (>80 years old) symptoms were similar to chronic

subdural hematoma A subdural hematoma (SDH) is a type of bleeding in which a Hematoma, collection of blood—usually but not always associated with a traumatic brain injury—gathers between the inner layer of the dura mater and the arachnoid mater of the meninges ...

or normal pressure

hydrocephalus Hydrocephalus is a condition in which an accumulation of cerebrospinal fluid (CSF) occurs within the brain. This typically causes increased intracranial pressure, pressure inside the skull. Older people may have headaches, double vision, poor ...

: ** Dementia **

Urinary incontinence Urinary incontinence (UI), also known as involuntary urination, is any uncontrolled leakage of urine. It is a common and distressing problem, which may have a large impact on quality of life. It has been identified as an important issue in geria ...

** Hemiparesis ** Headache ** Seizures

Location-specific symptoms

* A

supratentorial In anatomy, the supratentorial region of the brain is the area located above the tentorium cerebelli. The area of the brain below the tentorium cerebelli is the infratentorial region. The supratentorial region contains the cerebrum, while the infra ...

arachnoid cyst can mimic a

Ménière's disease Ménière's disease (MD) is a disease of the inner ear that is characterized by potentially severe and incapacitating episodes of vertigo, tinnitus, hearing loss, and a feeling of fullness in the ear. Typically, only one ear is affected initial ...

attack. * Frontal arachnoid cysts have been associated with depression.Cummings JL, Mega MS. ''Neuropsychiatry and Behavioral Neuroscience'', Oxford University Press, USA; 2Rev Ed, 2003 Jan 23;208. () * Cysts on the left temporal lobe have been associated with

psychosis Psychosis is a condition of the mind that results in difficulties determining what is real and what is not real. Symptoms may include delusions and hallucinations, among other features. Additional symptoms are incoherent speech and behavior ...

. A left fronto-temporal cyst showed symptoms of

alexithymia Alexithymia is a personality trait characterized by the inability to identify and describe emotions experienced by oneself. The core characteristic of alexithymia is marked dysfunction in emotional awareness, social attachment, and interpersonal ...

. * Cyst on the right

sylvian fissure In neuroanatomy, the lateral sulcus (also called Sylvian fissure, after Franciscus Sylvius, or lateral fissure) is one of the most prominent features of the human brain. The lateral sulcus is a deep fissure in each hemisphere that separates the ...

resulted in new onset of

schizophrenia Schizophrenia is a mental disorder characterized by continuous or relapsing episodes of psychosis. Major symptoms include hallucinations (typically hearing voices), delusions, and disorganized thinking. Other symptoms include social withdra ...

-like symptoms at age 61. * A patient with a cyst on the left

middle cranial fossa The middle cranial fossa, deeper than the anterior cranial fossa, is narrow medially and widens laterally to the sides of the skull. It is separated from the posterior fossa by the clivus and the petrous crest. It is bounded in front by the pos ...

had auditory

hallucinations A hallucination is a perception in the absence of an external stimulus that has the qualities of a real perception. Hallucinations are vivid, substantial, and are perceived to be located in external objective space. Hallucination is a combinatio ...

migraine Migraine (, ) is a common neurological disorder characterized by recurrent headaches. Typically, the associated headache affects one side of the head, is pulsating in nature, may be moderate to severe in intensity, and could last from a few hou ...

-like headaches, and periodic

paranoia Paranoia is an instinct or thought process that is believed to be heavily influenced by anxiety or fear, often to the point of delusion and irrationality. Paranoid thinking typically includes persecutory beliefs, or beliefs of conspiracy concer ...

* Patients with left temporal lobe cysts had mood disturbances similar to

manic depression Bipolar disorder, previously known as manic depression, is a mental disorder characterized by periods of depression and periods of abnormally elevated mood that last from days to weeks each. If the elevated mood is severe or associated with ...

(bipolar disorder) and were known to show outward aggression

Causes

The exact cause of arachnoid cysts is not known. Researchers believe that most cases of arachnoid cysts are developmental malformations that arise from the unexplained splitting or tearing of the arachnoid membrane. In some cases, arachnoid cysts occurring in the middle fossa are accompanied by underdevelopment (

hypoplasia Hypoplasia (from Ancient Greek ὑπo- ''hypo-'' 'under' + πλάσις ''plasis'' 'formation'; adjective form ''hypoplastic'') is underdevelopment or incomplete development of a tissue or organ.temporal lobe The temporal lobe is one of the four Lobes of the brain, major lobes of the cerebral cortex in the brain of mammals. The temporal lobe is located beneath the lateral fissure on both cerebral hemispheres of the mammalian brain. The temporal lobe ...

. The exact role that temporal lobe abnormalities play in the development of

middle fossa The middle cranial fossa, deeper than the anterior cranial fossa, is narrow medially and widens laterally to the sides of the skull. It is separated from the posterior fossa by the clivus and the petrous crest. It is bounded in front by the po ...

arachnoid cysts is unknown. There are some cases where hereditary disorders have been connected with arachnoid cysts. Some complications of arachnoid cysts can occur when a cyst is damaged because of minor

head trauma A head injury is any injury that results in trauma to the skull or brain. The terms ''traumatic brain injury'' and ''head injury'' are often used interchangeably in the medical literature. Because head injuries cover such a broad scope of inju ...

. Trauma can cause the fluid within a cyst to leak into other areas (e.g.,

subarachnoid space In anatomy, the meninges (, ''singular:'' meninx ( or ), ) are the three membranes that envelop the brain and spinal cord. In mammals, the meninges are the dura mater, the arachnoid mater, and the pia mater. Cerebrospinal fluid is located in th ...

). Blood vessels on the surface of a cyst may tear and bleed into the cyst (intracystic

hemorrhage Bleeding, hemorrhage, haemorrhage or blood loss, is blood escaping from the circulatory system from damaged blood vessels. Bleeding can occur internally, or externally either through a natural opening such as the mouth, nose, ear, urethra, vag ...

), increasing its size. If a blood vessel bleeds on the outside of a cyst, a collection of blood (

hematoma A hematoma, also spelled haematoma, or blood suffusion is a localized bleeding outside of blood vessels, due to either disease or trauma including injury or surgery and may involve blood continuing to seep from broken capillary, capillaries. A he ...

) may result. In the cases of intracystic hemorrhage and hematoma, the individual may have symptoms of increased pressure within the cranium and signs of compression of nearby nerve (neural) tissue. Some scientists debate whether arachnoid cysts are a true congenite condition or if this should be separated from secondary cysts. A recent study shows differences in communication between the arachnoid cyst and the subarachnoid space by CT cisternography. A comparison of arachnoid cyst fluid and CSF in a series of patients show differences in chemical composition. Arachnoid cysts can also occur secondary to other disorders such as

Marfan syndrome Marfan syndrome (MFS) is a multi-systemic genetic disorder that affects the connective tissue. Those with the condition tend to be tall and thin, with long arms, legs, fingers, and toes. They also typically have exceptionally flexible joints a ...

arachnoiditis Arachnoiditis is an inflammatory condition of the arachnoid mater or 'arachnoid', one of the membranes known as meninges that surround and protect the nerves of the central nervous system, including the brain and spinal cord. The arachnoid can be ...

, or

agenesis of the corpus callosum Agenesis of the corpus callosum (ACC) is a rare birth defect in which there is a complete or partial absence of the corpus callosum. It occurs when the development of the corpus callosum, the band of white matter connecting the two hemispheres ...

Diagnosis

Temporale Arachnoidalzyste links CT axial

Diagnosis is principally by

MRI Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio waves ...

. Frequently, arachnoid cysts are incidental findings on MRI scans performed for other clinical reasons. In practice, diagnosis of symptomatic arachnoid cysts requires symptoms to be present, and many with the disorder never develop symptoms. Additional clinical assessment tools that can be useful in evaluating a patient with arachnoid cysts include the mini-mental state examination (MMSE), a brief questionnaire-based test used to assess

cognition Cognition refers to "the mental action or process of acquiring knowledge and understanding through thought, experience, and the senses". It encompasses all aspects of intellectual functions and processes such as: perception, attention, thought, ...

Classification

Arachnoid cysts can be found on the brain or on the

spine Spine or spinal may refer to: Science Biology * Vertebral column, also known as the backbone * Dendritic spine, a small membranous protrusion from a neuron's dendrite * Thorns, spines, and prickles, needle-like structures in plants * Spine (zoolog ...

. Intracranial arachnoid cysts usually occur adjacent to the arachnoidal cistern.Arachnoid cyst. (n.d.). Gale Encyclopedia of Neurological Disorders. Retrieved September 10, 2006, from Answers.com Web site: http://www.answers.com/topic/arachnoid-cyst Spinal arachnoid cysts may be extradural, intradural, or perineural and tend to present with signs and symptoms indicative of a

radiculopathy Radiculopathy, also commonly referred to as pinched nerve, refers to a set of conditions in which one or more nerves are affected and do not work properly (a neuropathy). Radiculopathy can result in pain (radicular pain), weakness, altered sensati ...

. Arachnoid cysts may also be classified as primary (congenital) or secondary (acquired) and have been reported in humans, cats, and dogs. Arachnoid cysts can be relatively

asymptomatic In medicine, any disease is classified asymptomatic if a patient tests as carrier for a disease or infection but experiences no symptoms. Whenever a medical condition fails to show noticeable symptoms after a diagnosis it might be considered asy ...

or present with

insidious Insidious may refer to: * ''Insidious'' (film series), a horror film series consisting of the films listed below ** ''Insidious'' (film), a 2010 American supernatural horror film ** '' Insidious: Chapter 2'', a 2013 sequel ** '' Insidious: Chapt ...

symptoms; for this reason, diagnosis is often delayed.

Treatment

Most arachnoid cysts are asymptomatic and do not require treatment. Treatment may be necessary when symptomatic. A variety of procedures may be used to decompress (remove pressure from) the cyst. * Surgical placement of a

cerebral shunt A cerebral shunt is a device permanently implanted inside the head and body to drain excess fluid away from the brain. They are commonly used to treat hydrocephalus, the swelling of the brain due to excess buildup of cerebrospinal fluid (CSF). If ...

: ** An internal shunt drains into the subdural compartment. ** A cystoperitoneal shunt drains to the

peritoneal cavity The peritoneal cavity is a potential space between the parietal peritoneum (the peritoneum that surrounds the abdominal wall) and visceral peritoneum (the peritoneum that surrounds the internal organs). The parietal and visceral peritonea are lay ...

. *

Fenestration Fenestration may refer to: * Fenestration (architecture), the design, construction, or presence of openings in a building * Used in relation to fenestra in anatomy, medicine and biology * Fenestration, holes in the rudder of a ship to reduce the w ...

: **

Craniotomy A craniotomy is a surgical operation in which a bone flap is temporarily removed from the skull to access the brain. Craniotomies are often critical operations, performed on patients who are suffering from brain lesions, such as tumors, blood clots ...

with excision ** Various

endoscopic An endoscopy is a procedure used in medicine to look inside the body. The endoscopy procedure uses an endoscope to examine the interior of a hollow organ or cavity of the body. Unlike many other medical imaging techniques, endoscopes are insert ...

techniques are proving effective, including laser-assisted techniques. * Drainage by

needle aspiration Fine-needle aspiration (FNA) is a diagnostic procedure used to investigate lumps or masses. In this technique, a thin (23–25 gauge (0.52 to 0.64 mm outer diameter)), hollow needle is inserted into the mass for sampling of cells that, aft ...

burr hole Trepanning, also known as trepanation, trephination, trephining or making a burr hole (the verb ''trepan'' derives from Old French from Medieval Latin from Greek , literally "borer, auger"), is a surgical intervention in which a hole is drill ...

. * Capsular resection * Pharmacological treatments may address specific symptoms such as seizures or pain.

Prognosis

Most arachnoid cysts are asymptomatic, and do not require treatment. Where complications are present, leaving arachnoid cysts untreated may cause permanent severe neurological damage due to the progressive expansion of the cyst(s) or

(bleeding). However, with treatment most individuals with symptomatic arachnoid cysts do well. More specific prognoses are listed below: * Patients with impaired preoperative

had postoperative improvement after surgical decompression of the cyst. * Surgery can resolve psychiatric manifestations in selected cases.

Epidemiology

Arachnoid cysts are seen in up to 1.1% of the populationFlaherty AW. ''The Massachusetts General Hospital Handbook of Neurology'' 2000 Jan 1;105. () with a gender distribution of 2:1 male:female. Only 20% of these have symptoms, usually from secondary

. A study that looked at 2,536 healthy young males found a prevalence of 1.7% (95% CI 1.2 to 2.3%). Only a small percentage of the detected abnormalities require urgent medical attention.

References

External links

{{DEFAULTSORT:Arachnoid Cyst Congenital disorders Central nervous system disorders