Acute flaccid myelitis (AFM) is a serious condition of 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 ...
.
Symptoms include rapid onset of arm or leg weakness and decreased reflexes
In biology, a reflex, or reflex action, is an involuntary, unplanned sequence or action and nearly instantaneous response to a Stimulus (physiology), stimulus.
Reflexes are found with varying levels of complexity in organisms with a nervous s ...
.[ Difficulty moving the eyes, speaking, or swallowing may also occur.][ Occasionally, ]numbness
Hypoesthesia or numbness is a common side effect of various medical conditions that manifests as a reduced sense of touch or sensation, or a partial loss of sensitivity to sensory stimuli. In everyday speech this is generally referred to as num ...
or pain may be present.[ Complications can include trouble breathing.][
The cause of most cases is unclear as of 2018.][ More than 90% of recent cases have followed a mild ]viral infection
A viral disease (or viral infection) occurs when an organism's body is invaded by pathogenic viruses, and infectious virus particles (virions) attach to and enter susceptible cells.
Structural Characteristics
Basic structural characteristics, s ...
such as from enteroviruses
''Enterovirus'' is a genus of Positive sense#RNA sense in viruses, positive-sense single-stranded RNA viruses associated with several human and mammalian diseases. Enteroviruses are named by their transmission-route through the intestine ('enteri ...
. While polio
Poliomyelitis, commonly shortened to polio, is an infectious disease caused by the poliovirus. Approximately 70% of cases are asymptomatic; mild symptoms which can occur include sore throat and fever; in a proportion of cases more severe s ...
can cause AFM, since 2014, it has not been involved in cases in the United States. The underlying mechanism involves damage to the spinal cord's grey matter
Grey matter is a major component of the central nervous system, consisting of neuronal cell bodies, neuropil (dendrites and unmyelinated axons), glial cells (astrocytes and oligodendrocytes), synapses, and capillaries. Grey matter is distingui ...
. Diagnosis may be supported by medical imaging
Medical imaging is the technique and process of imaging the interior of a body for clinical analysis and medical intervention, as well as visual representation of the function of some organs or tissues (physiology). Medical imaging seeks to rev ...
of the spine, nerve conduction studies
A nerve conduction study (NCS) is a medical diagnostic test commonly used to evaluate the function, especially the ability of electrical conduction, of the motor and sensory nerves of the human body. These tests may be performed by medical specia ...
, and 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 ...
testing.[
Treatment involves ]supportive care
Symptomatic treatment, supportive care, supportive therapy, or palliative treatment is any medical therapy of a disease that only affects its symptoms, not the underlying cause. It is usually aimed at reducing the signs and symptoms for the comfor ...
.[ ]Physical therapy
Physical therapy (PT), also known as physiotherapy, is one of the allied health professions. It is provided by physical therapists who promote, maintain, or restore health through physical examination, diagnosis, management, prognosis, patient ...
may be recommended.[ Occasionally, ]mechanical ventilation
Mechanical ventilation, assisted ventilation or intermittent mandatory ventilation (IMV), is the medical term for using a machine called a ventilator to fully or partially provide artificial ventilation. Mechanical ventilation helps move air ...
is required to support breathing.[ Outcomes are variable.][ The condition is rare and occurs most commonly in children.][ Fewer than one in 500,000 children is affected per year in the United States.][ Although the illness is not new, an increase in cases has been seen since 2014 in the United States.][ In 2018, 233 cases were confirmed in the United States.]
Signs and symptoms
Symptoms include:
* Difficulty moving the eyes or drooping eyelids
* Facial droop or weakness
* Difficulty with swallowing or slurred speech
* Sudden arm or leg weakness
A summary of the condition by the Centers for Disease Control and Prevention
The Centers for Disease Control and Prevention (CDC) is the national public health agency of the United States. It is a United States federal agency, under the Department of Health and Human Services, and is headquartered in Atlanta, Georgi ...
(CDC) in 2014:
Causes
, the U.S. CDC regarded the cause of AFM as having "a variety of possible causes such as viruses, environmental toxins, and genetic disorders", listing poliovirus, nonpolio enteroviruses, West Nile virus
West Nile virus (WNV) is a single-stranded RNA virus that causes West Nile fever. It is a member of the family ''Flaviviridae'', from the genus ''Flavivirus'', which also contains the Zika virus, dengue virus, and yellow fever virus. The virus ...
, and adenoviruses among the potential causes. More than 90% of people with AFM reported having symptoms consistent with a mild viral infection before the onset of AFM.
Much research has focused on the nonpolio enteroviruses 68 (EV-D68) and 71 (EV-A71), a common cause of hand, foot, and mouth disease
Hand, foot, and mouth disease (HFMD) is a common infection caused by a group of enteroviruses. It typically begins with a fever and feeling generally unwell. This is followed a day or two later by flat discolored spots or bumps that may blis ...
in infants and young children, members of the enterovirus D and enterovirus A species, respectively, as suspected causes. Some evidence supports a causal role of EV-D68. Coxsackievirus A16 may also play a role in some cases.
A 2014 Morbidity and Mortality Weekly Report
The ''Morbidity and Mortality Weekly Report'' (''MMWR'') is a weekly epidemiological digest for the United States published by the Centers for Disease Control and Prevention (CDC). It was originally established as ''Weekly Health Index'' in 1930, ...
report noted the difficulty of establishing causation by the virus. Avindra Nath, clinical director of the National Institute of Neurological Disorders and Stroke
The National Institute of Neurological Disorders and Stroke (NINDS) is a part of the U.S. National Institutes of Health (NIH). It conducts and funds research on brain and nervous system disorders and has a budget of just over US$2.03 billion. The ...
and president of the International Society for NeuroVirology
The International Society for NeuroVirology (ISNV) was founded to promote research into disease-causing viruses that infect the human brain and nervous system. The ISNV membership includes scientists and clinicians from around the world who work i ...
, compared the situation to the prolonged investigations that led to confirmation of HIV
The human immunodeficiency viruses (HIV) are two species of ''Lentivirus'' (a subgroup of retrovirus) that infect humans. Over time, they cause acquired immunodeficiency syndrome (AIDS), a condition in which progressive failure of the immune ...
as the cause of AIDS
Human immunodeficiency virus infection and acquired immunodeficiency syndrome (HIV/AIDS) is a spectrum of conditions caused by infection with the human immunodeficiency virus (HIV), a retrovirus. Following initial infection an individual m ...
. In response to the suggestion that the enterovirus might be taking over the role of polio, Nath said that EV-D68 was far less virulent and spread much more slowly than polio, and that unlike in polio, only a few cases of paralysis
Paralysis (also known as plegia) is a loss of motor function in one or more muscles. Paralysis can also be accompanied by a loss of feeling (sensory loss) in the affected area if there is sensory damage. In the United States, roughly 1 in 50 ...
were seen per thousand children infected. He also suggested that adults with respiratory diseases should also be evaluated for neurological deficits, and that infectious disease should be considered as a cause when patients presented with neurological symptoms.
A subsequent report described 29 cases of EV-D68-associated AFM in Europe in 2016, noting, "these probably represent only the tip of the iceberg."
CDC sees 2018 as a record year, annual documented cases of AFM reached a record 238 nationwide. The relatively lower circulation in 2020 may reflect the use of COVID-19 pandemic infection mitigation measures.
Because of the EV-D68 surge in 2022 Health Alert Network (HAN) released a notice for Healthcare providers and hospitals. The CDC warned clinicians that EV-D68 detections have continued to be high. "Sentinel surveillance sites are reporting a higher proportion of EV-D68 positivity in children who are hinovirus and/or enteroviruspositive compared to previous years," the agency wrote. Clinicians should be aware of "the potential for an increase in AFM cases in the upcoming weeks." CDC urges healthcare providers to consider EV-D68 as a possible cause of acute, severe respiratory illness and a potential increase in AF
cases
Diagnosis
AFM is diagnosed by examining a person's nervous system
In biology, the nervous system is the highly complex part of an animal that coordinates its actions and sensory information by transmitting signals to and from different parts of its body. The nervous system detects environmental changes th ...
in combination with reviewing images of the spinal cord. A doctor can examine a person's nervous system and the places on the body where he or she has weakness, poor muscle tone, and decreased reflexes. In addition, a doctor can do magnetic resonance imaging
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 wave ...
to look at a person's brain and spinal cord, do laboratory tests on the cerebrospinal fluid (CSF, the fluid around the brain and spinal cord), and may check nerve conduction
An action potential occurs when the membrane potential of a specific cell location rapidly rises and falls. This depolarization then causes adjacent locations to similarly depolarize. Action potentials occur in several types of animal cells, ca ...
(impulse sent along a nerve fiber) and response.
Diagnosis of AFM requires acute onset limb paralysis and at least one gray-matter spinal-cord lesion. CSF should show pleocytosis
In medicine, pleocytosis (or pleiocytosis) is an increased cell count (from Greek ''pleion'', "more"), particularly an increase in white blood cell count, in a bodily fluid, such as cerebrospinal fluid. It is often defined specifically as an increa ...
.[
]
Prevention
The CDC recommends, "To prevent infections in general, persons should stay home if they are ill, wash their hands often with soap and water, avoid close contact (such as touching and shaking hands) with those who are ill, and clean and disinfect frequently touched surfaces."
Treatment
Treatment involves supportive care.[ Physical therapy may be recommended.][ Occasionally ]mechanical ventilation
Mechanical ventilation, assisted ventilation or intermittent mandatory ventilation (IMV), is the medical term for using a machine called a ventilator to fully or partially provide artificial ventilation. Mechanical ventilation helps move air ...
is required to support breathing.
If immunoglobulin
An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the ...
, corticosteroid
Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex of vertebrates, as well as the synthetic analogues of these hormones. Two main classes of corticosteroids, glucocorticoids and mineralocorticoids, are involv ...
s, plasma exchange
Plasmapheresis (from the Greek πλάσμα, ''plasma'', something molded, and ἀφαίρεσις ''aphairesis'', taking away) is the removal, treatment, and return or exchange of blood plasma or components thereof from and to the blood circulati ...
, or antiviral medication
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 ...
are useful is unclear.
Outcomes
Studies from 2014 to 2017 indicated a poor outcome for many cases. Seven of 61 cases with EVD68 detected and eight long‐term follow‐ups had full recovery; two deaths were described in severely immunocompromised people (one with EVD68 and one with both EVD68 and coxsackie A16 detected).
Six of 10 children in Denver were sent home for outpatient treatment. Some of the children with mild and moderate cases have recovered partially from temporary limb weakness but still have permanent weakness, whereas those with more severe cases have not recovered as much. Intensive physical therapy and occupational therapy
Occupational therapy (OT) is a global healthcare profession. It involves the use of assessment and intervention to develop, recover, or maintain the meaningful activities, or ''occupations'', of individuals, groups, or communities. The field of ...
may be beneficial for recovery.
Epidemiology
A seasonal pattern is seen in outbreaks, with a marked increase in cases reported in the late summer and early fall.
The CDC has determined and submitted to GenBank
The GenBank sequence database is an open access, annotated collection of all publicly available nucleotide sequences and their protein translations. It is produced and maintained by the National Center for Biotechnology Information (NCBI; a part ...
complete or nearly complete genomic sequences for three known strains of the virus, which are "genetically related to strains of EV-D68 virus that were detected in previous years in the United States, Europe, and Asia."
While rates of paralytic symptoms appear to be correlated with the number of respiratory infections, in initial anecdotal reports, the cases are not clustered within a family or school, suggesting that the paralysis ''per se'' is not directly contagious, but arises as a very rare complication of the common respiratory infection.
Cases of similar illnesses have been reported in Canada, Northern Europe, and Japan. Over 90% of reported cases are in children.
History
AFM has only been formally tracked since 2014, since the incidence has spiked in recent years.
A group in Texas reported having observed a pattern in 2013 of one to four cases per year with similar polio-like characteristics.[ (audio)]
In 2014, the CDC Morbidity and Mortality Weekly Report
The ''Morbidity and Mortality Weekly Report'' (''MMWR'') is a weekly epidemiological digest for the United States published by the Centers for Disease Control and Prevention (CDC). It was originally established as ''Weekly Health Index'' in 1930, ...
and a CDC Clinician Outreach and Communication Activity (COCA) conference call, noted that many cases had neck, back, or extremity pain, but otherwise those affected generally had normal sensation in their limbs. A few participants in the conference call discussed whether pain, later abating, might precede the onset of paralysis.
An October 2014 report described outbreaks in California and Colorado, suggesting that the number of cases might be 100 or more nationwide. Diagnosis included a detailed medical history
The medical history, case history, or anamnesis (from Greek: ἀνά, ''aná'', "open", and μνήσις, ''mnesis'', "memory") of a patient is information gained by a physician by asking specific questions, either to the patient or to other peo ...
, MRI imaging, and the elimination of transverse myelitis
Transverse myelitis (TM) is a rare neurological condition wherein the spinal cord is inflamed. The adjective ''transverse'' implies that the spinal inflammation (myelitis) extends horizontally throughout the cross section of the spinal cord; the ...
or Guillain–Barré syndrome
Guillain–Barré syndrome (GBS) is a rapid-onset muscle weakness caused by the immune system damaging the peripheral nervous system. Typically, both sides of the body are involved, and the initial symptoms are changes in sensation or pain often ...
as potential causes. Physicians were using an online mailing list to communicate about similar cases in Alabama
(We dare defend our rights)
, anthem = "Alabama (state song), Alabama"
, image_map = Alabama in United States.svg
, seat = Montgomery, Alabama, Montgomery
, LargestCity = Huntsville, Alabama, Huntsville
, LargestCounty = Baldwin County, Al ...
and Kansas
Kansas () is a state in the Midwestern United States. Its capital is Topeka, and its largest city is Wichita. Kansas is a landlocked state bordered by Nebraska to the north; Missouri to the east; Oklahoma to the south; and Colorado to the ...
. The largest known cluster of cases was in Colorado, with 29 total, 12 of whom had been reported from August and onwards of that year.
Three of four cases treated in Alabama involved a complete inability to move one arm, reminiscent of peripheral nerve injury
Nerve injury is an injury to nervous tissue. There is no single classification system that can describe all the many variations of nerve injuries. In 1941, Seddon introduced a classification of nerve injuries based on three main types of nerve f ...
:
Children's Mercy Hospital
Children's Mercy Kansas City is a 390 bed comprehensive pediatric medical center in Kansas City, Missouri, that integrates clinical care, research and medical education to provide care for pediatric patients from birth through adulthood. The h ...
, which had three or four cases in 2014, reported that the MRI images and symptoms closely mimicked polio. They reported: "The sudden onset of flaccid paralysis in single or multiple limbs with absolutely no sensory findings, the MRIs all showing uniformly a signal increase in the ventral horns of the spinal cord — this is exactly the same region of the spinal cord affected in polio ... Almost all of the patients have an increase in their white blood cells
White blood cells, also called leukocytes or leucocytes, are the cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders. All white blood cells are produced and derived from mult ...
in the cerebrospinal fluid. Some of the patients have brainstem
The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is cont ...
findings and cranial-nerve findings."
Of 64 patients meeting the CDC criteria before October 29, 2014, 80% had had a preceding respiratory illness and 75% reported fever in the days leading up to limb weakness, the onset of which was generally abrupt. By November 20, the number of confirmed cases stood at 88 from 29 states.
The CDC requested that physicians provide information about cases meeting these criteria: patients diagnosed after August 1, 2014, who are no older than 21 years of age, showing acute onset of focal limb weakness, with a spinal-cord lesion largely restricted to grey matter visualized by MRI.
In November 2018, the CDC reported that they were investigating 286 cases, with at least 116 confirmed cases in 31 states. The CDC is setting up a task force to investigate the causes and to find treatments.
References
{{DEFAULTSORT:Acute Flaccid Myelitis
Neurological disorders in children
Symptoms and signs: Nervous and musculoskeletal systems
Wikipedia medicine articles ready to translate
Central nervous system disorders
Myelin disorders