Acute flaccid myelitis
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| Acute flaccid myelitis | |
|---|---|
| Other names | Acute flaccid paralysis with anterior myelitis, polio-like syndrome[1] |
.jpg) | |
| Magnetic resonance imaging of the spinal cord in a case of AFM showing cord swelling in (d) which has resolved three weeks later in (e).[2] | |
| Specialty | Neurology[3] |
| Symptoms | Weakness, decreased reflexes, trouble swallowing or speaking[3] |
| Complications | Trouble breathing, urinary retention[3] |
| Usual onset | Rapid[3] |
| Causes | Generally unknown; thought to be caused by viral infection[4] |
| Diagnostic method | Medical imaging, nerve conduction studies, cerebral spinal fluid testing[3][5] |
| Differential diagnosis | Transverse myelitis, Guillain–Barré syndrome, acute disseminated encephalomyelitis[3][5] |
| Treatment | Supportive care, physical therapy, mechanical ventilation[3][5] |
| Prognosis | Variable[5] |
| Frequency | Rare[4] |
Acute flaccid myelitis (AFM) is a serious condition of the spinal cord.[3][5] Symptoms include rapid onset of arm or leg weakness and decreased reflexes.[3] Difficulty moving the eyes, speaking, or swallowing may also occur.[3] Occasionally, numbness or pain may be present.[3] Complications can include trouble breathing.[3]
The cause of most cases is unclear as of 2018.[4] More than 90% of recent cases have followed a mild viral infection such as from enteroviruses.[4] While polio can cause AFM, since 2014, it has not been involved in cases in the United States.[3][6] The underlying mechanism involves damage to the spinal cord's grey matter.[3] Diagnosis may be supported by medical imaging of the spine, nerve conduction studies, and cerebrospinal fluid testing.[3][5]
Treatment involves supportive care.[5][3] Physical therapy may be recommended.[3] Occasionally, mechanical ventilation is required to support breathing.[3] Outcomes are variable.[5] The condition is rare and occurs most commonly in children.[4] Fewer than one in 500,000 children is affected per year in the United States.[3] Although the illness is not new, an increase in cases has been seen since 2014 in the United States.[3] In 2018, 233 cases were confirmed in the United States.[7]
Signs and symptoms include:
- Difficulty moving the eyes or drooping eyelids
- Facial droop or weakness
- Difficulty with swallowing or slurred speech
- Sudden arm or leg weakness[8]
A summary of the condition by the Centers for Disease Control and Prevention (CDC) in 2014:[9]
Common features included acute focal limb weakness and specific findings on magnetic resonance imaging (MRI) of the spinal cord consisting of nonenhancing lesions largely restricted to the grey matter. In most cases, these lesions spanned more than one level of the spinal cord. Some also had acute cranial nerve dysfunction with correlating nonenhancing brainstem lesions on MRI. None of the children experienced altered mental status or seizures. None had any cortical, subcortical, basal ganglial, or thalamic lesions on MRI. Most children reported a febrile respiratory illness in the two weeks preceding development of neurologic symptoms. In most cases, cerebrospinal fluid (CSF) analyses demonstrated mild-moderate pleocytosis (increased cell count in the CSF) consistent with an inflammatory or infectious process.
Causes
As of October 2018[update], 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, and adenoviruses among the potential causes.[3][7] More than 90% of people with AFM reported having symptoms consistent with a mild viral infection before the onset of AFM.[11]
Much research has focused on the nonpolio enteroviruses 68 (EV-D68) and 71 (EV-A71), a common cause of hand, foot, and mouth disease in infants and young children, members of the enterovirus D and enterovirus A species, respectively, as suspected causes.[7] Some evidence supports a causal role of EV-D68.[12] Coxsackievirus A16 may also play a role in some cases.[13]
A 2014 Morbidity and Mortality Weekly Report report noted the difficulty of establishing causation by the virus.[14] Avindra Nath, clinical director of the National Institute of Neurological Disorders and Stroke and president of the International Society for NeuroVirology, compared the situation to the prolonged investigations that led to confirmation of HIV as the cause of AIDS. 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 were seen per thousand children infected. He also suggested that adults with respiratory diseases should be evaluated for neurological deficits, and that infectious diseases should be considered as a cause when patients present with neurological symptoms.[15]
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".[16]
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.[17]
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 [rhinovirus and/or enterovirus] positive 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 AFM cases Archived 2022-10-31 at the Wayback Machine.
Diagnosis
AFM is diagnosed by examining a person's nervous system in combination with reviewing images of the spinal cord.[18] 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 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 (impulse sent along a nerve fiber) and response.[19]
Diagnosis of AFM requires an acute onset of limb paralysis and at least one gray-matter spinal-cord lesion. CSF should show pleocytosis.[20]
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."[14]
Treatment
Treatment involves supportive care.[5][3] Physical therapy may be recommended.[3] Occasionally mechanical ventilation is required to support breathing.[3][7]
If immunoglobulin, corticosteroids, plasma exchange, or antiviral medication are useful is unclear.[5][7]
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).[21]
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 may be beneficial for recovery.[22][23][24]
