Acute Flaccid Myelitis

Pediatric Pearls - Acute Flaccid Myelitis

Sol Behar MD, Ilene Claudius MD and Jennifer Lanning MD

Take Home Points

• Complete a neurologic exam on any patient not moving an extremity.
• If the patient can’t raise a limb after a viral prodrome, acute flaccid myelitis needs to be ruled out.
• Some cases of acute flaccid myelitis have been confused for nursemaid’s elbow.

• Acute flaccid myelitis is uncommon enough that we aren’t familiar with it but it is something we can’t miss.
• Lanning is an emergency medicine physician who has expertise in this condition as well as a personal story to tell.
• Lanning’s daughter Claire turned 6 in the fall of 2016. She had just started kindergarten. She was a very healthy and fully vaccinated girl. She first developed some upper respiratory symptoms. She had nasal congestion and dry cough. After a week of these symptoms, she developed low grade fevers and complained about headache and neck soreness. She was not meningitic. The following day, she vomited twice and had low energy. Lanning’s husband took her to see their pediatrician. She sent them home with ondansetron.
• The following morning, Claire came into their bedroom. She was crying. She told them she needed them to carry her to the bathroom because her neck hurt so badly she couldn’t walk. Now she was meningitic. Her neck was stiff. She refused to range it. Lanning took her immediately to the pediatric emergency department.
• In the ED, she had blood work drawn and a lumbar puncture. The lumbar puncture showed a CSF pleocytosis but it looked viral. She was started on empiric antibiotics until the cultures came back. She was admitted to the floor.
• That night, her astute nurse noticed that Claire had a cranial nerve six palsy. The pediatric neurology service was consulted. She had an MRI with and without contrast. Unfortunately, this showed widespread gray matter lesions all over her brainstem. All of the damage was infratentorial. There are some pathogens known to cause gray matter lesions in this location. One is enterovirus, specifically strains D68 and A71.
• Her daughter had stool, respiratory and CSF studies sent to the CDC. She eventually tested positive for D68 enterovirus.
• Claire started to decompensate. She had autonomic instability. She became tachycardic, then bradycardic. She was hypertensive. She was tachypneic and taking fast and shallow breaths. As they were sitting her up to use the commode, Lanning noticed that Claire was not meningitic anymore but she was flaccid. She could move her fingers and toes but could not lift her extremities from the bed. She couldn’t roll over in bed. She was incontinent to stool and urine.
• Claire was not confused or altered. The next day she had an MRI of the whole spine with and without contrast. She had gray matter lesions in the anterior horn cells throughout the entire cervical and thoracic spine. It extended through her conus. She was diagnosed with acute flaccid myelitis.
• Not all children will be meningitic. There is spectrum of disease. Some children will present with only a single flaccid limb. Some will present with meningitis with or without paralysis. Some have presented with respiratory distress or arrest from the field due to acute, profound paralysis.
• Can this wax and wane? Once paralysis hits, it is fixed. These children have acute paralysis that develops over a few hours to a day. It won’t improve and return. If there are no neurologic findings on your exam, it argues against acute flaccid myelitis.
• Has there been any progress in identifying the cause of acute flaccid myelitis? There has been good literature suggesting that enterovirus D68 and A71 have been the driving force behind the new cases of AFM. There were outbreaks in 2012, 2014, 2016 and 2018. However, the CDC has not released a statement implicating enterovirus in AFM. Enterovirus has not been found in all AFM patients. This may be because enterovirus is very difficult to culture. It is possible that there are other etiologies we haven’t found.
• The viral prodrome is variable. It is usually respiratory or eye symptoms. There may be some loose stools or vomiting.
• A well-appearing two year old presents with a complaint of not using one arm. There is no history of trauma. No nuchal rigidity. There is no evidence of meningitis. The affected limb is flaccid. What is your work-up?
• AFM is not diagnosed based on history or exam alone. Check a CBC, comprehensive metabolic panel and culture. The child will need a lumbar puncture. It is important to collect extra CSF for add-ons and send-outs. They will need an expedited MRI with and without contrast of their spine. You can’t rely on a non-contrast MRI to catch these lesions.
• What is the differential diagnosis? It includes Guillain-Barre syndrome(GBS), tick paralysis or stroke. AFM has some clear differences from these etiologies.
• How does AFM differ from ADEM? ADEM is acute disseminated encephalomyelitis. This is associated with confusion and altered mental status. It is an autoimmune disorder. It may be triggered by recent viral illness. In ADEM, there is destruction of myelin or the white matter. This can happen throughout the brain and spinal cord. These patients are typically encephalopathic.
• In contrast, AFM is strictly a disease of the gray matter. Enterovirus may also affect the brainstem but there is no personality change, hallucinations or confusion.
• What treatment did Claire receive? Treatment should be started as soon as a diagnosis of acute flaccid myelitis is made. Claire received IVIG. She also received high dose fluoxetine. An in vitro study a few years ago showed high dose fluoxetine has anti-enteroviral effects. Treatment is experimental because this is an emerging disease. Current recommendations are for IVIG and plasmapheresis if symptoms persist. Fluoxetine has not been shown effective in the available data. It is not currently recommended at this time. Patients six months to two years after diagnosis have shown improvement after nerve and muscle transfers.
• Steroids are controversial because it is unclear if this is a direct viral attack or an autoimmune reaction to the viral infection.
• Is this progressive? There is a risk of progression of paralysis. If there is any sign of respiratory compromise, brainstem or bulbar symptoms, the patient should go to the ICU.
• What is the prognosis? All children with AFM will improve from their nadir. However, the degree of improvement varies. There are a handful of cases of complete recovery but most will have residual deficits. The nadir is usually reached within 5 days of fever symptoms.