Acute disseminated encephalomyelitis (ADEM) is an inflammatory neurological condition that affects the brain and spinal cord and is seen primarily in children. ADEM is often preceded by a viral infection, and in dozens of cases diagnosed since the beginning of the pandemic, the coronavirus has been identified as a likely trigger.
Jonathan D. Santoro, MD, Director, Neuroimmunology and Demyelinating Disorders at Children’s Hospital Los Angeles, offers important insights about the condition and its potential link to COVID-19.
What is ADEM and how is it diagnosed?
ADEM is an inflammatory brain condition that can cause children to have altered mental status, seizures or focal neurological deficits. The symptoms are related to where inflammation is present in the brain, and for this reason, ADEM can look different in every patient.
Children may get sick with something relatively benign like a mild cold, something that a parent wouldn’t even take them to a pediatrician for, and then a few weeks after they present with this neurologic phenomenon. Children with ADEM come in with a variety of symptoms—weakness, sensory changes, gait disturbance, vision changes, and changes in mentation, also called encephalopathy. When there is a suspicion that a child may have ADEM, we perform an MRI to pinpoint where the inflammation is located. Some children with ADEM will have an associated antibody (myelin oligodendrocyte glycoprotein or MOG), which may increase the chance of relapse.
How common (or rare) is this condition?
ADEM is quite rare—occurring in only 1 in 125,000 to 250,000 children—and the average age is between 3 and 8 years. Many children who are diagnosed with ADEM will need specialty care like we provide at Children’s Hospital Los Angeles.
What treatments are available for ADEM?
Immune treatments are the staple for children who develop ADEM, and when administered early, they can often get children back to themselves. In most cases, intravenous steroids and immunoglobulin (IVIg) provide rapid improvement, although severe cases may require more aggressive immune suppression. After that, patients may need intensive inpatient physical, occupational and speech therapy. The good news about ADEM is the chance of relapse is generally low.
Is there a connection between ADEM and COVID-19?
The COVID-19 pandemic has revealed that this particular coronavirus can, in some circumstances, cause ADEM. While the exact rates are unknown, both adults and children are at risk for ADEM associated with or following infection with SARS-CoV-2. Coronavirus does much of its injury to the body by activating inflammation in the body, and for this reason, neurologists were not surprised to see that the brain, like other organ systems, would be susceptible in some individuals. While ADEM associated with the coronavirus is treatable and responds to similar immune treatments to individuals with non-COVID-19-associated ADEM, doctors remain uncertain if some treatments are better than others. Importantly, there is no way to prevent ADEM associated with COVID-19 except to avoid infection. Also, evidence indicates that getting vaccinated greatly reduces the risk of ADEM.
What about AHEM—should parents be worried about this related condition?
AHEM stands for acute hemorrhagic encephalomyelitis, which is an extremely rare and very severe variant of ADEM. This form is so rare that most doctors won’t ever see a case in their career. For this reason, parents should not worry about AHEM. Of course, if a child is exhibiting any concerning symptoms or signs of ADEM, prompt evaluation and treatment is the best way to avoid neurological injury.
