A unique case of multiphasic ADEM or what else?

Background: Acute disseminated encephalomyelitis (ADEM) is a monophasic post-infectious demyelinating disease, clinically defined by the acute onset of polyfocal neurological deficits including encephalopathy. A subset of ADEM patients will subsequently be diagnosed with relapsing disorders, including recurrent DEM (RDEM), multiphasic DEM (MDEM), neuromyelitis optica spectrum disorders (NMOSD) and multiple sclerosis (MS). Here we describe the case of an adult patient, who presented two ADEM-like episodes after a very long (8 years) symptoms-free period. Clinical case: A 48 years old man presented a first case of sub-acute onset of encephalopathy and dysarthria with MRI findings suggestive for ADEM for which he underwent an intravenous and oral steroid treatment followed by a complete clinical remission. After 8 years he presented a new sub-acute onset of encephalopathy and balance disorders with the onset of new lesions at the MRI. The search for oligoclonal band (OCB) showed a single CSF-restricted IgG band. Suspecting a new ADEM episode he was treated with intravenous steroids without benefit and 3 apheresis sessions with clinical improvement followed by an oral steroid treatment. After 2 months he experienced a paroxysmal episode of dysarthria, upper and lower left limbs impairment and urge incontinence with a stable new brain and spinal cord MRI. The search for anti-aquaporin-4 and anti-MOG (cell-based assay) antibodies was repeated twice within a 6 months span and resulted in both cases negative. The patient was treated with Rituximab (1g followed by 1g after 15 days, followed by 1g after 6 months) with stability of the neurological and radiological examinations at the last follow-up. Conclusions: To the best of our knowledge, this is the first case of MDEM in which the two episodes of ADEM occurred 8 years apart. Although this case fulfills the diagnostic criteria for MDEM, the time elapsed between the two episodes is very long. Therefore, we cannot exclude that this disease might be a new nosological entity that could be included in the expanding range of demyelinating diseases.