Non-Syndromic Tumefactive Demyelinating Lesions in the Pediatric Population: Four Case Reports and Review of the Literature.

Introduction: Tumefactive demyelinating lesions (TDLs) are large lesions (> 2 cm) seen in demyelinating syndromes such as multiple sclerosis, myelin oligodendrocyte glycoprotein antibody-associated disorder, and neuromyelitis optica spectrum disorder. They rarely occur in children and most often have a monophasic course. TDLs can cause severe presentations given their size, edema, and associated mass effect, making prompt diagnosis and effective treatment crucial. Patient Description: We present four adolescents with TDLs who tested negative for aquaporin-4-IgG and myelin oligodendrocyte glycoprotein (MOG)-IgG and did not meet diagnostic criteria for any known demyelinating disorder. All four patients underwent extensive and inconclusive workup for the etiology of their radiographic and clinical findings and received multiple immunomodulators with some clinical improvement, although three of the four had multiple relapses. Conclusions: TDLs that do not meet criteria for the known demyelinating syndromes can cause significant neurological sequelae. We describe four adolescents with neurological symptoms associated with TDLs. Given the rare but serious occurrence of these non-syndromic TDLs, more well-powered studies are critical to guide diagnosis, management, and response to therapies and eventually develop evidence-based protocols to manage other patients with similar presentations.