Asymptomatic extensive right cerebral hemispheric lesion in an adult with histopathological findings consistent with mild malformation of cortical development with oligodendroglial hyperplasia and epilepsy: illustrative case.

backgroundA mild malformation of cortical development (MCD) with oligodendroglial hyperplasia and epilepsy (MOGHE) is characterized by increased Olig2-positive atypical cells in the white matter and is associated with drug-resistant intractable epilepsy, typically the frontal and temporal lobes. MOGHE is a newly classified subtype of focal cortical dysplasia associated with epilepsy, according to the latest International League Against Epilepsy guidelines. There have been no reports of MOGHE without epilepsy and associated with extensive lesions. OBSERVATIONS: A 31-year-old man was incidentally diagnosed with an extensive right cerebral hemispheric lesion on MRI. Pathological examination of the biopsy sample showed no evidence of an invasive tumor but revealed an increase in Olig2-positive cells, consistent with MOGHE. Sanger sequencing showed no IDH1/2, histone H3 TERTpromoter, or SLC35A2 mutations. Electroencephalography showed no evidence of epilepsy. LESSONS: This case suggests the existence of a condition with similar histological findings to MOGHE but without epilepsy. The authors propose naming this condition "mild malformation of cortical development with oligodendroglial hyperplasia and no epilepsy." https://thejns.org/doi/10.3171/CASE24827.