A case of neurosarcoidosis presenting as hippocampal sclerosis: Clinicopathological correlation and proposed mechanistic link

Neurosarcoidosis is a rare manifestation of systemic sarcoidosis, typically affecting the meninges, cranial nerves, and hypothalamic-pituitary axis. Parenchymal brain involvement-particularly of the hippocampus-is uncommon and only rarely associated with epilepsy or hippocampal sclerosis (HS). Here, we describe a rare coexistence of biopsy-proven neurosarcoidosis and hippocampal sclerosis, suggesting secondary hippocampal injury due to chronic inflammation presenting with drug-resistant right mesial temporal lobe epilepsy (MTLE). We reviewed the clinical electrophysiological imaging and histopathological findings of a 47-year-old male who underwent anterior temporal lobectomy (ATL) after seizure onset which was localized to the right anterior to mid temporal region. Preoperative MRI was consistent with mesial temporal sclerosis. Histopathological analysis revealed both classic features of HS (neuronal loss and gliosis) and non-caseating granulomas diagnostic of neurosarcoidosis distributed within the medial temporal lobe and involving the amygdala. These findings suggest chronic inflammation may have contributed to hippocampal injury and epileptogenesis. The patient became seizure-free postoperatively. This case underscores the potential for neurosarcoidosis to mimic isolated MTLE and coexist with HS as a rare co-localized pathology. It raises the hypothesis that immune-mediated inflammation may play a pathogenic role in hippocampal degeneration. Recognition of such cases may enhance diagnostic accuracy and inform surgical planning in epilepsy associated with systemic inflammatory disorders.