To describe a case of probable neurosarcoidosis presenting as limbic encephalitis

Sarcoidosis is a disease characterized by non-caseating granulomatous inflammation, that affects multiple systems throughout the body with neurological involvement reported in only 5-15% cases. Neurological presentation includes cranial neuropathies, meningeal disease, parenchymal disease, spinal cord involvement, vasculopathy and peripheral nervous system disease. Limbic encephalitis is not a typical presentation of neurosarcoidosis.

Case report

37-year-old male presents with emergence of daily headaches for two months, anosmia, and mild deficits in verbal memory. Brain MRI demonstrated T2 hyperintensities in the bilateral inferotemporal lobes with patchy leptomeningeal enhancement. CSF studies were notable for a lymphocytic pleocytosis, elevated protein, and borderline hypoglycorrhachia. Extensive laboratory evaluation was unrevealing, including serum and CSF autoimmune encephalopathy panels. Hilar lymphadenopathy observed on CT imaging was confirmed on biopsy as non-caseating granulomatous inflammation, suggestive of sarcoidosis. 

This patient was diagnosed with probable neurosarcoidosis based on Zajicek criteria. To our knowledge, this is only the second case report worldwide that describes neurosarcoidosis presenting as limbic encephalitis, and the first where autoimmune (paraneoplastic) etiologies were definitively excluded. This case outlines a unique presentation of neurosarcoidosis, which should be considered in the differential of limbic encephalitis.