Isolated Neurosarcoidosis Presenting as Chronic Progressive Pachymeningitis.

Neurologic manifestations of sarcoidosis are rare, and even rarer still are cases of isolated neurosarcoidosis. The clinical presentation of isolated neurosarcoidosis can be highly variable, and diagnosis is particularly challenging, the gold standard being tissue biopsy. We describe a patient with a history of atypical parkinsonian syndrome and chronic right frontal lobe infarct who developed weakness, imbalance, and gait disequilibrium in 2008, with magnetic resonance imaging at that time showing leptomeningeal and nodular enhancements in the bilateral frontal and parietal lobes. The patient had an extensive negative workup in 2010 but ultimately did not receive a definitive diagnosis with a tissue biopsy until 2020. The patient also notably failed a 3-month course of steroids after his biopsy due to a lack of symptomatic improvement. This case highlights the clinical variability and diagnostic difficulties of isolated neurosarcoidosis. We also highlight that our patient did not have any symptomatic improvement on steroids, which do typically provide some relief for patients.