Asymptomatic and Subtle CT Lung Lesion Leading to a Diagnosis of Neurosarcoidosis: A Case Report

Background : Sarcoidosis is a systemic granulomatous disease of unknown aetiology that commonly affects the lungs, lymph nodes, and skin. Neurological involvement rarely occurs, which is referred to as neurosarcoidosis (NS). Although NS has been the subject of many publications, a universally accepted definition is yet to be established. Diagnostically, a significant challenge lies in acquiring neural tissues for histopathological confirmation. We report a rare case of probable NS with minimal pulmonary sarcoidosis. Case presentation : A previously healthy 52-year-old male was admitted to our department because of walking disability. The initial non-contrast magnetic resonance imaging (MRI) at presentation revealed no abnormalities. However, subsequent contrast-enhanced MRI revealed multiple small nodular-enhancing lesions along the leptomeninges of the brain and throughout the spinal cord. Cerebrospinal fluid (CSF) analysis showed inflammation within the central nervous system, ruling out infections or tumours. Chest computed tomography (CT) performed at the time of admission revealed micronodules without lymphadenopathy in the left upper lobe. Although the findings were minor, we performed a biopsy of the lesion. Based on the pathological findings and exclusionary diagnosis, the patient was diagnosed with provable NS and pulmonary sarcoidosis. Intravenous methylprednisolone and oral prednisone were administered, and the outcome was favourable. Conclusion : In sarcoidosis, contrast-enhanced MRI plays a critical role in detecting lesions that may not be visible on non-contrast scans. When NS is suspected, even minimal abnormalities observed in the lungs should prompt consideration of a biopsy, given that pulmonary involvement is the most frequent manifestation of systemic sarcoidosis.