Abstract
BACKGROUND: Epidemiologically, hypothalamic neurosarcoidosis occurs in middle-aged individuals with pituitary dysfunction. Older patients rarely develop hypothalamic neurosarcoidosis with incomplete hemiparesis. OBSERVATIONS: MRI in a 75-year-old man with incomplete left hemiparesis revealed an enhanced mass lesion in the hypothalamus and tuber cinereum, with enhanced satellite nodules in the right basal ganglia. Transcortical neuroendoscopic biopsy was performed to confirm the pathological diagnosis. Narrow-band imaging (NBI) of the mass lesion revealed an abnormal vascular structure with a cyan color. A biopsy was successfully performed, and pathological evaluation and additional analyses led to a final diagnosis of sarcoidosis. Steroid treatment was administered, and follow-up MRI revealed that almost all lesions had disappeared, with resolution of the left hemiparesis. LESSONS: Neurosarcoidosis should be considered as a differential diagnosis of multiple solid cerebral mass lesions in older patients. Detecting characteristic vascular constructions using NBI allows for the accurate identification of lesions. https://thejns.org/doi/10.3171/CASE25578.