Neurosarcoidosis mimicking multiple meningiomas: illustrative case

BACKGROUND: Among intracranial extra-axial lesions, meningioma and solitary fibrous tumor are common differential diagnoses, whereas neurosarcoidosis is rare. Because its manifestations are diverse and nonspecific, establishing a preoperative diagnosis is often difficult. The authors report a case of neurosarcoidosis presenting as multiple intracranial extra-axial lesions and review its clinical and surgical features. OBSERVATIONS: A 64-year-old man with no significant medical history presented with blurred vision in his left eye. Gadolinium-enhanced MRI revealed multiple, uniformly enhancing, extra-axial lesions. Meningioma was suspected, and craniotomy with tumor resection was performed. Intraoperative frozen-section analysis suggested meningioma, and maximal safe resection was achieved. However, postoperative histopathological evaluation revealed noncaseating granulomatous inflammation, confirming neurosarcoidosis. Corticosteroid therapy initiated on postoperative day 18 led to marked lesion reduction on follow-up MRI. The patient developed transient left oculomotor nerve palsy, which gradually improved over 9 months. LESSONS: Although pre- and intraoperative diagnosis of neurosarcoidosis is challenging, characteristic T2-weighted imaging findings and intraoperative appearance may aid differentiation. Considering steroid-responsive dural inflammation during surgical planning may help minimize invasiveness and complications. https://thejns.org/doi/10.3171/CASE25954.