A case of trigeminal nerve neurosarcoidosis initially presenting with isolated neurological findings mimicking trigeminal schwannoma: a case report and review of the literature.

[BACKGROUND] Sarcoidosis is a granulomatous inflammatory disease primarily affecting the lungs. Central nervous system involvement is rare, occurring in approximately 5-10% of cases. Isolated lesions of the cranial nerve, particularly affecting the trigeminal nerve, are even less common. These lesions can closely resemble more well-known tumors, such as trigeminal schwannomas, meningioma, and multiple sclerosis, which can complicate diagnosis when a solitary mass in Meckel's cave is the initial finding.

[CASE PRESENTATION] We report a case of a 45-year-old white man who presented with several months of right facial discomfort and numbness in the mandibular (V3) distribution consistent with trigeminal neuralgia. Magnetic resonance imaging of the brain revealed an avidly contrast-enhancing lesion in the right Meckel's cave along the trigeminal nerve. The patient underwent a skull base surgical exploration and resection. Histopathological, immunohistochemistry, and infectious screening of the resected tissue demonstrated noncaseating granulomas with no evidence of neoplastic or infectious etiologies. Lab work of angiotensin-converting enzyme levels and inflammatory markers were within normal limits. Importantly, the patient had presented with isolated trigeminal neurological symptoms, and thoracic abnormalities of mediastinal and hilar calcified lymph nodes with perilymphatic nodules were discovered only during the postoperative systemic evaluation prompted by the histopathological diagnosis. The patient started high-dose corticosteroid therapy following the operation, and his trigeminal pain and neurological symptoms improved substantially; he remained stable for the entirety of the 12-month follow-up duration.

[CONCLUSION] This case highlights the diagnostic challenges of trigeminal nerve lesion. There are no specific imaging features on magnetic resonance imaging that reliably distinguish neurosarcoidosis from tumors such as schwannomas or meningiomas. Therefore, neurosarcoidosis should be included in the differential diagnosis of contrast-enhancing Meckel's cave masses, even in patients without known systemic sarcoidosis. Tissue biopsy can be invaluable in determining inflammatory lesions and preventing overly aggressive resections. Once diagnosed, neurosarcoidosis is typically managed with high-dose corticosteroids and follow-up, often leading to symptom improvement. Timely histological confirmation and collaborative, multidisciplinary management are essential for achieving correct diagnosis and favorable outcomes.