Spontaneous regression of a trochlear nerve schwannoma: A case report

Background: Trochlear nerve schwannoma is exceedingly rare. Little is known about its natural history, and, therefore, no consensus has been established regarding its optimal management. Case Description: A 60-year-old male presented with diplopia during vertical gaze. The neurological examination demonstrated a positive Bielschowsky head tilt test, with no other neurological abnormalities. The magnetic resonance imaging (MRI) revealed a well-demarcated, multiloculated cystic lesion near the right tentorial incisura that showed heterogeneous enhancement on gadolinium-enhanced T1-WI; the lesion was diagnosed as a trochlear nerve schwannoma. Because the patient had isolated right trochlear nerve palsy and only minimal radiological evidence of brainstem compression, observation with symptomatic treatment using prism glasses was selected. The MRI performed 3 months later showed tumor enlargement, at 6 months tumor had begun to shrink, by 9 months, diplopia had resolved and prism glasses were no longer required, and at 12 months, there was further tumor shrinkage. Conclusion: This case demonstrated that trochlear nerve schwannomas can undergo spontaneous regression. This case demonstrates that, in the absence of brainstem symptoms, initial observation may be a reasonable management strategy, with stereotactic radiosurgery or open surgery being reserved for cases of tumor growth or symptom progression.