Surgical Treatment of Trochlear Nerve Schwannomas: Case Series and Systematic Review.

BACKGROUND AND AIM: Cranial nerve schwannomas almost always arise from sensory or mixed nerves. Motor cranial nerves, such as the trochlear nerve, are rarely associated with schwannomas. And, no consensus has yet been made for surgical intervention due to the low number of published cases for trochlear nerve schwannomas. This study comprises the systematic review of the literature and our experience for surgically treated trochlear nerve schwannomas. METHODS: Three databases (Web of Science, PubMed, and Cochrane Library) were searched without date restrictions. Studies were included if they were published in the English literature, and presented patients with any age who underwent surgical treatment for trochlear schwannoma. And, data extracted from the included studies were combined with our experience. RESULTS: Forty-one studies, presenting 43 patients, met the inclusion criteria. The total number of patients was 45 after adding our experience. The most common symptoms were diplopia (62,2%), headache (46,7%), and motor weakness (37,8%). Mean age during the diagnosis was 45,1 years. Although the subtemporal transtentorial approach (n=14) is the most preferred method, its application has decreased in recent years. And in the last decade, the lateral suboccipital approach (n=11) has gained popularity. Residual postoperative trochlear nerve deficit was detected in 81% of the patients. The probability of neurological deficit was statistically associated with neither tumor volume (p = 0,914) and location (p = 0,669), nor resection rate (p = 0,554). CONCLUSIONS: Although trochlear schwannomas are quite rare cases and their treatment involves challenges, a total resection with the proper approach would provide the most desirable results.