Secondary trigeminal neuralgia due to vestibular schwannoma.

Secondary trigeminal neuralgia is an infrequent accompaniment of vestibular schwannoma occurring in <1% instances. Multiple theories have been proposed to account for this, including secondary infliction of neurovascular conflict by displacement of trigeminal nerve or vessel by the tumor, direct tumor-related compression of the nerve, arachnoid adhesions or brainstem distortion. Microsurgical resection of vestibular schwannoma, and careful inspection and treatment of any associated neurovascular conflict affords the best outcomes for both tumor control and pain control. Neurovascular conflict is not consistently demonstrated at surgeries, and it has been postulated that arachnoid dissection at surgery resolves the vascular contact. SRS has also been utilized as a useful treatment modality, especially in surgically unfit candidates, in various combinations such as tumor targeting alone, tumor followed by nerve targeting (salvage) and single-session tumor and nerve targeting. The long-term pain control is modest with SRS, and recurrences usually occur within 2 years. Dual targeting to tumor and nerve appears to offer best pain outcomes at probably slightly increased risk of facial numbness. The heterogeneity in the reported literature precludes strong conclusions both in terms of exact mechanism of the condition or comparison of treatment modalities and outcomes, and warrants well-designed prospective studies.