Central demyelination in the pathogenesis of trigeminal neuralgia associated with cerebellopontine angle tumors: case report with ultrastructural trigeminal root analysis.

OBJECTIVE: To describe the surgical and ultrastructural findings in the trigeminal root of a patient with trigeminal neuralgia (TN) associated with a cerebellopontine epidermoid tumor, and to relate these to literature reports of patients with vascular compression-related TN. CLINICAL
PRESENTATION: A 39-year-old woman presented with right TN. She had a 10-year history of lancinating pain paroxysms in the second and third trigeminal branches. Pain exhibited trigger areas and improved partially with carbamazepine. Cranial magnetic resonance imaging revealed an epidermoid tumor in the right cerebellopontine angle that distorted and compressed the right trigeminal root. TECHNIQUE: The tumor was resected. At operation, the trigeminal root appeared distorted and compressed by the tumor. A small partial rhizotomy was performed, and the biopsy was processed for ultrastructural study. Complete relief of the symptoms was achieved with no deficits after the procedure. Pathologic changes in the biopsy included axonal loss, demyelination, and the presence of abundant collagen infiltrates and myelin debris. No inflammatory cells were present. In some areas, myelin-denuded axons were in close apposition, allowing the presence of axon-to-axon interactions. These findings are similar to others described previously regarding patients with vascular compression-related TN.
CONCLUSION: Compression injury to the trigeminal root leading to demyelination is a major determinant in the pathogenesis of TN.