2019 Volume 28 Issue 1 Pages 33-39
A 53-year-old man with trigeminal neuralgia and a recurrent epidermoid tumor at the cerebellopontine angle is reported. After craniotomy and subtotal tumor resection, his trigeminal neuralgia, facial palsy, and cerebellar ataxia showed considerable improvement. However, mild trigeminal neuralgia persisted. Three years later, the tumor recurred in association with exacerbation of trigeminal neuralgia. He refused a second operation and consulted us for stereotactic radiosurgery. Gamma knife surgery was carried out targeting the whole tumor with 12.5 Gy at the margins, including the right trigeminal nerve. Although tumor shrinkage was not marked, his neuralgia showed dramatic improvement within one day and resolved completely after one month without any complications. Treatment with carbamazepine was no longer required.
The mechanism underlying this pain relief is unclear, since significant mechanical decompression or decreased chemical stimulation of the trigeminal nerve by the tumor was not confirmed. It is possible that spontaneous impulses were generated at a site of demyelination where the trigeminal nerve was distorted or showed focal indentation, and gamma knife surgery was successful in reducing hyperactive cranial nerve dysfunction, through electrophysiological effects. In this case, the clinical effect of gamma knife surgery could be considered as radiosurgical neuromodulation.
Although total surgical resection is the main treatment for epidermoid tumors, radiosurgery can play an important role in controlling the residual tumor and improving the distressing symptoms associated with hyperactivity of the trigeminal nerve.
