Glossopharyngeal neuralgia referred from a pontine lesion.

Paroxysmal pain in the form of glossopharyngeal neuralgia is less frequent and less well understood than that of trigeminal neuralgia. Diagnostic confusion can arise especially when both conditions occur in the one patient. We report a patient with a 20-year history of left-sided glossopharyngeal neuralgia with trigger zones in both the trigeminal and glossopharyngeal dermatomal distributions. Magnetic resonance imaging revealed a single T2-weighted hyperintense signal in the left pons with no other abnormality. It is postulated that ephaptic transmission between central pain fibers and the trigeminal or glossopharyngeal fibers, which both enter the spinal trigeminal tract, resulted, respectively, in conventional and "referred" glossopharyngeal neuralgia.