Syncope induced by glossopharyngeal neuralgia: sympathetic outflow to muscle.

We studied a patient who regularly developed asystole and fainted during attacks of glossopharyngeal neuralgia. A cardiac pacemaker did not prevent syncope. Spontaneous sympathetic activity in muscle nerves disappeared during the attacks, and blood pressure fell despite a functioning pacemaker. Fainting probably resulted from abnormal spread of afferent impulses from the neuralgic trigger zone in the pharynx to brainstem vasomotor centers. Presumably, the pacemaker failed to prevent syncope because of the profound sympathetic inhibition that coincided with cardiac vagal excitation.