Mechanisms of syncope in glossopharyngeal neuralgia.

Syncope is a rare presentation of glossopharyngeal neuralgia (GN). The mechanisms of the syncope were studied in a patient with recurrent episodes comprising prolonged cardiac standstill and arterial hypotension. During attacks, no supraventricular or ventricular potentials were recorded in the ECG. Atropine prevented the cardiac arrest without affecting the pain, indicating the vagus as the efferent limb of the reflex asystole. Following atropine blood pressure continued to fall during GN attacks, suggesting abolition of sympathetic tone. Indeed, serum norepinephrine levels fell during these attacks. Infiltration of either vagus above the clavicle with local anesthetics did not abolish the cardiac asystole. Carbamazepine and a dual chamber pacemaker were effective in controlling the symptoms of the patient. The results suggest that, during a neuralgic attack, the stimulation excites both vagi, causing asystole and simultaneously abolishes sympathetic tone.