Trigeminal pain under vagus nerve stimulation.

Three epilepsy patients treated by cyclic continuous vagus nerve stimulation (VNS) experienced trigeminal pain during the periods of stimulation, which was reported as toothache in the left lower jaw, ipsilateral to the side of stimulation. The symptom occurred with a latency of days to weeks following an increase in stimulation current intensity (SCI). Trigeminal pain was reversible with decrease in SCI, or subsided due to habituation. These findings show that clinically relevant effects of VNS on nociception may occur. Because of the late onset and variable form of this side effect, trigeminal pain may not be regarded as VNS-related which may result in unnecessary diagnostic and therapeutic procedures.