Asystole from tetanic stimulation of the accessory nerve.

An asystolic cardiac arrest is reported which occurred at the same time as supramaximal tetanic stimulation over the accessory nerve in order to evoke contractions in the trapezius and sternocleidomastoid muscles. The cause may have been the inadvertent stimulation of one or more of the cranial nerves of the carotid sheath at the base of the skull: the cranial root of the accessory nerve, the vagus, the sino-carotid branch of the glossopharyngeal nerve or the hypoglossal nerve. The most likely culprit, if not the vagus itself, was the cranial root of the accessory nerve which both functionally and anatomically should be seen as an integral part of the vagus. It is suggested that stimulation of any nerve in the carotid sheath should be approached with caution and that a tetanic stimulus to this area might best be avoided.