Topical anesthesia on the cranial nerve V prevents intraoperative arousal events during microvascular decompression surgery

Abstract

Objectives: It is an established fact that during neurosurgery of microvascular decompression (MVD) on the cranial nerve V, hemodynamic turbulence is evoked by the intervention on the brain stem. However, a possible arousal response should happen on BIS index monitoring during the surgery if the circulatory turbulences were evoked by stimuli on the intervened trigeminal nerve, separate from the brain stem reflex. The authors confirmed that the effectiveness of topical anesthesia on the exposed nerve would suppress intraoperative arousal response on BIS, as well as circulatory turbulence with a case of trigeminal neuralgia. In order to exclude interference of the brain stem reflex, a case of MVD on the cranial nerve VII, a neurosurgical candidate of the hemifacial tic, was selected as the control. Results: The backgrounds of both female cases were approximated for age, body height and weight, as well as past histories of hypertension and controlled diabetic stages. Furthermore, there was no carbamazepine, which alleviates trigeminal discharge, dispensed to either patient. During surgical intervention on the cranial nerve V, arousal responses burst on the BIS index followed by episodes of hypertension and tachycardia. Those events were repeatedly resistant to attempts to increase anesthesia with propofol in bolus increments. They completely ceased immediately after topical application of lidocaine directly on the exposed nerve root. The effect lasted 1 h and repeated maneuvers with recurrent episodes also responded perfectly. Meanwhile, there was an uneventful surgical course in the control case of MVD on the cranial nerve VII. Conclusion: Topical anesthesia with lidocaine on the exposed cranial nerve V during MVD surgery prevented intraoperative arousal response and circulatory turbulence, thus, avoiding an excessive increase of general anesthesia.