Intraoperative neurophysiology for surgery in and around the brainstem: role of brainstem mapping and corticobulbar tract motor-evoked potential monitoring.

INTRODUCTION

New advancements of intraoperative neurophysiology for surgery in and around the brainstem have been described. NEUROPHYSIOLOGICAL TECHNIQUES: Brainstem mapping (BSM) is applied to locate cranial nerves and their motor nuclei (CMN) on the floor of the fourth ventricle. Corticobulbar tract (CBT) motor-evoked potential (MEP) monitoring is used to achieve on-line monitoring of the cranial motor nerves' functional integrity.

DISCUSSION: Each of these procedures bears a specific role: BSM can help avoid direct damage to CMNs on the fourth ventricular floor; CBT-MEP can provide simultaneous feedback on the functional integrity of the CBT and CMN during surgery, eventually leading to "tailored" modifications of the surgical procedure, based upon neurophysiological responses.

CONCLUSIONS

CBT-MEP monitoring has less restriction in terms of clinical indications, but a combination of both procedures is essential for functional preservation of CMNs during surgery in and around the brainstem.