Intraoperative neurophysiological monitoring in vestibular schwannoma surgery: advances and clinical implications.
OBJECTIVE
Intraoperative neurophysiological monitoring has become an integral part of vestibular schwannoma surgery. The aim of this article was to review the different techniques of intraoperative neurophysiological monitoring in vestibular schwannoma surgery, identify the clinical impact of certain pathognomonic patterns on postoperative outcomes of facial nerve function and hearing preservation, and highlight the role of postoperative medications in improving delayed cranial nerve dysfunction in the different reported series.


METHODS
The authors performed a review of the literature regarding intraoperative monitoring in acoustic/vestibular schwannoma surgery. The different clinical series representing different monitoring techniques were reviewed. All the data from clinical series were analyzed in a comprehensive and comparative model.


RESULTS
Intraoperative brainstem auditory evoked potential monitoring, direct cochlear nerve action potential monitoring, and facial nerve electromyography are the main tools used to assess the functional integrity of an anatomically intact cranial nerve. The identification of pathognomonic brainstem auditory evoked potential and electromyography patterns has been correlated with postoperative functional outcome. Recently, perioperative administration of intravenous hydroxyethyl starch and nimodipine as vasoactive and neuroprotective agents was shown to improve vestibular schwannoma functional outcome in few reported studies.


CONCLUSIONS
Recent advances in electrophysiological technology have considerably contributed to improvement in functional outcome of vestibular neuroma surgery in terms of hearing preservation and facial nerve paresis. Perioperative intravenous nimodipine and hydroxyethyl starch may be valuable additions to surgery.
Youssef
A Samy
AS
Department of Neurosurgery, University of South Florida, Tampa, Florida 33606, USA. ayoussef@health.usf.edu
Downes
Angela E
AE
D000200:Action Potentials / Q000502:physiology; D003056:Cochlear Nerve / Q000502:physiology; D004576:Electromyography / Q000706:statistics & numerical data; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology; D005154:Facial Nerve / Q000502:physiology; D005158:Facial Paralysis / Q000175:diagnosis / Q000517:prevention & control; D006309:Hearing / Q000502:physiology*; D034381:Hearing Loss / Q000517:prevention & control; D006801:Humans; D006895:Hydroxyethyl Starch Derivatives / Q000494:pharmacology / Q000627:therapeutic use; D016239:MEDLINE / Q000706:statistics & numerical data; D016343:Monitoring, Intraoperative / Q000379:methods* / Q000706:statistics & numerical data; D009464:Neuroma, Acoustic / Q000601:surgery*; D009482:Neurophysiology / Q000379:methods* / Q000706:statistics & numerical data; D009553:Nimodipine / Q000494:pharmacology / Q000627:therapeutic use; D019990:Perioperative Care / Q000379:methods; D011183:Postoperative Complications / Q000517:prevention & control*; D016896:Treatment Outcome
D006895:Hydroxyethyl Starch Derivatives; D009553:Nimodipine