Neurophysiological Evaluation and Intraoperative Monitoring in Peripheral Nervous System Tumors

Neurophysiological preoperative studies are valuable tools that supplement and support the clinical decisions and surgical plans of peripheral nerve sheath tumors. Clinical management and treatment decisions are also based on the diagnostic certainty afforded by electrodiagnostic studies, which are more sensitive and specific than clinical examinations regarding the nature and localization of a nerve lesion. Nerve ultrasonography is increasingly being introduced as a complement of neurophysiological examination and the perioperative suite before nerve surgery, providing additional anatomic information in real time and consequently improving the surgical strategy. Intraoperative neurophysiologic monitoring improves localization and understanding of the underlying pathophysiology of peripheral nerve lesions and detects changes in neurologic function during surgery. It provides significantly better information than visual inspection of the operative field, minimizing postoperative neurologic deficits due to surgical manipulation (e.g., stretching, compression, heating from electrocauterization, constriction, or clamping of local blood vessels). However, a deep knowledge of anatomy and neurophysiology is necessary, as is understanding and performing the challenging technical aspects of these studies to provide accurate information to enhance patient outcomes. As in any multidisciplinary setting, constant and accurate communication between the neurophysiological, anesthesia, and surgical team is essential to meet these goals. This chapter discusses the neurophysiological evaluation before surgery, including the nerve ultrasonography applied to complete the functional exam and the intraoperative neurophysiological techniques applied to the surgery of peripheral nerve tumors, including their use, advantages, and limits.