Localization of Motor Cortex with Median Nerve Somatosensory Evoked Potentials

  • M. R. Nuwer


Motor cortex localization can be helpful during a craniotomy. Somatosensory evoked potentials (SSEP) can help with this task. The primary cortical SSEP from median nerve stimulation is generally easily and quickly defined on the exposed cerebral cortex. Several types of recording electrodes can be used. Interpretation is usually based upon several features, including the maximum N20 amplitude, phase reversal of N20-P20 across the central fissure, and the presence of small step-like negative potentials leading up to the N20 over the primary sensory cortex. Localization of the motor cortex is most often applied in situations in which the surgeon can use some discretion in defining the limits of a resection or the location of a biopsy.

It can be advantageous to identify the motor cortex during a craniotomy. The complexities fo sulci and gyri anatomy are somewhat too variable and unpredictable to be reliable by themselves. Somatosensory evoked potentials (SSEP) provide a means of helping the surgeon identify the primary postcentral somatosensory cortex, thereby also establishing the location of the precentral motor cortex. This technique is relatively quick and simple, and it can be used without substantial problems or complications in many various circumstances.


Motor Cortex Median Nerve Evoke Potential Primary Somatosensory Cortex Median Nerve Stimulation 
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Copyright information

© Springer-Verlag Berlin Heidelberg 1991

Authors and Affiliations

  • M. R. Nuwer
    • 1
    • 2
  1. 1.Department of NeurologyUniversity of California, Los AngelesLos AngelesUSA
  2. 2.Reed Neurological Research CenterLos AngelesUSA

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