Intraoperative Cortical Mapping Techniques and Limitations

Abstract

Cortical mapping is the gold standard for intraoperative localization of eloquent cortex. Stimulation mapping provides a tool to balance the benefits of maximal surgical resection with the risks of damage to eloquent cortex or subcortical fiber tracts. Certain mapping techniques, such as cortical stimulation sensory and language mapping, require an awake cooperative patient, and necessitate specific anesthetic considerations when performing mapping or evoked potential monitoring. Somatosensory-evoked potentials (SSEPs) can be used to quickly and reliably locate Rolandic cortex. SSEPs and motor-evoked potentials (MEPs) can be used for continuous monitoring of sensory and motor cortex and subcortical fiber tracts during surgical resection. Language mapping is performed when there is a surgical lesion in the language-dominant temporal, posterior frontal, or anterior parietal lobe. Wada testing may be needed to lateralize language function preoperatively when language lateralization is in doubt, and is required in certain patient subgroups based on handedness and lesion location. The specific intraoperative techniques of SSEP mapping and monitoring, MEP mapping and monitoring, and cortical stimulation mapping of motor, sensory, and language cortices are presented.