Magnetic Source Imaging Speech Mapping: Comparison with Direct Cortical Stimulation Speech Mapping

Abstract

Using visual and auditory word recognition tasks, receptive speech areas were mapped using whole head magnetic source imaging (MSI) in 13 patients that subsequently underwent perioperative speech mapping. Six patients received a left temporal lobectomy for epilepsy, one patient had a left temporal arteriovenous malformation, five patients had tumors, and one patient had left frontal cortical dysplasia. MSI speech mapping was performed by presenting the patient with either an audible or visual sequence of words and asking when a word was repeated. Sources of the recorded magnetic fields were modeled as equivalent current dipoles at four millisecond intervals. The magnetoencephalography (MEG) recorded dipoles were then coregistered with magnetic resonance imaging scans using fiducial markers to give the MSI output. Patients then underwent either awake craniotomies or placement of subdural grid electrodes with perioperative speech mapping as part of their surgical treatment. Cortical language sites were identified by interruption of several...