Detection of face motor activation in the precentral gyrus with functional thermography following inconclusive direct electrical stimulation mapping: illustrative case

BACKGROUND The leading method of identifying critical functional regions during brain tumor resection is direct electrical stimulation (DES). In awake craniotomy patients, DES employs electric current to induce functional responses or task inhibition. In contrast, thermography uses infrared imaging to detect regions of increased blood flow from patient tasks, inferring the location of functional activity similarly to blood oxygen level– dependent (BOLD) functional magnetic resonance imaging (fMRI). DES seldom produces no detectable response, but the case herein is an example featuring the subsequent use of thermography. OBSERVATIONS The authors present the case of a 40-year-old male in whom awake craniotomy DES for high-grade glioma re-resection produced no detectable response at the upper levels of tolerated current amplitude. Following inconclusive DES, infrared thermography was performed with a lip-pursing task, and face motor activation was thermally detected in regions corroborated by both preoperative BOLD fMRI and literature on BOLD fMRI face motor mapping. LESSONS The lack of a detectable DES response was attributed to significant peritumoral edema, as evidenced by preoperative fluid-attenuated inversion recovery MRI. Findings indicate that infrared thermography overcomes the limitations of DES in an extensive edema setting and that thermography offers a useful complement to standard cortical mapping protocols for resection planning.