Clinical significance of intraoperative bidirectional corticocortical evoked potential monitoring to evaluate language function.

Abstract

Objective: Awake craniotomy is commonly used to resect lesions located near the language area during brain surgery. However, it is often difficult to perform language tasks due to several limitations such as difficulty in awakening during surgery and intraoperative seizures. This study investigated the clinical significance of bidirectional corticocortical evoked potential (CCEP) monitoring as a new approach to evaluate intraoperative language function.

Methods: This study enrolled 12 patients who underwent awake brain tumor resection with intraoperative CCEP monitoring to assess language function. Electrodes were placed on the frontal and temporoparietal lobes based on the location of the arcuate fasciculus identified with preoperative diffusion tensor imaging to measure CCEPs intraoperatively in two directions: from the frontal lobe to the temporoparietal lobe of the language-dominant side, and vice versa. Correlations between CCEP amplitudes or latencies before and after tumor removal in each direction and postoperative language function assessed with the Western Aphasia Battery were analyzed.

Results: Nine of the 12 patients showed language-related CCEP responses in both directions before, during, and after tumor removal. One patient who showed decreased CCEP amplitudes in both directions after tumor removal exhibited aphasia for as long as 1 month postoperatively. In contrast, of the 6 patients whose CCEP amplitude in only a single direction was reduced or disappeared, 4 had no deterioration of language function and the other 2 had temporary deterioration of language function during the 1st postoperative week, which improved by 1 month postoperatively.

Conclusions: This study indicated that bidirectional CCEP measurement may increase the precision of intraoperative language function monitoring.