Pre- to Postoperative Longitudinal Follow-up of Phoneme Perception in Glioma Patients: Evidence from the Mismatch Negativity and P300

Abstract

Background and Aims: Glioma growth in eloquent language areas induces adaptive activation changes in the language network. The present study aimed to (1) investigate the pre-to postoperative evolution of neural phoneme perception processes in glioma patients and (2) assess if event-related potentials (ERPs) reflecting phoneme perception can provide added value to the diagnostic approach in individuals undergoing awake surgery. Methods and Procedures:In five persons undergoing an awake craniotomy for the resection of a glioma, pre-and postoperative behavioural language assessment (Aachen Aphasia Test, Comprehensive Aphasia Test and Boston Naming Test) and electrophysiological investigation of phoneme perception was performed. For the latter, ERPs were obtained through the administration of an inattentive (Mismatch Negativity; MMN) and attentive (P300) oddball paradigm containing a phonemic articulation place contrast during EEG recording.Outcomes and Results: Aberrant phoneme categorization processing was evidenced in all five participants preoperatively based on the MMN and P300 amplitude and latency. Moreover, mild behavioural impairments were found in four participants at this time. Postoperatively, three out of five participants reached behavioural ceiling effects, while four individuals displayed normalization of electrophysiological measures. Conclusions:While neural processing of phoneme contrasts was preoperatively affected by glioma-induced disturbances, a high potential for postsurgical plasticity was shown. As four participants presented with a high grade glioma, tumour grade might partially account for this pattern. Addition of electrophysiological tests to the language assessment could provide benefits in both the pre-and postoperative clinical diagnostic approach in glioma patients. These preliminary results need validation in a larger sample.