Surgical resection of gliomas WHO grade II and III located in the opercular region.

Background: Surgery in the opercular region especially in the dominant hemisphere impose a major challenge for the neurosurgeon due to the close vicinity to functional important motor and speech areas. The purpose of the present study is to analyse on a homogenous patient group pre- and postoperative functional deficits with regard to different speech qualities (e.g. aphasia, apraxia), and to correlate these data with MR and intraoperative monitoring results.

Method: Fourteen patients with suspected low grade astrocytomas in the opercular region consecutively treated by surgery were eligible for this study (histology revealed 3 WHO grade III tumours). Degree and duration of postoperative deficits were retrospectively evaluated according to tumour location and boundaries on MR, intraoperative neuromonitoring results and extent of tumour resection.

Findings: Postoperatively, 8 patients showed speech or language disturbances, in 4 patients combined with motor deficits mainly of the contralateral upper extremity. Fifty percent of the neuropsychologically tested patients exhibited speech apraxia while the other 50% had a true aphasic syndrome. Recovery of the latter deficits was in general faster and more complete. The severity and duration of postoperative deficits was in good correlation with the distance of the resection margin to the next positive stimulation point(s), and a distance of more than 0.5 cm proved to avoid major impairments. The distribution of functional important stimulation points in relation to the tumour extension was not predictable, and -- unexpectedly -- up to 50% of these sites were found overlaying the tumour.

Interpretation: Surgery for WHO grade II and III gliomas in the opercular region can result in speech apraxia or an aphasic syndrome with or without concomitant motor deficits. Intraoperative cortical electrical stimulation is essential in resecting tumours in the opercular region to avoid permanent morbidity.