Difficulty in identification of the frontal language area in patients with dominant frontal gliomas that involve the pars triangularis

Abstract

OBJECTIVE Identification of language areas using functional brain mapping is sometimes impossible using current methods but essential to preserve language function in patients with gliomas located within or near the frontal language area (FLA). However, the factors that influence the failure to detect language areas have not been elucidated. The present study evaluated the difficulty in identifying the FLA in dominant-side frontal gliomas that involve the pars triangularis (PT) to determine the factors that influenced failed positive language mapping. METHODS Awake craniotomy was performed on 301 patients from April 2000 to October 2013 at Tokyo Women's Medical University. Recurrent cases were excluded, and patients were also excluded if motor mapping indicated their glioma was in or around the motor area on the dominant or nondominant side. Eighty-two consecutive cases of primary frontal glioma on the dominant side were analyzed for the present study. MRI was used for all patients to evaluate whether tumors involved the PT and to perform language functional mapping with a bipolar electrical stimulator. Eighteen of 82 patients (mean age 39 ± 13 years) had tumors that showed involvement of the PT, and the detailed characteristics of these 18 patients were examined. RESULTS The FLA could not be identified with intraoperative brain mapping in 14 (17%) of 82 patients; 11 (79%) of these 14 patients had a tumor involving the PT. The negative response rate in language mapping was only 5% in patients without involvement of the PT, whereas this rate was 61% in patients with involvement of the PT. Univariate analyses showed no significant correlation between identification of the FLA and sex, age, histology, or WHO grade. However, failure to identify the FLA was significantly correlated with involvement of the PT (p < 0.0001). Similarly, multivariate analyses with the logistic regression model showed that only involvement of the PT was significantly correlated with failure to identify the FLA (p < 0.0001). In 18 patients whose tumors involved the PT, only 1 patient had mild preoperative dysphasia. One week after surgery, language function worsened in 4 (22%) of 18 patients. Six months after surgery, 1 (5.6%) of 18 patients had a persistent mild speech deficit. The mean extent of resection was 90% ± 7.1%. Conclusions Identification of the FLA can be difficult in patients with frontal gliomas on the dominant side that involve the PT, but the positive mapping rate of the FLA was 95% in patients without involvement of the PT. These findings are useful for establishing a positive mapping strategy for patients undergoing awake craniotomy for the treatment of frontal gliomas on the dominant side. Thoroughly positive language mapping with subcortical electrical stimulation should be performed in patients without involvement of the PT. More careful continuous neurological monitoring combined with subcortical electrical stimulation is needed when removing dominant-side frontal gliomas that involve the PT.

Awake craniotomy with transcortical motor evoked potential monitoring for resection of gliomas in the precentral gyrus: utility for predicting motor function

“…Surgery was performed according to the previously published concept of information-guided brain tumor removal with the goal of maximal resection of the tumor with minimal risk of permanent postoperative neurological deficits. 12,13,16,17 The following methods have been published previously. 17,18 Intraoperative MRI (AIRIS II; Hitachi Medical Corporation) and updated neuronavigation were used routinely.…”

“…12,13,16,17 The following methods have been published previously. 17,18 Intraoperative MRI (AIRIS II; Hitachi Medical Corporation) and updated neuronavigation were used routinely. Surgery was generally performed with maximal possible removal of the area defined by enhancement visualized on contrast-enhanced T1-weighted MRI for tumors showing complete or ringed enhancement and suspected to be grade IV gliomas and removal of the area defined by signal hyperintensity on T2-weighted MRI for non-or partially contrast-enhanced tumors suspected to be grade I, II, or III gliomas.…”

“…The following methods have been published previously. 17 In all patients, tumor removal was performed during an awake craniotomy. For intraoperative brain mapping, electrical stimulation of the cortex was applied with repetitive square-wave biphasic currents of alternating polarity (pulse width, 0.2 msec; frequency, 50 Hz; duration, 1-2 seconds), using an Ojemann cortical stimulator (OCS-1; Integra Radionics, Inc.) and a bipolar electrode with an interpolar distance of 5 mm.…”

“…The tumor resection rate was assessed with intraoperative MRI and postoperative MRI performed within 48 hours after surgery. As in the previously published method, 17,18 for semiautomatic volumetry to evaluate the extent of resection (EOR) in the present study, we used 3D Slicer 4.0, which is freely downloadable from the website http://www.slicer.org. 2 For tumors that showed complete or ringed contrast enhancement and were suspected to be grade IV gliomas, we calculated EOR by comparing the contrast-enhanced area on T1-weighted images obtained intraoperatively to that on corresponding images obtained preoperatively; for non-or partially contrast-enhanced tumors suspected to be grade I, II, or III tumors, EOR was calculated based on areas of signal hyperintensity on intra-and preoperative T2-weighted images.…”

Cortico-cortical evoked hemodynamic responses in human language systems using intraoperative near-infrared spectroscopy during direct cortical stimulation

“…[15][16][17][18][19]. However, even such methods may fail to identify language areas due to complicated and delicate technical problems, lack of patient cooperation, and interpretation of the results [20,21]. A recent study reported the efficacy of intraoperative language network monitoring by means of cortico-cortical evoked potentials (CCEPs) [22].…”