Surgical resection of gliomas in the dominant inferior frontal gyrus: Consecutive case series and anatomy review of Broca's area

Abstract

Introduction: There is a general lack of consensus on both anatomic definition and function of Broca's area, often localized to the pars triangularis (pT) and pars opercularis (pOp) of the left inferior frontal gyrus (IFG). Given the belief that this region plays a critical role in expressive language functions, resective surgery is often avoided to preserve function. However, the putative role of Broca's area in speech production has been recently challenged. The current study aims to investigate the plausibility of glioma resection and neurological outcomes in "Broca's area".

Methods: We report a single-surgeon, consecutive case series feasibility study describing the resection of gliomas within the IFG. Presentation, mapping, functional outcome, and extent of resection variables were considered for analysis.

Results: All included patients had tumors located in the traditional "Broca's area", eight (53.33 %) additionally extending into the insular and subinsular regions. All patients except for one, presented with speech-language deficits preoperatively. Awake brain surgery for tumor resection with direct cortical and subcortical stimulation and intraoperative neuropsychological evaluation was carried out in all individuals. During stimulation, positive speech-language sites within the IFG were identified in ten patients. Two patients (13.33 %) experienced a decline in naming during intraoperative cognitive monitoring and thirteen (86.66 %) had a stable performance throughout surgery. At two-week follow-up, all patients had recovery of language functions compared to initial presentation. Overall extent of resection (EOR) was 60.35 % ( ± 29.60) with residual tumor being the greatest within the insular and subinsular areas. EOR was stratified in anatomical regions within the IFG, being the pOr the area with the greatest EOR (97.4 %), followed by the pT (84.1 %), pOp (83.8 %), and vPMC (80 %).

Conclusion: The belief that Broca's area is not safe to resect is challenged. Adequate mapping and careful patient selection allow maximum safe resection of tumors located in the traditional "Broca's area", with low risk of postoperative morbidity.

Keywords: Awake surgery; Brain mapping; Brain tumor; Broca’s area; Glioma; Inferior frontal gyrus.