AUTHOR=Hazem Sally Rosario , Awan Mariam , Lavrador Jose Pedro , Patel Sabina , Wren Hilary Margaret , Lucena Oeslle , Semedo Carla , Irzan Hassna , Melbourne Andrew , Ourselin Sebastien , Shapey Jonathan , Kailaya-Vasan Ahilan , Gullan Richard , Ashkan Keyoumars , Bhangoo Ranjeev , Vergani Francesco 

TITLE=Middle Frontal Gyrus and Area 55b: Perioperative Mapping and Language Outcomes

JOURNAL=Frontiers in Neurology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/neurology/articles/10.3389/fneur.2021.646075

DOI=10.3389/fneur.2021.646075

ISSN=1664-2295

ABSTRACT=<p><bold>Background:</bold> The simplistic approaches to language circuits are continuously challenged by new findings in brain structure and connectivity. The posterior middle frontal gyrus and area 55b (pFMG/area55b), in particular, has gained a renewed interest in the overall language network.</p><p><bold>Methods:</bold> This is a retrospective single-center cohort study of patients who have undergone awake craniotomy for tumor resection. Navigated transcranial magnetic simulation (nTMS), tractography, and intraoperative findings were correlated with language outcomes.</p><p><bold>Results:</bold> Sixty-five awake craniotomies were performed between 2012 and 2020, and 24 patients were included. nTMS elicited 42 positive responses, 76.2% in the inferior frontal gyrus (IFG), and hesitation was the most common error (71.4%). In the pMFG/area55b, there were seven positive errors (five hesitations and two phonemic errors). This area had the highest positive predictive value (43.0%), negative predictive value (98.3%), sensitivity (50.0%), and specificity (99.0%) among all the frontal gyri. Intraoperatively, there were 33 cortical positive responses—two (6.0%) in the superior frontal gyrus (SFG), 15 (45.5%) in the MFG, and 16 (48.5%) in the IFG. A total of 29 subcortical positive responses were elicited−21 in the deep IFG–MFG gyri and eight in the deep SFG–MFG gyri. The most common errors identified were speech arrest at the cortical level (20 responses−13 in the IFG and seven in the MFG) and anomia at the subcortical level (nine patients—eight in the deep IFG–MFG and one in the deep MFG–SFG). Moreover, 83.3% of patients had a transitory deterioration of language after surgery, mainly in the expressive component (<italic>p</italic> = 0.03). An increased number of gyri with intraoperative positive responses were related with better preoperative (<italic>p</italic> = 0.037) and worse postoperative (<italic>p</italic> = 0.029) outcomes. The involvement of the SFG–MFG subcortical area was related with worse language outcomes (<italic>p</italic> = 0.037). Positive nTMS mapping in the IFG was associated with a better preoperative language outcome (<italic>p</italic> = 0.017), relating to a better performance in the expressive component, while positive mapping in the MFG was related to a worse preoperative receptive component of language (<italic>p</italic> = 0.031).</p><p><bold>Conclusion:</bold> This case series suggests that the posterior middle frontal gyrus, including area 55b, is an important integration cortical hub for both dorsal and ventral streams of language.</p>