Face processing deficits following brain tumours: Behavioural correlates and surgery-sensitive hotspots

Introduction Face processing deficits have mostly been documented in single cases/small samples, and rarely following brain tumours. Right hemisphere functions in general are under-investigated in brain tumour patients, despite the need to preserve them during surgery. We assessed anatomical correlates of a critical right hemisphere function, face processing, and specifically deficits in memorizing and recognizing unknown faces; decoding emotional expressions; and whether deficits are preferentially right lateralized, or could also be observed following left hemisphere damage. Methods 110 patients with unilateral tumours were evaluated before/after surgery and at 6 months follow-up with a battery of tasks tapping different face processing levels: Benton Face Recognition Test (BFRT), Recognition Memory Test for Faces (RMT-F), Ekman 60-Faces Test (EK-60F) for emotional expressions. Behavioural analyses assessed the prevalence of face related deficits across hemispheres and surgery effects. Voxel-based Lesion Symptom Mapping (VLSM) provided more refined anatomical analysis. Results Deficits in BFRT & RMT-F were more frequent after right hemisphere tumours, while EK-60F impairments were more evenly distributed. Furthermore, deficits in BFRT and EK-60F significantly worsened post-surgery. VLSM mapped deficits in RMT-F in right hippocampal/middle temporal lesions. Furthermore, surgery in right Fusiform Face Area/Hippocampus led to greater deficits in BFRT, an association not visible pre-surgery. Likewise, lower post-surgery EK-60F scores were found after left Amygdala/Hippocampal damage. Conclusions Results highlight the key role of right temporal lobe for many aspects of face processing, with only emotion recognition being also associated with the left hemisphere. The sensitivity of facial processing hotspots to surgical damage demands careful monitoring.