Electrical Excitability of the Angular Gyrus

The angular gyrus (AG) is a circumscribed area between the parietal and temporal lobes and its exact function is not clear. The purpose of the present Study Was to investigate the feasibility of intraoperative electrical stimulation of the AG in humans. The AG was electrically stimulated in five cases with the assistance of neuronavigation. Two different stimulation techniques were applied: bipolar cortical stimulation and monopolar cortical stimulation. After monopolar cortical stimulation, a compound muscle action potential was recorded from the contralateral arm muscles in three patients. In the remaining two patients no compound muscle action potential was elicited after monopolar cortical Stimulation, The latency of the recorded compound Muscle action potential from the thenar muscle ranged from 30.3 to 32.7 milliseconds and from the two forearm flexors was 28.7 and 29.7. Bipolar stimulation generated a motor response in the contralateral extremity in three research subjects but no motor response in two. Response was obtained in all three research subjects with the combination of 40 Hz and a duration of 4 or 6 seconds. Because this is to their knowledge the first report demonstrating a functional Output of Exner's area to the motor cortex, it Would be difficult to suggest all the pathways and functions of this complex connectivity. The aim of the pilot study presented here was to investigate file feasibility of electrical stimulation of the AG. The findings presented here show that intraoperative electrical stimulation of the AG is possible. Although the results are limited by the small number of patients investigated, they are encouraging and Suggest that it is worthwhile to continue research in this area.