Intraoperative electrical stimulation of the gyrus angularis

Background: 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.

Methods: The AG was electrically stimulated in five cases with the assistance of neuronavigation. Two different stimulation techniques were applied: bipolar (BCS) and monopolar (MCS).

Results: After MCS, a compound muscle action potential (CMAP) was recorded from the contralateral arm muscles in three patients. In the remaining two patients no CMAP was elicited following MCS stimulation. The latency of the recorded CMAP from the thenar muscle ranged from 30.3 to 32.7ms 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 40Hz and a duration of 4s or 6s.

Conclusion: Because this is to our 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 the feasibility of electrical stimulation of the angular gyrus. 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.