P03.05 The use of subcortical intraoperative electrical stimulation mapping for assessment of executive functions: A summary of the evidence so far

Abstract

Abstract BACKGROUND Over the past years, the functional subcortical architecture of the brain has been increasingly acknowledged in neurosurgical planning. A method to study anatomo-functional correlations is direct electrical stimulation (DES). DES is widely used by neurosurgeons and considered as a reliable tool to minimize the occurrence of permanent postoperative motor, language and visual deficits. In recent years, DES has also been used for mapping of other cognitive functions, such as executive functions. MATERIAL AND METHODS We systematically summarized the evidence so far from DES studies on subcortical pathways that are involved in the following three executive functions: (1) inhibitory control, (2) working memory and (3) cognitive flexibility. RESULTS We only found twelve articles that reported on intraoperative electrical stimulation of white matter pathways to map executive functions and explicitly clarified which subcortical tract was stimulated. The results indicate that the second branch of the right superior longitudinal fasciculus (SLF-II) is involved in inhibitory control, the first branch of the right superior longitudinal fasciculus (SLF-I) and the third branch of the left superior longitudinal fasciculus (SLF-III) are involved in working memory and the cingulum is involved in cognitive flexibility. CONCLUSION We were unable to draw any specific conclusions, nor unequivocally established the pathways involved in executive functions due to heterogenous study characteristics, methods and tasks, and the limited number of studies that assessed these relationships. Clearly, neurosurgical groups are exploring novel methods to assess cognition during awake neurosurgery, but are far from consensus on indications and protocols, which complicated the comparison and summarization of findings. We will discuss possible approaches for future research to obtain converging and more definite evidence for the involvement of subcortical pathways in specific executive functions.