Preserving the basal temporal language area: A paradigm shift in predicting verbal memory outcomes after dominant temporal lobectomy

Objective

While standard anterior temporal lobectomy (aTL) is widely used for treating drug-resistant temporal epilepsy, predicting postoperative cognitive outcomes in the dominant hemisphere often fails at the individual level. Resection of the Basal Temporal Language Area (BTLA) was already shown to predict verbal impairment post-aTL. This study investigates the impact of the BTLA resection on verbal memory (VM).

Methods

Cortical electrical stimulations via SEEG electrodes were used to identify the BTLA during a visual naming test in the dominant ventral temporal cortex (VTC) of 21 patients, subsequently treated with a tailored aTL. The extent of BTLA resection was quantified and its correlation with VM evolution was assessed early (<1 year) and late (>1 year) postoperatively using a free delayed recall test.

Results

The BTLA was located 6–76 mm from the temporal tip, showing significant interindividual variability. The average VTC resection extent was 27 mm, tailored according to SEEG data to preserve as much of the BTLA as possible. A significant correlation was found between the extent of BTLA resection and VM decline both early and late postoperatively. While VTC resection extent was independently associated with early VM decline, only BTLA resection extent correlated with long-term VM impairment.

Conclusions

Our results suggest the BTLA to be involved, not only in lexical access, but possibly also in declarative memory. On a practical level, precise individual mapping of the BTLA appears crucial for predicting long-term cognitive outcomes post-aTL. This could inform surgical approaches to minimize cognitive impairment in the dominant temporal epilepsy surgery.