Background and objectives: Stereo-EEG-guided radiofrequency thermocoagulation (RFTHC) has been proposed as relatively safe from a cognitive perspective; however, there is a lack of evidence based on neuropsychological assessments supporting this. This study is the first prospective evaluation of neuropsychological outcomes associated with stereo-EEG-guided RFTHC in patients with focal drug-resistant epilepsy.
Methods: This cohort study involved prospective recruitment of consecutive patients undergoing stereo-EEG from 2 Australian centers. A comprehensive neuropsychological assessment was administered before implantation and 3 months after RFTHC (M = 104.51 days, SD = 29.25). Outcomes across cognitive domains were assessed at a group level with repeated measures t tests. Factorial repeated measures analyses of variance compared memory and language outcomes according to whether dominant mesial temporal lobe (mTL) structures were coagulated. Reliable change indices (RCIs) were computed to explore psychometrically reliable changes at an individual level.
Results: The sample comprised 39 patients who underwent stereo-EEG (M = 37.08 ± 9.67 years, range = 17-56 years, 54% female). Nineteen (49%) had a language dominant epileptogenic zone (EZ), 16 (41%) a nondominant EZ, and 4 (10%) a bilateral EZ. All patients underwent RFTHC with a mean of 11.87 (SD = 6.82, range = 2-29) coagulation sites. Ten patients (26%) had RFTHC within the dominant mTL. At a group level, RFTHC was not associated with a significant decline on any neuropsychological measures (all comparisons p > 0.05). Subgroup analyses revealed a decline in delayed verbal recall after RFTHC of dominant mTL structures (F(1,37) = 4.46, p = 0.04, ηp2 = 0.11, 95% CI [0-0.30]; medium to large effect), although it did not remain statistically significant after correction for false discovery rate. No statistically significant group differences were observed on visual memory or language measures post-RFTHC (all comparisons p > 0.05). RCI revealed that after RFTHC within the dominant mTL, 20% of patients experienced a decline in verbal memory and 10% in visual memory. By contrast, 7% declined in verbal memory and 10% in visual memory post-RFTHC outside the dominant mTL.
Discussion: While these findings support the current view that RFTHC is cognitively benign for most cases, the results raise the question of a verbal memory decline after coagulation of the dominant mTL. Individualized neuropsychological counseling before stereo-EEG is essential to avoid unanticipated deficits.