Memory and language risk assessment with Wada test in patients candidates for epilepsy surgery

To determine post-surgical cognitive risk and associated factors according to lesion location in a sample of patients evaluated for epilepsy surgery with Wada test at the Fundacion Instituto Neurologico de Colombia.

An observational, retrospective, analytical study was completed in patients with drug-resistant temporal lobe epilepsy candidates for epilepsy surgery treated from 2001 to 2021, who completed the Wada test as part of the pre-surgical evaluation. A descriptive analysis of sociodemographic, clinical, imaging and neuropsychological variables was completed; a multivariate logistic regression was performed analyzing factors associated with resection risk in patients with left lesions. RESULTS A total of 369 patients were included, 54.74% of the cases were women, with a median age of seizure onset of 11 years. 92.66% of the cases had lesional epilepsy and 68.56% were secondary to hippocampal sclerosis. Left hemisphere was the most frequently affected (65.68%) being dominant for memory and language in most of the patients with a proportion of 42.82% and 81.3%, respectively. The median functional adequacy was 43.75 (IQR 0-75) and the functional reserve was 75 (IQR 25 -93.75). In 104 patients, the Wada test determined a resection risk. In patients with a left lesion, it was found that functional reserve (PRadjusted 0.99, CI 95% 0.9997-0.9998) and having a right hemispheric dominance for memory (PRadjusted 0.92, CI 95% 0.547-0.999) were protective factors for post-surgical resection risk.

Wada test is a useful tool for surgical decision-making in patients with drug-resistant temporal lobe epilepsy. When considering cognitive risk, components such as memory dominance and functional reserve should be considered as protective factors for postsurgical cognitive function preservation in patients with left lesions.