Cognition in adults with bottom-of-sulcus dysplasia and the consequences of focal resection

To determine whether there are cognitive consequences of bottom-of-sulcus dysplasia (BOSD) when assessed as adults and whether focal resection of these lesions leads to change in cognition.

We studied 42 adults, of whom 39 underwent focal resection targeting the lesion. Neuropsychological assessments were tailored to the clinical epileptology.

On average, patients were 30 (15-56) years old at the time of assessment. Epilepsy duration was 21 (3-48) years. Seizure onset ranged between 3 months and 26 years. Fifteen patients (36%) had an age of onset of 12 years or older. Older age of seizure onset correlated with fewer cognitive measures impacted (r = -0.34, p = .026). Frontal (52%) and parietal (33%) lobes were common BOSD locations. Confrontation naming was assessed in 20 patients, 11 (55%) of whom were impaired. Of these 11 patients, 8 (73%) had a left-sided BOSD. Verbal fluency was assessed in 23 patients, 13 (57%) of whom were impaired. Of these 13 patients, 11 (85%) had a frontal BOSD. Processing speed and attention were assessed in 35 patients and deficits were seen in 17% to 20%, though milder reductions were more consistently seen. At post-surgical follow-up (M = 8.07 years, SD = 4.91 years), 59% of patients were seizure free. As a group, there was no evidence of post-surgical cognitive decline after focal resection of the BOSD; processing speed (p < .05) improved post-surgically.

In adults with BOSD, an earlier age of seizure onset is accompanied by a greater degree of cognitive comorbidity. Naming is commonly affected, particularly for those with left sided BOSDs. Executive dysfunction is common, particularly for patients with a frontal BOSD. Focal lesionectomy is associated with favourable seizure outcome and is cognitively safe with potential for improvement in processing speed.