Neuropsychological outcomes of subtemporal selective amygdalohippocampectomy via a small craniotomy

Abstract

OBJECT The objectives of this study were to describe a novel minimal-access subtemporal approach for selective resection of the amygdala and hippocampus in patients with medically refractory mesial temporal lobe epilepsy (MTLE) due to hippocampal sclerosis, and to analyze the related outcomes. METHODS The authors analyzed data from all cases involving patients with unilateral MTLE due to hippocampal sclerosis who were treated with selective amygdalohippocampectomy via the posterior subtemporal approach through a relatively small craniotomy, without a neuronavigation system, at their institution during the period from September 2010 to September 2012. Data were obtained on baseline characteristics, preoperative evaluations of unilateral mesial temporal sclerosis, surgical complications, and Engel class seizure outcomes. All patients underwent memory testing, IQ testing, and language testing. RESULTS The mean duration of follow-up was 33.6 months (range 24–48 months). There were no deaths and no cases of significant postoperative morbidity. One patient had a mild complication. At 2-year follow-up, 19 patients were seizure free (Engel Class I outcome). Verbal memory scores obtained at 3 months and at 2 years after surgery were significantly lower than preoperative scores for patients who underwent surgery on the left side of the brain (p < 0.05). Pictorial memory scores were higher following surgery compared with before surgery regardless of whether patients underwent left- or right-sided brain surgery. There was also improvement in performance IQ and total IQ following surgery in both groups. For patients who underwent right-sided brain surgery, verbal comprehension and semantic fluency testing scores were significantly higher at both 3 months and 2 years after surgery than before surgery. For patients who underwent left-sided brain surgery, scores on all language tests were significantly lower at 3 months after surgery than before surgery. Verbal comprehension testing scores returned to the preoperative level at 2 years after surgery. CONCLUSIONS The posterior subtemporal approach through a relatively small craniotomy allows adequate exposure and safe resection of mesial temporal structures and effectively reduces medically intractable MTLE. It preserves IQ but may have a detrimental effect on verbal memory and language ability.