Brain Advance Access originally published online on December 5, 2007
Brain 2008 131(2):535-542; doi:10.1093/brain/awm296
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Seizure outcome after resective epilepsy surgery in patients with low IQ
1Institute of Neuroscience and Physiology, Epilepsy Research Group, 2Institute of Clinical specialities, Department of Paediatrics, Sahlgrenska Academy at Göteborg University, Göteborg, Sweden and 3Department of Clinical Neurophysiology, Akademiska University Hospital, Uppsala, Sweden
Correspondence to: Kristina Malmgren, Institute of Neuroscience and Physiology, Epilepsy Research Group, Sahlgrenska Academy at Göteborg University, Guldhedsgatan 19, 1 tr, SE 413 45 Göteborg, Sweden E-mail: Kristina.malmgren{at}neuro.gu.se
Epilepsy surgery has been questioned for patients with low IQ, since a low cognitive level is taken to indicate a widespread disturbance of cerebral function with unsatisfactory prognosis following resective surgery. The prevalence of epilepsy in patients with cognitive dysfunction is, however, higher than in the general population and the epilepsy is often more severe and difficult to treat. It is therefore important to try to clarify whether IQ predicts seizure outcome after resective epilepsy surgery. The Swedish National Epilepsy Surgery Register, which includes data on all epilepsy surgery procedures in Sweden since 1990, was analysed for all resective procedures performed 1990–99. Sustained seizure freedom with or without aura at the 2-year follow-up was analysed as a function of pre-operative IQ level categorized as IQ <50, IQ 50–69 and IQ 
70 and was also adjusted for the following variables: age at epilepsy onset, age at surgery, pre-operative seizure frequency, pre-operative neurological impairment, resection type and histopathological diagnosis. Four hundred and forty-eight patients underwent resective epilepsy surgery in Sweden from 1990 to 1999 and completed the 2-year follow-up: 72 (16%) had IQ <70, (18 with IQ <50 and 54 with IQ 50–69) and 376 IQ 70. There were 313 adults and 135 children 
18 years. Three hundred and twenty-five patients underwent temporal lobe resections (TLR) and 123 underwent various extratemporal resections (XTLR). At the 2-year follow-up, 56% (252/448) of the patients were seizure free: 22% (4/18) in the IQ <50 group, 37% (20/54) in the IQ 50–69 group and 61% (228/376) in the IQ 70 group. There was a significant relation between IQ category and seizure freedom [odds ratio (OR) 0.41, 95% confidence interval (CI) 0.27–0.62] and this held also when adjusting for clinical variables [OR 0.58 (95% CI 0.35–0.95)]. In this population-based epilepsy surgery series, IQ level was shown to be an independent predictor of seizure freedom at the 2-year follow-up. However, many of the low-IQ patients benefit from surgery, especially patients with lesions. Low IQ should not exclude patients from resective epilepsy surgery, but is an important prognostic factor to consider in the counselling process.
Key Words: epilepsy surgery; focal epilepsy; seizure outcome; low IQ
Abbreviations: AED, antiepileptic drug; FLR, frontal lobe resection; HE, hemispherectomy; MLR, multilobe resection; OLR, occipital lobe resection; PLR, parietal lobe resection; RCPM, Raven Coloured Progressive Matrices; TLR, temporal lobe resection; WAIS-R, Wechsler Adult Intelligence Scale-Revised; WISC, Wechsler Intelligence Scale for Children; WPPSI-R, Wechsler Preschool and Primary Scale of Intelligence-Revised
Received June 14, 2007. Revised September 28, 2007. Accepted November 14, 2007.