Cognitive decline in severe intractable epilepsy.
OBJECTIVE
To explore the relation between seizure-related variables and cognitive change in patients with severe intractable epilepsy.


METHODS
A retrospective analysis of data from 136 patients who had undergone a cognitive assessment on two occasions at an interval of > or =10 years. Cognitive measures included tests of memory and executive skills in addition to intelligence quotients (IQ). Details were available regarding seizure type and frequency in the intertest interval.


RESULTS
Cognitive decline was severe and occurred across a wide range of cognitive functions. The frequency of generalised tonic-clonic seizures was the strongest predictor of decline. Complex partial seizure frequency was associated with a decline in memory and executive skills but not in IQ. Seizure-related head injuries and advancing age carried a poor cognitive prognosis, whereas periods of remission were associated with a better cognitive outcome. Early age at onset was not implicated, and duration of epilepsy was a much less potent predictor of cognitive decline than has been reported in cross-sectional studies. No evidence indicated that a higher level of cognitive function protected against cognitive decline.


CONCLUSIONS
Our findings, together with those from animal studies and surgically treated patients, suggest that seizures can have a direct adverse effect on cognition and that good seizure control even after years of intractability can have a beneficial impact on cognitive prognosis. This study was based on individuals who merited two cognitive assessments > or =10 years apart and hence is biased in favor of those with the most severe forms of refractory epilepsy and those with decline.
Thompson
Pamela J
PJ
Department of Clinical and Experimental Epilepsy, Institute of Neurology UCL, London, UK. pam.thompson@epilepsynse.org.uk
Duncan
John S
JS
D000328:Adult; D003072:Cognition Disorders / Q000175:diagnosis* / Q000453:epidemiology; D015897:Comorbidity; D004827:Epilepsy / Q000175:diagnosis* / Q000453:epidemiology / Q000628:therapy; D004830:Epilepsy, Tonic-Clonic / Q000175:diagnosis / Q000453:epidemiology / Q000628:therapy; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging; D008297:Male; D009483:Neuropsychological Tests / Q000706:statistics & numerical data; D011379:Prognosis; D012044:Regression Analysis; D012189:Retrospective Studies; D012720:Severity of Illness Index; D013575:Syncope / Q000175:diagnosis / Q000453:epidemiology; D016896:Treatment Outcome; D006113:United Kingdom / Q000453:epidemiology