Etiology of epilepsy is a factor in determining cognitive function and intellectual changes over time. The main distinction is between symptomatic epilepsy (which has an identified cause such as stroke or cortical dysplasia) and idiopathic epilepsy (which has no identified cause other than genetic factors).
Lennox5 recognized that cognitive function was twice as likely to deteriorate in the presence of a known cause of epilepsy even if the idiopathic group had more frequent seizures.
In another study, children with idiopathic epilepsy were more likely to conform to the expected normal distribution of intellectual ability for their age.54
A third study demonstrated that patients with symptomatic epilepsy had a mean 6-point drop in IQ during follow-up periods between 1 and 9 years. A group of normal controls had a drop of 0.7 points.17
More recent work has confirmed the poorer prognosis in patients with symptomatic epilepsy. In a longitudinal study of a group of 72 patients with epilepsy, those with the symptomatic form had a significantly lower IQ (89.1) than those with idiopathic epilepsy (102.5) on initial evaluation.23 At their last evaluation, the symptomatic group scored 88.9, versus 104.1 for the idiopathic group.
Reviewed and revised May 2004 by Steven C. Schachter, MD, epilepsy.com Editorial Board.
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