The distribution of epilepsy types varies by age, etiology, provider diagnostic capabilities, and assessment criteria. No recent US study has examined the distribution of epilepsy types in a large, population-based sample of people with epilepsy. We used MarketScan data from January 1, 2010 through September 30, 2015, to estimate the proportion of epilepsy types among all (N=370,570) individuals diagnosed with epilepsy. We identified cases of epilepsy as individuals with at least one International Classification of Disease, 9th version (ICD-9) diagnostic code of 345.X and the use of at least one antiseizure drug described in the 2015 MarketScan Redbook. Unspecified epilepsy was more common (36.8%) than focal-localized epilepsy (24.6%), generalized convulsive epilepsy (23.8%), generalized nonconvulsive epilepsy (8.9%), other forms of epilepsy (5.2%), infantile spasm (0.3%), and epilepsia partialis continua (0.3%). The high proportion of epilepsy classified as unspecified might be lowered by improved training in epilepsy diagnosis and coding.
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