The Early Childhood Epilepsy Severity Scale (E-Chess)

Purpose: We have developed the Early Childhood Epilepsy Severity Scale (E-Chess) to quantify the severity of epilepsy in infants and young children with tuberous sclerosis as an aid to the evaluation of treatment efficacy and the investigation of the influence of epilepsy severity on development. Methods: Twenty infants aged 11-36 months with a diagnosis of tuberous sclerosis participated in the study. From the literature, six potential measures of epilepsy severity were identified: time period over which seizures occurred; seizure frequency; number of seizure types; occurrence and duration of status epilepticus; number of anticonvulsant medications used; response to treatment. The variables were given a score, usually from 0 to 3, a higher score indicating greater severity. For each child, these variables were scored over consecutive 1 year time periods by three independent raters. We employed restricted and nonrestricted factor analytic models to identify the latent structure of the six items. Results: The six severity items had a unidimensional structure. All severity indicators loaded highly on the latent epilepsy severity factor (>0.77), with the exception of the status indicator which had a poor loading (<0.40) and was excluded from further analyses. Goodness of fit indices were all well within the acceptable criteria for model fit. The E-Chess score at 12 months was significantly predictive of scores at 24 and 36 months. Conclusions: A single continuous latent variable accounts for the variation in five of the six epilepsy severity indicators under study. These form the Early Childhood Epilepsy Severity Scale. The predictive validity of the E-Chess was satisfactory. The E-Chess provides an epilepsy severity score that can be easily used to assess epilepsy severity in tuberous sclerosis and would merit evaluation in other early onset childhood epilepsies.