Epilepsy Information

American Epilepsy Society Poster (Abst. 1.352)

Nonepileptic Seizures, epileptic seizures, and intrasubtest scatter

Authors: Robert Trobliger, L. Myers and M. Lancman

Nonepileptic seizures (NES) resemble epileptic seizures but are typically identified by a lack of epileptogenic activity on EEG studies. While the use of EEG studies remains the gold standard in separating such patients from those with epileptic seizures, patients in question are often also administered a battery of neuropsychological tests and questionnaires to provide further substantiation of their apparent psychological etiology. Proper diagnosis is important, as presentation of diagnostic findings may lead to cessation of or a decrease in seizure activity. The aim of this study is to explore the potential utility of another possible marker of nonepileptogenic seizures - amount of intrasubtest scatter on subtests of intelligence testing. In this case, it was suggested that patients with a history of seizure activity would demonstrate significantly greater amounts of scatter than those with suspected nonepileptic seizures. That is, it was suggested that organic factors would play a larger role than nonorganic factors in producing intrasubtest scatter.


A total of 26 cases were included in the study, 13 presurgical cases with a documented history of epileptogenic activity on EEG studies and 13 nonepileptic seizure cases with a documented history of no epileptogenic activity on EEG studies. The mean ages of the two samples were 43.69 and 42.46, and the mean education levels were 13.46 and 13.00, with no significant differences between the groups. All of the cases had previously completed a neuropsychological battery, including administration of the Wechsler Abbreviated Scale of Intelligence. There were no significant differences between the two groups for the WASI IQ indices or subtest raw or scaled scores. Amount of scatter was calculated for each of the four subtests for each patient. Differences in mean amounts of intrasubtest scatter on the four subtests between the two groups were examined using a MANOVA approach.

No significant differences were found between the two groups on the four WASI subtests using six different approaches for calculating intrasubtest scatter.

Analyses demonstrated no significant differences for amounts of intrasubtest scatter. Further research with intrasubtest scatter with larger samples may produce different results. These findings initially suggest little utility for employing intrasubtest scatter in distinguishing between those with epileptic seizures and those with nonepileptic seizures. This is consistent with research demonstrating no differences between the two groups on measures of intelligence or neuropsychological testing. However, the results also reinforce the suggestion that a given diagnosis should not be made on the basis of one clinical factor but rather a combination of factors. Furthermore, neuropsychological testing, and intrasubtest scatter in particular, remain important aspects of a patient’s evaluation for documenting current levels of cognitive functioning (as well as variability within such) as markers for possible treatment, depending on the severity and persistence of such.