Predictive value of induction of psychogenic seizures by suggestion

Induction by suggestion has previously been reported to be effective in the diagnosis of psychogenic seizures (PS). However, the sensitivity and specificity of this procedure has not previously been studied. Results of induction of PS by suggestion were analyzed in 93 patients with purely PS. The diagnosis of PS was based on the recording of a clinical event on video-electroencephalography, the absence of clinical or electroencephalography the absence of clinical or electroencephalographic evidence of epilepsy, and the subsequent followup and withdrawal of anticonvulsants supporting the diagnosis of PS. A control-group was composed of 20 patients with epilepsy in which induction was tried. Both groups were comparable for age, sex, and educational level. Induction was performed following a standardized protocol. The test was carried out placing a colored patch on the neck. The test was considered positive when the induced clinical events were typical, according to a witness familiar with the patient's seizures. Induction was positive in 72 of 93 cases with PS and in none with epilepsy. Sensitivity of this test for the diagnosis of PS was 77.4%, specificity 100%, positive predictive value 100%, and negative predictive value 48.7%.