Utility of different seizure induction protocols in psychogenic nonepileptic seizures

Psychogenic non epileptic seizure (PNES) can be induced by several induction tests but their relative usefulness has not been evaluated. In this study, we report the sensitivity and specificity of various induction tests in the diagnosis of PNES and assess their discomfort level. The induction tests were: (a) compression of temple region (CTR), (b) verbal suggestion (VS), (c) tuning fork application (TFA), (d) moist swab application (MSA), (e) torch light stimulation (TLS) and (f) saline injection (SI). Up to 3 trials were done for each test except for normal saline injection which was given once. For comparison of these tests, patients with epileptic seizures were included as controls. The time to precipitate PNES was recorded and patients' discomfort levels were noted on a 0-10 scale. Video EEG was recorded in the PNES patients. 140 patients with PNES and 50 controls with epileptic seizures were included. The diagnostic yield of CTR was 65.7%, TFA 61.4%, MSA 60.7%, SI 55.6%, VS 54.3% and TLS 40.7%. These tests did not induce seizures in the controls. All these tests had 100% specificity and 100% positive predictive value in the diagnosis of PNES. The maximum discomfort was reported with SI and minimum with MSA. The similarity of efficacy and discomfort with CTR and TFA appear to be the most optimal induction techniques when compared with VS, AMS, TLS, and SI.