Abstracts

Rationale: Neurologists often use seizure induction techniques to help identify dissociative seizures (DS, also known as functional seizures or psychogenic nonepileptic seizures) during video-EEG and clinic evaluations. In patients believed to have DS, successful induction produces habitual, stereotyped episodes that help confirm their diagnosis. We characterized patients evaluated for DS in epilepsy monitoring units and compared effectiveness of induction of DS with visual fixation on a moving finger (VF) and standard combined HV/IPS. We also explored the use of VF induction in an outpatient setting. Patients with induced DS can also be administered brief guided relaxation techniques to terminate DS, which serves as an initial treatment and a confirmation that induced episodes are non-epileptic.

Methods: This is a retrospective chart review approved by the Johns Hopkins University IRB. We reviewed all EMU patients seen in the past four years who were diagnosed with DS. We collected patient demographic data (including psychiatric history) and tabulated whether HV/IPS or VF were used on each patient, and if induction successfully produced a habitual episode. We characterized patients with spontaneous DS, patients who had inductions and those who had both. We also reviewed the yield of VF induction in outpatient visits. Patients with combined epileptic and dissociative seizures were excluded from analysis. We determined whether inpatient VF was effective compared to HV/IPS for inducing DS.

Results: We evaluated 239 EMU patients for possible DS during a four-year period. The patients averaged 38 years old (range: 16-89). 116 patients had induction with VF or HV/IPS induction; 41 had both spontaneous DS and induction procedures. A larger proportion of inpatients tested with VF induction had habitual DS (88.0%, n = 22) compared to patients who had HV/IPS induction (62.5%, n = 59) ( χ2 = 5.907, df = 1, p = 0.015). Demographic features were similar between patients who had spontaneous DS and those who did not, except that a higher proportion of male inpatients had spontaneous DS (82.7%) compared to female patients (58.8%) (χ2 = 10.06, df = 1, p< .01). A small portion of patients with suspected DS (4.6%, n = 11) did not experience any episodes during their EMU stay.



Outpatients who had VF induction in the clinic or via telemedicine were demographically similar to inpatients (Table 1). The success rate of DS induction by VF was similar between outpatients (84.2%, n = 16) and inpatients (88.0%, n = 22).


Conclusions: Approximately half of EMU patients required induction to identify and confirm DS (more frequently in female patients). Both VF and HV/IPS effectively provoked habitual DS in EMU patients, though VF was slightly more effective. VF is a simple technique that does not require equipment – the examiner slowly moves their index finger forward and backwards while the patient visually fixates on it. Use of VF induction in an outpatient setting produced similar results to VF induction in EMU patients. Although the study groups were not large, VF produced habitual dissociative seizures in the majority of both inpatients and outpatients and appears to be an efficient induction technique.

Funding: N/A