Video-electroencephalographic telemetry that captures a habitual attack is the reference standard for distinguishing dissociative attacks from epileptic seizures. The essential safeguard, and the reason home video is so valuable, is confirmation by the patient and family that the recorded event was typical; an atypical event proves nothing. Frequent attacks make capture likely, and the combination of a normal ictal electroencephalogram during a prolonged motionless event with closed eyes provides a documented diagnosis under staged diagnostic criteria.
The staged approach recognizes that video-electroencephalography is not universally available and grades certainty as possible, probable, clinically established or documented according to the history, the witnessed or recorded event and the investigations available. Home smartphone video reviewed by an experienced clinician can by itself support a clinically established diagnosis. Serum prolactin has fallen out of favour because it rises inconsistently, only after generalized and some focal seizures, requires a tightly timed paired sample, and is normal after many genuine seizures, so a normal value does not exclude epilepsy. Around 20 to 50 percent of patients admitted to video telemetry units for refractory epilepsy prove to have dissociative attacks, and 5 to 20 percent of patients with dissociative attacks also have coexistent epilepsy.
On the ABPN blueprint this item maps to the Diagnostic procedures axis, because the competency is selecting the test that will actually change management in a patient already mislabelled as drug resistant. Once documented, the antiseizure medications can be withdrawn and treatment redirected.
Incorrect Answers
- B. A normal interictal electroencephalogram neither confirms nor excludes epilepsy and has already been obtained repeatedly without diagnostic benefit.
- C. Prolactin measurement is unreliable, has fallen out of favour, and a normal value after an attack does not exclude an epileptic seizure.
- D. Repeated structural imaging in a patient with normal previous scans and frequent prolonged motionless events has an extremely low yield.
- E. Adding a fourth antiseizure medication before establishing the diagnosis exposes him to further adverse effects without addressing the actual problem.
Testing Pearls
- Video-electroencephalographic telemetry capturing a habitual attack is the diagnostic reference standard.
- Always confirm with patient and family that the recorded event was typical.
- Staged criteria grade certainty as possible, probable, clinically established or documented.
- Serum prolactin is unreliable and no longer recommended for routine differentiation.
- 5 to 20 percent of patients with dissociative attacks also have epilepsy.
References
- Jankovic J, Mazziotta JC, Newman NJ, Pomeroy SL, editors. Bradley and Daroff's Neurology in Clinical Practice. 8th ed. Philadelphia, PA: Elsevier; 2022. p. 2079.
- LaFrance WC, Baker GA, Duncan R, Goldstein LH, Reuber M. Minimum requirements for the diagnosis of psychogenic nonepileptic seizures: a staged approach: a report from the International League Against Epilepsy Nonepileptic Seizures Task Force. Epilepsia. 2013;54(11):2005-2018.
- Tannemaat MR, van Niekerk J, Reijntjes RH, Thijs RD, Sutton R, van Dijk JG. The semiology of tilt-induced psychogenic pseudosyncope. Neurology. 2013;81(8):752-758.
