Psychogenic nonepileptic seizures: should we use response to AEDS as a red flag for the diagnosis?

Lack of response to anti-epileptic drugs (AEDS) is considered a "red flag" pointing to a diagnosis of Psychogenic Nonepileptic Seizures (PNES). On the other hand, placebo effects are relevant in any medical condition with a complex psychosocial component. We aimed to evaluate the presence and frequency of a placebo response in patients with sole PNES and explore its impact on diagnostic delay.

We reviewed the medical records of 102 patients referred for video EEG monitoring and diagnosed with PNES. Patients with PNES and epilepsy were excluded. The response to AEDs was analyzed according to patients' reports and medical records. Patients were classified, according to the response to AEDs, in two groups: responders (patients achieving remission) and non-responders. Then, we compared the diagnostic delay from the first event to the final diagnosis between these groups.

Forty-seven patients (79.7%) with sole PNES who were using AEDs were identified. Twenty-two patients (46.8%) had reported complete or partial remission of PNES with mean response duration of 7.2 months (SD+9.6 months). The time delay of the diagnosis in the AED responder group was 10.6 years; the delay in non-responders was 5.6 years (p=0.035).

Patients with sole PNES receiving AEDs can go into PNES remission. A favorable response to AEDs is likely to be interpreted as supporting a diagnosis of epilepsy and is associated with diagnostic delay. Physicians should bear in mind that patients with PNES may be particularly vulnerable to placebo effects.