Orienting reaction may help recognition of patients with psychogenic nonepileptic seizures

Psychogenic nonepileptic seizures (PNES) are abrupt, paroxysmal changes in behavior or consciousness that may phenomenologically resemble epileptic seizures. Given the known association between anxiety and PNES, we hypothesized that in these subjects there may be evidence that the nervous system is hypersensitive to external stimuli. We aimed to test our hypothesis by means of the auditory startle reaction (ASR). By investigating ASR, we also had the opportunity to test presence of orienting reaction, which is generally defined as the second phase of response after the auditory stimulus, with longer latency.

We included 22 patients diagnosed as PNES and 25 age- and gender-matched healthy subjects. Clinical assessments and ASR recordings were performed. Electrophysiological findings were compared between patients with PNES and healthy subjects, including the presence of an orienting reaction. Orienting reaction was defined as a late response with latency between 100-1000ms.

The mean ages of patients with PNES and healthy subjects were 34.9±12.3 years and 33.3±10.9 years, respectively (P=0.709). All patients were diagnosed as having conversion disorder. Additionally, 19 patients had depressive disorder and four had anxiety. The recruitment pattern of muscles and probability were similar between patients with PNES and healthy subjects. Orienting reaction was solely observed in patients with PNES (n=13, 59.1% of the patients vs. no healthy subject). The sequence and contribution of muscles in the orienting reaction changed almost in all patients. The duration of these responses was long, sometimes more than 200ms.

PNES is associated with orienting reaction. This provides a possible electrophysiological marker of altered nervous system function in patients with PNES and may also reflect the distorted emotional processing in these patients.