Dissociation during Mirror Gazing Test in psychogenic nonepileptic seizures and functional movement disorders

Psychogenic nonepileptic seizures (PNES) and functional movement disorders (FMD) seem to represent the two ends of a continuum where different clinical phenotypes represent the manifestation of a common framework, involving dissociation. The aim of the present study was to assess dissociation and its subcomponents through the Mirror Gazing Test (MGT) in these functional neurological disorders (FNDs).

Eleven patients with PNES, 17 with FMD, and 18 healthy controls (HCs) underwent a 10-minute MGT and completed the Strange Face Questionnaire (SFQ), an ad-hoc questionnaire assessing the sensations and perceptions they had looking in the mirror, and a short version of the Clinician-Administered Dissociative States Scale (CADSS).

Patients with PNES, FMD, and HCs did not differ at the total score of the SFQ. Patients with PNES scored higher than HCs at the SFQ-subscale Dissociative Identity/Compartmentalization, at the CADSS Total Score and at its subscale Dissociative Amnesia, while patients with FMD scored higher than HCs at the CADSS subscale Depersonalization.

Patients with FMD reported more sensations falling in the detachment facet of dissociation, while patients with PNES in the compartmentalization one. We hypothesized that both facets of dissociation might be important pathophysiological processes for PNES and FMD and that different instruments (self-report clinical scales vs experimental tasks) might be able to detect different facets in different populations because they assess, respectively, "trait" and "state" dissociation.