Objective Recently, few studies have tried to compare patients affected by psychogenic non-epileptic seizures (PNES) and patients affected by functional motor symptoms (FMS) from a demographic, clinical and psychological angle. Nevertheless, as far as we are aware, no previous study has compared those two groups from an aetiopathological point of view. The aim of our study was to assess levels of dissociation and its subcomponents (detachment and compartmentalization), alexithymia and interoceptive sensitivity in patients with PNES and in patients with FMS.

Method We conducted a cross-sectional study recruiting 20 patients with PNES, 20 patients with FMS and 20 healthy subjects as a control group. All subjects underwent: Dissociative Experience Scale (DES), Somatoform Dissociation Questionnaire SDQ-20), Cambridge Depersonalization Scale (CDS), Toronto Alexithymia Scale (TAS-20), Hamilton Rating Scale for Depression (HAM-D), Hamilton Rating Scale for anxiety (HAM-A), heart beat detection task.

Results Our data suggest that PNES group scored significantly higher than the healthy control group on a measure of detachment CDS). As a result also the DES score, which is a measure of psychoform dissociation, was significantly higher that the healthy control group. On the other hand patients affected by FMS scored significantly higher than the healthy control group on a measure of compartmentalization but were no more likely to report experiences of detachment on the CDS. Our data suggest that patients affected by PNES and FMS are significantly more alexithymic than healthy controls, with a third of them patients reaching full criteria for alexithymia.

Conclusion We propose a model where a different stressor (psychological for PNES and physical for FMS) leads to the development of the specific symptom through specific aetiopathological mechanisms.