The Neuroconnective Endophenotype, A New Approach Toward Typing Functional Neurological Disorder: A Case-Control Study.

Objective: Functional neurological disorder (FND) is a core neuropsychiatric condition that includes both physical and mental symptoms. Recently, a validated clinical phenotype termed neuroconnective endophenotype (NEP), which includes several physical and psychological characteristics together with joint hypermobility (hypermobility spectrum disorders), was found at a significantly higher frequency among patients with anxiety. The purpose of the present study was to examine the presence of the NEP among patients with FND.

Methods: The authors conducted a multicenter case-control study comprising 27 FND patients and 27 healthy control participants (matched by sex and age) ages 13 to 58 years. Eight questionnaires were administered. Proportional differences were examined with Student's t tests, one-way analyses of variance, and chi-square tests.

Results: Differences between FND patients and control participants were observed. FND patients had higher sensory sensitivity, increased prevalence of hypermobility features (including relevant physical signs and symptoms), greater frequency of polarized behaviors, a greater number of both psychiatric and physical comorbidities, and an increase in the characteristics and sensations typical of anxiety. Particularly striking was the presence of the hypermobility spectrum in more than 75% of FND patients compared with 15% among control participants.

Conclusions: FND patients presented higher scores in all five dimensions included in the NEP. Thus, this phenotype, solidifying the original association between anxiety and the hypermobility spectrum, could help to identify an FND subtype when evaluating and managing FND patients, because it provides a new global view of patients' physical and mental symptoms.