Testing a Potential Marker of Attention for the Diagnosis of Functional Movement Disorders

Abstract

Background: The diagnosis of Functional Movement Disorders (FMD) mostly relies on clinical expertise, with a paucity of confirmatory tests available. More objective markers are needed. We determine whether an in-clinic attention task can aid in diagnosis. Methods: A single-site study comparing subjects with FMD, essential tremor (ET), and healthy controls (HC). Subjects completed a modified Stroop Interference task and standardized questionnaires assessing mood symptoms. Level of disability was estimated by modified Rankin Score (mRS). The primary endpoint was the difference in error rate and response time on the Stroop between groups. Data was analyzed using Wilcoxon test or Fisher’s exact test. Results: 50 subjects were screened and 35 recruited (12 FMD, 11 ET, and 12 HC). No significant differences were seen in task performance between groups, although the FMD group made the most errors and had the longest median response time. Significant between-group differences were found in reported symptom severity and health concerns, despite a similar mRS between FMD and ET groups. Discussion: A modified Stroop task was not able to distinguish with significance between FMD, ET, and HC. Self-reported questionnaire responses showed significant differences with higher prevalence of depression and anxiety and greater perceived disability in patients with FMD despite similar mRS.