To determine whether an in-clinic attention task can distinguish between patients with Functional Movement Disorders (FMD), neurological movement disorders (essential tremor (ET)), and healthy controls (HC).

FMD are movements that are perceived as involuntary, but not due to structural damage or disease in the nervous system. They are difficult to diagnose because they rely on clinical expertise in the absence of confirmatory tests. Objective markers that argue in favor of the diagnosis are needed.

A single-site study in which movement disorders neurologists identified subjects as having FMD or ET from clinic visits. HC were recruited from family members. Exclusion criteria included a Beck Depression Inventory (BDI) score > 17, a Montreal Cognitive Assessment < 24, or history of severe psychiatric disorder. Subjects completed a modified emotional Stroop task. Subjects also completed an FMD Inventory. Level of disability was scored using the modified Rankin Score (mRS). The primary endpoint was the difference in error rate and response time on the Stroop task between groups. Data was analyzed using Wilcoxon test or Fisher’s exact test as appropriate due to small sample size.

50 subjects were screened and 35 were recruited (12 FMD, 11 ET, and 12 HC). 11 subjects with FMD screen-failed due to high BDI. No statistically significant differences were seen in task performance between the groups, although the FMD group made the most errors and had the longest median response time. Significant between-group differences were found in various reported symptom severity and health concern scales, despite a similar mRS between the FMD and ET groups.

A modified emotional Stroop task was not able to distinguish with statistical significance between subjects with FMD, ET, and HC. Self-reported questionnaire responses showed significant differences between groups, lending validity to the FMD Inventory as a useful in-clinic tool for assessing patients with suspected FMD.