Mechanism of change in functional neurological (motor) disorder: a pilot study using a single-case experimental design

Abstract

Despite evidence supporting treatments like physical therapy, not all patients with Functional Neurological Disorder (FND) respond adequately. Identifying mechanisms of change in FND treatment could enhance outcomes. This pilot study investigates whether changes in "expectation of capability" predict and precede improvements in "physical functioning" as a mechanism of change in FND. A non-concurrent multiple baseline single-case experimental design (SCED) was conducted with five participants receiving physical therapy using repeated measurements of "expectation of capability" (VAS) and "physical functioning" (physical subscale of RAND-36). The Patient Specific Complaints (PSC) was administered pre- and post-treatment as a secondary measure of "physical functioning." Baseline-corrected Tau showed an increase in "expectation of capability" for one of three participants. Improvements in "physical functioning" were observed in three participants on the RAND-36 and in four on the PSC. Linear mixed-effect models (LMM) indicated a concurrent association between "expectation of capability" and "physical functioning," though no predictive relationship was found. This study provides preliminary insights into a potential mechanism underlying recovery in FND. Changes in "expectation of capability" and "physical functioning" appear to be concurrently associated rather than sequentially ordered. Research with larger samples and refined methodologies is necessary to better understand these changes.