The MASC (Mobility of Arm SCore): A short and side-specific tool to assess functional impairment in patients with suspected thoracic outlet syndrome.

Introduction: Thoracic Outlet Syndrome (TOS) is characterized by the positional compression of the brachial plexus and/or subclavian vessels in the cervico-thoraco-brachial region, unilaterally or bilaterally. The functional impact is currently assessed by questionnaires that do not allow side-specific assessment. The Mobility of Arm Score (MASC) questionnaire was designed to be short and assess the functional impact of suspected TOS, emphasizing dynamic tasks and side-specific evaluations.

Methods: We prospectively recruited 200 patients referred to the vascular medicine department of the University Hospital of Angers for suspected TOS. They completed the disability of the arm and shoulder (DASH) and MASC questionnaires. Feasibility was evaluated by comparing the rates of scorable questionnaires using the McNemar test. Pearson's correlation coefficients were calculated to examine the relationship between MASC from the most affected arm and the DASH and Quick-DASH (Q-DASH) scores.

Results: The rate of scorable questionnaires was significantly higher for the MASC (98.5%) than for the DASH (90,5%; p < 0.001) or Quick-DASH (94%; p< 0.001). Pearson correlation coefficients between the MASC score for the most affected arm and the DASH and Q-DASH scores were 0.835 (p<0.001) and 0.825 (p< 0.001), respectively.

Conclusion: The MASC questionnaire demonstrated excellent feasibility and a strong correlation with the DASH and Quick-DASH questionnaires. It offers valuable insights into the laterality of the symptoms, in patients with suspected TOS. Future research should explore the sensitivity to changes of the MASC in the longitudinal follow-up of treated patients to validate these preliminary findings.