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Paquette P.1,2, Higgins J.1,2, Gagnon D.H.1,2
1Université de Montréal, School of Rehabilitation, Faculty of Medicine, Montréal, Canada, 2Centre for Interdisciplinary Research in Rehabilitation of Greater Montreal-Institut de Réadaptation Gingras-Lindsay-de-Montréal, Centre Intégré Universitaire de Santé et de Services Sociaux du Centre-Sud-de-l'Île-de-Montréal, Montréal, Canada
Background: Neural mobilization exercises are advocated for individuals affected by carpal tunnel syndrome (CTS). However, little is known about the mechanisms underlying the potential beneficial effects of these exercises. The use of ultrasound imaging measures to quantify median nerve integrity and neurodynamics at the wrist, and of transcranial magnetic stimulation to quantify corticospinal excitability may increase understanding of the effects of these exercises in individuals with CTS.
Purpose: To assess the effects of a home-based neural mobilization program on median nerve integrity and neurodynamics at the wrist (i.e., cross-sectional area and longitudinal excursion) and corticospinal excitability of a thumb muscle.
Methods: Fifteen individuals with confirmed CTS (6 males, 9 females; mean age=48.1±13.1 years; 90% bilateral involvement) completed a four-week, home-based neural mobilization exercise program targeting the median nerve. This program involved upper limb and neck movements that simultaneously increased tension at one end of the nerve bed and released tension at the other (i.e., sliding paradigm). Clinical and laboratory assessments were completed bilaterally before and after the program. Pain and upper limb function were assessed using the West Haven-Yale Multidimensional Pain Inventory and the Disability of the Arm, Shoulder and Hand questionnaires, respectively. Ultrasound images and videos were recorded transversely at the proximal carpal tunnel and longitudinally about five centimeters proximal to the wrist, during three distinct neural mobilization techniques. Using custom image analysis software, the median nerve cross-sectional area and longitudinal excursion were computed. Transcranial magnetic stimulation was performed to evoke motor responses of the abductor pollicis brevis muscle. Corticospinal excitability was calculated by computing the slope of the recruitment curve fitted with a four-parameter sigmoidal function. Paired-sample t-tests and mixed-model analyses of variance for repeated measures were used to determine if pain and functional disabilities of the upper arm, median nerve cross-sectional area, longitudinal nerve excursions, and corticospinal excitability differed significantly following completion of the program. Effect sizes of the neural mobilization program on outcomes were also estimated.
Results: For self-reported outcomes, large and medium statistically significant improvements were found for pain (d=1.07, p 0.01) and upper limb function (d=0.53, p=0.02). Small, non-significant differences were found in the median nerve cross-sectional area (d≤0.10, p≥0.32) and longitudinal excursion (h2≤0.04 p≥0.30) bilaterally. Although not statistically significant, a tendency toward increased excitability was observed on the most symptomatic side (d=0.41, p=0.14).
Conclusion(s): The mechanisms underlying the effects of neural mobilization exercises in individuals with CTS remain unclear although they may preferentially influence corticospinal excitability in comparison to median nerve integrity at the wrist. Corticospinal excitability is a known biomarker of cortical plasticity and could explain the improvement found in self-reported outcomes of pain and function. Future projects should evaluate if greater and additional differences would arise by increasing the duration of the program and by using a different type of neural mobilization (e.g., tensioner) and if these changes would be maintained over time.
Implications: Adding interventions that facilitate corticospinal excitability to musculoskeletal physical therapy interventions traditionally targeting the wrist, hand and fingers may enhance therapeutic effectiveness among individuals with CTS.
Funding acknowledgements: This project was funded by the Ordre professionnel de la physiothérapie du Québec and the Québec Rehabilitation Research Network.
Topic: Musculoskeletal: upper limb
Ethics approval: This project was approved by the ethics committee of the Centre for Interdisciplinary Research in Rehabilitation of Greater Montreal: CRIR-1071-0415.
All authors, affiliations and abstracts have been published as submitted.
