BILATERAL MOVEMENT REGULATE IMBALANCED INTERHEMISPHERIC INHIBITION IN PATIENTS WITH LATERAL ELBOW EPICONDYLALGIA

Y. Sato^1,2, S. Takanaka², S.-I. Izumi^2,3

¹Tohoku Fukushi University, Course of Rehabilitation, Department of Health Sciences, Sendai, Japan, ²Tohoku University Graduate School of Medicine, Department of Physical Medicine and Rehabilitation, Sendai, Japan, ³Tohoku University Graduate School of Biomedical Engineering, Department of Physical Medicine and Rehabilitation, Sendai, Japan

Background: Patients with lateral elbow epicondylalgia (LE) have sensory deficits on the non-affected side. The deficits suggest an alteration of the cerebral hemispheres. Previous study revealed that the excitability of the primary motor cortex in patients with LE was less than that of healthy participants. Furthermore, we have demonstrated that interhemispheric inhibition (IHI) is altered in patients with LE. These findings imply that alteration of the cerebral hemispheres could be a new target for physical therapy.
The bilateral movement, defined as synchronous training of the right and left limbs, were known as an effective intervention for regulating imbalanced IHI in stroke patients. Even in patients with LE, the bilateral movement may regulate imbalanced IHI and have a potential for effective intervention to facilitate physical therapy.

Purpose: To investigate whether bilateral movement regulates IHI in patients with LE.

Methods: Twelve right-handed patients with right LE participated in this study. We measured IHI between homologous primary motor cortex (M1) by analyzing the ipsilateral silent period (iSP) evoked by single‐pulse focal TMS. iSP duration was considered the parameter indicating IHI in this study, an increased iSP duration means greater interhemispheric inhibition. In this study, the iSP duration of both directions was recorded under two conditions. In unilateral conditions, TMS pulses were delivered homologous M1 during voluntary dorsiflexion of the unilateral wrist joint. In bilateral conditions, TMS pulses were delivered homologous M1 during voluntary dorsiflexion of both wrist joints simultaneously. The iSP duration was calculated as the time course between iSP onset and offset in averaged EMG. The iSP onset was defined as the point at which EMG of extensor carpi radialis brevis (ECRB) fell below 75% of the mean pre-TMS EMG for more than 5 ms in the time window of 30–60 ms after the TMS. The offset of iSP was defined as the point at which the EMG returned more than 75% of the mean pre‐TMS EMG. The iSP duration in the EMG from right ECRB (TMS pulses were delivered in right hemisphere; iSP_RH-LH) and in the EMG from left ECRB (TMS pulses were delivered in left hemisphere; iSP_LH-RH) in two conditions were used for statistical analysis. A repeated ANOVA was performed comprising within-subjects factors of conditions and directions. Post hoc test was performed with the Bonferroni correction.

Results: Repeated ANOVA revealed significant interaction (F (1, 11) = 19.860, p < 0.001), and post hoc test revealed that iSP_RH-LH at bilateral condition was significantly reduced from iSP_RH-LH at uilateral condition (p < 0.001).

Conclusions: Imbalanced interhemispheric inhibition is regulated during bilateral movement in patients with LE.

Implications: Bimanual movement may be an effective intervention for patients with LE.

Funding acknowledgements: This work was supported by MEXT KAKENHI Grant Number JP20K19385.

Keywords:
Lateral elbow pain
Interhemispheric Inhibition
Bilateral movement

Topics:
Musculoskeletal: upper limb
Pain & pain management

Did this work require ethics approval? Yes

Institution: Tohoku University Graduate School of Medicine

Committee: the Ethics Committee of Tohoku University Graduate School of Medicine

Ethics number: 2021‐1‐656