Alteration of Interhemispheric Inhibition in Patients With Lateral Epicondylalgia

Yosuke Sato; Shun Takanaka; Shin-Ichi Izumi

doi:10.1016/j.jpain.2023.11.023

Alteration of Interhemispheric Inhibition in Patients With Lateral Epicondylalgia

J Pain. 2023 Dec 6:104440. doi: 10.1016/j.jpain.2023.11.023. Online ahead of print.

Authors

Yosuke Sato¹, Shun Takanaka², Shin-Ichi Izumi³

Affiliations

¹ Course of Rehabilitation, Department of Health Sciences, Tohoku Fukushi University, Aoba-ku, City, Miyagi, Japan; Department of Physical Medicine and Rehabilitation, Tohoku University Graduate School of Medicine, Sendai City, Miyagi, Japan.
² Department of Physical Medicine and Rehabilitation, Tohoku University Graduate School of Medicine, Sendai City, Miyagi, Japan.
³ Department of Physical Medicine and Rehabilitation, Tohoku University Graduate School of Medicine, Sendai City, Miyagi, Japan; Graduate School of Biomedical Engineering, Tohoku University, Sendai City, Miyagi, Japan.

PMID: 38065465
DOI: 10.1016/j.jpain.2023.11.023

Abstract

Patients with lateral epicondylalgia (LE) show alterations in the primary motor cortex (M1) contralateral to the affected side. Cortical alterations have been investigated by measuring intracortical facilitation/inhibition; however, their association with pain remains controversial. Furthermore, no studies have investigated changes in interhemispheric inhibition (IHI). IHI can be assessed using the ipsilateral silent period (iSP) known as the temporary inhibition of electromyographic activity evoked by transcranial magnetic stimulation in the ipsilateral M1 of the contracting muscle. To better understand the relationship between cortical alterations and pain in LE, this observational study investigated the relationship between iSP and pain in LE. Twenty-seven healthy volunteers and 21 patients with LE were recruited. The duration of iSP in the extensor carpi radialis brevis was measured. The IHI asymmetry ratio was calculated to determine the IHI balance. Pain and disability were scored using the Japanese version of the patient-rated elbow evaluation. We observed increased inhibitory input from the ipsilateral M1 on the affected side to the contralateral M1 in LE. Additionally, the IHI balance correlated with pain severity. Hence, regulating imbalanced IHI can potentially decrease lateral elbow pain in LE. PERSPECTIVE: Patients with lateral epicondylalgia (LE) experience persistent pain and cortical alterations. However, there is no established relationship between cortical alterations and pain. This study demonstrated that the interhemispheric inhibition (IHI) balance is correlated with pain. Regulating imbalanced IHI can potentially decrease lateral elbow pain in patients with LE.

Keywords: Interhemispheric inhibition; Ipsilateral silent period; Lateral epicondylalgia; Pain; Transcranial magnetic stimulation.