Differential Effect of M1 and Cerebellar Repetitive Transcranial Magnetic Stimulation on Balance Performance in Stroke

Comprehensive Summary

The primary motor cortex and the cerebellum are the leading brain regions involved in balance and movement. These areas have been studied using noninvasive brain stimulation to determine when balance improves after stroke; however, no optimal stimulation targets have been identified. Due to this, the researchers used repetitive transcranial magnetic stimulation (rTMS) to assess balance in individuals and compare the roles of the primary motor cortex and the cerebellum. Individuals who have chronic stroke were used in this study with a single application of 5-Hz rTMS to each of the aforementioned areas. To assess balance, the Limits of Stability (LOS) and the modified Clinical Test of Sensory Interaction on Balance (mCTSIB) were tested before and after rTMS. The results showed that rTMS had significant improvements in the primary motor cortex compared with the cerebellum when using LOS. Using the mCTSIB sway index, when assessed under eyes-closed conditions, the primary motor cortex improved on firm surfaces, and the cerebellum improved on foam surfaces. Although the researchers emphasize the need for future studies, they concluded that the primary motor cortex and the cerebellum are viable targets that improve a patient's balance using rTMS. Future research would provide information on noninvasive brain stimulations that are tailored to patients, which could be helpful, as the primary motor cortex is involved in anticipatory balance, and the cerebellum is involved in reactive balance, which was determined based on the LOS and mCTSIB sway index.

Outcomes and Implications

One of the most debilitating symptoms associated with strokes is impairments in an individual's balance, which can cause them to not only fall, but also lead to long-term disabilities. It is important to understand the brain regions associated with balance, and that can cause impairments following stroke. This study provides important results on balance performance following noninvasive brain stimulation of the primary motor cortex and the cerebellum. Although future research is needed, the authors claim that understanding the specific brain regions associated with different balance deficits can help create individualized treatment plans.