Objective: To explore the possible relationship between corticomotor inhibition assessed by transcranial magnetic stimulation (TMS) and balance performance in individuals with Parkinson’s disease (PD). Also, to investigate whether the correlations were different when corticomotor inhibition was assessed in different postural positions.

Background: Balance dysfunction is a major issue in people with PD. It may worsen progressively with disease progression. Increasing evidence supports the involvement and participation of the motor cortex in postural control. Abnormal changes in corticomotor excitability were observed in PD, especially disinhibition in the primary motor cortex (M1). These alterations are related to their motor symptom severity and disease progression. It is supposed that the abnormalities in corticomotor inhibition affect balance performance in people with PD.

Method: Thirty-nine people suffering from PD with Hoehn and Yahr stages 1-3 were recruited. All participants received TMS measures of corticomotor inhibition involving corticospinal inhibition and intracortical inhibition in three different positions (lying, sitting, and standing). Balance performance was evaluated, including static, dynamic, and functional balance.

Results: Participants’ ages ranged from 52 to 76, and the disease duration was between 2 months and 30 years. The majority of the individuals were in the early stages of the disease, with 59% being in stages 1 and 1.5. Our findings showed both corticospinal inhibition and intracortical inhibition were related to functional balance. Individuals with lower corticomotor inhibition have poor balance performance. Furthermore, the results showed the TMS outcomes of corticomotor inhibition in the sitting position to be stable and sensitive.

Conclusion: The present study established the relationship between corticomotor inhibition and balance performance in PD. In all three positions of TMS measurements, the results during the resting state (lying and sitting) were similar. However, sitting was recommended for the measurement protocol of TMS in PD. The present findings may provide a possible interpretation of the modulation of cortical excitability related to balance performance.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/relationship-between-balance-performance-and-corticomotor-inhibition-in-individuals-with-parkinsons-disease/