Mirror therapy reduces excessive variability of motor network in stroke patients: a randomized controlled trial.

Background: Mirror therapy (MT) has been demonstrated as an effective intervention for promoting motor recovery post-stroke. Existing neuroimaging studies have demonstrated that the efficacy of MT is associated with its effect to increase the strength of brain activity and functional connectivity in the bilateral M1. However, its modulation on brain dynamics, which also hold physiological significance, remains unknown.

Aim: To investigate the potential influence of MT on brain dynamics in stroke patients.

Design: A randomized, single-blinded, controlled trial.

Setting: Inpatient.

Population: Fifty first-ever unilateral stroke patients with motor dysfunctions were recruited and randomly assigned to either an MT group (N.=25) or a conventional therapy (CT) group (N.=25) for a 4-week intervention.

Methods: Motor function assessments and resting-state fMRI scans were conducted both before and after the intervention. Images from sixteen healthy subjects were used as controls. A dynamic analysis of the fMRI data was performed using measures of the dynamic fractional amplitude of low-frequency fluctuation (dfALFF) and dynamic voxel-mirrored homotopic connectivity (dVMHC).

Results: Aberrant dynamics, characterized by increased variability (decreased stability) in spontaneous activity and interhemispheric functional connectivity in sensorimotor networks, were observed in stroke patients. MT but not CT intervention led to reduced variability of spontaneous activity in the ipsilesional primary motor cortex (M1) and interhemispheric M1 functional connectivity, which further exhibited a correlation with motor improvement. Notably, reduced variability of spontaneous activity showed significant mediation effects in the prediction of motor recovery with reduced variability of interhemispheric functional connectivity.

Conclusions: MT may reduce the excessive variability of interhemispheric M1 functional connectivity, thereby stabilizing the activity of ipsilesional M1 and then facilitating motor recovery.

Clinical rehabilitation impact: This study highlights the unique role of MT in addressing abnormal brain dynamics, emphasizing its addition to standard rehabilitation protocols.