Greater Cortical Activation and Motor Recovery Following Mirror Therapy Immediately after Peripheral Nerve Repair of the Forearm

Cortical reorganization occurs immediately after peripheral nerve injury, and early sensorimotor training is suggested during nerve regeneration. The effect of mirror therapy and classical sensory relearning on cortical activation immediately after peripheral nerve repair of the forearm is unknown. Six participants were randomly assigned to the mirror-therapy group or the sensory-relearning group. Sensorimotor training was conducted in a mirror box for 12 weeks. The mirror-therapy group used mirror reflection of the unaffected hand in order to train the affected hand, and the sensory-relearning group trained without mirror reflection. Semmes-Weinstein Monofilaments (SWM) test, static 2-point discrimination test (S-2PD), grip strength, and the Disabilities of the Arm, Shoulder and Hand (DASH) scores were measured at baseline, the end of the intervention (T1), and 3 months after the intervention (T2). Finger and manual dexterity were measured at T1 and T2, and a functional MRI (fMRI) was conducted at T1. All participants showed improvement in the SWM, S-2PD tests, upper extremity function, and grip strength after the intervention at T1, except for the participant who injured both the median and ulnar nerves in the sensory-relearning group. In addition, the mirror-therapy group had better outcomes in finger dexterity and manual dexterity, and fMRIs showed greater activation in the multimodal association cortices and ipsilateral brain areas during motor tasks. This study provides evidence-based results confirming the benefits of early sensorimotor relearning for cortical activation in peripheral nerve injury of the forearm and different neuroplasticity patterns between mirror therapy and classical sensor relearning.