Brain remodeling after chronic median nerve compression in a rat model.

Carpal tunnel syndrome is the most common compressive neuropathy, presenting with sensorimotor dysfunction. In carpal tunnel syndrome patients, irregular afferent signals on functional magnetic resonance imaging are associated with changes in neural plasticity during peripheral nerve injury. However, it is difficult to obtain multi-point neuroimaging data of the brain in the clinic. In the present study, a rat model of median nerve compression was established by median nerve ligation, i.e., carpal tunnel syndrome model. Sensory cortex remodeling was determined by functional magnetic resonance imaging between normal rats and carpal tunnel syndrome models at 2 weeks and 2 months after operation. Stimulation of bilateral paws by electricity for 30 seconds, alternating with 30 seconds of rest period (repeatedly 3 times), resulted in activation of the contralateral sensorimotor cortex in normal rats. When carpal tunnel syndrome rats received this stimulation, the contralateral cerebral hemisphere was markedly activated at 2 weeks after operation, including the primary motor cortex, cerebellum, and thalamus. Moreover, this activation was not visible at 2 months after operation. These findings suggest that significant remodeling of the cerebral cortex appears at 2 weeks and 2 months after median nerve compression.