Sensory cortical re-mapping following upper-limb amputation and subsequent targeted reinnervation: a case report

This case study demonstrates the ability of sensory cortical representations to remap following arm amputation and subsequent targeted reinnervation (TR). Previous human studies have demonstrated functional plasticity in the primary sensory cortex months or years after amputation of the upper arm, forearm, the hand or a single finger, or after subsequent replantation. Targeted reinnervation, a surgical procedure that re-routes inactive, residual sensorimotor nerves previously responsible for innervating the missing limb to alternative muscle groups and skin areas [1-3], has shown the ability to restore a subject's sensation in the reinnervated skin areas. Whether this new technique causes analogous cortical remapping in a similar timeframe as following hand replantation is still unknown. In order to answer this question, high-density electroencephalography was used to study whether the original sensory cortical territory was regained after TR. Before TR, we found that the cortical response to sensory electrical stimulation in the residual limb showed a diffuse bilateral pattern without a clear focus in either the time or spatial domain, Two years after TR, the sensory map of the reinnervated median nerve shifted back to a close-to-normal, predominantly contralateral pattern. The overall trend of TR-induced sensory remapping is similar to previous reports related to hand replantation but occurs over a slower timeframe. This relatively slower progress after TR as compared to after hand replantation could be because TR is performed months or even years after amputation, while hand replantation was performed immediately after the injury. This work provides new evidence for long term plasticity in the human brain.