Case Studies in Neuroscience: Evidence of motor thalamus reorganization following bilateral forearm amputations.

Following injury, functional improvement can result from central nervous system plasticity. Use-dependent plasticity of motor systems is evident, for example, in recovery of function resulting from rehabilitative interventions. Here, we present a single patient who underwent bilateral microelectrode-guided stereotactic implantation of deep brain stimulating leads for the treatment of essential tremor 52 yr following bilateral arm amputations. The tremor affected his upper extremities and had rendered him unable to perform fine motor tasks with his prostheses, significantly reducing his independence. We found a large territory of neurons in the ventral intermediate nucleus of his thalamus that responded to shoulder protraction, the movement that he used to control fine motor movements of his terminal hook prostheses. We propose that reorganization of this motor nucleus may have occurred secondary to a use-dependent gain of function in neurons that were previously involved in hand movement. NEW & NOTEWORTHY We had a unique opportunity to record neurons in the ventrointermediate (Vim) motor nucleus of thalamus in a patient with essential tremor, decades following bilateral forearm amputations. We demonstrate that a large region of Vim is active during shoulder protraction-the movement used to operate the patient's mechanical prostheses. We suggest that this provides evidence of human motor thalamic plasticity.