Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Previous studies have shown that after injury to the hand representation in primary motor cortex (M1), size of the spared hand representation decreased dramatically unless the unimpaired hand was restrained and monkeys received daily rehabilitative training using the impaired fingers. The goal of this study was to determine if restriction of the unimpaired hand was sufficient to retain spared hand area after injury or if retention of the spared area required repetitive use of the impaired limb. After infarct to the hand area of M1 in adult squirrel monkeys, the unimpaired hand was restrained by a mesh sleeve over the unimpaired arm. Monkeys did not receive rehabilitative training. Electrophysiologic maps of M1 were derived in anesthetized monkeys before infarct and 1 month after infarct by using intracortical microstimulation. One month after the lesion, the size of the hand representation had decreased. Areal changes were significantly smaller than those in animals in a previous study that had received daily repetitive training after infarct (p < 0.05). Areal changes were not different from those in a group of animals that received neither rehabilitative intervention nor hand restraint after injury. These results suggest that retention of hand area in M1 after a lesion requires repetitive use of the impaired hand.

No abstract

Purpose:To examine the possibility of performing highresolution MRI (microneurography) on peripheral nerves. Materials and Methods:A specific radio frequency (RF) coil was developed to probe the human median nerve at a magnetic field strength of 9.4 T and tested on three excised samples by acquiring microneurograms. Results:The microneurograms revealed neuronal tissue constituents at subfascicular level. The contrast features on proton-density and T1-and T2-weighted images were described and compared. The microscopic water movement was quantified using diffusion weighting parallel and orthogonal to the neuronal fiber orientation. The characteristics of anisotropic diffusion in the median nerve were comparable to those reported from other biological tissues (white matter and kidney). Conclusion:The results overall suggest that microneurography might provide new noninvasive insights into microscopic gross anatomy of the peripheral nerve, injury evaluation, and efficacy of repair, although the feasibility at current clinically relevant field strengths is yet to be determined.

Application of these imaging techniques to clinical scanners could provide physicians with a tool that is capable of grading the severity of nerve injuries and providing indications for surgery in the early postinjury phase.