People with cerebral palsy have a wide variation in type and severity of motor symptoms. Current clinical classification schemes have been recognized as inadequate for prescribing therapy, and anatomical imaging has limited usefulness for the same purpose. Ideally, a non-invasive measure could be found that both correlates with motor function and is useful for predicting response to interventions such as tendon transfer and botulinum toxin injection. One of the principal methods used to study the human motor systems is transcranial magnetic stimulation (TMS), a non-invasive technique that activates the primary motor cortex. A map of a muscle's representation in motor cortex can be made by stimulation at several points on the scalp. In cerebral palsy one hemisphere may contain the maps of muscles from right and left, and the physical separation of upper and lower extremity muscles may be abnormally small. Quantification of such map abnormalities provides a new way to describe motor system pathology. In the proposed research, the geometry of limb representations will be directly measured by TMS and functional MRI. Metrics will be derived from the distance between one hemisphere's motor representations of a muscle of each limb with one of the other. The distance between muscle representations will be correlated primarily with two measures of motor functioning, the Melbourne Assessment and Gross Motor Function Measure. Anatomical brain abnormalities will be identified by conventional MRI, and used to examine the distribution of the TMS metrics within classes of brain abnormalities. Functional MRI will be used to identify areas of cortex active during movement, then compared with the TMS-derived motor maps. A control group will also be studied to provide norms for comparison. This study will lead to an understanding of motor disability in terms of representational abnormalities in the primary motor cortex. Because the TMS measurements are non-invasive, painless, and relatively rapid, this method has promise for motor general application in understanding, classifying, and treating patients with cerebral palsy. ? ?
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