Intracortical and interhemispheric excitability changes in arm amputees: A TMS study

Abstract

ObjectiveTo evaluate cortical circuits and excitability of the motor cortex in the hemisphere contralateral to the affected (AH) and to the unaffected arm (UH), in upper limb amputees. MethodsMotor evoked potentials (MEP) were recorded in 17 subjects who had upper limb amputation: 11 trans-radial (TR) and 6 trans-humeral (TH). Motor thresholds (MT), short interval intracortical inhibition (SICI), and interhemispheric inhibition (IHI) in the available arm muscles of the stump were evaluated. ResultsThere was no significant difference in MT between hemispheres. SICI was preserved in TR but not in TH group. Additionally, in the TR group, the MEP amplitudes in AH were higher than in UH. A significant IHI was observed in the whole sample but not in each hemisphere or patient group. ConclusionsIn our population of TR amputees, we found increased corticospinal excitability in the AH with preserved intracortical inhibition. This finding was not observed in the TH population. SignificanceUnderstanding the changes in intracortical excitability in amputees may enhance knowledge of the functional reorganization of the brain in the post-amputation phase, bringing useful information for prosthetic rehabilitation.