Case series evidence for changed interhemispheric relationships in cortical structure in some amputees

Limb amputation and related changes in body feelings are associated with cortical functional reorganization that is reflected by increased interhemispheric asymmetry of body maps in the postcentral somatosensory cortex (PCS). As a pilot test to determine if limb amputation affects interhemispheric symmetry in PCS structure, we used MRI and computational morphometry to examine interhemispheric relationships of PCS thicknesses in a case series of eight lower limb amputees compared with 11 control subjects. As a further control, the same relationships were compared in the lateral occipital visual cortex (LOV) which, by nature of its visual connectivity, would be expected to be less related to amputation. The PCS thicknesses in the left and right hemispheres were positively related in control subjects, but not in amputees. The range of the PCS interhemispheric thickness differences (ID) in amputees was larger than the range in control subjects, and four of eight amputees had PCS ID that were at or above the maximal control subject ID. In contrast, LOV thicknesses in the two hemispheres were positively related and LOV ID ranges were similar in both amputees and control subjects. The results from this case series suggest the hypothesis that amputation alters PCS interhemispheric thickness relationships in some amputees. Further tests of this hypothesis would be useful to determine whether changes in structural symmetry contribute to known post-amputation alterations in PCS functional map symmetry and body feeling.