Cortical reintegration after facial allotransplantation

Neural plasticity of the brain or its ability to reorganize following injury has likely coincided with the successful clinical correction of severe deformity by facial transplantation since 2005. In this study, we present the cortical reintegration outcomes following syngeneic hemifacial vascularized composite allograft (VCA) in a small animal model. Specifically, changes in the topographic or-ganization and unit response properties of the rodent whisker-barrel somatosensory system were assessed following hemifacial VCA. Clear differences emerged in the barrel-cortex system when comparing naive and hemiface transplanted animals. Neurons in the somatosensory cortex of transplanted rats had decreased sensitivity albeit increased directional sensitivity compared with naive rats and evoked responses in transplanted animals were more temporally dispersed. In addition, receptive fields were of-ten topographically mismatched with the indication that the mismatched topography reorganized within adjacent barrel (same row-arc bias following hemifacial transplant). These results suggest subcortical changes in the thalamus and/or brainstem play a role in hemifacial transplantation cortical plasticity and demonstrate the discrete and robust data that can be derived from this clinically relevant small animal VCA model for use in optimizing postsurgical outcomes.NEW & NOTEWORTHY Robust rodent hemifacial transplant model was used to record functional changes in somatosensory cor-tex after transplantation. Neurons in the somatosensory cortex of face transplant recipients had decreased sensitivity to stimula-tion of whiskers with increased directional sensitivity vs. naive rats. Transplant recipient cortical unit response was more dispersed in temporary vs. naive rats. Despite histological similarities to naive cortices, transplant recipient cortices had a mix of topographically appropriate and inappropriate whiskered at barrel cortex relationships.

Automated summary

This study examines the cortical reintegration outcomes following hemifacial vascularized composite allograft (VCA) in a small animal model. The results suggest that there are changes in the somatosensory system and topographic organization in the barrel-cortex system after hemifacial VCA. The findings also indicate subcortical changes in the thalamus and/or brainstem may play a role in cortical plasticity following hemifacial transplantation.