Cortical reorganization after digit-to-hand replantation - Case report

Functional recovery after digit-to-hand replantation depends on the interac tion of various factors. In addition to peripheral mechanisms, cortical and subcortical reorganization of digit representation may play a substantial role in the recovery process. However, cortical processes during the first months after replantation are not well understood. In this 25-year-old man who had traumatically lost digits II to V (DII-V) o n his right hand, the authors used magnetoencephalographic source imaging t o document the recovery of somatosensory cortical responses after tactile s timulation at four sites on the replanted digits. Successful replantation o f DIV and DV was accomplished at the original position of Dm and DIV with m ixed innervation. Cortical evoked fields could be recorded starting from th e 10th week after digit-to-hand replantation. Initially, signals from all s ites showed decreased amplitudes and prolonged latencies. In the subsequent six recordings obtained between the 12th and 55th week postreplantation, a continuous increase in amplitude but only a slight recovery of latencies w ere observed. Components of the recorded somatosensory evoked fields were l ocalized in the primary somatosensory cortex (SI). The localizations of the replanted DIV showed a gradual lateral-inferior shift in the somatosensory cortex over time, indicating cortical reorganization caused by altered per ipheral input. The authors infer from this shift that the original cortical area of the missing finger (DII) was taken over by the replanted finger. From these data the authors conclude that magnetic source imaging might be a reliable noninvasive method to evaluate surgical nerve repair and that co rtical reorganization of SI is involved in the regeneration process followi ng peripheral nerve injury.