Normalized activation in the somatosensory cortex 30years following nerve repair in children: an fMRI study

The clinical outcome following a peripheral nerve injury in the upper extremity is generally better in young children than in teenagers and in adults, but the mechanism behind this difference is unknown. In 28 patients with a complete median nerve injury sustained at the ages of 1-13years (n=13) and 14-20years (n=15), the cortical activation during tactile finger stimulation of the injured and healthy hands was monitored at a median time since injury of 28years using functional magnetic resonance imaging (fMRI) at 3 Tesla. The results from the fMRI were compared with the clinical outcome and electroneurography. The cortical activation pattern following sensory stimulation of the median nerve-innervated fingers was dependent on the patient's age at injury. Those injured at a young age (1-13years) had an activation pattern similar to that of healthy controls. Furthermore, they showed a clinical outcome significantly superior (P=0.001) to the outcome in subjects injured at a later age; however, electroneurographical parameters did not differ between the groups. In subjects injured at age 14-20years, a more extended activation of the contralateral hemisphere was seen in general. Interestingly, these patients also displayed changes in the ipsilateral hemisphere where a reduced inhibition of somatosensory areas was seen. This loss of ipsilateral inhibition correlated to increasing age at injury as well as to poor recovery of sensory functions in the hand. In conclusion, cerebral changes in both brain hemispheres may explain differences in clinical outcome following a median nerve injury in childhood or adolescence.