Neurophysiological studies on patients with sutured median nerves: Faulty sensory localization after nerve regeneration and its physiological correlates

Abstract

In this study 11 patients who had sustained a total traumatic transection of the median nerve at the wrist were investigated 5 to 12 years after nerve suture. Clinical and electrophysiological examinations were carried out, including conventional electromyography and electroneurography. In addition, percutaneous microelectrode explorations of the sutured nerves were done proximal to the site of injury. In all cases the functional neural recovery was incomplete as evaluated by conventional electrophysiological techniques. Primary skin afferent fibers reflecting activity in single regenerated myelinated fibers had virtually normal properties but their peripheral conduction velocity was abnormally slow. The identified units could be categorized as belonging to the four main types of mechanoreceptive units encountered in normal human glabrous skin. Multiunit responses from low-threshold mechanoreceptors had qualitatively normal characteristics but were typically evoked from abnormal types of receptive fields spread out in patches in reinnervated skin. The faulty sensory localization of cutaneous stimuli in nerve regeneration was possibly due to misinterpretation at central levels of signals deriving from misdirected outgrowing fibers innervating these skin patches.