Abstract
Background Animal studies have demonstrated complex cortical reorganization following peripheral
nerve lesion. Central projection fields of intact nerves supplying skin areas which
border denervated skin, extended into the deafferentiated cortical representation
area. As a consequence of nerve lesions and subsequent reorganization an increase
of the somatosensory evoked potentials (SEPs) was observed in cats when intact neighbouring
nerves were stimulated. An increase of SEP-components of patients with nerve lesions
may indicate a similar process of posttraumatic plastic cortical reorganization.
Methods To test if a similar process of post-traumatic plastic cortical reorganization does
occur in humans, the SEP of intact neighbouring hand nerves were recorded in 29 patients
with hand nerve lesions. To hypothetically explain the observed changes of SEP-components,
SEP recording following paired stimulation of the median nerve was performed in 12
healthy subjects.
Results Surprisingly 16 of the 29 patients (55.2%) showed a reduction or elimination of N35,
P45 and N60. Patients with lesions of two nerves showed more SEP-changes than patients
with a single nerve lesion (85.7%; 6/7 nerves; vs. 34.2%; 13/38 nerves; Fisher’s exact
test, p < 0.05). With paired stimulation a suppression of the amplitude of N20, P25
and P45 (p < 0.05; sign test), and a marked increment of N35 (p < 0.05; sign test)
and N60 (not significant; sign test) of the second response could be observed.
Conclusion The results of the present investigation do not provide evidence of collateral innervation
of peripherally denervated cortical neurons by neurons of adjacent cortical representation
areas. They rather suggest that secondary components of the excitatory response to
nerve stimulation are lost in cortical areas, which surround the denervated region.
