The Journal of Neuroscience, December 15, 2000, 20(24):9277-9283
Neuroplastic Changes Related to Pain Occur at Multiple Levels of
the Human Somatosensory System: A Somatosensory-Evoked Potentials Study
in Patients with Cervical Radicular Pain
Michele
Tinazzi1,
Antonio
Fiaschi1,
Tiziana
Rosso1,
Franco
Faccioli2,
Johannes
Grosslercher2, and
Salvatore M.
Aglioti3
Dipartimenti di Scienze Neurologiche e della Visione,
1 Sezione di Neurologia Riabilitativa and
2 Sezione di Neurochirurgia, Università di Verona,
37134 Verona, Italy, and 3 Dipartimento di Psicologia,
Università di Roma "La Sapienza," and Istituto di Ricovero e
Cura a Carattere Scientifico, Fondazione Santa Lucia, 00179 Rome,
Italy
Studies suggest that pain may play a major role in determining
cortical rearrangements in the adult human somatosensory system. Most
studies, however, have been performed under conditions whereby pain
coexists with massive deafferentation (e.g., amputations). Moreover, no
information is available on whether spinal and brainstem changes
contribute to pain-related reorganizational processes in humans. Here
we assess the relationships between pain and plasticity by recording
somatosensory-evoked potentials (SEPs) in patients who complained of
pain to the right thumb after a right cervical monoradiculopathy caused
by compression of the sixth cervical root, but did not present with
clinical or neurophysiological signs of deafferentation. Subcortical
and cortical potentials evoked by stimulation of digital nerves of the
right thumb and middle finger were compared with those obtained after
stimulation of the left thumb and middle finger and with those obtained
in a control group tested in comparable conditions. Amplitudes of spinal N13, brainstem P14, parietal N20 and P27, and frontal N30 potentials after stimulation of the painful right thumb were greater than those of the nonpainful left thumb and showed a positive correlation with magnitude of pain. This right-left asymmetry was
absent after stimulation of the patients' middle fingers and in
control subjects. Results suggest that chronic cervical radicular pain
is associated with changes in neural activity at multiple levels of the
somatosensory system. The absence of correlation between the amplitude
of spinal, brainstem, and cortical components of SEPs suggests that
enhancement of cortical activity is not a simple amplification of
subcortical enhancement.
Key words:
pain; upper limb SEPs; somatosensory-evoked potentials; somatosensory system; deafferentation; brain plasticity; cervical
radiculopathy
Copyright © 2000 Society for Neuroscience 0270-6474/00/20249277-07$05.00/0