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

Abstract

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 somatosensoryevoked 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.

The Effect of Cervical Spine Manipulation on Postural Sway in Patients With Nonspecific Neck Pain

“…Similar findings have been noted in several other studies of the effects of cervical manipulation on individuals with neck pain (Haavik-Taylor & Murphy, 2010a. These findings are significant as previous studies have noted that SEP peak amplitudes generated from painful regions are greater than those elicited from asymptomatic regions, or from controls (Kakigi, Shibasaki, & Ikeda, 1989;Tinazzi, Fiaschi, et al, 2000;Tinazzi, Priori, et al, 2000;Tinazzi et al, 2004;Tinazzi et al, 1998).…”

“…While the exact mechanisms underlying these changes are yet to be determined it is interesting to note that the increases in SEP amplitudes shown by Tinazzi et al were positively correlated with the magnitude of the patients pain (Tinazzi, Fiaschi, et al, 2000;Tinazzi et al, 2004). …”

“…Neuroplastic changes in both the sensory and motor cortices have been seen to take place after only brief periods of painful stimulation Tinazzi, Fiaschi, et al, 2000;. In conjunction with the alterations seen within the musculoskeletal system, it is suggested that these central changes may contribute to the development of chronicity of symptoms and provide an explanation for the changes in muscle activity and functional performance deficits seen in patients with painful disorders .…”

“…A group led by Tinazzi used somatosensory evoked potentials (SEPs) to observe the passage of sensory information from the periphery up, through the spinal cord to supraspinal centres. The results from their studies indicated that symptomatic individuals (including carpal tunnel syndrome, cervical radicular pain and trigeminal neuralgia) have shown greater amplitudes of SEP spinal N13, brainstem P14, parietal N20 and N27 and the frontal N30 peaks in response to stimulation 28 of the painful side, than nerves of asymptomatic individuals (Tinazzi, Fiaschi, et al, 2000;Tinazzi et al, 2004;Tinazzi et al, 1998). The specificity of these changes in peak amplitudes is significant.…”

“…It is proposed that this impairment in postural control is the result of impaired cervical proprioceptive input and 9 maladaptive changes in the central process of sensorimotor integration . Maladaptive changes in response to pain and altered proprioceptive input have been observed on numerous levels of the central nervous system (Avanzino et al, 2013;Tinazzi et al, 2000;. Such changes are thought to be responsible for the development, maintenance and progression of functional disturbances seen in neck pain patients .…”