Pathophysiological mechanisms of central neuropathic pain after spinal cord injury

Abstract

After spinal cord injury (SCI), between 10% and 20% of the patients may develop central neuropathic pain. This type of chronic pain usually is a very bothersome sequel and represents a major therapeutic challenge since conventional medical and surgical pain therapies generally are ine ective. This review focuses on recent advances in the understanding of the pathophysiology of this pain syndrome. Important clinical features of central neuropathic pain after SCI include loss of sensations mediated by spinothalamic pathways combined with development of abnormal pain perception (spontaneous continuous pain and abnormally evoked pain). Up-regulation of neuronal activity leading to spontaneous and evoked neuronal hyperactivity/hyperexcitability, may be the neurophysiological substrate for development of abnormal pain perception. This paper describes some neurochemical changes that may be important for the induction and maintenance of neuronal hyperactivity and abnormal pain perception: Increased excitatory glutaminergic activity involving N-methyl-D-aspartate (NMDA) receptor activation, may trigger the intracellular cascade reaction leading to upregulation of neuronal activity/excitability. Changes in voltage-sensitive Na + channels may contribute to changes in nerve membrane excitability. Other important mechanisms may be loss of endogenous inhibition, including reduced g-amino-butyric acid (GABA)ergic, opioid and monoaminergic inhibition. These various mechanisms may provide new targets for treatment of a pain syndrome that traditionally has been so di cult to handle.

Botulinum toxin type A for neuropathic pain in patients with spinal cord injury

“…In a recent study looking into placebo effects in peripheral nerve injury‐induced chronic neuropathic pain, there were placebo effects regarding hyperalgesia but none for spontaneous or evoked pain 50. Considering that the mechanisms of neuropathic pain in SCI differ from those caused by peripheral nerve injury, the placebo effects may also be different between SCI‐induced neuropathic pain and pain caused by injury to the peripheral nerve 53, 54. The subjects enrolled in this study had moderate to severe neuropathic pain, with VAS scores > 40 and durations > 3 months.…”

Maintenance of exercise participation in individuals with spinal cord injury: effects on quality of life, stress and pain

“…Such health issues include a propensity to chronic pain and stress, 1 and a reduction in perceived quality of life (PQOL). 2 To emphasize the importance of these issues, it should be noted that several mechanisms may be responsible for the existence of chronic pain, 3,4 which may coexist above, at and below the level of the SCI. 5 The existence of this pain has been found to increase the already heightened stress levels in individuals with SCI and further decrease their quality of life.…”

The amelioration of the suffering associated with spinal cord injury with subperception transcranial electrical stimulation

“…2 The types of pain associated with spinal cord injury (SCI) however, present a major therapeutic challenge. 3,4 Recent surveys 5 ± 7 of SCI subjects in various countries indicate that more than 60% of the respondents experience chronic pain/dysaesthesiae, the majority of whom describe their pain as severe. Consequently, subjects with SCI tend to be maintained on high doses and/or multiple medications from relatively young ages.…”