Truini A, Galeotti F, La Cesa S, Di Rezze S, Biasiotta A, Di Stefano G, Tinelli E, Millefiorini E, Gatti A, Cruccu G.Mechanisms of pain in multiple sclerosis: A combined clinical and neurophysiological study. Pain. 2012 Jul. [Epub ahead of print]
In this clinical and neurophysiological study, we examined the clinical characteristics and underlying mechanisms of neuropathic pain related to multiple sclerosis. A total of 302 consecutive patients with multiple sclerosis were screened for neuropathic pain by clinical examination. In patients selected for having ongoing extremity pain or Lhermitte‘s phenomenon, we recorded somatosensory evoked potentials (sensation triggered electrical signalling), mediated by Aβ non-nociceptive fibres (non pain nerve fibre often transmitting signals from the muscle), and laser-evoked potentials (Laser triggered nerve impulse), mediated by Aδ nociceptive (pain) fibres (These respond to cold and pressure of contact). Of the 302 patients, 92 had pain (30%), and 42 (14%) neuropathic pain. Patients with neuropathic pain had more severe multiple sclerosis, as assessed by the expanded disability severity score, than those without pain. Whereas, in patients with ongoing neuropathic pain, laser evoked potentials were more frequently abnormal than somatosensory evoked potentials, we found the opposite in patients with Lhermitte‘s phenomenon. Our data underline the clinical importance of pain in multiple sclerosis and indicate that a more severe disease is associated with a higher risk of developing neuropathic pain. The prevalence of pain that we found, which was lower than that reported in previous studies, may reflect the lesser disease severity in our patients. Neurophysiological data show that whereas ongoing extremity pain is associated with spinothalamic pathway damage, Lhermitte’s phenomenon is related to damage of non-nociceptive pathways.
The spinothalamic tract is a sensory pathway originating in the spinal cord. It transmits information to the thalamus about pain, temperature, itch and crude touch. This study indicates that the more severe your MS is the more likely you are to have pain. If you have Lhermittes sign (tingling down neck and limbs when you bend your head forward) this may involve a different nerve signalling pathway compared to other pains that are sent via pain/sensation pathways. There are lots of other posts on pain in MS on the Blog.