Hypoalgesia, Hyperalgesia Linked to Multiple Sclerosis Lesion Location
Although chronic pain — most often of neuropathic origin — is a hallmark of MS, distinguishing neuropathic from nociceptive pain remains challenging.
In patients with multiple sclerosis (MS), lesions in the right dorsolateral prefrontal cortex and posterior periventricular area may be associated with hypo and hyperalgesia, according to results from a study presented at the 7th joint ECTRIMS-ACTRIMS meeting, held October 25-28, 2017 in Paris, France.1
Although chronic pain — most often of neuropathic origin — is a hallmark of MS, distinguishing neuropathic from nociceptive pain remains challenging.2 In an endeavor to determine whether these 2 types of pain are associated with region-specific lesions, researchers at the Queen Square Multiple Sclerosis Centre, University College London Institute of Neurology, in the United Kingdom, examined the magnetic resonance imaging (MRI) scans of patients with MS. A total of 208 patients >18 years old (67.3% women; mean age, 55.2±9.4 years) were included in the study. Among them, 176 had relapsing remitting MS and 28 had progressive MS.
The disability level of all patients was assessed by neurostatus-certified neurologists using the Expanded Disability Status Scale (EDSS) and the Kurtzke Functional Systems score. People with peripheral nerve disease or clinical depression were excluded from the study. The cohort comprised 96 patients in the pain group (PAIN+; patients with persistent pain [ie, pain for >3 months]), and 112 patients in the PAIN- group. Mean EDSS score in the cohort was 2.0±2.0.
Lesions on fluid-attenuated inversion recovery MRI scans were delineated with a semiautomated edge-finding tool (JIM v. 6.0, Xinapse Systems, Aldwincle, UK), and images were analyzed using Voxel-based lesion symptom mapping methods.3 Researchers found a correlation between lesion volume and clinical disability in both groups (PAIN+: Spearman correlation coefficient, r: 0.442; P <.0001; PAIN-: r: 0.319; P =.0014). In addition, “lesions of the right dorsolateral prefrontal area were significantly more prevalent in patients without pain, whereas periventricular posterior lesions were significantly more prevalent in patients with persistent pain.”
The investigators concluded that, “Right dorsolateral prefrontal lesions may induce hypoalgesia, whereas posterior periventricular lesions may induce hyperalgesia in [people with] MS,” adding, “hypoalgesia mechanism induced by the right dorsolateral prefrontal lesions in patients with MS may be similar to those occurring in Alzheimer´s disease and the opposite of those occurring in anxious syndromes.”
- Plantone D, Ferraro D, Vitetta F, et al. Neuroradiological characterization of multiple sclerosis patients with chronic pain. Presented at: 7th Joint ECTRIMS-ACTRIMS Meeting. October 25-28, 2017; Paris, France. Poster P368.
- Truini A, Barbanti P, Pozzilli C, Cruccu G. A mechanism-based classification of pain in multiple sclerosis. J Neurol. 2013;260(2):351-367.
- Rorden C, Karnath H-O, Bonilha L. Improving lesion-symptom mapping. J Cogn Neurosci. 2007;19(7):1081-1088.