Pain Phenotypes in Individuals With Multiple Sclerosis

Multiple sclerosis (MS) is a chronic, progressive, autoimmune disease of the central nervous system characterized by inflammatory demyelination and axonal damage. Pain is common among individuals with MS and may substantially affect functioning and quality of life. Different pain mechanisms may coexist in individuals with MS; however, the contribution of nociceptive, neuropathic, nociplastic, and mixed pain phenotypes in this population remains insufficiently characterized. This cross-sectional observational study will include individuals with a definite diagnosis of MS who experience chronic pain. Participants will undergo a comprehensive clinical assessment to determine their predominant pain phenotype. Pain phenotyping will incorporate clinical history, pain characteristics and distribution, hypersensitivity findings, comorbidities, and quantitative sensory testing. Quantitative sensory testing will include static tactile mechanical detection, thermal perception, static mechanical allodynia, dynamic mechanical allodynia, and vibration perception. Testing will be performed under standardized environmental conditions and initially at the participant's most painful body region. In addition to pain phenotyping, pain intensity, pain distribution, pain catastrophizing, fatigue, health-related quality of life, and MS disease severity will be evaluated. Clinical characteristics will subsequently be compared among participants with different pain phenotypes to investigate the potential clinical impact of pain mechanisms in individuals with MS.