Lower thermal and discomfort thresholds may predispose multiple sclerosis (MS) patients to chronic pain, but a possible effect of fibromyalgia (FM) comorbidity has never been investigated. Aims were to investigate the thermal and discomfort thresholds in the evaluation of pain intensity between MS patients with FM (PFM+) and MS patients with pain not associated to FM (PFM-).
One hundred thirty three MS patients were investigated for chronic pain. FM was assessed according to the 1990 ACR diagnostic criteria. An algometer was used to measure the thresholds in the patients and 60 matched healthy subjects.
Chronic pain was present in 88 (66.2%) patients; 12 (13.6%) had neuropathic pain, 22 (17.3%) were PFM+ and 65 (48.9%) PFM-. PFM+ were predominantly female (p = 0.03) and had a greater EDSS (p = 0.01) than NoP; no other significant differences emerged than PFM-. The thresholds were lower in MS patients than controls (p < 0.01), mainly in the PFM+. FM severity influenced the thermal threshold (p < 0.001), while the female gender influenced the discomfort threshold (p < 0.001).
Thermal and discomfort thresholds were lower in patients than controls and were the lowest in PFM+. Their more severely impaired thermal threshold supports a neurophysiological basis of such association.