Abstract
BACKGROUND: Fibromyalgia syndrome (FMS) is a chronic widespread pain condition with mixed peripheral and central contributions. Patients display hypersensitivities to a spectrum of stimuli. Patients' blunt pressure pain thresholds are typically reduced, and sometimes (∼15%) gentle brushstroke induces allodynia. However, aftersensations after these stimuli have not, to our knowledge, been reported. METHODS: We examined the perception of blunt pressure and "pleasant touch" in FMS. Patients were first interviewed and completed standard psychometric questionnaires. We then measured their sensitivity to blunt pressure and perception of pleasant touch, including aftersensations; patients were followed up for 5 days to evaluate lingering pain from blunt pressure. RESULTS: We recruited 51 patients with FMS and 16 pain-free healthy controls (HCs) at a UK Pain Management Centre. Forty-four patients completed the aftersensation protocol. Most patients reported pain after the application of less mechanical pressure than the level of pressure at which HCs reported pain; median arm and leg thresholds for the patients with FMS were 167 kPa and 233 kPa, respectively. Eighty-four percent (31/37) of patients reported ongoing pain at the site of pressure application 1 day after testing, and 49% (18/37) still perceived pain at 5 days. Aftersensations after brushstroke were common in the FMS group, reported by 77% (34/44) of patients with FMS vs 25% (4/16) of HCs; 34% (15/44) of patients, but no HCs, perceived these aftersensations as uncomfortable. For patients with FMS who experienced aftersensations, brushstroke pleasantness ratings were reduced, and the skin was often an important site of pain. CONCLUSION: Pain after blunt pressure assessment typically lingers for several days. Aftersensations after brushstroke stimulation are a previously unreported FMS phenomenon. They are associated with tactile anhedonia and might identify a clinically distinct subgroup.