Generalized and symptom-specific sensitization of chronic itch and pain

• Published in: Journal of the European Academy of Dermatology and Venereology Vol. 21; no. 9; pp. 1187 - 1192
• Main Authors: Van Laarhoven, AIM, Kraaimaat, FW, Wilder-Smith, OH, Van De Kerkhof, PCM, Cats, H, Van Riel, PLCM, Evers, AWM
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01-10-2007
• Subjects: Adult; Analysis of Variance; Case-Control Studies; central sensitization; Chronic Disease; chronic itch; chronic pain; Dermatitis, Atopic - complications; Dermatitis, Atopic - physiopathology; Electric Stimulation; Female; Fibromyalgia - complications; Fibromyalgia - physiopathology; Humans; Pain - etiology; Pain - physiopathology; Pain Measurement; Pain Threshold; Physical Stimulation; Pruritus - etiology; Pruritus - physiopathology; Quantitative Sensory Testing; Sensory Thresholds; symptom-specific mechanisms
• ISSN: 0926-9959; 1468-3083
• DOI: 10.1111/j.1468-3083.2007.02215.x

Background  Physicians are frequently confronted with patients reporting severe itch and pain. Particularly in patients suffering from persistent itch and pain, central and peripheral sensitization processes are assumed to be involved in the long‐term maintenance and aggravation of the symptoms. The present study explores generalized and symptom‐specific sensitization processes in patients suffering from persistent itch and pain. Specifically, it examines whether patients with chronic itch and pain are more sensitive to somatosensory stimuli (generalized sensitization) and simultaneously perceive somatosensory stimuli as a symptom of their main physical complaint, e.g. pain in chronic pain patients (symptom‐specific sensitization).
Methods  Thresholds for different mechanical and electrical sensory stimuli of Quantitative Sensory Testing were determined in 15 female patients suffering from chronic itch associated with atopic dermatitis, 15 female chronic pain patients diagnosed with fibromyalgia, and 19 female healthy controls. Intensities of itch and pain sensations were rated on a visual analogue scale.
Results  As expected, the patient groups had significantly lower tolerance thresholds for the somatosensory stimuli applied than the healthy controls, supporting generalized sensitization. Moreover, patients with chronic itch consistently reported more itch, while patients with chronic pain partly reported more pain in response to analogous somatosensory stimuli than the healthy controls and the other patient group, indicating symptom‐specific sensitization.
Conclusion  The present study provides preliminary support that both generalized and symptom‐specific sensitization processes play a role in the regulation and processing of somatosensory stimulation of patients with chronic itch and pain.