Background: Pruritus, or itch, is the most prevalent symptom of allergic and inflammatory skin disease. Although it is known that itch induces activation of a neural network in the brain, the temporal dynamics of the network as well as the pathophysiology and neurobiology are not well understood.
Objectives: The study aimed to elucidate (i) the temporal dynamics of the itch response identified in earlier studies and (ii) the relationship between central and subjective responses to itch.
Methods: Using a novel time-series analysis, we performed a double-blind, placebo-controlled, randomized, within-subject functional magnetic resonance imaging (fMRI) study of the cerebral processing of histamine-induced itch in healthy volunteers (n = 16) by tracking the 8-min period following a single skin prick.
Results: Histamine-induced itch compared with saline resulted in significant area under the curve blood oxygen level dependent (BOLD) signal changes in the middle/superior temporal gyrus and right inferior frontal gyrus/insula. We observed negative itch-induced BOLD signal changes compared with saline in (i) the pregenual anterior cingulate cortex (ACC)/medial frontal gyrus, (ii) subgenual ACC/ventral striatum, (iii) bilateral temporal pole/parahippocampal gyrus and (iv) several regions within the cerebellum. We noted a trend significance in the left precentral gyrus part of the motor cortex. The BOLD signal change in several of these regions correlated with perception of itch intensity.
Conclusions: In contrast to other fMRI studies we observed a multifocal negative signal. An improved understanding of both activated and deactivated brain regions during the itch response may in the long term facilitate development of more effective management strategies.
© 2012 The Authors. BJD © 2012 British Association of Dermatologists.