Brain correlates of acupuncture and anti-histamine alleviation of allergen-induced itch in patients with atopic eczema
Final Report Abstract
Chronic itch is a prevalent symptom of many inflammatory skin disorders, including atopic dermatitis (AD). While conventional systemic approaches to reduce AD itch have shown limited efficacy and/or significant side effects, several recent studies have demonstrated effectiveness of acupuncture for reducing itch in healthy adults and AD. Furthermore, recent evidence suggests that acupuncture effects are partly mediated at the brain level, though specific brain mechanisms underlying acupuncture anti-pruritic effects are currently unknown. We evaluated n=14 AD patients (age: 25.4±9.1yrs) showing type-I-sensitivity to grass or birch pollen, cat or dog dander, Dermatophagoides farinae or pteronyssinus. A previously validated itch modulation model was used to create a block design paradigm in conjunction with fMRI (3T, Siemens Trio, Germany). Itch was induced with subject-specific allergen prick testing, and its intensity experimentally increased and decreased using a thermode (Medoc, Israel) alternating between cool (25°C) and warm (32°C) temperature epochs, respectively. Following each scan run, itch was rated using a VAS (0-100). Brain response to itch was investigated before and after real and sham acupuncture. Clinically-relevant allergen itch produced activation in anterior insula (aIns), anterior middle cingulate cortex (aMCC), dorsolateral and ventrolateral frontal gyri, and striatum (putamen, caudate). Real, but not sham, acupuncture was found to reduce itch sensation (ACUP: base=66±18, post=44±18, p<0.001; SHAM: base=57±17, post=58±22,p>0.6). Following real acupuncture, there was diminished itch-evoked brain activity in right alns, aMCC, and several striatal areas (putamen, caudate, and nucleus accumbens). There was also less itchevoked deactivation in a region of S1 contralateral to the acupuncture stimulation. Striatal response to itch may reflect procedural memory and affective/motivational aspects of itch, consistent with the urge to scratch. Down-regulation of brain regions thought to process salience (alns, aMCC) and affective/motivational (striatum) components of itch in AD, may underlie the efficacy of acupuncture in relieving itch in this clinical population.
