Temperature modulated histamine-itch in lesional and nonlesional skin in atopic eczema - a combined psychophysical and neuroimaging study.
BACKGROUND
Itch is the major symptom of many allergic diseases; yet it is still difficult to measure objectively. The aim of this study was to use an evaluated itch stimulus model in lesional (LS) and nonlesional (NLS) atopic eczema (AE) skin and to characterize cerebral responses using functional magnetic resonance imaging (fMRI).


METHODS
Thermal modulation was performed on a histamine stimulus in randomized order on LS or NLS in rapid alternating order from 32 degrees C (warm) to 25 degrees C (cold). Subjective itch ratings were recorded. Additionally, fMRI measurements were used to analyze the cerebral processing (n = 13). Healthy skin (HS) of age-matched volunteers served as control (n = 9).


RESULTS
Mean VAS itch intensity was significantly (P < 0.0001) higher during the relative cold [55.2 +/- 8.3% (LS); 48.6 +/- 8.2% (NLS)] compared to the relative warm blocks [36.0 +/- 7.3% (LS); 33.7 +/- 7.6% (NLS)]. Compared to HS, the itch response was delayed in LS and NLS. Itch intensity was perceived highest in LS, followed by NLS and HS. For NLS, fMRI revealed at the beginning of the itch provocation a cerebral deactivation pattern in itch processing structures (thalamus, prefrontal, cingulate, insular, somatosensory and motor cortex). During the course of stimulation, the cerebral deactivation was reduced with time and instead an activation of the basal ganglia occurred. In contrast LS showed an activation instead of deactivation pattern already at the beginning of the stimulation in the above mentioned structures.


CONCLUSIONS
Moderate short-term temperature modulation led to a reproducible, significant enhancement of histamine-induced itch with the strongest effect in LS. The differences in itch perception and itch kinetics between healthy volunteers and NLS in patients point towards an ongoing central inhibitory activity patients with AE, especially at the beginning of the itch provocation.
Department of Dermatology and Allergy Biederstein, Technische Universität München, Munich, Germany.
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F
Pfab
M
M
Valet
T
T
Sprenger
J
J
Huss-Marp
G I
GI
Athanasiadis
H J
HJ
Baurecht
A
A
Konstantinow
C
C
Zimmer
H
H
Behrendt
J
J
Ring
T R
TR
Tölle
U
U
Darsow
D000328:Adult; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000502:physiology*; D002648:Child; D003876:Dermatitis, Atopic / Q000503:physiopathology*; D006632:Histamine / Q000494:pharmacology; D006801:Humans; D008279:Magnetic Resonance Imaging; D010465:Perception / Q000502:physiology; D011537:Pruritus / Q000139:chemically induced / Q000503:physiopathology*; D012867:Skin / Q000187:drug effects / Q000294:innervation / Q000503:physiopathology; D013696:Temperature
D006632:Histamine