Department of Dermatology and Allergy Biederstein, Technische Universität München, Munich, Germany.
Allergy. 2010 Jan;65(1):84-94. doi: 10.1111/j.1398-9995.2009.02163.x. Epub 2009 Oct 5.
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).
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).
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.
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.
瘙痒是许多过敏性疾病的主要症状；然而，仍然很难客观地衡量。本研究的目的是使用经过评估的瘙痒刺激模型，在病变（LS）和非病变（NLS）特应性皮炎（AE）皮肤中，并使用功能磁共振成像（fMRI）来描述大脑反应。
在 LS 或 NLS 上以随机顺序进行热调制，以快速交替顺序从 32°C（温暖）到 25°C（寒冷）进行组胺刺激。记录主观瘙痒评分。此外，使用 fMRI 测量来分析大脑处理（n=13）。年龄匹配的健康志愿者的皮肤（HS）作为对照（n=9）。
相对寒冷（LS：55.2±8.3%；NLS：48.6±8.2%）时的平均 VAS 瘙痒强度明显（P<0.0001）高于相对温暖（LS：36.0±7.3%；NLS：33.7±7.6%）。与 HS 相比，LS 和 NLS 的瘙痒反应延迟。LS 的瘙痒强度最高，其次是 NLS 和 HS。对于 NLS，fMRI 在瘙痒刺激开始时显示出瘙痒处理结构（丘脑、前额叶、扣带回、岛叶、躯体感觉和运动皮层）中的大脑去激活模式。在刺激过程中，大脑去激活随时间减少，而基底节出现激活。相比之下，LS 在刺激开始时已经显示出上述结构的激活而不是去激活模式。
适度的短期温度调制导致组胺诱导的瘙痒显著增强，LS 的效果最强。健康志愿者和 AE 患者 NLS 之间的瘙痒感知和瘙痒动力学差异表明，AE 患者存在持续的中枢抑制活动，尤其是在瘙痒刺激开始时。
