Innovative Neurophysiological Methods in Itch Research: Long-latency Evoked Potentials after Electrical and Thermal Stimulation in Patients with Atopic Dermatitis

Abstract

The aim of this study was to examine the findings of innovative neurophysiological methods of itch research. Short-latency and pain-related somatosensory-evoked potentials after electrical stimulation, as well as long-latency evoked potentials after thermal stimulation were studied in 38 patients with atopic dermatitis (AD) and 26 healthy volunteers. Quantitative Sensory Testing of thermal perception was performed in 22 patients with AD from the main AD group and in 15 healthy volunteers. Brain hyperactivity to electrical stimuli, delayed thermal-evoked potentials and elevated thermal thresholds were revealed in patients with AD compared with healthy controls. The data indicate small nerve fibre dysfunction in patients with AD, which may contribute to the pathogenesis of AD and chronic itch. The study demonstrates objective approaches to assess the function of small nerve fibres in patients with chronic itch.

Pathophysiology of pruritus in primary localized cutaneous amyloidosis

“…We measured the WDT and HPT bilaterally at the upper back, lateral arms and shins, as cutaneous amyloidosis typically occurs over these areas. We found that the WDT was elevated in patients with PLCA, but the raised HPT was not statistically significant, similarly to a previous study in AD . HPT thresholds can be less accurate in diagnosing SFN, as pain responses are significantly affected by cognitive and emotional states of patients .…”

Pruritus intensity assessment: challenge for clinicians

“…In contrast, our group found an even higher sensory threshold to electric current stimulation in patients with atopic dermatitis or psoriasis than in healthy volunteers, although no significant differences were found between subjects with atopic dermatitis and psoriasis [43]. Our results are in accordance with the observations made by Yudina et al, who documented elevated thermal thresholds in patients with atopic dermatitis [40].…”

“…However, it was also suggested that subjects with chronic pruritus might also be more sensitive to itchy stimuli due to lowering of itch threshold at the periphery [37][38][39][40]. For instance, it was observed that tactile threshold in patients with nodular prurigo was lower than in controls and this abnormality was reversed by capsaicin, suggesting the involvement of neuropeptides, mainly substance P [37].…”

The impact of atopic dermatitis on sexual health

“…Unpleasant sensations, such as itching, pain and paraesthesias, likely influence impaired sexual health beyond the lesions themselves. Sensory disorders are very frequent in patients with AD . Atopic patients frequently have hyperknesis (an increased perception of itch) and alloknesis (a touch‐evoked itch) .…”

“…Sensory disorders are very frequent in patients with AD. 13,14 Atopic patients frequently have hyperknesis (an increased perception of itch) and alloknesis (a touch-evoked itch). 25 Although it has been never explored, we believe that these disorders seriously limit patient sexual desire and whole body perception in men as well as in women, especially of the genital area and the breasts.…”