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Quantitative pilomotor axon reflex test: a novel test of pilomotor function - PubMed

Quantitative pilomotor axon reflex test: a novel test of pilomotor function

Timo Siepmann et al. Arch Neurol. 2012 Nov.

Abstract

Background: Cutaneous autonomic function can be quantified by the assessment of sudomotor and vasomotor responses. Although piloerector muscles are innervated by the sympathetic nervous system, there are at present no methods to quantify pilomotor function.

Objective: To quantify piloerection using phenylephrine hydrochloride in humans.

Design: Pilot study.

Setting: Hospital-based study.

Participants: Twenty-two healthy volunteers (18 males,4 females) aged 24 to 48 years participated in 6 studies.

Interventions: Piloerection was stimulated by iontophoresis of 1% phenylephrine. Silicone impressions of piloerection were quantified by number and area. The direct and indirect responses to phenylephrine iontophoresis were compared on both forearms after pre treatment to topical and subcutaneous lidocaine and iontophoresis of normal saline.

Results: Iontophoresis of phenylephrine induced piloerection in both the direct and axon reflex–mediated regions, with similar responses in both arms. Topical lidocaine blocked axon reflex–mediated piloerection post-iontophoresis (mean [SD], 66.6 [19.2] for control impressions vs 7.2 [4.3] for lidocaine impressions;P.001). Subcutaneous lidocaine completely blocked piloerection.The area of axon reflex–mediated piloerection was also attenuated in the lidocaine-treated region postiontophoresis (mean [SD], 46.2 [16.1]cm2 vs 7.2 [3.9]cm2; P.001). Piloerection was delayed in the axon reflex region compared with the direct region. Normal saline did not cause piloerection.

Conclusions: Phenylephrine provoked piloerection directly and indirectly through an axon reflex–mediated response that is attenuated by lidocaine. Piloerection is not stimulated by iontophoresis of normal saline alone.The quantitative pilomotor axon reflex test (QPART) may complement other measures of cutaneous autonomic nerve fiber function.

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Figures

Figure 1
Figure 1. Phenylephrine induced piloerection

Direct and axon-reflex mediated piloerection after iontophoresis of phenylephrine on the dorsal forearm: The inner circle delineates the region of phenylephrine application (direct response). The outer circle delineates the margins of the axon-reflex mediated response.

Figure 2
Figure 2. Attenuation of axon-reflex mediated piloerection by pretreatment with topical lidocaine gel

(A) Silicone impression scans after phenylephrine iontophoresis of a subject without and (B) with lidocaine pretreatment. Hair follicle impressions are dark spots on the yellow silicone.

Figure 3
Figure 3. Subcutaneous lidocaine injections abolish axon-reflex mediated piloerection

Piloerection spread in the surrounding region ceases at the border of the lidocaine injection region. The small arrows point to lidocaine injections.

Figure 4
Figure 4. Delayed onset of piloerection in the axon-reflex region

Photographs of the dorsal forearm of a subject at different points in time after phenylephrine iontophoresis. Maximal piloerection in the direct region occurs after 13.3±5.8 seconds whereas maximal piloerection in the indirect region occurred 600±90 seconds post-iontophoresis.

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