Department of Neurological Sciences, University of Bologna, Bologna, Italy.
Clin Neurophysiol. 2011 Sep;122(9):1854-9. doi: 10.1016/j.clinph.2011.02.024. Epub 2011 Mar 23.
Small fiber neuropathy (SFN) may involve somatic and autonomic fibers. Assessment of somatic epidermal nerve fiber density (ENFs) is considered the gold standard test in the diagnosis of SFN. By contrast, autonomic involvement in SFN is more difficult to ascertain. Here we investigate peripheral sympathetic outflow by microneurography in patients with selective small nerve fiber involvement of different origin with and without autonomic symptoms to ascertain the ability of microneurography and the corresponding skin organ effector responses (sympathetic skin activity-SSR and skin vasomotor reflex-SVR) to disclose autonomic involvement.
We studied 59 patients with SFN because of reduced leg ENFs and normal conduction studies. Thirty patients reported only burning paresthesia (somatic SFN) whereas 29 patients complained of additional autonomic dysfunctions (autonomic SFN). They underwent microneurography from peroneal nerve with the recording of muscle sympathetic nerve activity (MSNA), skin sympathetic nerve activity (SSNA) and the corresponding SSR and SVR in the same innervation field. Thirty age and sex-matched healthy subjects served as controls.
Patients with autonomic SFN mainly complained of loss of sweating. They showed a significant absence of indirect (SSR and SVR) and direct (MSNA and SSNA) sympathetic tests compared to somatic SFN patients and controls. SSNA, SSR and SVR were more often absent than MSNA. In addition, SSR and SVR were absent in all patients with no recordable SSNA but no significant relationship was found with MSNA recording.
SSR and SVR, simple indirect tests of sympathetic activity, could help to disclose autonomic involvement in SFN with a good sensitivity mainly in patients with sweating dysfunctions although they expressed autonomic failure in only one sympathetic branch.
Microneurographic evaluation of sympathetic activity, technically more difficult than indirect tests, was a useful functional tool contributing to the diagnosis and extension of autonomic involvement in SFN. Our data showed that the skin sympathetic branch is more often involved than the muscle sympathetic branch in SFN.
小纤维神经病（SFN）可能涉及躯体和自主纤维。评估躯体表皮神经纤维密度（ENF）被认为是诊断 SFN 的金标准测试。相比之下，SFN 的自主神经受累更难确定。在这里，我们通过微神经记录法研究了不同来源的选择性小纤维神经受累且伴有或不伴有自主症状的患者的外周交感传出，以确定微神经记录法及其相应的皮肤器官效应器反应（交感皮肤活动-SSR 和皮肤血管运动反射-SVR）揭示自主神经受累的能力。
我们研究了 59 例因下肢 ENF 降低和正常传导研究而患有 SFN 的患者。30 例患者仅报告烧灼感（躯体 SFN），而 29 例患者抱怨额外的自主神经功能障碍（自主 SFN）。他们从腓肠神经进行微神经记录，记录肌肉交感神经活动（MSNA）、皮肤交感神经活动（SSNA）以及同一神经支配区域的相应 SSR 和 SVR。30 名年龄和性别匹配的健康受试者作为对照组。
有自主 SFN 的患者主要抱怨出汗丧失。与躯体 SFN 患者和对照组相比，他们的间接（SSR 和 SVR）和直接（MSNA 和 SSNA）交感测试明显缺失。SSNA、SSR 和 SVR 比 MSNA 更常缺失。此外，在没有可记录 SSNA 的所有患者中，SSR 和 SVR 均缺失，但与 MSNA 记录无显著关系。
SSR 和 SVR 是交感活动的简单间接测试，可以帮助发现 SFN 中的自主神经受累，主要在出汗功能障碍的患者中具有较高的敏感性，尽管它们仅在一个交感分支中表达自主衰竭。
与间接测试相比，交感神经活动的微神经记录评估技术更难，但它是一种有用的功能工具，有助于诊断和扩展 SFN 中的自主神经受累。我们的数据表明，在 SFN 中，皮肤交感神经分支比肌肉交感神经分支更常受累。
