An electrophysiological approach to the evaluation of regional sympathetic dysfunction: a proposed classification

The importance to physicians of maintaining a level of understanding of illnesses and their treatment continues to reveal itself in a most striking fashion when it comes to the progressive interest recently directed to disorders of the autonomic nervous system (ANS). In particular, the relevance to pain practitioners of disease states which directly involve the sympathetic portion of the ANS has increased markedly following the international renaming of reflex sympathetic dystrophy (RSD) and causalgia to complex regional pain syndrome (CRPS) Type I and Type II respectively, as well as sympathetically maintained pain (SMP). Subsequently it has become better understood that many other forms of neuropathic pain also demonstrate local abnormalities of the sympathetic nervous supply to the skin within the painful territory, thereby increasing the diagnostic value of these (often subtle) cutaneous clinical signs.

The objectives of this presentation include (a) a concise review of laboratory tests that are currently used in the evaluation of the autonomic nervous system, (b) a discussion of those procedures that were developed for the assessment of sympathetic sudomotor function, (c) a review of the anatomic pathways subserving those electrophysiological methods for sudomotor testing, and (d) the current diagnostic classification for regional abnormalities of sympathetic sudomotor dysfunction.

Methods used in the preparation of this article have included a review of (a) historic clinical and laboratory articles (or translations thereof) regarding the medical importance of disorders of the autonomic nervous system, dating back to more than 155 years ago (b) anatomic and electrophysiological basis for electroneurodiagnostic sudomotor testing, and (c) the author's proposal for a diagnostic classification of regional sympathetic sudomotor dysfunction.