Sympathectomy for neuropathic pain.

BACKGROUND

Neuropathic pain is defined as pain initiated or caused by a primary lesion or dysfunction in the nervous system. Some examples of this condition are phantom limb pain, post-stroke pain and complex regional pain syndrome type I (reflex sympathetic dystrophy) and type II (causalgia). Treatment options include drugs, physical treatments, surgery and psychological interventions. The concept that many neuropathic pain syndromes, particularly RSD and causalgia are "sympathetically maintained pains" has historically led to attempts to temporarily or permanently interrupt the sympathetic nervous system. Chemical sympathectomies use alcohol or phenol injections to destroy the sympathetic chain, but this effect is temporary until regeneration of the sympathetic chain occurs. Surgical ablation can be performed by open removal or electrocoagulation of the sympathetic chain, or minimally invasive procedures using stereotactic thermal or laser interruption.

OBJECTIVES

The review aimed to assess the effects of both chemical and surgical sympathectomy for neuropathic pain. Secondary objectives were to compare the effects of sympathectomy with no treatment, placebo or conventional treatment, and to evaluate whether the technique of sympathectomy influences the outcomes of the procedure.

SEARCH STRATEGY

We searched MEDLINE and EMBASE up to February 2003 and the latest issue of the Cochrane Library (Issue 1, 2003). We screened references in the retrieved articles, literature reviews and book chapters. We also contacted experts in the field of neuropathic pain.

SELECTION CRITERIA

Clinical trials and observational studies assessing the effects of sympathectomy (surgical or chemical) for neuropathic pain of both central or peripheral origin were included.

DATA COLLECTION AND ANALYSIS

Two reviewers applied the selection criteria to titles and abstracts. Full articles of potentially eligible trials were obtained and the same reviewers applied the inclusion criteria to the studies. The methodological quality of the studies was evaluated. The studies were also evaluated for clinical relevance according to a classification developed by our group. Statistical pooling was not possible due to heterogeneity of data; instead a narrative description of each included study was performed.

MAIN RESULTS

We included four studies. One randomized trial comparing radiofrequency sympatholysis with phenol sympathectomy was rated as low methodological quality and it showed that radiofrequency sympatholysis does not offer advantage over phenol techniques. However, a modified technique produced sympatholysis comparable to that produced by 6% phenol, with less incidence of post-sympathectomy neuralgia.

REVIEWER'S CONCLUSIONS: The practice of surgical and chemical sympathectomy is based on poor quality evidence, uncontrolled studies and personal experience. Furthermore, complications of the procedure may be significant, in terms of both worsening the pain or producing a new pain syndrome; and abnormal forms of sweating (compensatory hyperhidrosis and pathological gustatory sweating). Therefore, more clinical trials of sympathectomy are required to establish the overall effectiveness and potential risks of this procedure.