Cervico‐thoracic or lumbar sympathectomy for neuropathic pain and complex regional pain syndrome
This review is an update of a review first published in Issue 2, 2003, which was substantially updated in Issue 7, 2010. The concept that many neuropathic pain syndromes (traditionally this definition would include complex regional pain syndromes (CRPS)) are "sympathetically maintained pains" has historically led to treatments that interrupt the sympathetic nervous system. Chemical sympathectomies use alcohol or phenol injections to destroy ganglia of the sympathetic chain, while surgical ablation is performed by open removal or electrocoagulation of the sympathetic chain or by minimally invasive procedures using thermal or laser interruption.
To review the evidence from randomised, double blind, controlled trials on the efficacy and safety of chemical and surgical sympathectomy for neuropathic pain, including complex regional pain syndrome. Sympathectomy may be compared with placebo (sham) or other active treatment, provided both participants and outcome assessors are blind to treatment group allocation.
On 2 July 2013, we searched CENTRAL, MEDLINE, EMBASE, and the Oxford Pain Relief Database. We reviewed the bibliographies of all randomised trials identified and of review articles and also searched two clinical trial databases, ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform, to identify additional published or unpublished data. We screened references in the retrieved articles and literature reviews and contacted experts in the field of neuropathic pain.
Randomised, double blind, placebo or active controlled studies assessing the effects of sympathectomy for neuropathic pain and CRPS.
Data collection and analysis
Two review authors independently assessed trial quality and validity, and extracted data. No pooled analysis of data was possible.
Only one study satisfied our inclusion criteria, comparing percutaneous radiofrequency thermal lumbar sympathectomy with lumbar sympathetic neurolysis using phenol in 20 participants with CRPS. There was no comparison of sympathectomy versus sham or placebo. No dichotomous pain outcomes were reported. Average baseline scores of 8‐9/10 on several pain scales fell to about 4/10 initially (1 day) and remained at 3‐5/10 over four months. There were no significant differences between groups, except for "unpleasant sensation", which was higher with radiofrequency ablation. One participant in the phenol group experienced post sympathectomy neuralgia, while two in the radiofrequency group and one in the phenol group complained of paraesthesia during needle positioning. All participants had soreness at the injection site.
The practice of surgical and chemical sympathectomy for neuropathic pain and CRPS is based on very little high quality evidence. Sympathectomy should be used cautiously in clinical practice, in carefully selected patients, and probably only after failure of other treatment options. In these circumstances, establishing a clinical register of sympathectomy may help to inform treatment options on an individual patient basis.
Sebastian Straube, Sheena Derry, R Andrew Moore, Peter Cole
Plain language summary
Cervico‐thoracic or lumbar sympathectomy for neuropathic pain
Chronic pain due to damaged nerves is called neuropathic pain and is common. Some people consider that certain types of neuropathic pain (reflex sympathetic dystrophy and causalgia, now known collectively as Complex Regional Pain Syndrome (CRPS)) are caused by the sympathetic nervous system. Sympathectomy is a destructive procedure that interrupts the sympathetic nervous system. Chemical sympathectomies use alcohol or phenol injections to destroy sympathetic nervous tissue (the so‐called "sympathetic chain" of nerve ganglia). Surgical ablation can be performed by open removal or electrocoagulation (destruction of tissue with high‐frequency electrical current) of the sympathetic chain, or by minimally invasive procedures using thermal or laser interruption. Nerve regeneration commonly occurs following both surgical or chemical ablation, but may take longer with surgical ablation.
This systematic review found only one small study (20 participants) of good methodological quality, which reported no significant difference between surgical and chemical sympathectomy for relieving neuropathic pain. Potentially serious complications of sympathectomy are well documented in the literature, and one (neuralgia) occurred in this study.
The practice of sympathectomy for treating neuropathic pain is based on very weak evidence. Furthermore, complications of the procedure may be significant.
Sebastian Straube, Sheena Derry, R Andrew Moore, Peter Cole
Implications for practice
The first update (Straube 2010) of a previous Cochrane review (Mailis‐Gagnon 2003) used refined inclusion criteria. It demonstrated that the practice of sympathectomy for neuropathic pain is based on little high quality evidence. This current update did not identify any additional information. Only one pilot study, with 20 participants and in CRPS type I (which cannot serve as a model for other neuropathic pain conditions), satisfied our inclusion criteria. There was no comparison of sympathectomy versus sham or placebo. Lower quality evidence seems to suggest that sympathectomy for neuropathic pain can work, at least in some cases. The risk‐benefit assessment is complicated by the fact that serious complications of sympathectomy are common. Because there is no good evidence for the effectiveness of sympathectomy－particularly with regard to long term effectiveness outcomes－it should be used with caution, in carefully selected patients, after thorough assessment, and probably only after failure of other treatment options or in palliative cases, or both. This stands in contrast to the use of pharmacotherapy in neuropathic pain, where there is high quality evidence (see, for example, Moore 2009 and Moore 2011).
Implications for research
High quality evidence from double blind RCTs with placebo (sham) comparators would be needed to determine whether sympathectomy is effective in the relief of neuropathic pain. Studies would need to be conducted in different neuropathic pain syndromes to determine when－if at all－sympathectomy is effective. Studies would also need to assess different types of sympathectomy to determine which is best. Furthermore, comparison would be needed with less invasive techniques (neuropathic pain medications, local anaesthetic blocks, and botulinum toxin). Double‐blinding is needed to ensure high study quality and guard against biases but would be a considerable challenge in direct comparisons between sympathectomy and less invasive techniques and would probably involve sham procedures in some participants.
Given the adverse event profile associated with sympathectomy and given the known, albeit limited, efficacy for pharmacotherapy in neuropathic pain, the question arises of whether large double blind RCTs are likely to be conducted. Furthermore, there may be ethical arguments against conducting such trials other than in selected individuals (after failure of pharmacotherapy). It would, however, be helpful to compile a registry of sympathectomy cases.