Spinal cord stimulation for neuropathic pain: an evidence-based analysis.
OBJECTIVE
The objective of this health technology policy assessment was to determine the effectiveness of spinal cord stimulation (SCS) to manage chronic intractable neuropathic pain and to evaluate the adverse events and Ontario-specific economic profile of this technology.


OBJECTIVE
SCS is a reversible pain therapy that uses low-voltage electrical pulses to manage chronic, intractable neuropathic pain of the trunk or limbs. Neuropathic pain begins or is caused by damage or dysfunction to the nervous system and can be difficult to manage. The prevalence of neuropathic pain has been estimated at about 1.5% of the population in the United States and 1% of the population in the United Kingdom. These prevalence rates are generalizable to Canada. Neuropathic pain is extremely difficult to manage. People with symptoms that persist for at least 6 months or who have symptoms that last longer than expected for tissue healing or resolution of an underlying disease are considered to have chronic pain. Chronic pain is an emotional, social, and economic burden for those living with it. Depression, reduced quality of life (QOL), absenteeism from work, and a lower household income are positively correlated with chronic pain. Although the actual number is unknown, a proportion of people with chronic neuropathic pain fail to obtain pain relief from pharmacological therapies despite adequate and reasonable efforts to use them. These people are said to have intractable neuropathic pain, and they are the target population for SCS. The most common indication for SCS in North America is chronic intractable neuropathic pain due to failed back surgery syndrome (FBSS), a term that describes persistent leg or back and leg pain in patients who have had back or spine surgery. Neuropathic pain due to complex regional pain syndrome (CRPS), which can develop in the distal aspect of a limb a minor injury, is another common indication. To a lesser extent, chronic intractable pain of postherpetic neuralgia, which is a persistent burning pain and hyperesthesia along the distribution of a cutaneous nerve after an attack of herpes zoster, is also managed with SCS. For each condition, SCS is considered as a pain management therapy only after conventional pain therapies, including pharmacological, nonpharmacological, and surgical treatments, if applicable, have been attempted and have failed.


METHODS
The SCS technology consists of 3 implantable components: a pulse generator, an extension cable, and a lead (a small wire). The pulse generator is the power source for the spinal cord stimulator. It generates low-voltage electrical pulses. The extension cable connects the pulse generator to the lead. The lead is a small, insulated wire that has a set of electrodes at one end. The lead is placed into the epidural space on the posterior aspect of the spinal cord, and the electrodes are positioned at the level of the nerve roots innervating the painful area. An electrical current from the electrodes induces a paresthesia, or a tingling sensation that masks the pain. Before SCS is initiated, candidates must have psychological testing to rule out major psychological illness, drug habituation, and issues of secondary gain that can negatively influence the success of the therapy. Successful candidates will have a SCS test stimulation period (trial period) to assess their responsiveness to SCS. The test stimulation takes about 1 week to complete, and candidates who obtain at least 50% pain relief during this period are deemed suitable to receive a permanent implantation of a spinal cord stimulator


METHODS
The Medical Advisory Secretariat (MAS) reviewed all published health technology assessments of spinal cord stimulation. Following this, a literature search was conducted from 2000 to January, 2005 and a systematic review of the literature was completed. The primary outcome for the systematic review was pain relief. Secondary outcomes included functional status and quality of life. After applying the predetermined inclusion and exclusion criteria, 2 randomized controlled trials (MAS level 2 evidence), and 2 prospective non-randomized controlled trials with a before-and-after-treatment study design (MAS level 3a evidence) were retrieved and reviewed.


RESULTS
The authors of 6 health technology assessments concluded that evidence exists to support the effectiveness of SCS to decrease pain in various neuropathic pain syndromes. However, the quality of this evidence varied among reports from weak to moderate. The systematic review completed by MAS found high quality level 2 evidence that SCS decreases pain and level 3a evidence that it improves functional status and quality of life in some people with neuropathic pain conditions. The rate of technical failures was approximately 11%, which included electrode lead migration and/or malposition. Procedural complications included infection and dural puncture; each occurred at a rate of 1.2%.


CONCLUSIONS
SCS may be considered for patients with chronic, neuropathic pain for whom standard pain treatments have failed and when there is no indication for surgical intervention to treat the underlying condition.