Spinal cord stimulator: how it works, who it is for, risks and recovery

Guy’s and St Thomas’ explains that a spinal cord stimulator system is made up of an implanted battery attached to a small lead. The leads are programmed to create a small electrical field, placed next to a nerve, and the field can reduce a specific type of pain. Once implanted, the system is controlled by the patient using a handheld controller. Spinal cord stimulation is sometimes called neuromodulation.

Cambridge University Hospitals describes the principle as delivering small electrical fields to the spinal cord that mask areas of pain by changing the pain messages your body sends to your brain. One or two leads are placed in the epidural space of the spine under X-ray control, and the lead is connected under the skin to a battery device surgically placed in the buttock.

Two types of stimulation are described. Lower frequency stimulation produces a tingling sensation in the painful area, while high frequency stimulation is usually not felt. The type is chosen by the pain consultant and depends on the pain condition.

NICE technology appraisal TA159 recommends spinal cord stimulation as a treatment option for adults with chronic pain of neuropathic origin who continue to experience pain measuring at least 50 mm on a 0 to 100 mm visual analogue scale for at least 6 months despite appropriate conventional medical management, and who have had a successful trial of stimulation. NICE does not recommend it for chronic pain of ischaemic origin except in the context of research.

Guy’s and St Thomas’ lists the conditions it recommends spinal cord stimulation for: pain caused by an injury to the nerves (neuropathic) rather than damage to other tissues such as joints and muscles; failed back surgery syndrome when the pain is neuropathic; complex regional pain syndrome; and severe chronic pain that limits daily life where all reasonable therapies, such as painkillers and physiotherapy, have not worked. Cambridge lists failed back surgery syndrome (persistent spinal pain syndrome), complex regional pain syndrome and neuropathic pain.

It is not a first-line treatment. Both trusts say that traditional therapies, such as medications, TENS, physiotherapy and injections, should have been tried first, and Guy’s and St Thomas’ says it cannot be used as a stand-alone treatment, so patients must engage with all elements of the treatment pathway.

The two trusts give overlapping lists of situations where it might not be offered. According to Guy’s and St Thomas’ and Cambridge, these include:

• mechanical pain such as pain from arthritis or spinal instability

• widespread pain beyond the area a system can cover

• physical problems that make safe fitting impossible, such as major spinal conditions, extensive spinal metalwork or extensive scar tissue in the epidural space

• an active infective illness

• some chronic illnesses, for example multiple sclerosis or severe respiratory disease

• mental health conditions that might stop you managing the device or care pathway

• excessive use of alcohol, prescription medicines or recreational drugs

• a very low or very high body mass index (Guy’s and St Thomas’ gives below 18 or above 35)

• a nickel or other metal allergy to device components

• age under 18

NICE says assessment should be by a multidisciplinary team. Guy’s and St Thomas’ describes a pain consultant assessment, a joint psychology and physiotherapy appointment looking at how pain affects quality of life, and for most patients a 2-week pre-implant pain management programme. The psychologist also discusses how you might feel if the trial does not help. Cambridge describes an education seminar with the nurse specialists, a nurse specialist clinic, a psychologist appointment, and a pre-operative assessment about four weeks before the trial.

The trial is carried out in theatre under local anaesthetic and light sedation, with stimulation leads sited in the epidural space and the system tested. If the trial is successful you proceed to the full implant, which involves inserting the battery in a day case procedure, occasionally with an overnight stay. Guy’s and St Thomas’ says patients on high doses of opioid medicine (the equivalent of 100mg of oral morphine) have a less effective response and may be asked to reduce or stop for at least 6 weeks before the trial.

Cambridge says spinal cord stimulation is effective in five to seven out of ten cases, but also that it can relieve pain in some people with certain types of chronic pain and is only one part of a treatment strategy. Guy’s and St Thomas’ is clear that it might reduce the intensity of the pain but cannot resolve it completely.

Because of this, realistic goals are usually improvement in pain intensity, activity and sleep rather than complete relief. The psychological preparation described by both trusts is designed to set expectations and to support the use of other pain management skills alongside the device.

Cambridge lists the possible risks and complications. These include a painful battery or connection site, infection (less than five in 100 people, which may mean the whole system needs to be removed), bleeding, severe headache, leads that move or do not work and may need another operation, unpleasant stimulation, failure to capture the area of pain or no pain relief, allergic reaction leading to removal, a decrease in pain relief with time, and nerve damage leading to pain, numbness and weakness that may be temporary or permanent. Paralysis is described as extremely rare (two patients in one million).

Ask your team for the figures that apply at their centre, because they can differ between hospitals and devices.

Cambridge advises that some physical activities may need to be avoided in the first 12 weeks to help prevent the leads moving. You must tell any future surgeon and anaesthetist that you have a stimulator. Depending on the device, an MRI scan may not be possible, although CT scans and X-rays are allowed. Stimulators may set off airport detectors and shop anti-theft devices, and strong magnets may turn the stimulator off. It also says that you should not drive with the device on if you have low frequency stimulation.

Follow-up is regular. Cambridge describes appointments at one week, four weeks, 12 weeks, six months, nine months and 12 months after implant, then yearly reviews. Battery replacement is a simple day surgery procedure, according to the trust.

In the NHS, referral is via a GP or hospital specialist to a pain service and then to a neuromodulation team, and eligibility is shaped by NICE guidance and local commissioning policy. Private pain clinics may also offer assessment and implantation. In either setting the same principles apply: a multidisciplinary assessment, a trial before permanent implant, clear information about risks, and a plan for long-term follow-up and device support.

NICE adds that if different systems are equally suitable for a person, the least costly should be used, taking into account acquisition costs, the anticipated longevity and the support package offered.