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A spinal cord stimulator (SCS) or dorsal column stimulator (DCS) is a type of implantable neuromodulation device (sometimes called a "pain pacemaker") that is used to send electrical signals to select areas of the spinal cord (dorsal columns) for the treatment of certain pain conditions. SCS is a consideration for people who have a pain condition that has not responded to more conservative therapy. [1] There are also spinal cord stimulators under research and development that could enable patients with spinal cord injury to walk again via epidural electrical stimulation (EES). [2] [3]
The most common use of SCS is failed back surgery syndrome (FBSS) in the United States and peripheral ischemic pain in Europe. [4] [5]
As of 2014 the FDA had approved SCS as a treatment for FBSS, chronic pain, complex regional pain syndrome, intractable angina, as well as visceral abdominal and perineal pain [1] and pain in the extremities from nerve damage. [6]
Once a person has had a psychological evaluation and deemed an appropriate candidate for SCS, a temporary implant is placed, called a trial, to determine the best stimulation pattern, and the person is sent home for three to ten days with an external pulse generator. If pain control and increased activity was achieved, a permanent system, with leads and a pulse generator, is placed. [7]
SCS may be contraindicated in people who have coagulation related disorders, or are on anticoagulant therapy. [1] Other contraindications include local and systemic infection, pacemakers, or those people for whom pre-surgical imaging studies show have anatomy that makes placement difficult, or if concerns arise during psychological evaluation. [8] [9] [10]
Complications with SCS range from simple easily correctable problems to devastating paralysis, nerve injury and death. In a 7-year follow-up, the overall complication rate was 5–18%. The most common complications include lead migration, lead breakage, and infection. Other complications include rotation of the pulse generator, haematomas (subcutaneous or epidural), cerebrospinal fluid (CSF) leak, post dural puncture headache, discomfort at pulse generator site, seroma and transient paraplegia. [11]
Some people find the tingling sensation caused by older model SCS to be unpleasant.
The most common hardware related complication is lead migration, in which the implanted electrodes move from their original placement. With this complication, recapturing paraesthesia coverage can be attempted with reprogramming. [12] In circumstances involving major lead migration a reoperation may be required to reset the lead placement. [13] Studies differ greatly in reporting the percentage of people who have lead migration but the majority of studies report in the range of 10-25% of lead migration for spinal cord stimulation. [13]
The neurophysiological mechanisms of action of spinal cord stimulation are not completely understood but may involve masking pain sensation with tingling by altering the pain processing of the central nervous system. [14] The mechanism of analgesia when SCS is applied in neuropathic pain states may be very different from that involved in analgesia due to limb ischemia. [15] [16] In neuropathic pain states, experimental evidence shows that SCS alters the local neurochemistry in dorsal horn, suppressing the hyperexcitability of the neurons. Specifically, there is some evidence for increased levels of GABA release, serotonin, and perhaps suppression of levels of some excitatory amino acids, including glutamate and aspartate. In the case of ischemic pain, analgesia seems to derive from restoration of the oxygen demand supply. This effect could be mediated by inhibition of the sympathetic system, although vasodilation is another possibility. It is also probable that a combination of the two above mentioned mechanisms is involved. [17]
Spinal cord stimulators are placed in two different stages: a trial stage followed by a final implantation stage. First, the skin is prepped and draped utilizing sterile technique. The epidural space is accessed with loss of resistance technique using a 14-gauge Tuohy needle. The lead is fed through carefully with fluoroscopic guidance to the appropriate spinal level. This process is repeated to place another lead adjacent to the first. Fluoroscopy is used often during the procedure to identify proper placement of the SCS leads. The lead placement depends on the patient's pain location. Based on previous studies, the lead placement for patients with low back pain is typically T9 to T10. The device technician will then turn on the stimulation, typically starting at a very low frequency. The patient is prompted to describe the sensation perceived by activation of the leads, and the technician will calibrate the SCS to achieve the maximum paresthesia coverage of the patient's targeted pain area. Finally, the leads are anchored externally to reduce risk of lead migration, the site is cleaned, and a clean dressing is applied. Once the patient has recovered from the procedure, the device is once again tested and programmed. [18]
Patients who are candidates for stimulator placement should be screened for contraindications and comorbidities. The following should be considered prior to stimulator trial: [1]
In order to assess the efficacy of the spinal cord stimulator before implantation, a trial must be performed. This trial begins with placement of temporary leads into the epidural space and connected percutaneously to an external generator. The trial typically lasts 3–7 days followed by a 2-week reprieve before SCD implantation to ensure that there is no infection from the trial. [13] [20] Successful trial is defined by at least 50% reduction in pain and 80% paresthesia overlap of the original area of pain. If a patient has sudden changes in their pain, then further investigation is needed for possible lead migration or stimulator malfunction. [9]
Electrotherapy of pain by neurostimulation began shortly after Melzack and Wall proposed the gate control theory in 1965. This theory proposed that nerves carrying painful peripheral stimuli and nerves carrying touch and vibratory sensation both terminate in the dorsal horn (the gate) of spinal cord. [21] It was hypothesized that input to the latter could be manipulated to "close the gate" to the former. As an application of the gate control theory, Shealy et al. [22] implanted the first spinal cord stimulator device directly on the dorsal column for the treatment of chronic pain and in 1971, Shimogi and colleagues first reported the analgesic properties of epidural spinal cord stimulation. Since then this technique has undergone numerous technical and clinical developments.
At this time neurostimulation for the treatment of pain is used with nerve stimulation, spinal cord stimulation, deep brain stimulation, and motor cortex stimulation.
SCS has been studied in people with Parkinson's disease [23] and angina pectoris. [24]
Research on improving the devices and software has included efforts to increasing the battery life, efforts to develop closed loop control, and combining stimulation with implanted drug delivery systems. [23]
SCS is being studied to treat spinal cord injury. In August 2018, The European Commission's Horizon 2020 Future and Emerging Technologies program announced a $3.5 million funding grant for the four-nation project team that is building a prototype of an implant designed to 'rewire' the spinal cord. [25] In September 2018, Mayo Clinic and UCLA reported that spinal cord stimulation supported with physical therapy can help people with paralysis to regain their ability to stand and walk with assistance. [26] In December 2019, the first double blinded, randomized controlled pivotal study in the history of spinal cord stimulation was published in Lancet Neurology. [27]
Deep brain stimulation (DBS) is a neurosurgical procedure involving the placement of a medical device called a neurostimulator, which sends electrical impulses, through implanted electrodes, to specific targets in the brain for the treatment of movement disorders, including Parkinson's disease, essential tremor, dystonia, and other conditions such as obsessive-compulsive disorder (OCD) and epilepsy. While its underlying principles and mechanisms are not fully understood, DBS directly changes brain activity in a controlled manner.
Spinal anaesthesia, also called spinal block, subarachnoid block, intradural block and intrathecal block, is a form of neuraxial regional anaesthesia involving the injection of a local anaesthetic or opioid into the subarachnoid space, generally through a fine needle, usually 9 cm (3.5 in) long. It is a safe and effective form of anesthesia usually performed by anesthesiologists that can be used as an alternative to general anesthesia commonly in surgeries involving the lower extremities and surgeries below the umbilicus. The local anesthetic with or without an opioid injected into the cerebrospinal fluid provides locoregional anaesthesia: true analgesia, motor, sensory and autonomic (sympathetic) blockade. Administering analgesics in the cerebrospinal fluid without a local anaesthetic produces locoregional analgesia: markedly reduced pain sensation, some autonomic blockade, but no sensory or motor block. Locoregional analgesia, due to mainly the absence of motor and sympathetic block may be preferred over locoregional anaesthesia in some postoperative care settings. The tip of the spinal needle has a point or small bevel. Recently, pencil point needles have been made available.
Transcutaneous electrical nerve stimulation is the use of electric current produced by a device to stimulate the nerves for therapeutic purposes. TENS, by definition, covers the complete range of transcutaneously applied currents used for nerve excitation although the term is often used with a more restrictive intent, namely to describe the kind of pulses produced by portable stimulators used to reduce pain. The unit is usually connected to the skin using two or more electrodes which are typically conductive gel pads. A typical battery-operated TENS unit is able to modulate pulse width, frequency, and intensity. Generally, TENS is applied at high frequency (>50 Hz) with an intensity below motor contraction or low frequency (<10 Hz) with an intensity that produces motor contraction. More recently, many TENS units use a mixed frequency mode which alleviates tolerance to repeated use. Intensity of stimulation should be strong but comfortable with greater intensities, regardless of frequency, producing the greatest analgesia. While the use of TENS has proved effective in clinical studies, there is controversy over which conditions the device should be used to treat.
Epidural administration is a method of medication administration in which a medicine is injected into the epidural space around the spinal cord. The epidural route is used by physicians and nurse anesthetists to administer local anesthetic agents, analgesics, diagnostic medicines such as radiocontrast agents, and other medicines such as glucocorticoids. Epidural administration involves the placement of a catheter into the epidural space, which may remain in place for the duration of the treatment. The technique of intentional epidural administration of medication was first described in 1921 by Spanish military surgeon Fidel Pagés.
Neuropathic pain is pain caused by damage or disease affecting the somatosensory system. Neuropathic pain may be associated with abnormal sensations called dysesthesia or pain from normally non-painful stimuli (allodynia). It may have continuous and/or episodic (paroxysmal) components. The latter resemble stabbings or electric shocks. Common qualities include burning or coldness, "pins and needles" sensations, numbness and itching.
Joshua Philip Prager M.D., M.S. is an American physician. Prager specializes in pain medicine and is the executive director of Center for the Rehabilitation Pain Syndromes (CRPS) at UCLA Medical Plaza.
Failed back syndrome or post-laminectomy syndrome is a condition characterized by chronic pain following back surgeries. Many factors can contribute to the onset or development of FBS, including residual or recurrent spinal disc herniation, persistent post-operative pressure on a spinal nerve, altered joint mobility, joint hypermobility with instability, scar tissue (fibrosis), depression, anxiety, sleeplessness, spinal muscular deconditioning and even Cutibacterium acnes infection. An individual may be predisposed to the development of FBS due to systemic disorders such as diabetes, autoimmune disease and peripheral blood vessels (vascular) disease.
Pelvic pain is pain in the area of the pelvis. Acute pain is more common than chronic pain. If the pain lasts for more than six months, it is deemed to be chronic pelvic pain. It can affect both the male and female pelvis.
Sacral nerve stimulation, also termed sacral neuromodulation, is a type of medical electrical stimulation therapy.
Responsive neurostimulation device is a medical device that senses changes in a person's body and uses neurostimulation to respond in the treatment of disease. The FDA has approved devices for use in the United States in the treatment of epileptic seizures and chronic pain conditions. Devices are being studied for use in the treatment of essential tremor, Parkinson's disease, Tourette's syndrome, depression, obesity, and post-traumatic stress disorder.
Electroanalgesia is a form of analgesia, or pain relief, that uses electricity to ease pain. Electrical devices can be internal or external, at the site of pain (local) or delocalized throughout the whole body. It works by interfering with the electric currents of pain signals, inhibiting them from reaching the brain and inducing a response; different from traditional analgesics, such as opiates which mimic natural endorphins and NSAIDs that help relieve inflammation and stop pain at the source. Electroanalgesia has a lower addictive potential and poses less health threats to the general public, but can cause serious health problems, even death, in people with other electrical devices such as pacemakers or internal hearing aids, or with heart problems.
Continuous wound infiltration (CWI) refers to the continuous infiltration of a local anesthetic into a surgical wound to aid in pain management during post-operative recovery.
Neurostimulation is the purposeful modulation of the nervous system's activity using invasive or non-invasive means. Neurostimulation usually refers to the electromagnetic approaches to neuromodulation.
Spinal stenosis is an abnormal narrowing of the spinal canal or neural foramen that results in pressure on the spinal cord or nerve roots. Symptoms may include pain, numbness, or weakness in the arms or legs. Symptoms are typically gradual in onset and improve with leaning forward. Severe symptoms may include loss of bladder control, loss of bowel control, or sexual dysfunction.
Interventional pain management or interventional pain medicine is a medical subspecialty defined by the National Uniforms Claims Committee (NUCC) as, " invasive interventions such as the discipline of medicine devoted to the diagnosis and treatment of pain related disorders principally with the application of interventional techniques in managing sub acute, chronic, persistent, and intractable pain, independently or in conjunction with other modalities of treatment". Medicare Payment Advisory Commission (MedPAC) defined interventional techniques as, "minimally invasive procedures including, percutaneous precision needle placement, with placement of drugs in targeted areas or ablation of targeted nerves; and some surgical techniques such as laser or endoscopic diskectomy, intrathecal infusion pumps and spinal cord stimulators, for the diagnosis and management of chronic, persistent or intractable pain". Minimally invasive interventions such as facet joint injections, nerve blocks, neuroaugmentation, vertebroplasty, kyphoplasty, nucleoplasty, endoscopic discectomy, and implantable drug delivery systems are utilized in managing subacute or chronic pain.
Occipital nerve stimulation (ONS), also called peripheral nerve stimulation (PNS) of the occipital nerves, is used to treat chronic migraine patients who have failed to respond to pharmaceutical treatments.
Neuromodulation is "the alteration of nerve activity through targeted delivery of a stimulus, such as electrical stimulation or chemical agents, to specific neurological sites in the body". It is carried out to normalize – or modulate – nervous tissue function. Neuromodulation is an evolving therapy that can involve a range of electromagnetic stimuli such as a magnetic field (rTMS), an electric current, or a drug instilled directly in the subdural space. Emerging applications involve targeted introduction of genes or gene regulators and light (optogenetics), and by 2014, these had been at minimum demonstrated in mammalian models, or first-in-human data had been acquired. The most clinical experience has been with electrical stimulation.
A lumbar anterior root stimulator is a type of neuroprosthesis used in patients with a spinal cord injury or to treat some forms of chronic spinal pain. More specifically, the root stimulator can be used in patients who have lost proper bowel function due to damaged neurons related to gastrointestinal control and potentially allow paraplegics to exercise otherwise paralyzed leg muscles.
Peter Sean Staats is an American physician, specializing in interventional pain medicine. He is the founder of the Division of Pain Medicine at the Johns Hopkins School of Medicine, and was the Division's chief for nearly a decade. He is a past president of the North American Neuromodulation Society, the New Jersey Society of Interventional Pain Medicine,the American Society of Interventional Pain Physicians ( ASIPP) the World Institute of Pain ( WIP), The Southern Pain Society.
Epidural lysis of adhesions (LOA), also known as percutaneous adhesiolysis or the Racz procedure, is a minimally invasive spine surgery which involves the dissolution of epidural scar tissue by mechanical means to facilitate the spread of analgesics in an effort to alleviate pain. It is a type of percutaneous adhesiolysis procedure commonly used to treat chronic pain resulting from failed back surgery syndrome wherein scar tissue has formed around the nerves and causes pain. Evidence suggests the procedure may also be effective in treating spinal stenosis and radicular pain caused by a herniated disc.