Spinal cord stimulation

The spinal cord stimulation ( english stimulation spinal cord or SCS) is a minimally invasive form of therapy for chronic neuropathic pain . The posterior column of the spinal cord by means of one or more in the epidural space introduced electrodes by small electrical currents to stimulate ( neurostimulation ).

Spinal cord stimulation is an established therapy. A pulse generator (battery) and one or more electrodes are implanted in the patient. The therapy is controlled and powered by the pulse generator that is usually implanted under the abdominal wall or in the lower back / buttocks area.

There are various program forms that the pulse generator can "play". It can, for. B. the current strength and the pulse duration can be changed. Some of the stimulation parameters can be set and adjusted using an external programming device.

Common to the different variants of the target spinal cord stimulation, the pathological spontaneous activity in the dorsal horn neurons to stimulate or to normalize. In addition, the individual effects are very complex and result from a complex reaction to the current. Both electrochemical and biochemical transmitters and anatomical structures in the spinal cord, but also anatomical connections between the core areas of the spinal cord and core areas of the brain play a role.

Spinal cord stimulation is one of the techniques that emerged from the suggestion of gate control theory in the 1960s and was introduced by C. Norman Shealy .

Indications

Due to the anatomy of the spinal cord or the nerve supply, the stimulation u. a. Lower back pain and sciatica , i.e. pain radiating to the lower extremities , can be treated. Often it is chronic neuropathic pain; They come about through nerve damage or impairment, so the cause lies in the nervous system itself. The list of diagnoses that can be responsible for this is long. In particular, patients whose pain is of chronic and neuropathic origin are often refractory to conservative therapies .

There are a number of approved indications that are recognized by health insurance companies . This includes:

• Therapy-refractory (not responding to the usual therapies), chronic back and / or leg pain (lumbar sciatica)
• the peripheral arterial disease (PAD)
• the complex regional pain syndrome I and II (CRPS / Sudeck's disease )
• Chronic pain after spinal surgery ( Postdiskectomy Syndrome / Failed Back Surgery Syndrome)
• chronic nerve root irritation ( radiculopathy / polyradiculopathy).

Study situation

There are extensive observations of treatment series on peripheral arterial occlusive disease as well as a randomized study from 1999 by Klomp et al.

In 2000, Kemmler et al. presented a study on the effect of spinal cord stimulation in patients with complex regional pain syndromes I and II.

From 2008 there is a randomized study by Kumar et al. to therapy-refractory sciatica.

In the SCS comparison study Senza-RCT, which was published for the first time in mid-2015, which was randomized, prospective , controlled by the FDA and carried out as a multi-center study , evidence level Ib has proven that especially the use of high-frequency pulses at defined, spatially limited hotspots ( Spinal cord sarealen) brings better treatment results than conventional SCS procedures - both for chronic back and leg pain. The Ib classification corresponds to the highest level of evidence that a clinical study can ever achieve.

The high effectiveness of the high-frequency spinal cord stimulation was also confirmed in the long-term monitoring of the test subjects over 24 months. This emerges from the data published in September 2016 from the continuation of the “Senza RCT” study, which continued to be randomized, controlled and carried out as a multi-center study.

According to a small series (n = 20), applications with frequencies between 1 and 10 kHz do not differ in effectiveness.

treatment

Spinal cord stimulation is only used to treat chronic pain and is only used when simpler, non-invasive treatment methods ( painkillers , physiotherapy , etc.) do not provide pain relief for the patient in the long term.

As a treatment option for chronic neuropathic back pain, however, spinal cord stimulation is established in modern neurosurgery and classified with recommendation grade B in the S3 guideline 'Epidural spinal cord stimulation for the treatment of chronic pain'.

The electrodes are usually implanted in a stationary manner. One or more electrodes are used in the epidural space in order to be able to deliver the pain-relieving impulses there. These impulses are generated by a pulse generator usually implanted in the lower back or in the abdominal area, i.e. in the abdominal region.

The individual effect of the spinal cord stimulation is checked in a test phase before the electrodes are permanently implanted. During this test phase, the spinal cord is stimulated by an external device that the patient wears on his belt. The success of the treatment or the pain intensity is documented by the patient. On this basis, a decision is made about further therapy together with the doctor.

If the effect is insufficient, the electrodes can be removed again. All that remains is a small scar on the back. If the desired effect is shown, i.e. the pain is reduced by half on the VAS scale , the final pulse generator is connected and implanted.

Low frequency spinal cord stimulation

For successful treatment of the conventional spinal cord stimulation, which operates with current pulses of 40 to 70 Hz, a cover of the pain area with the through stimulation triggered Kribbel paresthesia an important criterion , without the low-frequency electrodes do not implanted can be. Since the patient's feedback is necessary for the effective placement of the electrodes, their implantation takes place under sedation , which enables the patient to give direct feedback about the correct stimulation location; at the same time, the risks associated with general anesthesia are avoided. In this treatment, the patient can adapt the pulse strength to the activities performed (sitting, walking, lying) or to the body posture.

High frequency spinal cord stimulation

→ Main article : High frequency spinal cord stimulation

The high-frequency spinal cord stimulation works with 10,000 Hz (= 10 kHz) outside of the perception range. The amplitudes of the current frequency are very close to one another and the current strength to be used is very low, so that tingling paresthesia does not even arise. The effective position of the electrodes can be reliably ensured by means of an impedance measurement, i.e. electrical resistance measurement , and an X-ray control in two planes: The implantation can thus take place under general anesthesia . In high-frequency therapy, the fine adjustment of the pulse generator takes place within the specialist doctor's office hours and independently of the activities.

Spinal ganglion stimulation - DRG

Electrodes on the spinal ganglia L4 and L5 shortly after implantation.

The spinal ganglion stimulation ( English Dorsal root ganglion , DRG), based on a change in positioning of the electrodes. These are placed directly on the spinal ganglion in order to limit the effect to the area supplied by the nerve fiber. This allows better results for pain in the extremities. Kribbel paresthesia here are known only in a few cases.

advantages

• Depending on the procedure, test stimulation can or must be carried out after implantation of the electrodes and before implantation of the pulse generator. The patient tests the stimulation for a few days or weeks via a cable to which an external test generator is connected. In a second step, the pulse generator is then implanted or the electrode is removed. In the case of peripheral arterial occlusive disease stage III and IVa (according to Fontaine), implantation can also be performed at one time.
• The often achieved reduction in drug pain therapy can prevent or reduce undesirable drug effects, including both acute ( nausea , dizziness, etc.) and chronic (organ damage, constipation, etc.).
• By reprogramming other or new areas of pain can be stimulated.

disadvantage

• Not all types and locations of pain can be treated with spinal cord stimulation. The effectiveness has been proven for neuropathic pain and thus for a whole range of indications and diagnoses that are responsible for chronic back and / or leg pain.
• Since the patients often experience a considerable improvement during the treatment (the pain intensity decreases; analgesics can be reduced or even discontinued), their participation in life improves. Since this also increases their activity , in the worst case the electrodes or - especially for patients who lose weight due to increased movement - the pulse generator can slip. But both can be repositioned.
• After a few years, the pacemaker unit often has to be replaced through another minor surgical procedure , as the battery runs out . Rechargeable devices, on the other hand, can be easily charged using an external charger . The charging time and frequency depend on the stimulation settings of the implant. The battery is also subject to wear (decrease in capacity over the years), but it is much less necessary to replace it.
• Many implants are not approved for use in MRI diagnostics, or only to a limited extent.

Individual evidence

1. ↑ CN Shealy, JT Mortimer, JB Reswick, Electrical inhibition of pain by stimulation of the dorsal columns: preliminary clinical report, Anesthesia and Analgesia, Volume 46, 1967, pp. 489-491
2. ↑ ^{a b} S-3 guideline "Epidural spinal cord stimulation for the therapy of chronic pain". In: AWMF Register No. 008/023. Working Group of the Scientific Medical Associations, accessed on December 16, 2016 . 
3. ^ Klomp, HM: Spinal cord stimulation in critical limb ischemia: a randomized trial . In: The Lancet 1999, 353: 1040-1044.
4. ↑ Kemmler, MA et al .: Spinal chord stimulation in patients with chronic reflex sympathetic dystrophy . In: N Eng J Med (2000), 343: 618-624.
5. ↑ Kumar, K. et al .: The effects of spinal cord stimulation in neuropathic pain are sustained: a 24-month follow-up of the prospective randomized controlled multicentertrial of the effectiveness of spinal cord stimulation . In: Neurosurgery (Ed.): 2008, vol. 63/4: 762-770 .
6. ↑ Kapural L. et al .: Novel 10 kHz High Frequency Therapy (HF10 Therapy) is Superior to Traditional Low Frequency Spinal Cord Stimulation for the Treatment of Chronic Back and Leg Pain: The SENZA-RCT Randomized Controlled Trial. In: Anesthesiology (2015), V 123, No. 4. Accessed September 8, 2016 . 
7. ↑ Kapural L. et al .: Comparison of 10-kHz High-Frequency and Traditional Low-Frequency Spinal Cord Stimulation for the Treatment of Chronic Back and Leg Pain: 24-Month Results From a Multicenter, Randomized, Controlled Pivotal Trial . In: Neurosurgery (Ed.): (2016), V 79, No. 5 .
8. ↑ amanda: No difference in pain relief between 1kHz and 10kHz spinal cord stimulation in PROCO RCT - NeuroNews International . In: NeuroNews International . September 5, 2017 ( neuronewsinternational.com [accessed October 31, 2017]).
9. ↑ Chronic Pain: Innovation in Neuromodulation: Dorsal Root Ganglion Stimulation (DRG) , Forum Sanitas - Das informative medical magazine, 1st edition 2017, pp. 12-14. Retrieved November 19, 2017.

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