By artificially stimulating sensitive nerve fibers with a low-intensity electric current, neurostimulators reduce pain by bypassing their natural transmission mechanism to the brain.

Neurostimulation helps relieve pain by acting locally, unlike drug treatments. Its effect is immediate and its action easily adjustable by the patient himself. The undeniable advantage of this technique is to provide the patient with a means of treating his pain which is tailor-made and autonomous. But in no case does the neurostimulator treat the cause of the pain. Depending on the “severity” and chronicity of the pain, two types of neurostimulators exist:

The medullary or percutaneous neurostimulator (PENS)

It is a kind of pacemaker, surgically implanted under the abdomen or in the lower back, which sends electrical signals to the spinal cord through a probe. The parameters of the current delivered are defined by the doctor and can be adjusted by the patient.

Composition of the spinal cord stimulator

• The neurostimulator: titanium case 5 cm by 5 cm and 1 cm thick, generator of electric current and connected to the stimulation probe. Neurostimulators are either rechargeable or renewable every 2 to 5 years;
• The probe: electrode made of a conductive metal wire covered with an insulator installed in the epidural space along the spine;
• The programmer: remote control used to adjust the parameters of the electric current. The doctor sets a range for the parameters and the patient himself personalizes his daily setting according to his needs. The latest models operate via Bluetooth using an application that can be downloaded from a smartphone or tablet.

The transcutaneous neurostimulator (TENS)

These neurostimulators are much less invasive than the first ones and are commonly used by physiotherapists and chiropractors. The electrical impulses are delivered by electrodes placed on the patient’s skin in the area to be stimulated.

Composition of the transcutaneous neurostimulator

• Electrodes to be placed on the skin connected to a generator.
• A current generator with several programs depending on the desired action.

The percutaneous neurostimulator

The sensations of pain are transmitted to the brain via sensitive nerve pathways. Pain messengers all pass through the “pain portal” in the spinal cord. This door is more or less open, allowing more or less information to pass. Percutaneous neurostimulation works by closing this door, thus blocking the passage of pain: this is called gate control, which makes it possible to reduce or even completely eliminate pain. The sensation felt in the area usually painful is then a painless paresthesia (tingling, tingling).

The transcutaneous neurostimulator

Transcutaneous neurostimulation operates three levers to reduce pain:

• the electrical impulses pass through the skin and stimulate the sensitive nerve fibers near the electrodes, which blocks the transmission of the pain message to the brain;
• they stimulate muscle contraction, which improves blood circulation in the affected area;
• finally, they induce the production of endorphins, which are natural analgesics.

Indications and contraindications

Benefits and indications of PENS

Medullary neurostimulation, or percutaneous, is prescribed in the event of chronic pain of neurological origin (sciatica, cruralgia, cervico-brachial neuralgia, algodystrophy) or traumatic (peripheral nerve injury, post-traumatic or post-surgical pain, pain related to a phantom member). In most cases, PENS cuts the pain in half, making it possible to reduce or even stop the associated drug treatments. PENS is generally well tolerated, is not addictive, and the risk of complications is low.

Benefits and indications of TENS

Transcutaneous neurostimulation is indicated in cases of acute localized pain existing for less than 3 months in the limbs or back. It helps relieve muscle and joint pain, and is a good alternative or a complement to usual drug treatments. It is a painless technique, devoid of addiction and side effects.

Using a TENS

The use of TENS is recommended as soon as the pain appears. The treatment can be carried out 3 times a day for 30 minutes per session. The electrodes should be applied to clean, dry, injury-free skin, spaced approximately 2,5 cm apart in the area of ​​the painful area to be treated. The program is then chosen according to needs: the intensity, frequency and duration of the electrical pulses can be adjusted.

Its analgesic action is manifested by tingling, tapping, a sensation of massage and sometimes muscle contraction. When the sensations become unpleasant, the intensity should be reduced.

Precautions to be taken with TENS

It is not recommended to use a TENS:

• in the event of pregnancy;
• if another electronic implant is present;
• in case of skin lesions;
• on the head, carotids or front of the neck.

You should stop using TENS if:

• the treated pain does not improve after five days of treatment, or even gets worse;
• the treatment causes an unpleasant feeling, headache or skin irritation.

L’implantation du PENS

The implantation of a spinal cord stimulator is done in several stages:

• the placement of the electrode along the spine is done during a first surgical intervention. The electrode is connected to an external generator. A remote control allows you to adjust the intensity of the stimulation as needed;
• after a one-week trial period to assess the efficacy of the treatment and the patient’s tolerance, a decision is made to continue therapy. If the pain reduction is at least 50% and the patient’s quality of life is improved, the final implantation of the neurostimulator under the skin is performed. The patient then takes control of the neurostimulator with his remote control or smartphone.

Precautions to be taken with PENSs

The operation of the PENS can be disturbed by devices generating an electromagnetic field (high-voltage transformers, induction hob, security gates, etc.).

• Sports or any movement involving torso rotation should be avoided, as they may displace the electrode and require further surgery to replace it;
• MRIs should be avoided: in all cases, it is necessary to inform the medical staff of the wearing of a PENS.

The different models of TENS

Before acquiring a personal transcutaneous neurostimulator, it is recommended to have a medical opinion.

The choice of a TENS is based on several criteria:

• the number of programs available depending on the use you want to make of them:
• the number of channels: 2-channel models can stimulate 2 zones, while 4-channel models can stimulate 4;
• power supply: by batteries or rechargeable battery;
• the frequency of the current (number of pulses per second): between 1 and 150 Hz. The more the frequency increases, the more the contracting effect increases;
• the duration of the pulse: 180 µs for an analgesic action, and up to 400 µs for a contracting effect;
• corded or wireless model;
• disposable or reusable carbon electrodes, with or without conductive gel;
• compliance with European medical standards (CE marking), manufacturer’s warranty (minimum 1 year);
• prefer a known brand (Compex, Slendertone, Schwa-Medico).