Neurodestructive procedures or neurodestruction (synonyms: neuroablation, neurolysis, neurosurgical pain therapy) is an invasive, destructive (“destroying”) intervention for the long-term elimination of nerves or nerve plexuses. This pain therapeutic measure targets the sensitive function of the nerves and is usually effective on a temporary basis as, for example, regenerative processes progress and may require re-intervention. Because neurodestruction is a highly complication- and risk-prone procedure, the indication should be strict and intervention should be considered the last stage of therapy.
Indications (areas of application)
- Extremely severe chronic pain conditions – e.g., tumor pain.
- Improvement of severe spasticity after spinal cord injury.
Contraindications
Since the indications, because of the significant complications and risks, are very narrow and a careful cost-benefit analysis is mandatory, the contraindications arise from the indications mentioned.
Before surgery
Before surgery, a detailed medical history must be taken and the patient must be informed about possible complications. Radiographic examination of the spine or other target anatomic structures, in addition to thorough clinical inspection, ensures planning of the procedure. Platelet aggregation inhibitors (blood thinning medications) should be discontinued approximately 5 days beforehand. This must be checked with the aid of a blood test (coagulation parameters). To support wound healing or the success of the therapy, it is recommended that the patient stop nicotine consumption.
The procedure
Destruction of the nerve tissue is performed either under fluoroscopic control (real-time X-ray film) or under CT control (computed tomography). Neurotoxic substances are applied percutaneously (through the skin) to the target tissue. The following neurolytics may be used for this purpose:
- Ammonium salts
- Ethanol (ethanol)
- Glycerol
- Cresol
- Phenol
Beforehand, a test injection with local anesthetics is performed. This measure has a diagnostic character and indicates the correct location of the intervention. In addition, the test injection allows a prognostic statement regarding the effectiveness of the following neurodestruction. However, these precautions do not give complete certainty. The effect of neurolytics is nonspecific and may be reversible or irreversible, so repetition may be necessary. Destruction of nervous tissue can also be accomplished with the aid of thermocoagulation or cryosurgery (kyrotherapy, icing). In addition to direct chemical or thermal neurodestruction, the following neurodestructive procedures should be mentioned:
- Chordotomy – The procedure is based on surgical transection of the pain pathway in the spinal cord, called the tractus spinothalamicus (anterior cord). Anterior cord transection is also known as anterolateral chordotomy.
- Neurolysis – External neurolysis refers to the surgical release of adhesions around a nerve, such as in scarring after injury or fracture. Internal neurolysis refers to the exposure of intact nerve fibers from an endoneural scar (scar within a nerve fiber bundle after injury to the nerve) to restore function by decompression of the nerve fibers.
- Rhizotomy – In this procedure, depending on the target region, the posterior root in the posterior horn of the spinal cord is cut at the level of the corresponding spinal cord segment. This results in the elimination of pain and temperature sensation and the perception of touch stimuli.
After surgery
After surgery, close monitoring of the patient is necessary. In addition to surgical follow-up (e.g., in the case of a rhizotomy), the patient’s neurologic status must also be closely monitored to detect potential complications early.
Potential complications
Depending on the location of the target tissue, there is always a risk of co-destruction of other nerve fibers, so the picture of neurologic complications varies depending on the site of intervention and is very broad.
- Failure to achieve therapeutic success.
- Chemical destruction of adjacent structures as well as the spinal cord.
- Chemical destruction of distant lying organs by intravascular injection (into a vessel) of neurolytics
- Chemical neuritis (inflammation of the nerve) of the affected nerve with the appearance of new pain.
- Deafferentation pain (phantom limb pain).
- Mechanical injury to adjacent structures
- Motor failures
- Myelitis (inflammation of the spinal cord)