Radiofrequency Pain Treatment

Dimitris Papadopoulos MD Fellow Of Interventional Pain Practice (FIPP)

Updated 03 February, 2011

GENERAL

There are two types of radiofrequency (RF), conventional (CRF) and intermittent or pulsed radiofrequency (PRF).

In CRF, a continuous radiofrequency electric field (RFEF) is applied through an electrode to the active tip of a special needle and controlled heat is generated as a result of ion friction. When aimed at some target nerve, this heat (80-90°C) leads to nerve ablation and interruption of pain signals that are sent to the spinal cord and brain.

In PRF, the electric field is interrupted when temperature reaches 42°C and, as a consequence, the heat applied on the target nerve is non-ablative since it does not exceed 42°C. It has a rather neuromodulatory effect, reducing significantly pain signal conduction.

The radiofrequency electric field  is produced by a special radiofrequency generator and applied to the target with a special needle that has an active non-insulated end. An electrode that is connected with the generator, is inserted through the needle. The generator has a screen with indications providing detailed information in the various parameters of the technique. (2,3,4,5)

INDICATIONS

Radiofrequency treatment is indicated for the treatment of nociceptive pain, as well as for some other types of neuropathic pain (with continuous and limited distribution) that are resistant to conservative treatment. This includes pain of unknown aetiology, such as the 12th rib syndrome or radicular pain that cannot be explained by any anatomic abnormality.

Neuropathic pain can be treated with radiofrequency if the nerve function remains at least partially intact, as for example in the cases of postoperative scar neuropathic pain, pressure-induced pain or pain due to nerve irritation. Pain induced by herniated intervertebral disc or peripheral neuropathy falls also within this category.

Radiofrequency treatment is not indicated when the pain is of central origin (impairment or disorder of the central nervous system, brain or spinal cord) or when there is severe psychopathology.



COMMON RADIOFREQUENCY TREATMENTS

Conventional radiofrequency applied to the medial branch of the posterior ramus of the spinal nerve. This branch of the spinal nerve innervates the facet joints of the spine. These joints may cause chronic pain in the lower back or/and neck and more rarely in the chest due to degenerative changes, injury or poor positioning.

Pulsed radiofrequency and more rarely conventional radiofrequency applied to the  dorsal root ganglion (DRG) or to the part of the nerve that is the closest to the intervertebral foramen (if approaching DRG is not anatomically feasible). The treatment is indicated in radicular pain or radiculopathy from herniated intervertebral disc, radiculitis of unclear aetiology and the 12th rib syndrome. (2,4,6,7,29,32,33)

Intradiscal cooled radiofrequency. It is applied to treat chronic disc pain due to  intradiscal degeneration, by ablating nociceptive receptors of the posterior part of the  annulus fibrosus of the disc. These receptors produce pain signals that are interpreted by the brain as low back pain.

Conventional radiofrequency in the sympathetic chain. The sympathetic chain is affected by many diseases, such as vascular insufficiency, pain of sympathetic aetiology, metastatic or osteoporotic fracture pain and discogenic pain due to intradiscal degeneration.

Conventional radiofrequency in visceral nerves. It is highly effective in the treatment of visceral abdominal pain from  malignant diseases involving the upper abdominal viscera (pancreas, liver, stomach etc) but also in some cases of benign pain (chronic pancretatitis, irritable bowel syndrome).(15)

Pulsed radiofrequency in peripheral nerves. It is applied in cases of post-injury peripheral neuropathy. (1,9)

Conventional or pulsed radiofrequency in the sphenopalatine ganglion. It is indicated in painful diseases resistant to conservative treatment, such as cluster headache and atypical prosopalgia. (16)

Conventional radiofrequency in the gasserian ganglion. Highly effective treatment for cases of trigeminal neuralgia that are resistant to conservative treatment.(10,11)

DESCRIPTION OF THE TECHNIQUE

The technique is applied under local anaesthesia and fluoroscopic guidance. The patient does not need to be hospitalized and can go home a few hours after the intervention is completed. If considered necessary, light conscious sedation can be administered in order for the patient to be more relaxed and cooperative with the physician.

After following all antiseptic measures, a special needle is advanced to the target point with absolute accuracy and when the final proper site is confirmed with fluoroscopy from different views, an electrode that is connected with the radiofrequency generator is inserted through the needle.

Then follows sensory testing with nerve stimulation in order to bring the active tip of the needle as close as possible to the target. Once this is achieved, motor testing follows. The patient’s response to such a type of stimulation is observed in order to ensure that the active tip of the needle is within a safety distance from the motor nerve which is not the target.

Then, a local anaesthetic is administered and the electrode is heated with one of the two types of radiofrequency at the selected temperature for a few minutes and acts therapeutically. The rise of temperature is not painful for the patient because of the local anaesthesia provided.

RESULTS

Radiofrequency treatment is a safe and effective method for the treatment of several chronic pain syndromes. Should the pain be significantly reduced with the first radiofrequency application, the treatment can be applied repetitively. There is strong clinical evidence that radiofrequency treatment is effective in trigeminal neuralgia, radicular nerve pain and spinal pain  Lord 2002). In a large study, 92,5% of patients with trigeminal neuralgia reported excellent or satisfactory relief after therapy of the trigeminal ganglion with conventional radiofrequency (Chen 2001).

Large randomized control studies (RCT) provide evidence for the denervation of facet joints in the lumbar and cervical spine with application of radiofrequency to the medial nerve branch. According to the latest review of the American Society of Interventional Pain Physicians (ASIPP) concerning interventional treatment of chronic spinal pain, facet joint denervation in the lumbar and cervical spine is a strongly  evidence-based technique for  a short period  (3-6 months) and moderately evidence-based for a long period (> 1 year).

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