Pulsed Radiofrequency Treatment

The mechanism of action of PRF is currently undergoing extensive research. At the moment, most studies point towards an alteration in synaptic transmission, in a neuromodulatory-type effect. There is, however, an ongoing discussion on whether or not the effect of PRF is minimally ablative. Considering the physical events around the electrode, even if a certain level of destruction does occur during PRF, the degree of clinical relevance is questionable, as PRF has demonstrated a remarkable margin of safety.

Biological changes in tissues during PRF can occur due to the thermal effects, the high intensity electric fields, or as a result of both. PRF applies short pulses of radiofrequency signals from a radiofrequency generator to the neural tissue.

Commercially available RF generators provide PRF signals with pulse durations ranging from 5 to 50 ms and pulse frequency ranging from 1 to 10 Hz, but the most commonly used sequence is a pulse frequency of 2 Hz and a pulse width of 20 ms. The intrinsic radiofrequency oscillation frequency within each pulse is still about 420 kHz, which is the same as for RF. In PRF, because the pulse duration is only a small percentage of the time between pulses, the average tissue temperature rise for the same RF voltage is much less for pulsed radiofrequency than for conventional radiofrequency. For this reason, higher voltages can be applied to the electrode in PRF in RF, without raising the average tissue temperature near the electrode into the denaturation range above 45°C.

Notwithstanding the uncertainty regarding the extent of the thermal effects, the effects of the high-intensity electric fields have been well established. In general, PRF can produce far stronger electrical fields than RF. However, as the electric fields wane rapidly with increasing distance from the tip, there is very little destruction that results. Majority of the target tissues are thus subjected to low or moderate-strength electric fields, which may, in fact, play an important role in the mode of action of PRF.

• Cervical radicular pain
• Thoracic radicular pain
• Intercostal neuralgia
• Occipital neuralgia
• Inguinal pain
• Chronic shoulder pain
• Myofascial pain syndrome
• Phantom limb pain
• Chronic abdominal pain
• Scar pain
• Peripheral nerve pain

Injections are generally avoided in patients with systemic infection or skin infection over puncture site, bleeding disorders or coagulopathy, allergy to local anaesthetics or any of the medications to be administered.

Pulsed radiofrequency treatment is contraindicated in patients with pacemakers and or any other neural implants (spinal cord stimulator, deep brain stimulator).

The procedure is done on an outpatient basis. The procedure is performed under ultrasound guidance to ensure accuracy of needle placement. Specialized equipment including radiofrequency machine, probe and RF needle is utilized to heat the nerve up to a temperature of 42°C. Patients need to be aware that the outcome of the procedure is variable and they may not receive the desired benefits. Similarly, they must be aware of the transient nature of the therapeutic benefits and that there may need repeated injections.

Generally local anaesthetic is injected around the nerve following nerve ablation. The local anaesthetic is responsible for immediate pain relief, where as pulsed radiofrequency takes 4 to 6 weeks to provided sustained pain relief.

Complications are rare, particularly if the injections are performed using a precise needle-positioning technique. Possible complications include bruising, infection, hematoma, nerve injury and reaction to the injectates. Infection can be avoided with appropriate aseptic precautions. Severe allergic reactions to local anaesthetics are uncommon. Steroid injections may produce local reactions, occurring most often immediately after injection. These local reactions last for 24 to 48 hours, and are relieved by application of ice packs. Post-procedural pain flare-up may occasionally occur, and may be treated with painkillers. Neurological complications including paraesthesias and numbness have been described but are rare.