Pulsed radiofrequency of the sural nerve for the treatment of chronic ankle pain.

BACKGROUND The application of radiofrequency (RF) has been successfully used in the treatment of chronic pain conditions, including facet arthropathy, sacroiliac joint pain, groin pain, radicular pain, cervicogenic headaches, and phantom limb pain. Due to the neurodestructive effect of continuous RF ablation and possible deafferentation sequelae, only pulsed radiofrequency (PRF) has been applied to peripheral sensory nerves. There are no previous reports of successful PRF application to the sural nerve. OBJECTIVES To report on the successful use of PRF to the sural nerve for the treatment of ankle pain. To discuss current theories on the mechanism by which PRF produces pain relief. METHODS The report presented here describes the case of a 39-year old patient who sustained injury to her ankle. The patient was complaining of pain in the distribution of the sural nerve, which was confirmed by electrodiagnostic studies. The pain did not respond to oral and topical analgesics. The patient had short-term relief with a sural block with bupivacaine and triamcinolone. The patient then underwent PRF application to the right sural nerve for 240 seconds at 45 volts. RESULTS The patient reported complete relief. There was no pain recurrence 5 months after the procedure. LIMITATIONS This report describes a single case report. CONCLUSIONS It is conceivable that PRF may provide long-term pain relief in cases of sural nerve injury. The exact mechanism of the antinociceptive effect is still unknown. Possible mechanisms include changes in molecular structure by the electric field, early gene expression, stimulation of descending inhibitory pathways, and transient inhibition of excitatory transmission.