Abstract ID: A30
Abstract Title: Pulsed Radiofrequency Neuromodulation: A Novel Treatment for Post-Orchiectomy Pain
Authors: Weingarten T1, Tiede J2, Turley T3
The Mayo Clinic Rochester MN 1, The Mayo Clinic Rochester MN 2, The Mayo Clinic Rochester MN 3
Poster Type: Either
ABSTRACT BODY
Introduction: Pulsed radiofrequency (PRF) neuromodulation is an evolving technique used to treat a variety of pain conditions. We describe PRF to treat post-orchiectomy pain.
Case Report:A 40 year-old male was referred for management of chronic hemi-scrotal pain. An investigation including urinalysis, cystoscopies, ultrasound and MRI failed to establish a diagnosis. Pain management at outside institutions consisted of oral opiates, epidural corticosteroid injections and eventually, a left orchiectomy, which resulted in a significant exacerbation of his pain. His initial postoperative course was complicated by a hematoma and a questionable wound infection. A series of post-orchiectomy ilioinguinal nerve blocks with local anesthetics were ineffective. Anticonvulsant pharmacotherapy was not tolerated secondary to cognitive side effects. Upon presentation to our clinic, he complained of debilitating, shooting pains into the left hemi-scrotum. Diagnostic injections of the left genitofemoral and ilioinguinal nerves with lidocaine and bupivacaine resulted in concordant responses. We performed PRF to both these nerves. The left genitofemoral nerve was identified by electrical stimulation with .5V at 50Hz using a 50mm 22-G SMK needle with a 4mm active tip. PRF was performed for 240sec with 20msec pulses at 2 Hz and a voltage output between 50-60V adjusted to keep the needle tip below 42ºC. This procedure was repeated for the ilioinguinal nerve. The treatment was non-painful. The subject reported 100% improvement in pain post-procedure. 4 days post-procedure he underwent a reexploration of the scrotum. He experienced no post-operative pain and required no analgesics post-operatively. At his 3 month follow up, he continued to have 100% benefit.
Discussion:PRF differs from radiofrequency ablation in that it is non-destructive, leaving neural tissues intact. Delivery of high energy to nerves at physiologic temperatures results in disruption of nociceptive transmission(1). PRF delivers high energy pulses at a low-frequency. The low pulse frequency allows heat, a by-product, to dissipate keeping the electrode cool. It is unclear how PRF works, but it has been demonstrated that c-fos expression in the dorsal columns increases after rats were treated with PRF(2). PRF has been used primarily to treat chronic back pain and head pain. Cohen, et al, reported the use of PRF to treat post-hernioplasty pain in two patients and post-vasectomy pain in one patient(3). He reported >90% pain relief six months after a single treatment. Our case is the first report of using PRF to treat post-orchiectomy pain. One interesting caveat is that our patient not only experienced pain relief in the immediate post-procedure period, but had post-operative analgesia 4 days following the PRF treatment. PRF is a relatively new technique and requires rigorous investigation to determine its efficacy and safety before widespread acceptance. Our observation of post-operative analgesia certainly needs to be reconfirmed by further investigation but does have exciting implications for perioperative and chronic pain management.
References:(1) Slappendel R. Pain 73 (1997). (2) Van Zundert J.Anesthesiology 102(2005). (3)Cohen SP. Urology 61 (2003).
ATTACHED FILES
Reg Anesth Pain Med 2005; 30(3):A30