Measuring the Quality of Pudendal Nerve Perineural Injections.

Background: Pudendal neuropathy is a tunnel syndrome characterized by pelvic pain and may include bowel, bladder, or sexual dysfunction or a combination of these. One treatment method, pudendal nerve perineural injections (PNPIs), uses infiltration of bupivacaine and corticosteroid around the nerve to provide symptom relief. Bupivacaine also anesthetizes the skin in the receptive field of the nerve that is injected. Bupivacaine offers rapid pain relief for several hours while corticosteroid provides delayed pain control often lasting 3 to 5 weeks. Not all pudendal nerve blocks may provide complete pain relief but long-term pain control from the steroid appears to be associated with immediate response to bupivacaine. We offer a method of evaluating the quality of a pudendal block on the day it is performed using pinprick sensation evaluation.

Objective: To demonstrate that pinprick sensory changes provide a simple and rapid method of measuring response to local anesthetic and pain reduction provided by a PNPI on the day it is performed. This response defines the quality of each PNPI.

Study Design: This is a case series based on retrospective review of a private practice database that is maintained by HealthEast hospitals in Minnesota. Database information includes standard physical examination, recording techniques, and treatment processes that had been in place for several years.

Setting: Private practice in United States.

Methods: Patients with a diagnosis of pudendal neuropathy are treated with PNPIs. Two hours after each block, 2 endpoints are measured: response to a sensory pinprick examination of the pudendal territory and difference in patient-reported pain level before and after nerve block. Fifty-three men from a private practice treating only pelvic pain received the treatment in 2005. Reported pain level was not recorded for 2 patients.

Results: Bupivacaine in perineural injections produces varying degrees of analgesia or hypalgesia to pinprick. Normal pinprick response suggests pudendal nerves were not penetrated by bupivacaine. Patient responses varied from complete, i.e. all 6 branches anesthetized to none. Most men had 2 - 5 nerve branches anesthetized. One man had a single nerve branch that responded to bupivacaine. Three men failed to respond to local anesthetic.Changes in pre-PNPI to post-PNPI pain scores were significantly decreased (n = 51, P-value < 0.0001), indicating that bupivacaine in the PNPI reduced pain. Forty-one patients (80.4%) indicated less pain after the procedure and only 2 patients (4.0%) indicated more pain. The number of nerve branches successfully anesthetized was also significantly correlated with change in score. On average, an additional successful nerve branch anesthetized corresponded to a drop of about 0.66 in the change score (n = 51, P - value = 0.0005).

Conclusion: PNPIs relieve pain. Anesthesia affected all 6 pudendal nerve branches in only 13.2% of patients. Complete pain relief occurred in 39.2%. This argues against use of perineural pudendal blockade as a diagnostic test. Pain relief after PNPI is associated with number of nerve branches that are anesthetized. At 2 hours after a PNPI its quality (the number of the 6 nerve branches with reduced response to pinprick from the perineural local anesthetic) is associated with subjective reduction of pain.

Key Words: Pudendal neuralgia, chronic perineal pain, pudendal nerve block, sensory examination, neurologic examination, pain management, chronic pelvic pain syndrome.