Role of 3 Tesla MR Neurography and CT-guided Injections for Pudendal Neuralgia: Analysis of Pain Response.

BACKGROUND: Magnetic resonance neurography (MRN) has an increasing role in the diagnosis and management of pudendal neuralgia, a neurogenic cause of chronic pelvic pain. OBJECTIVE: The objective of this research was to determine the role of MRN in predicting improved pain outcomes following computed tomography (CT)-guided perineural injections in patients with pudendal neuralgia. STUDY DESIGN: This study used a retrospective cross-sectional study design. SETTING: The research was conducted at a large academic hospital. METHODS: Patients: Ninety-one patients (139 injections) who received MRN and CT-guided pudendal blocks were analyzed. INTERVENTION: A 3Tesla (T) scanner was used to evaluate the lumbosacral plexus for pudendal neuropathy. Prior to receiving a CT-guided pudendal perineural injection, patients were given pain logs and asked to record pain on a visual analog scale. MEASUREMENT: MRN findings for pudendal neuropathy were compared to the results of the CT-guided pudendal nerve blocks. Injection pain responses were categorized into 3 groups - positive block, possible positive block, and negative block.Statistical Tests: A chi-square test was used to test any association, and a Cochran-Armitage trend test was used to test any trend. Significance level was set at .05. All analyses were done in SAS Version 9.4 (SAS Institute, Inc., Cary, NC). RESULTS: Ninety-one patients (139 injections) who received MRN were analyzed. Of these 139 injections, 41 were considered positive (29.5%), 52 of 139 were possible positives (37.4%), and 46 of 139 were negative blocks (33.1%). Of the patients who had a positive pudendal block, no significant difference was found between the MRN result and the pudendal perineural injection response (P = .57). Women had better overall response to pudendal blocks, but this response was not associated with MRN findings (P = .34). However, positive MRN results were associated with better pain response in men (P = .005). Patients who reported bowel dysfunction also had a better response to pudendal perineural injection (P = .02). LIMITATIONS: Some limitations include subjectivity of pain reporting, reporting consistency, absence of a control group, and the retrospective nature of the chart review. CONCLUSION: Pudendal perineural injections improve pain in patients with pudendal neuralgia and positive MRN results are associated with better response in men. KEY WORDS: MRI, MRN, CT injection, pudendal neuralgia, pudendal nerve, pelvic pain, chronic pelvic pain, pudendal neuropathy.