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OBJECTIVE Nervus intermedius neuralgia (NIN) or geniculate neuralgia is a rare facial pain condition consisting of sharp, lancinating pain deep in the ear and can occur alongside trigeminal neuralgia (TN). Studies on the clinical presentation, intraoperative findings, and ultimately postoperative outcomes are extremely limited. The aim of this study was to examine the clinical presentation and surgical findings, and determine pain-free survival after sectioning of the nervus intermedius (NI). METHODS The authors conducted a retrospective chart review and survey of patients who were diagnosed with NIN at one institution and who underwent neurosurgical interventions. Pain-free survival was determined through chart review and phone interviews using a modified facial pain and quality of life questionnaire and represented as Kaplan-Meier curves. RESULTS The authors found 15 patients with NIN who underwent microsurgical intervention performed by two surgeons from 2002 to 2016 at a single institution. Fourteen of these patients underwent sectioning of the NI, and 8 of 14 had concomitant TN. Five patients had visible neurovascular compression (NVC) of the NI by the anterior inferior cerebellar artery in most cases where NVC was found. The most common postoperative complaints were dizziness and vertigo, diplopia, ear fullness, tinnitus, and temporary facial nerve palsy. Thirteen of the 14 patients reportedly experienced pain relief immediately after surgery. The mean length of follow-up was 6.41 years (range 8 months to 14.5 years). Overall recurrence of any pain was 42% (6 of 14), and 4 patients (isolated NIN that received NI sectioning alone) reported their pain was the same or worse than before surgery at longest follow-up. The median pain-free survival was 4.82 years ± 14.85 months. The median pain-controlled survival was 6.22 years ± 15.78 months. CONCLUSIONS In this retrospective review, sectioning of the NI produced no major complications, such as permanent facial weakness or deafness, and was effective for patients when performed in addition to other procedures. After sectioning of the NI, patients experienced 4.8 years pain free and experienced 6.2 years of less pain than before surgery. Alone, sectioning of the NI was not effective. The pathophysiology of NIN is not entirely understood. It appears that neurovascular compression plays only a minor role in the syndrome and there is a high degree of overlap with TN.

INTRODUCTION Pain relief following microsurgery for trigeminal neuralgia (TN) may be related to multiple factors including pain type, degree of neurovascular conflict, arterial compression, and location of compression. The objective of this study was to construct a predictive scoring system based on clinical and radiographic factors that can preoperatively prognosticate long-term outcomes in TN following surgery. METHODS 275 patients with Type 1 or Type 2 TN underwent microvascular decompression (MVD) or internal neurolysis (IN) following a preoperative high-resolution MRI. Outcome data was obtained retrospectively by chart review and/or phone follow-up. Characteristics of neurovascular conflict were obtained from preoperative MRI. Factors that resulted in a probability value of <0.05 on univariate logistic regression analyses were entered into a multivariate cox regression analysis in a backward stepwise fashion. For the multivariate analysis, significance at the 0.15 level was used. A prognostic system was then devised with three possible scores (0/1, 2, or 3) and survival analyses were conducted. RESULTS >Univariate predictors of pain-free survival were pain type (P = 0.013), presence of any vessel (P = 0.042), and neurovascular compression severity (0.038). Scores of 0/1, 2, and 3 were found to be significantly different in regard to pain-free survival (log rank, P = 0.008). At 5 and 10 years there were 42, 57, and 72% and 42,52, and 58%, pain free survival in groups 0/1, 2, and 3, respectively. TN1 patients with severe neurovascular conflict (score of 3) had the best outcome, which was significantly better that TN1 patients without neurovascular conflict (score of 1) (log rank, P = 0.005). Severe neurovascular conflict is more likely to have arterial compression (99%) (P< 0.001). CONCLUSION Pain-free survival of TN patients after microsurgery can be predicted in a step-wise statistically significant fashion, by a simple scoring system based on preoperative clinical and radiographic findings.