Surgical Management of Geniculate Neuralgia, Clinical Series, and Anatomical Study

Background Geniculate neuralgia is an uncommon syndrome that typically causes severe paroxysmal neuralgic pain centered in the ear. The traditional management consists of medical treatment and surgery for refractory cases. The objective is to review the presentation, treatment, and complications of patients surgically treated at Mayo Clinic, Rochester, in the past 16 years. Surgical nuances and technique to correctly identify nervus intermedius in its cisternal segment are described.

Methods A prospectively maintained neurosurgical database from 2000 to 2016 was searched. Demographic, clinical data, treatment parameters, and outcomes were reviewed and statistically analyzed. Fourteen sides of eight formalin-fixed brains were examined to describe the location of nervus intermedius at the brainstem.

Results Ten patients were surgically treated for geniculate neuralgia in our institution from 2000 to 2016. The median age was 45 years, seven females, and three males. All subjects presented primarily with ear pain. Preoperative pharmacologic treatments were trialed for a median 50 months (range, 1–240). A retrosigmoid approach was performed in all the cases: three patients underwent sectioning of nervus intermedius only; five patients underwent sectioning of nervus intermedius and microvascular decompression (MVD) of nerves V, VII–VIII, IX and X; and two patients underwent sectioning of nervus intermedius, IX and upper rootlets of X. Surgical intervention resulted in immediate sustained postoperative pain relief in 9 patients (90%), with baseline hearing and facial nerve function preserved in 9 (90%) and 10 patients (100%), respectively. At a median follow-up of 6 months (range, 3–90 months; one lost to follow-up after hospital discharge), five patients reported sustained postoperative relief (56%), and four had discontinued their preoperative analgesic medications entirely (44%). Sustained pain relief was associated with nervus intermedius sectioning with additional extensive microvascular decompression (100 vs. 0%, p = 0.008); by contrast, poor long-term pain control was associated with sectioning of the glossopharyngeal nerve and vagus rootlets (0 vs. 50%, p = 0.04). Nervus intermedius was identified in all the brainstems studied. Nervus intermedius was densely adherent to the medial superior aspect of the VIII cranial nerve in its origin at the brainstem a few millimeters before its fibers joined the VII cranial nerve in the cerebellopontine cistern. A small vein of less than 1 mm in caliber was present in 86% of the cases between the VII and VIII cranial nerves at the brainstem. Nervus intermedius was found immediately lateral to this vein.

Conclusion Geniculate neuralgia is an uncommon disease. Surgical treatment is reserved for cases that are refractory to medical treatment. In our series, 90% patients had complete immediate pain relief with a sustained response in 56% at a median of 6 months of follow-up. Sectioning of nervus intermedius associated with additional MVD of any significant arterial compression of nerves V, VII–VIII, IX, and X was associated with better outcome. Nervus intermedius is densely adherent to the medial superior aspect of the vestibulocochlear nerve at the brainstem before it joins the facial nerve in the cisternal segment. This portion of the nerve is optimal for visualization and sectioning of the nerve.