Nervus intermedius and the surgical management of geniculate neuralgia

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OBJECTIVE

Geniculate neuralgia (GN) is an uncommon craniofacial pain syndrome attributable to nervus intermedius (NI) dysfunction. Diagnosis and treatment can be challenging, due to the complex nature of ear sensory innervation, resulting in clinical overlap with trigeminal neuralgia (TN) and glossopharyngeal neuralgia (GPN).

METHODS

A retrospective review of a prospective neurosurgical database at our institution was performed, 2000–2017, with a corresponding systematic literature review. Pain outcomes were dichotomized as unfavorable for unchanged/worsened symptoms versus favorable if improved/resolved. Eight formalin-fixed brains were examined to describe NI at the brainstem.

RESULTS

Eleven patients were surgically treated for GN—9 primary, 2 reoperations. The median age was 48, 7 patients were female, and the median follow-up was 11 months (range 3–143). Seven had ≥ 2 probable cranial neuralgias. NI was sectioned in 9 and treated via microvascular decompression (MVD) in 2. Five patients underwent simultaneous treatment for TN (4 MVD; 1 rhizotomy) and 5 for GPN (3 MVD; 2 rhizotomy). Eleven reported symptomatic improvement (100%); 8 initially reported complete resolution (73%). Pain outcomes at last contact were favorable in 8 (73%)—all among the 9 primary operations (89% vs 0%, p = 0.054). Six prior series reported outcomes in 111 patients.

CONCLUSIONS

GN is rare, and diagnosis is confounded by symptomatic overlap with TN/GPN. Directed treatment of all possible neuralgias improved pain control in almost all primary operations. Repeat surgery seems a risk factor for an unfavorable outcome. NI is adherent to superomedial VIII at the brainstem; the intermediate/cisternal portion is optimal for visualization and sectioning.

ABBREVIATIONS BMI = body mass index; CN = cranial nerve; GN = geniculate neuralgia; GPN = glossopharyngeal neuralgia; MVD = microvascular decompression; NI = nervus intermedius; TN = trigeminal neuralgia.

Article Information

Correspondence Michael J. Link: Mayo Clinic, Rochester, MN. link.michael@mayo.edu.

INCLUDE WHEN CITING Published online August 10, 2018; DOI: 10.3171/2018.3.JNS172920.

Disclosures The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

© AANS, except where prohibited by US copyright law.

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Figures

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    Flow diagram demonstrating clinical trajectories for 11 patients treated for GN.

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    Anterior view of the left cerebellopontine angle in an anatomical specimen. The NI is consistently located at the superomedial aspect of CN VIII at its origin in the brainstem before joining CN VII. A small venous vessel is most of the time encountered between CN VII and the CN VIII–NI complex at the brainstem (asterisk). Figure is available in color online only.

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