Intraoperative and anatomical descriptions of intracranial connections between the glossopharyngeal and vagus nerves: clinical implications

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Abstract
Object: Knowledge of the variations in the nerves of the posterior cranial fossa may be important during skull base approaches. To the authors' knowledge, intracranial neural interconnections between the glossopharyngeal and vagus nerves have not been previously investigated. Methods: The senior author (A.C.G.) noted the presence of an intracranial interneural connection between the glossopharyngeal and vagus nerves during microvascular decompression surgery in a patient suffering from hemifacial spasm. To further investigate the approximate incidence and significance of such an interneural connection, the authors studied 40 adult human cadavers (80 sides) and prospectively evaluated 16 additional patients during microvascular procedures of the posterior cranial fossa. Results: In the cadavers, the incidence of intracranial neural connections between the glossopharyngeal and vagus nerves was 2.5%. The only such connection found in our series of living patients was in the patient in whom the connection was initially identified. These interconnections were more common on the left side. Based on our findings, we classified these neural connections as Types I and II. In the cadavers, the length and width of this connection were approximately 9 mm and 1 mm, respectively. Histological analysis of these connections verified their neural content. Conclusions: Although these connections are rare and the significance is unknown, knowledge of them may prove useful to surgeons who operate in the posterior fossa region so that they may avoid inadvertent traction or transection of these interconnections. Additionally, such connections might be considered in patients with recalcitrant neuralgia after microvascular decompression and rhizotomy of the glossopharyngeal nerve.

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