Article
The intermediate nerve and its contiguous structures in the cerebellopontine angle – An anatomical study
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Authors
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A. Alfieri
- Klinik und Poliklinik für Neurochirurgie, Universitätsklinikum Halle
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E. Peschke
- Institut für Anatomie und Zellbiologie, Martin-Luther-Universität Halle-Wittenberg
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J. Fleischhammer
- Klinik und Poliklinik für Neurochirurgie, Universitätsklinikum Halle; Institut für Anatomie und Zellbiologie, Martin-Luther-Universität Halle-Wittenberg
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C. Strauss
- Klinik und Poliklinik für Neurochirurgie, Universitätsklinikum Halle
| Published: | April 28, 2011 |
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Outline
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Objective: In cerebellopontine angle surgery, the intermediate nerve (IN) is an often neglected and underestimated anatomical structure. The goal of our study was to analyze the large variations in the course of the IN and its anastomoses and its anatomical relationship to the facial and the vestibulocochlear nerve.
Methods: Eight human subjects and thirteen isolated human brains were investigated with an operating microscope. Morphometric and topographic data regarding the root-entry-zone, the bundles, the vascular relationships, and complementary anatomical features of the IN were collected. Accordingly, the anatomical relation of the intermediate nerve to the facial and the vestibulocochlear nerves in the cerebellopontine angle was determined.
Results: The following variants of exit-root-zone were documented: directly from the brain stem in 31%, together with the vestibulo-cochlear nerve in 31%, from the facial nerve in 13%, and from both the facial and cochlear in 25% of the specimens. The number intermediate nerve roots varied from 1 to 5 (median 2.94 ± 1.12). The length of the cisternal segment of the intermediate nerve from the brainstem to the porus was a mean of 36.93 ± 3.08 mm. In the dissected cadavers the intermediate nerve reached the facial nerve 1.44 mm proximal to the internal acoustic meatus (SD 3.33 mm). The diameter of the IN reached a mean of 0.7 ± 0.24 mm. In 80% of cases, a vein between the root exit zones was documented.
Conclusions: The anatomical results showed a large variability regarding the location of the exit from the brain stem of the IN with a constantly observed merging with the facial nerve in proximity of the internal acoustic meatus. Moreover, the described vein may serve as orientation landmark.
