Article
Central myelin-peripheral myelin transitional zone of the Nervus Intermedius. Features and importance for microsurgery in the cerebellopontine angle.
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Published: | September 11, 2012 |
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Question: The aim of this study was to confirm the presence and to evaluate the histological and ultrastructural features of the central myelin-peripheral myelin transitional zone - also referred to as Obersteiner-Redlich zone (ORZ) or glial/schwann junction- of the nervus intermedius (NI).
Methods: Ten NI specimens from five fresh cadavers were microscopically analyzed for structural differences between their CNS and PNS segments. The ORZ was analyzed under a light microscope and the exact location of the ORZ was confirmed by immunohistochemical staining using an Olig2 antibody.
Results: The diameter of the NI showed a mean of 0.62 mm (range: 0.5–0.8 mm, SEM: 0.033). The cisternal segment of the NI from the brainstem to the porus acusticus internus had a mean length of 13.97 mm (range: 9–18.8 mm, SEM: 1.13). The mean extent of central myelin was 0.5 mm (range: 0.189–0.797 mm, SEM: 0.067 mm) from the brainstem on the medial side and 0.33 mm (range: 0.102–0.546 mm, SEM: 0.06 mm) on the lateral side. Moreover, the length of the ORZ had a mean of 0.279 mm (range: 0.024–0.5 mm, SEM: 0.06 mm) on the medial side and 0.134 mm (range: 0.059–0.233 mm, SEM: 0.018 mm) on the lateral side. The ORZ of the NI appears closer to the brainstem compared with the other cranial nerves.
Conclusions: Our results indicate that the ORZ of the NI is closer to the brainstem in respect to the other cranial nerves. The NI ORZ may play a role in the pathogenesis of intermediate neuralgia or spasms as a vulnerable area concerning vascular compression. The exact location of the ORZ may play a role in diagnostic preoperative imaging and in the planning of surgical procedures for NIN.