[Endoscopy of porus acousticus internus]

The anatomical relationships between the arterial loop and the nerve in the porus acousticus region in 50 adult specimens were studied by endoscopy via the postsigmoid approach. No trauma to the intracranial structure occurred during the study. It was found that in 68 percent of specimens a cerebellar arterial loop existed in the porus acousticus region. There were six patterns of relationship between the arterial loop and the acoustico-facial boundle. A loop between the nerves, a loop under the nerves and a loop above the nerves were the common types. In 62 percent of specimens which presented a loop in this region, the loops were in close relationship with the canal or porus. In the remaining 38 percent the loops did not show any relationship with the canal. The findings were symmetrical in only 40 percent. The separation of the vestibular and the cochlear nerves could be seen in 51.1% of the specimens. The advantages of endoscopy in this region were discussed.