[Microanatomy of the cranial segment of the vestibulocochlear nerve. Possible correlations with the symptoms of neurovascular compression syndrome].

The objective of the present study was to elucidate the topographic features of the nerve fibers belonging to the acoustic and vestibular analyzers located in the intracranial cranial segment of human vestibulocochlear nerve (VCN). A total of 16 samples of the intracranial cranial segment of the human vestibulocochlear nerve isolated from the region enclosed between the exit of VCN from the brainstem and its entrance into the internal acoustic meatus were available for the investigation. Prior to fixation of the samples, the VCN segments were marked in correspondence with their intravital anatomical location in the posterior cranial fossa. Cross sections of the PCN segments were stained with hematoxylin and eosin as well as according to the van-Hison method. The cross sections were made either at the exit of the nerve from the brainstem (N1), its entrance into the internal acoustic meatus (N3) or in-between these sites (N2). The morphometric analysis of the sections and the statistical treatment of the data obtained were performed with the use of the Diamfor hardware and software complex («Diamfor», Russia). The digitized images of the PCN sections were prepared using amVizo 103 microvisor (Russia). It was shown that the intracranial segment of the human vestibulocochlear nerve consists of two isolated groups of nerve fibers differing in terms of staining density, size, and the degree of myelinization. The mutual location of the fibers forming the cochlear and vestibular nuclei (CN and VN respectively) varies. Namely, CN near the internal acoustic foramen occupies the antero-posterior position with respect to VN. In the middle part of VCN, CN-forming fibers are located at the anetro-inferoposterior surface of the nerve. The nerve fibers of both CN and VN are similarly arranged near the lateral surface of the brain stem.