Magnetic resonance cisternography used to determine precise topography of the facial nerve and three components of the eighth cranial nerve in the internal auditory canal and cerebellopontine cistern

Abstract

It is more accurate to describe the CN and IVN as coursing beneath the SVN in either the IAC or cerebellopontine cistern, rather than stating that the three components rotate, as reported in cadaver studies. The MR cisternography studies provided quite detailed information about the topography of the four components and the relationship between the blood vessels and cranial nerves in the IAC and the cerebellopontine cistern.

A Radiological Study on the Topographical Relationships between the Vestibular, Cochlear and Facial Nerves

“…The FN and reported that the nerves rotated counterclockwise in the right ear and clockwise in the left ear along their course from the inner ear to the end of the brainstem [2]. An MRI study by Ryu et al also showed spatial changes of the nerves of the IAC, reporting that the inferior vestibular and the cochlear nerves passed below the superior vestibular nerve rather than rotating toward the brainstem [3].…”

“…The anatomy of the neural structures in the IAC has been the subject of numerous histological, surgical and radiological investigations owing to its clinical and functional importance [1][2][3][4]7].…”

“…Our findings are in agreement with a previous MRI study reported by Ryu et al but differ from previous cadaver studies. We believe this is due to the distortion of the normal spatial relationships in the A B C absence of cerebrospinal fluid and blood supply as well as the shrinkage of the nerves through formalin fixation and the displacement of the nerves that may have occurred during harvesting of the specimens [1,3,7]. The present study shows that near the brainstem the VCN is most frequently rectangular (60%) or round (31%) in shape but that it changes into a crescent shape in the cerebellopontine cistern when approaching the porus acousticus (89%).…”

“…Cadaver studies always carry the risk that the anatomical relationships and shapes of the component of the nerves in the IAC and cerebellopontine cisterns may have been altered due to the absence of cerebellopontine fluid and blood supply as well as the formalin fixation, which results in the shrinkage of nerves [3][4][5][6][7]. Therefore, anatomical studies must be conducted in living human tissue to define the true anatomical relationships among these nerves within the IAC and cerebellopontine cistern [3].…”

“…With the development of microsurgery and endoscopic surgery in the internal acoustic canal (IAC), the study of the topographical relationship between these two nerves in the human IAC becomes increasingly important for the diagnosis and surgical planning of acoustic schwannomas [2][3][4]. Additionally, depictions of cochlear nerve integrity may be important for diagnosis and management of sensorineural hearing loss [5].…”