Radiologic Findings of Vestibulocochlear Nerve Deficiency: CT and MRI

Park, Sang Yoo; Kim, Tae Hwan; Kim, Jin Hyung; Park, Jang Hyuck; Bong, Jung Pyo

Abstract

BACKGROUND AND OBJECTIVES
Sensorineural hearing loss (SNHL) could be caused by dysfunction of the cochlea, abnormality of vestibulocochlear nerve (VCN), or disorder of central auditory pathway. Among these causes, VCN deficiency is one of the causes of profound sensorineural hearing loss. The aim for this study was to evaluate radiologic characteristics of VCN deficiency by reviewing temporal bone computed tomography (TBCT) and magnetic resonance image (MRI) findings of patients with profound unilateral SNHL, diagnosed as VCN deficiency and also, we compared the width of the bony canal of the cochlear nerve (BCCN) between the normal and affected side on TBCT and tried to clarify the diagnositc value of BCCN. MATERIALS AND METHOD: We reviewed TBCT and temporal submillimetric axial and parasagittal 3D turbo spin echo (3D-TSE) T2-weighted MRI of 9 patients who were diagnosed as unilateral VCN deficiency. We evaluated MRI findings in terms of the presence and comparative size of the component nerves (facial, cochlear, superior vestibular, inferior vestibular nerve) then we classified the type of VCN deficiency, according to the Casselman's proposal. We compared the difference of width of IAC and BCCN between normal and affected side on TBCT. RESULTS: We could find the detail anatomic feature of VCN in IAC by parasagittal MRI and could classify the type of VCN deficiency of patients, based on the Casselman's classification. According to the result of the classification, 8 patients were type 2A and the other one was type 1. In the TBCT study, the size of IAC and BCCN of the affected 8 ears were smaller than that of side and one patient had normal IAC but narrow BCCN of the affected ear. CONCLUSION: In this study, we conclude that TBCT and MRI could be useful methods for diagnosis of VCN deficiency. Also, the hypoplastic bony canal of the cochlear nerve on TBCT is finding to overlook easily and may be another important indicator for evaluating VCN deficiency.