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Bony cochlear nerve canal and internal auditory canal measures predict cochlear nerve status

Published online by Cambridge University Press:  01 June 2017

E Tahir ,
M D Bajin ,
G Atay ,
B Ö Mocan  and
L Sennaroğlu
E Tahir*
Affiliation:
Department of Otolaryngology – Head and Neck Surgery, Hacettepe University, Ankara, Turkey
M D Bajin
Affiliation:
Department of Otolaryngology – Head and Neck Surgery, Hacettepe University, Ankara, Turkey
G Atay
Affiliation:
Department of Otolaryngology – Head and Neck Surgery, Hacettepe University, Ankara, Turkey
B Ö Mocan
Affiliation:
Department of Radiology, Hacettepe University, Ankara, Turkey
L Sennaroğlu
Affiliation:
Department of Otolaryngology – Head and Neck Surgery, Hacettepe University, Ankara, Turkey
*
Address for correspondence: Dr E Tahir, Department of Otorhinolaryngology – Head and Neck Surgery, School of Medicine, Hacettepe University, Sıhhiye, Ankara 06100, Turkey Fax: +90 312 311 3500 E-mail: emeltahir@hotmail.com
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Abstract

Objectives:

The bony cochlear nerve canal is the space between the fundus of the internal auditory canal and the base of the cochlear modiolus that carries cochlear nerve fibres. This study aimed to determine the distribution of bony labyrinth anomalies and cochlear nerve anomalies in patients with bony cochlear nerve canal and internal auditory canal atresia and stenosis, and then to compare the diameter of the bony cochlear nerve canal and internal auditory canal with cochlear nerve status.

Methods:

The study included 38 sensorineural hearing loss patients (59 ears) in whom the bony cochlear nerve canal diameter at the mid-modiolus was 1.5 mm or less. Atretic and stenotic bony cochlear nerve canals were examined separately, and internal auditory canals with a mid-point diameter of less than 2 mm were considered stenotic. Temporal bone computed tomography and magnetic resonance imaging scans were reviewed to determine cochlear nerve status.

Results:

Cochlear hypoplasia was noted in 44 out of 59 ears (75 per cent) with a bony cochlear nerve canal diameter at the mid-modiolus of 1.5 mm or less. Approximately 33 per cent of ears with bony cochlear nerve canal stenosis also had a stenotic internal auditory canal and 84 per cent had a hypoplastic or aplastic cochlear nerve. All patients with bony cochlear nerve canal atresia had cochlear nerve deficiency. The cochlear nerve was hypoplastic or aplastic when the diameter of the bony cochlear nerve canal was less than 1.5 mm and the diameter of the internal auditory canal was less than 2 mm.

Conclusion:

The cochlear nerve may be aplastic or hypoplastic even if temporal bone computed tomography findings indicate a normal cochlea. If possible, patients scheduled to receive a cochlear implant should undergo both computed tomography and magnetic resonance imaging of the temporal bone. The bony cochlear nerve canal and internal auditory canal are complementary structures, and both should be assessed to determine cochlear nerve status.

Keywords

CochleaCochlear NerveTomography, X-Ray ComputedHearing Loss, SensorineuralEar, Inner

Information

Type
Main Articles
Information
The Journal of Laryngology & Otology , Volume 131 , Issue 8 , August 2017 , pp. 676 - 683
Copyright
Copyright © JLO (1984) Limited 2017 

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