Functional magnetic resonance imaging may avoid misdiagnosis of cochleovestibular nerve aplasia in congenital deafness.
OBJECTIVE
To investigate a narrow internal auditory canal (IAC) syndrome using functional magnetic resonance imaging (fMRI) of the auditory cortex.


METHODS
The study design was a case report. The follow-up period lasted 18 months.


METHODS
The study was carried out in the audiology clinic of an ear, nose, and throat department and in the department of pediatric neuroradiology at a university hospital.


METHODS
Age-appropriate observational audiometry, objective audiovestibular tests, computed tomography (CT), magnetic resonance imaging (MRI), and (fMRI) of the auditory cortex were performed to analyze in detail the profound deafness of a young child.


RESULTS
Audiovestibular examination demonstrated both measurable hearing and normal vestibulo-ocular reflex, and CT showed narrow IACs combined with normal labyrinths. Axial MR images completed by sagittal sections perpendicular to the IAC delineated a single nerve that was initially supposed to be the facial nerve. No cochleovestibular nerve was identified. However, fMRI performed with the patient under general anesthesia demonstrated activation of the primary auditory cortex during 1-kHz monaural stimulation on the left side.


CONCLUSIONS
The absence of cochleovestibular nerve on MR studies cannot exclude connections between the inner ear and the central auditory pathways. This might be caused by a lack of spatial resolution of anatomical MR studies. The single nerve delineated within the IAC might also carry both facial and cochleovestibular fibers. Functional MRI can assess the cortical response to acoustic stimuli when aplasia of the cochleovestibular nerve is suspected. This case study illustrates a novel and atypical presentation of cochlear nerve dysplasia.
Thai-Van
H
H
Ear, Nose, and Throat Department, University Hospital Purpan, Toulouse, France.
Fraysse
B
B
Berry
I
I
Berges
C
C
Deguine
O
O
Honegger
A
A
Sevely
A
A
Ibarrola
D
D
Van
H T
HT
D000161:Acoustic Stimulation; D001299:Audiometry / Q000379:methods; D001303:Auditory Cortex / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D003056:Cochlear Nerve / Q000473:pathology*; D003638:Deafness / Q000150:complications* / Q000151:congenital*; D006801:Humans; D007223:Infant; D007700:Kinetics; D008279:Magnetic Resonance Imaging; D008297:Male; D017084:Otoacoustic Emissions, Spontaneous / Q000502:physiology; D010775:Photic Stimulation; D012027:Reflex, Vestibulo-Ocular / Q000502:physiology; D014057:Tomography, X-Ray Computed; D014725:Vestibular Nerve / Q000473:pathology*