Congenital unilateral hearing loss from cochlear nerve canal stenosis

@#A 2-month-old baby girl presented with a failed neonatal otoacoustic emission (OAE) hearing screening in the left ear. Combined Auditory Brainstem Response/Auditory Steady-State Response (ABR/ASSR) testing confirmed the presence of a unilateral left moderate to severe hearing loss. No Joint Committee on Infant Hearing (JCIH) risk factors for early childhood hearing loss1 were identified. She subsequently underwent computed tomography (CT) of the temporal bones to determine the presence of any inner ear malformation. No abnormalities of the internal auditory canal, cochlea, semicircular canals and ossicles were noted by the radiologist, and the study was officially reported as a “normal temporal bone CT scan.” Independent review of the CT imaging revealed the presence of a visually apparent disparity in the width of the cochlear nerve canals. (Figure 1) Measurement of the cochlear nerve canal width in the axial plane parallel to the infraorbitomeatal line2 using the length measurement tool in the DICOM imaging software (RadiAnt DICOM Viewer, Version 2024.1, Medixant) indicated a cochlear nerve canal width of 2.18 mm on the right and 1.02 mm on the left. (Figure 2) Applying the suggested cutoff point of 1.2 mm as described by Lin et al.,2 we identified the presence of left cochlear nerve canal stenosis as the etiology of the congenital unilateral hearing loss. The cochlear nerve canal, which has also been referred to as the bony canal for the cochlear nerve (BCNC), cochlear aperture, and cochlear fosette, is the bony transition point between the internal auditory canal and the cochlear modiolus. A relationship between a hypoplastic cochlear nerve canal and congenital sensorineural hearing loss was first suggested by Fatterpekar et al. in 2000.3 Subsequent studies confirmed the association between cochlear nerve canal stenosis and sensorineural hearing loss that ranges from near-normal to profound, with a statistically significant relationship between the degree of hearing loss and the degree of stenosis.4 Various cutoff points to define stenosis of the cochlear nerve canal have been identified in the medical literature. These cutoff points range from 1.2 mm to 1.7 mm when the canal width is measured in the axial plane.2 This particular case demonstrated clear-cut evidence of cochlear nerve canal stenosis, as it satisfied the smallest cutoff criteria (< 1.2 mm) seen in the medical literature. The identification of cochlear nerve canal stenosis as the cause of congenital sensorineural hearing loss is important not only from a diagnostic point, but also from a prognostic perspective. Cochlear nerve deficiency has been noted to be highly prevalent among pediatric patients with cochlear nerve canal stenosis,5 and this has significant negative implications in relation to rehabilitation with external hearing devices and cochlear implants.

Sudden sensorineural hearing loss from a Jugular Bulb Diverticulum

@#A 19-year-old woman presented with an 11-month history of sudden-onset left sided hearing loss accompanied by vertigo and headache. Audiometric testing revealed profound left- sided hearing loss. A contrast-enhanced MRI of the internal auditory canal performed 5 months after symptom onset was interpreted as showing a vascular loop, probably the anterior inferior cerebellar artery, abutting and indenting on the left vestibulocochlear nerve; and a prominent and high-riding left jugular bulb. In this study, the internal auditory canals were assessed to be of normal width, with walls that were smooth and sharply defined. A cerebral CT angiogram subsequently performed did not show any abnormal findings related to the previously identified vascular loop. On the basis of these radiologic findings, the patient was advised surgery by physicians at a tertiary- care institution, presumably to address the identified vascular loop. A second opinion was sought by the patient.

Fenestral otosclerosis: A subtle lesion easily missed

@#A 29-year-old Filipina of Chinese descent presented with progressive bilateral conductive hearing loss of several years’ duration. While working overseas, she consulted with an otolaryngologist and underwent computerized tomographic (CT) imaging of the temporal bone as part of her evaluation. She was informed that no abnormalities were identified in the imaging exam, and she was offered exploratory middle ear surgery with possible stapes surgery. She then sought a second opinion, with the intention of obtaining a more definitive diagnosis prior to any invasive medical intervention. A review of the CT imaging study, with particular emphasis on looking for radiologic evidence of otosclerosis, revealed the presence of a focal region of bone demineralization in the region of the fissula ante fenestram. (Figure 1) This finding is consistent with a diagnosis of fenestral otosclerosis.

Post-traumatic malleo-incudal complex dislocation

@#A 27-year-old man undergoes otolaryngologic evaluation for blunt head trauma suffered in a vehicular accident. With regards to the right ear, pertinent otologic findings include an ear canal laceration and a delayed-onset facial nerve paresis. Tuning fork testing reveals an abnormal Rinne test on the right (AC<BC). The radiologist’s interpretation of the computerized tomographic imaging study of the temporal bone indicated the presence of a longitudinal fracture of the right temporal bone with no disruption of the ossicular chain. (Figure 1) However, careful examination of the anatomy of the malleo-incudal complex in relation to the other structures in the epitympanum actually reveals findings indicative of a malleo-incudal complex dislocation. How can this discrepancy in the radiologic interpretation be accounted for? By what objective parameters can the presence of a malleoincudal complex dislocation be identified?

The Study Of Hrct And Mri Temporal Bone Findings In Pediatric Patients With Congenital Sensorineural Hearing Loss

Introduction -The incidence of Congenital Sensorineural hearing loss (SNHL) is approximately 1: 1000 live births. SNHLis either due to disorders of the inner ear or cochleovestibular cranial nerve. Radiological evaluation is necessary to detect or rule out causes of SNHL. Also, the treatment of SNHLis predominantly determined by the etiology of hearing loss. Aim & objective-Radiological assessment of various congenital inner ear malformations in pediatric age group patients with sensorineural hearing loss in a tertiary care centre.Material & Methods-This is a prospective study conducted between 1 January 2018 and 1 June 2019 in Department of Radiodiagnosis, SAIMS, Indore & included all paediatric patients (93 children), who came for HRCTand MRI temporal bone imaging with the clinical diagnosis of congenital sensorineural hearing loss (SNHL) / for evaluating congenital sensorineural hearing loss (SNHL).Results-In our study out of 93 paediatric patients , no significant radiological abnormality were detected in 68 patients (73.11%), however, 25 patients (26.88%) had various congenital anomalies of the inner ear and vestibulocochlear nerve. Most commonly affected organ was cochlea. Among these 25 patients only cochlea was involved in 7(28%), both Cochlea and semicircular canal in 4(16%), and Cochlea and vestibular aqueduct in 1 patient(4%). Isolated vestibular aqueduct dilatation was found in 8 (32%) patients. Isolated semicircular canal involvement and cochleovestibular nerve abnormality were seen in 3 (12%) and 2 (8%) patients respectively.Conclusion-In this study, imaging has helped us to detect various inner ear malformations in children with congenital sensorineural hearing loss. It is helpful for preoperative planning and preparation for cochlear implant in a tertiary care centre