Sensorineural Hearing Loss in A Child
Bernadette L. Koch, MD
DIFFERENTIAL DIAGNOSIS
Common
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Large Endolymphatic Sac Anomaly (IP-2)
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Fractures, Temporal Bone
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Semicircular Canal Dysplasia
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Labyrinthine Ossificans
Less Common
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Labyrinthitis
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Cochlear Nerve Deficiency
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Cystic Cochleovestibular Anomaly (IP-1)
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Lipoma, CPA-IAC
Rare but Important
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Common Cavity, Inner Ear
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Cochlear Aplasia, Inner Ear
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Labyrinthine Aplasia
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Vestibular Schwannoma
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Schwannoma, Facial Nerve, CPA-IAC
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
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History is important
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In setting of fluctuating or “cascading” sensorineural hearing loss (SNHL) in child who could hear at birth (without history of meningitis)
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Look for large vestibular aqueduct ± cochlear dysplasia and modiolar deficiency on CT
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Look for enlarged endolymphatic sac and duct with cochlear dysplasia and modiolar deficiency on MR
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Trauma: Look for fracture involving inner ear structures ± pneumolabyrinth on CT
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Genetic disorders: In CHARGE, Alagille, Waardenburg, Crouzon or Apert syndrome, look for semicircular canal (SCC) dysplasia
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Prior meningitis
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Look for labyrinthine ossificans on CT
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Look for enhancement or replacement of high T2 intensity with low T2 intensity within structures of membranous labyrinth on MR (depends on timing of imaging)
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Best imaging tool
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Thin-section T-bone CT identifies many congenital inner ear anomalies
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High-resolution T2 MR imaging identifies large endolymphatic sac, cochlear dysplasia; best to show cochlear nerve aplasia/hypoplasia
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Contrast MR best evaluates schwannoma, acute labyrinthitis, and lipoma
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Helpful Clues for Common Diagnoses
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Large Endolymphatic Sac Anomaly (IP-2)
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Most common congenital anomaly of inner ear found by imaging
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Vestibular aqueduct on CT ≥ 1.5 mm bony transverse dimension
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Newer literature suggests ≥ 2 mm at operculum or ≥ 1 mm at midpoint
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Look for associated cochlear dysplasia, modiolar deficiency, vestibule &/or SCC dysplasia
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Additional diagnosis information
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Avoidance of contact sports or other activities that may lead to head trauma is recommended in children with IP-2 anomaly
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Genetic testing for Pendred syndrome is becoming increasingly recommended in children with IP-2 anomaly
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Up to 15% of all patients with IP-2 will have Pendrin gene = Pendred syndrome, with severe profound bilateral SNHL; 50% with goiter and 50% of those with goiter, will be hypothyroid
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Fractures, Temporal Bone
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Thin-section T-bone CT (0.625-1 mm)
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Transverse or longitudinal fracture may cross inner ear structures, ± pneumolabyrinth
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Semicircular Canal Dysplasia
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Spectrum of abnormalities: 1 or more of SCC dysmorphic, hypoplastic, or aplastic
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Unilateral or bilateral: Bilateral more common in syndromic form
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Most common is short, dilated lateral SCC and vestibule forming single cavity
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Look for associated cochlear dysplasia, oval window atresia, and ossicular anomalies
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CHARGE syndrome
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Bilateral absence of all SCCs
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Associated anomalies: Small vestibule, absent cochlear nerve aperture (“isolated cochlea”), oval window atresia (± overlying tympanic segment of CN7), choanal atresia, coloboma
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Lateral SCC last to form embryologically, therefore if lateral SSC is normal, posterior superior should be normal
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Except if obliterated by labyrinthine ossificans or hypoplastic in Waardenburg and Alagille syndrome
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Labyrinthine Ossificans
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Synonyms: Labyrinthitis ossificans, labyrinthine ossification, chronic labyrinthitis, ossifying labyrinthitis
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Acute inflammatory response results in fibrous and then osseous replacement of membranous labyrinth
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May involve cochlea ± vestibule ± semicircular canals
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Bilateral in meningogenic form (meningitis) and in hematogenic form (blood-borne infections)
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Unilateral in tympanogenic form (middle ear infection)
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T-bone CT: High-attenuation bone deposition in formerly fluid-filled membranous labyrinth
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T2 MR: Focal or diffuse low intensity replaces high intensity fluid, with apparent “enlargement” of modiolus if cochlea is involved
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T1 C+: Enhancement of involved membranous labyrinth structures in early stage, may persist into ossifying stages
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Helpful Clues for Less Common Diagnoses
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Labyrinthitis
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Subacute inflammation of fluid-filled inner ear structures
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T-bone CT: Normal in early phases, may progress to labyrinthine ossificans
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T2 MR: Low intensity replaces normal fluid signal within membranous labyrinth structures
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T1 C+: Mild to moderate enhancement
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Cochlear Nerve Deficiency
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Very small or absent cochlear nerve with small IAC
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Cystic Cochleovestibular Anomaly (IP-1)
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Cochlea and vestibule form bilobed cyst
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Lipoma, CPA-IAC
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Fatty lesion of CPA, IAC ± inner ear
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Helpful Clues for Rare Diagnoses
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Common Cavity, Inner Ear
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Cystic cochlea and vestibule form a common cavity ± SCC absence or dysplasia
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Cochlear Aplasia, Inner Ear
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Absent cochlea
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Labyrinthine Aplasia
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Absent membranous labyrinth
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Vestibular Schwannoma
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Enhancing lesion ± cysts in CPA-IAC
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Rare in children
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Schwannoma, Facial Nerve, CPA-IAC
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Enlarged labyrinthine segment CN7 canal with enhancing tubular mass in CPA-IAC and labyrinthine segment of CN7
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Rare in children
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Image Gallery
![]() (Left) Axial bone CT shows a longitudinal temporal bone fracture
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