Inner Ear Lesion in a Child
H. Ric Harnsberger, MD
DIFFERENTIAL DIAGNOSIS
Common
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Fracture, T-Bone
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Large Endolymphatic Sac Anomaly (IP-2)
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Labyrinthine Ossificans
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Subarcuate Artery Pseudolesion
Less Common
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Semicircular Canal Dysplasia, CHARGE Syndrome
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Labyrinthitis
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Intralabyrinthine Hemorrhage
Rare but Important
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Cystic Cochleovestibular Anomaly (IP-1)
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Aplasia-Hypoplasia, Cochlear Nerve Canal
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Common Cavity, Inner Ear
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Cochlear Aplasia, Inner Ear
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Osteogenesis Imperfecta, T-Bone
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Branchiootorenal Syndrome, Inner Ear
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X-Linked Mixed Hearing Loss Anomaly
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Labyrinthine Aplasia
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
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Congenital lesions in differential diagnosis
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Congenital deafness has imaging diagnosis associated < 50%
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If imaging diagnosis is found, large endolymphatic sac anomaly (incomplete partition type 2) is most common diagnosis discovered
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All other inner ear congenital lesions that can be diagnosed by imaging are rare
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Imaging recommendations in childhood sensorineural hearing loss (SNHL)
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Begin with T-bone CT
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Add high-resolution T2 MR in axial and oblique sagittal plane when cochlear implant under consideration
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Define IAC size, integrity of cochlear nerve canal, presence of cochlear nerve
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Helpful Clues for Common Diagnoses
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Fracture, T-Bone
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Complex T-bone fractures may involve inner ear structures
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T-bone CT: Fracture line crosses inner ear ± pneumolabyrinth
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Large Endolymphatic Sac Anomaly (IP-2)
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Clinical clues: Bilateral congenital SNHL that appears in child with cascading hearing loss pattern
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Most common congenital imaging abnormality
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CT: Enlarged bony vestibular aqueduct + mild cochlear dysplasia
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MR: Enlarged endolymphatic sac + mild cochlear aplasia (modiolar deficiency, bulbous apical turn, scala vestibuli larger than scala tympani)
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Labyrinthine Ossificans
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Clinical clues: Child develops profound SNHL after episode of meningitis or middle ear infection
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Healing of suppurative labyrinthitis may result in osteoneogenesis within inner ear fluid spaces
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CT: Ossific plaques impinges on inner ear fluid spaces
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Define as cochlear and noncochlear for cochlear implant evaluation
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MR: High-resolution T2 shows encroachment on membranous labyrinthine fluid spaces
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Subarcuate Artery Pseudolesion
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Asymptomatic normal variant that disappears in 1st 2 years of life
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CT: Prominent canal passes beneath superior semicircular canal arch
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MR: Conspicuous high signal canal on T2 imaging underneath superior semicircular canal
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Helpful Clues for Less Common Diagnoses
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Semicircular Canal Dysplasia, CHARGE Syndrome
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Clinical clues: Colobomata, heart defects, choanal atresia, retardation, genitourinary problems, ear abnormalities
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CT: Bilateral semicircular canal absence, small vestibules, oval window atresia, cochlear nerve canal atresia
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MR: Cochlear nerve absence
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Labyrinthitis
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Clinical clue: Acute onset vertigo, hearing loss ± facial nerve paralysis
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CT: Acute phase normal
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MR: Often normal; if positive, diffuse enhancement of inner ear fluid spaces most common presentation
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Intralabyrinthine Hemorrhage
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Clinical clue: May be idiopathic or post-traumatic
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CT: Normal unless associated with trauma
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MR: High T1 signal in inner ear fluid
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Helpful Clues for Rare Diagnoses
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Cystic Cochleovestibular Anomaly (IP-1)
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Inner ear morphology: Inner ear looks like tilted “snowman” configuration on axial image
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CT: Cochlea and vestibule cystic; bony vestibular aqueduct usually normal
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MR: Both cochlea and vestibule are cystic; endolymphatic sac usually normal
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Aplasia-Hypoplasia, Cochlear Nerve Canal
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CT: Complete or partial bony narrowing of base of cochlear nerve canal
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MR: Fluid in cochlear nerve canal completely or partially replaced by low signal bone
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Cochlear nerve absent if aplasia of cochlear nerve canal
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Common Cavity, Inner Ear
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Inner ear morphology: Inner ear looks like single cyst
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CT: Single cyst with semicircular canals and vestibular aqueduct blended in
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MR: Single inner ear fluid-filled cyst
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Cochlear Aplasia, Inner Ear
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CT: Cochlea absent with variable deformity of vestibule, semicircular canals and vestibular aqueduct
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MR: Absent cochlea and cochlear nerve
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Osteogenesis Imperfecta, T-Bone
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Clinical clues: Blue sclera; mild form develops deafness by age 40 years
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Imaging same as cochlear otosclerosis
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CT: Active disease shows lucent foci in otic capsule surrounding cochlea
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MR: Active disease shows enhancing foci in otic capsule
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Branchiootorenal Syndrome, Inner Ear
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Clinical clues: Auricular deformity, prehelical pits, mixed hearing loss, branchial fistulae and renal abnormalities
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Genetics: 40% with clinical manifestations have mutations of EYA1 gene on chromosome 8q13.3
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CT: Hypoplastic apical turn of cochlea, medial deviation of facial nerve, funnel-shaped IAC and patulous eustachian tube
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X-Linked Mixed Hearing Loss Anomaly
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Clinical clues: Male child with bilateral mixed conductive and SNHL
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Open communication between IAC CSF pressure and cochlear fluid creates perilymphatic hydrops with “gusher” resulting if stapes disturbed
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CT: Cochlear nerve canal is enlarged with no modiolus
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