Middle Ear Lesion
H. Ric Harnsberger, MD
DIFFERENTIAL DIAGNOSIS
Common
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Chronic Otitis Media (COM)
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Acquired Cholesteatoma, Pars Flaccida
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Congenital Cholesteatoma, Middle Ear
Less Common
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Acute Otomastoiditis (AOM) with Coalescent Otomastoiditis
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Acquired Cholesteatoma, Pars Tensa
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Cholesterol Granuloma, Middle Ear
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COM with Tympanosclerosis
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COM with Ossicular Erosions
Rare but Important
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Rhabdomyosarcoma, Middle Ear
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Langerhans Histiocytosis, T-Bone
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Dehiscent Jugular Bulb
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Aberrant Internal Carotid Artery
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
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Otoscopic findings often provide critical clues to precise diagnosis of middle ear lesion in child
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Presence or absence of tympanic membrane (TM) rupture important
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Pars tensa &/or flaccida acquired cholesteatoma has ruptured TM
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Color and location of retrotympanic mass may be key to imaging diagnosis
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Helpful Clues for Common Diagnoses
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Chronic Otitis Media (COM)
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Otoscopy: Thickened tympanic membrane
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Bone CT: Linear, sporadic middle ear-mastoid tissue; mastoid air cells may be underpneumatized
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Acquired Cholesteatoma, Pars Flaccida
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Otoscopy: Rupture or retraction pocket affecting pars flaccida portion of tympanic membrane
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Bone CT: Nondependent soft tissue filling Prussak space with ossicle and/or bony wall erosions
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Possible complications: Tegmen tympani, lateral semicircular canal, facial nerve canal dehiscence
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Congenital Cholesteatoma, Middle Ear
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Otoscopy: White mass behind intact TM
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Bone CT: Smooth, well-circumscribed soft tissue mass filling middle ear; often medial to ossicle chain
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Ossicle erosion often absent
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Mastoid pneumatization often normal
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Helpful Clues for Less Common Diagnoses
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Acute Otomastoiditis (AOM) with Coalescent Otomastoiditis
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Otoscopy: Bulging, inflamed tympanic membrane
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Bone CT: Complete middle ear-mastoid opacification with mastoid trabecular breakdown
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Hint: Look on soft tissue windows for adjacent postauricular abscess or epidural abscess
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Acquired Cholesteatoma, Pars Tensa
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Otoscopy: Ruptured pars tensa portion of TM
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Bone CT: Meso- and hypotympanic soft tissue mass often extending posteriorly or medially
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Cholesterol Granuloma, Middle Ear
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Otoscopy: Blue-black material behind intact TM
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Bone CT: Middle ear soft tissue mass with minimal bony erosion
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MR: High T1 and high T2 signal of material in middle ear (ME)
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Hint: Old blood in cholesterol granuloma creates T1 shortening
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COM with Tympanosclerosis
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Otoscopy: Opaque, calcified tympanic membrane
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Bone CT: Postinflammatory calcifications may affect ossicles, ligaments or TM
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COM with Ossicular Erosions
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Otoscopy: Thickened TM without normal ossicle impressions
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Bone CT: Linear middle ear and mastoid air cell opacifications with partial ossicle absence
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Long process of incus-lenticular process and stapes hub most commonly affected
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Helpful Clues for Rare Diagnoses
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Rhabdomyosarcoma, Middle Ear
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Otoscopy: EAC “polyp”
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Bone CT: Destructive middle ear mass that often affects EAC, ossicles, surrounding bones, overlying dura
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Langerhans Histiocytosis, T-bone
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Otoscopy: Postauricular mass common
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Bone CT: Unilateral or bilateral (30%) destructive T-bone lesions affecting middle ear secondarily
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Mastoid air cell more commonly affected than petrous apex or inner ear
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Dehiscent Jugular Bulb
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Otoscopy: Blue lesion behind posteroinferior quadrant of TM
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Bone CT: Dehiscent sigmoid plate projects jugular bulb into posteroinferior middle ear cavity
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Aberrant Internal Carotid Artery
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Otoscopy: Reddish mass passes across inferior half of TM
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Bone CT: Tubular lesion passes into posteroinferior middle ear cavity through enlarged inferior tympanic canaliculus
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Aberrant ICA passes out of middle ear cavity anteroinferiorly by accessing posterolateral margin of horizontal petrous internal carotid artery
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Other Essential Information
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Best imaging tool for middle ear lesion in child: T-bone CT without contrast
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Thin-section, fat-saturated MR only used for further evaluation of larger lesions involving inner ear, floor middle cranial fossa or sigmoid sinus-posterior fossa
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Tumor or tumor-like lesions to consider in middle ear of child
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Rhabdomyosarcoma and Langerhans cell histiocytosis
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May be difficult to tell these 2 lesions apart
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Rhabdomyosarcoma, Middle Ear
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Unilateral; centered in middle ear cavity; may present with EAC “polyp”
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Langerhans Histiocytosis, T-Bone
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May be bilateral; centered around middle ear cavity, especially in mastoid; may present as postauricular mass
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Alternative Differential Approaches
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Otoscopic exam findings vs. diagnosis
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White middle ear (ME) mass with associated ruptured or retracted pars flaccida TM
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