Middle Ear Lesion

H. Ric Harnsberger, MD

DIFFERENTIAL DIAGNOSIS

Common

Less Common

Rare but Important

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Otoscopic findings often provide critical clues to precise diagnosis of middle ear lesion in child
- Presence or absence of tympanic membrane (TM) rupture important
  - Pars tensa &/or flaccida acquired cholesteatoma has ruptured TM
- Color and location of retrotympanic mass may be key to imaging diagnosis

Helpful Clues for Common Diagnoses

Chronic Otitis Media (COM)
- Otoscopy: Thickened tympanic membrane
- Bone CT: Linear, sporadic middle ear-mastoid tissue; mastoid air cells may be underpneumatized
Acquired Cholesteatoma, Pars Flaccida
- Otoscopy: Rupture or retraction pocket affecting pars flaccida portion of tympanic membrane
- Bone CT: Nondependent soft tissue filling Prussak space with ossicle and/or bony wall erosions
  - Possible complications: Tegmen tympani, lateral semicircular canal, facial nerve canal dehiscence
Congenital Cholesteatoma, Middle Ear
- Otoscopy: White mass behind intact TM
- Bone CT: Smooth, well-circumscribed soft tissue mass filling middle ear; often medial to ossicle chain
  - Ossicle erosion often absent
  - Mastoid pneumatization often normal

Helpful Clues for Less Common Diagnoses

Acute Otomastoiditis (AOM) with Coalescent Otomastoiditis
- Otoscopy: Bulging, inflamed tympanic membrane
- Bone CT: Complete middle ear-mastoid opacification with mastoid trabecular breakdown
  - Hint: Look on soft tissue windows for adjacent postauricular abscess or epidural abscess
Acquired Cholesteatoma, Pars Tensa
- Otoscopy: Ruptured pars tensa portion of TM
- Bone CT: Meso- and hypotympanic soft tissue mass often extending posteriorly or medially
Cholesterol Granuloma, Middle Ear
- Otoscopy: Blue-black material behind intact TM
- Bone CT: Middle ear soft tissue mass with minimal bony erosion
- MR: High T1 and high T2 signal of material in middle ear (ME)
  - Hint: Old blood in cholesterol granuloma creates T1 shortening
COM with Tympanosclerosis
- Otoscopy: Opaque, calcified tympanic membrane
- Bone CT: Postinflammatory calcifications may affect ossicles, ligaments or TM
COM with Ossicular Erosions
- Otoscopy: Thickened TM without normal ossicle impressions
- Bone CT: Linear middle ear and mastoid air cell opacifications with partial ossicle absence
  - Long process of incus-lenticular process and stapes hub most commonly affected

Helpful Clues for Rare Diagnoses

Rhabdomyosarcoma, Middle Ear
- Otoscopy: EAC “polyp”
- Bone CT: Destructive middle ear mass that often affects EAC, ossicles, surrounding bones, overlying dura
Langerhans Histiocytosis, T-bone
- Otoscopy: Postauricular mass common
- Bone CT: Unilateral or bilateral (30%) destructive T-bone lesions affecting middle ear secondarily
  - Mastoid air cell more commonly affected than petrous apex or inner ear
Dehiscent Jugular Bulb
- Otoscopy: Blue lesion behind posteroinferior quadrant of TM
- Bone CT: Dehiscent sigmoid plate projects jugular bulb into posteroinferior middle ear cavity
Aberrant Internal Carotid Artery
- Otoscopy: Reddish mass passes across inferior half of TM
- Bone CT: Tubular lesion passes into posteroinferior middle ear cavity through enlarged inferior tympanic canaliculus
  - Aberrant ICA passes out of middle ear cavity anteroinferiorly by accessing posterolateral margin of horizontal petrous internal carotid artery

Other Essential Information

Best imaging tool for middle ear lesion in child: T-bone CT without contrast
- 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
Tumor or tumor-like lesions to consider in middle ear of child
- Rhabdomyosarcoma and Langerhans cell histiocytosis
- May be difficult to tell these 2 lesions apart
- Rhabdomyosarcoma, Middle Ear
  - Unilateral; centered in middle ear cavity; may present with EAC “polyp”
- Langerhans Histiocytosis, T-Bone
  - May be bilateral; centered around middle ear cavity, especially in mastoid; may present as postauricular mass

Alternative Differential Approaches

Tags: EXPERTddx: Pediatrics

Aug 10, 2016 | Posted by drzezo in PEDIATRICS | Comments Off

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