Temporal bone (Dr. Collins) Flashcards
Etiology of acquired EAC exostosis
Prolonged exposure to cold water and wind (surfer’s ear)
acquired conductive hearing loss
Main differential consideration in suspected EAC exostosis
Osteoma
Medial canal fibrosis is the pathologic end point of what disease processes (4)
Chronic otitis externa
Sequelae of surgery/trauma
Radiation
Autoimmune disease
Pathogenesis of medial canal fibrosis
Fibrous tissue forms along medial aspect of bony EAC
Progresses to thick crescent of fibrous tissue along the lateral TM
What is the tegmen?
Thin bony covering overlying the mastoid air cells and middle ear cavity
How to do you determine the diameter of the vestibular aqueduct?
Measure at the midpoint (< 1.5 mm is normal)
What are the contents of the pyramidal eminence?
Stapedius muscle
Where does acquired cholesteatoma most commonly arise from?
Pars flaccida > pars tensa
Etiology of cholesteatoma
Perforation of TM
Subsequent formation of inflammatory mass
Chronic epithelial and keratin proliferation
Presentation of cholesteatoma
Painless otorrhea
Conductive hearing loss
Tullio phenomenon (noise induced vertigo)
Treatment of cholesteatoma
Mastoidectomy and resection
Which semi-circular canal is most affected by cholesteatoma?
Lateral semi-circular canal
Classic MRI finding of cholesteatoma
Diffusion restriction
Main difference between acquired and congenital cholesteatoma
Intact TM for congenital lesions
arises medial to the ossicles
Differential of a vascular (red) retro-tympanic lesion
Glomus juguloympanicum
Aberrent ICA
NOT
- Glomus vagale (in the neck)
- Dehiscent jugular bulb (blue lesion)
- Cholesteatoma (white lesion)
Vascular retro-tympanic lesions with pulsatile tinnitus
Aberrant ICA
Globus jugulare
Globus tympanicum
Characteristic MRI finding of a glomus jugulare paraganglionoma
Salt and pepper appearance
highly vascular lesion with flow voids
Main arterial supply of a glomus jugulare paraganglionoma
Ascending pharyngeal artery
pulsatile tinnitus, erosion of adjacent bone
Diagnosis of dehiscence of the jugular bulb
Dehiscent sigmoid plate
High-riding jugular bulb
Diagnosis of a high-riding jugular bulb
Can see the jugular bulb and IAC on same axial slice
Classic MRI finding of Bell’s palsy
Unilateral enhancement of the proximal facial nerve
Etiology of Bell’s palsy
Reactivation of HSV or zoster viruses
Main differential for unilateral enhancement of the proximal facial nerve, aside from Bell’s palsy
Perineural spread of tumor
will be thicker and more nodular
Function of superior petrosal nerve
Lacrimation
Bony erosion of what structure causes superior semicircular canal dehiscence
Arcuate eminence
Classic symptom of superior semicircular canal dehiscence
Tullio phenomenon (noise induced vertigo)
third window effect, allows pressure to influence the labyrinth
