What do structures look like?
Air (dark)
Fat (gray)
Calcifications (light)
Osseous structures (light) - walls of EAC, bony margins of the cranial cavity, ossicles, and bony labyrinth
What are the different reconstructed views for 3D images?
Coronal
Stenvers - coronal oblique reconstruction parallel to the petrous ridge; petrous temporal bone, IAC and bony labyrinth; used to assess CI, now a modified Stenvers view (posteroanterior projection to minimize radiation to the orbits, assess the integrity, positioning and depth of the electrodes)
Poschl - sagittal oblique view perpendicular to the petrous ridge
What contrast is used in CT?
Iodine based agents
IV administered
Done when soft tissue abnormality is suspected (preauricular region, external auditory canal, skull base pathology (infection/Inflammation, trauma, tumors with bony involvement (cancer))
Evaluation of the vasculature
Does CT provide good visualization of the cartilaginous and bony external canal anatomy?
Yes
Complementary to an otoscopic exam
What is keratosis obturans?
Relatively uncommon
Expansile accumulation, buildup of keratin in the ear canal
Keratin is the tough fibrous proteins that make up the skin (released by the skin cells to form hair, nails and protective barrier of skin)
Symptoms include: hearing loss, acute pain secondary to large plug of desquamated keratin, and evidence of chronic inflammation
Treatment: debridement of the canal, topical medicine
Differential diagnosis: EAC cholesteatoma presents as otorrhea, chronic dull pain secondary to invasion of squamous tissue in the canal wall
*Likely close to the TM
What does opacification mean?
Fluid filled
What surgery is done for CIs?
Mastoidectomy with open facial canal
If you can see the ear canal wall, are you dealing with something that is deteriorating the tissue or bone?
No
Do you need a CT to diagnose OME or eustachian tube dysfunction?
No
Only for severe, chronic cases where they suspect something else is going on
What is cholesterol granuloma?
Most common cystic lesion of the petrous area
Usually associated with chronic OM
Benign, expanding fluid filled mass
Symptoms: unilateral left sided HL, headache for 6 months
Does the appearance of a hemorrhage depend on the elapsed time since the event?
Yes
After 7-10 days, the high density of blood begins to decrease starting from the periphery of the lesion and mimics the appearance of an abscess
By 2-4 months, decreased density indicates cavity formation and appears vacant after absorption of the necrotic and hemorrhagic tissue
*Bright at first, changes over time
