Head And Neck -- Temporal Bone

Front 1

MIddle ear mass

Back 1

ACQUIRED CHOLESTEATOMA:
- epidermoid cyst composed of squamous epithelium.
- 2/2 chronic middle ear infections resulting in perforation of the tympanic membrane and conductive hearing loss.
- soft tissue mass in the Prussak space (epitympanum also called the lateral attic).
- blunting of the scutum (forms the lateral wall of the attic).
- erosion of the ossicles (favors cholesteatoma over chronic infection).
- may result in tegmen tympani (roof of the mastoid air cells), lateral semicircular canal, facial nerve canal or sigmoid sinus plate dehiscence
- when large, cholesteatomas may extend into the mastoid air cells and are hard to distinguish from chronic otitis media.
- Complications: coalescent mastoiditis, meningitis, epidural abscess, and venous sinus thrombosis.
FACIAL NERVE SCHWANNOMA
- may occur anywhere along the course of the facial nerve
- enlargement of the bony facial nerve canal.
- look for enhancement following contrast.
GLOMUS TYMPANICUM:
- paraganglioma that occurs within the middle ear along the cochlear promontory.
- highly vascular mass with flow voids and calcifications.
- as the mass grows, it fills the middle ear and encroaches on the ossicles.
NORMAL VARIANT VASCULATURE:
- Aberrant ICA: 2/2 regression of cervical and proximal petrous ICA and development of alternate anastomoses.
- Look for medial deviation of the ICA and narrowing of the ICA in the temporal bone.
- The collateral vessel extend into the middle ear and reconstitute the petrous ICA.
Dehiscent jugular bulb: occurs when the sigmoid plate of the jugular bulb is absent, allowing extension of jugular vein into the middle ear cavity.
CHOLESTEROL GRANULOMA:
- can occur in the middle ear and petrous apex
- 2/2 chronic inflammation
- soft tissue mass within the middle ear without osseous erosions.
- bluish/purplish discoloration of the tympanic membrane.
- hyperintense on T1 and T2WI.

Front 2

Temporal bone fractures:

Back 2

LONGITUDINAL TEMPORAL BONE FRACTURES:
- oriented parallel to the long axis of the temporal bone
- mc subtype (75%)
- look for blood products in the mastoid air cells, middle ear cavity, and external ear cavity.
- Complications:
1. Ossicular dislocation: most common complication. Look for ice cream (head of the malleus) falling off the "cone" (short process of the incus).
2. Facial nerve injury: less common; more commonly seen with transerse fx.
TRANSVERSE TEMPORAL BONE FRACTURES:
- fracture line is oriented perpendicular to the long axis of hte temporal bone.
- commonly involves the inner ear structures resulting in sensorineural hearing loss and vertigo.
- Facial nerve injury is also more common.
MIXED TEMPORAL BONE FRACTURES:
- look for involvement of vascular channels (jugular canal and petrous segment of ICA).
- inner ear structures
- facial nerve
- ossicles

Front 3

Inner ear congenital malformations

Back 3

LARGE VESTIBULAR AQUEDUCT SYNDROME
- common cuase of sensorineural hearing loss in early childhood
- affected pts hear normally at birth with bilateral hearing loss progressing oer the first few months
- look for enlargement of the vestibular aqueduct > 1.5 mm in diameter.
- associated abnormalities of the cochlea (fewer turns) and vestibule (enlargement)

CYSTIC COCHLEOVESTIBULAR ANOMALY
- arrested inner ear development resulting in cystic dilatation of the cochlea and vestibule
- pts have sensorineural hearing loss at birth
- dilated cochlea and vestibule demonstrate a figure of 8 appearance.
- semicircular canals may also be dilated.
- vestibular aqueduct is normal

CYSTIC COMMON CAVITY:
- instead of arrested development like cystic cochleovestibular anomaly, cystic common cavity refers to lack of development of the cochlea and vestibule.
- semicircular canals may be variably affected -- normal, dysplastic, absent.
- sensorinerual hearing loss at birth.
- single cystic cavity in place of normal inner ear structures.
COCHLEAR APLASIA
LABYRINTHINE OSSIFICANS:
- ossification of the membranous labyrinth due to some form of insult -- infectious, inflammatory, and hemorrhagic.
- look for increased density on CT
- on MRI, decreased signal replaces the normal fluid signal in the labyrinth on T2WI.

Front 4

Petrous apex lesion:

Back 4

CHOLESTEROL GRANULOMA
- 2/2 non-specific chronic inflammation
- MC = petrous apex and middle ear cavity
- Hypodense mass that may expand and erode the bone
- Hyperintense on T1 and T2WI due to hemorrhage within the lesions.
- Peripheral enhancment; no central enhancement.
MUCOCELE
- 2/2 entrapped secretions in an aerated petrous apex.
CONGENITAL CHOLESTEATOMA
- cholesteatoma = epidermoid that most commonly occur in the middle ear cavity or petrous apex.
- CT = hypodense and expansile
- May have T2 hyperintense foci due to cystic change.
- may have restricted diffusion
- Mild peripheral enhancement
APICAL PETROSITIS
- infection of pneumatized petrous apex often secondary to otitis media.
- fluid density within the petrous apex with enhancement post contrast 2/2 inflammation
- Gradenigo syndrome: retro-orbital pain and diplopia 2/2 deficits of the 6th cranial nerve due to petrous apicitis.
NEOPLASM
- Primary = chondrosarcoma
- Mets/myeloma/lymphoma