Temporal Bone

Question 1

pathology of external ear

Answer 1

EAC atresia, SCC, swimmer’s ear (acute external otitis), surfer’s ear (EAC exostosis), malignant otitis externa, acute external otitis, first branchial cleft cyst, keratosis obturans

Question 2

pathology of middle ear

Answer 2

hypoplasia of ossicles, cholesteatoma, otitis media, mastoiditis, glomus tympanicum, aberrant ICA, dehiscent jugular bulb, oval window atresia, facial nerve schwannoma

Question 3

pathology of inner ear

Answer 3

cochlear dysplasia, superior semicircular canal dehiscense, semicircular canal hypoplasia, enlarged vestibular aqueduct, otospongiosis/otosclerosis, Paget disease, fibrous dysplasia, labryrinthitis, petrous apicitis, cholesterol cyst

Question 4

middle ear contents

Answer 4

tympanic membrane
ossicles (malleius/incus/stapes)
stapedius muscle
facial nerve

Question 5

inner ear contents

Answer 5

cochlea, semicircular canals, vestibule, utricle, saccule, vestibular aqueduct, coclear aqueduct

Question 6

congenital EAC stenosis, hypoplasia, atresia

Answer 6

malformations of external ear

typically inner ear not involved since it has different embryological origin

Question 7

acute external otitis media

Answer 7

swimmers ear; bacterial infection of external ear since in high humidity

Question 8

EAC exostosis

Answer 8

surfer’s ear; exostosis of EAC in those who swim/surf in cold waters

Question 9

necrotizing external otitis

Answer 9

malignant otitis externa; seen in elderly diabetic/immunocompromised; Pseudomonas vs Aspergillus

extensive enhancement around external ear with associated bony erosion

Question 10

Keratosis obturans

Answer 10

keratin plugs within an enlarged EAC; seen in young patients with sinusitis and bronchiectasis

usually bilateral

Question 11

cholesteatoma

Answer 11

acquired cholestatoma, more common in middle ear

usually associated with bony erosion

white mass behind tympanic membrane; restricts diffusion

Question 12

EAC malignancy

Answer 12

SCC–usually sun exposure or chronic inflammation

Question 13

oval window separates?

Answer 13

air filled middle ear and fluid filled inner ear

Question 14

glomus tympanicum

Answer 14

extra adrenal pheochromocytoma (paraganglioma) of the middle ear

associated with pulsatile tinnitus or conductive eharing loss

vascular red mass behind the tympanic membrane

Question 15

facial nerve schwannoma

Answer 15

present with facial nerve palsy;

involve geniculate ganglion, followed by labryinthine and tympanic segments

Question 16

facial nerve segments

Answer 16

labryinthine, tympanic, mastoid

Question 17

labrinthine segment, tympanic membrane

Answer 17

IAC to geniculate ganglion; superior to cochlea

gives off greater suprficial petrosal nerve

Question 18

tympanic segment tympanic membrane

Answer 18

horizontal; courses under lateral semicircular canal

Question 19

mastoid segment tympanic membrane

Answer 19

descending; courses inferiorly then exits at the stylomastoid foramen

nerve to stapedius
chorda tympani

Question 20

cholesterol granuloma

Answer 20

cholesterol cyst; petrous apex lesion that may occur in the middle ear

giant cell reaction to cholesterol crystals initially incited by an obstructed air cell

blue mass behind tympanic membrane

Question 21

cholesteatoma, middle ear

Answer 21

non-neoplastic lesion of temporal bone; skin in the wrong place; white mass behind tympanic membrane

persistent fetal epithelial squamous cell nests, or due to sequela of tympanic membrane perforation, inflammation, trauma

more common in younger individuals (EAC cholesteatomas in older/middle aged)

Question 22

cochlear dysplasia

Answer 22

mondini deformity
incomplete development of cochlea resulting in confluence of apical/middle turns; intact basilar turn

incomplete partition type II

Question 23

michel aplasia

Answer 23

complete lack of development of inner ear

Question 24

enlarged vestibular aqueduct syndrome

Answer 24

may lead to progressive hearing loss while playing contact sports

vestibular aqueduct should not be larger than posterior semicircular canal; often seen at same level in axial plane

Question 25

otospongiosis

Answer 25

otosclerosis; bone dysplasia of otic capsule seen in young/middle aged women; bilateral usually types fenestral and retrofenestral

Question 26

retrofenestral and fenestral otospongiosis

Answer 26

fenestral: more common; fissula ante fenestrum (anterior to oval window) retrofenestral (cochlear): severe form; involve otic capsule and lateral wall of labryinth

Question 27

ddx of cochlear demineralization

Answer 27

retrofenestral otospongiosis, osteogenesis imperfecta, fibrous dysplasia, paget disease (based on age)

Question 28

labryinthitis

Answer 28

inflammation of inner ear: infectious/autoimmune 3 stages: acute > fibrous > labrytinthitis ossificans

Question 29

acute labyrinthitis

Answer 29

pus in inner ear; enhancement of inner ear may also look like cochlear/intralabyrinthine schwannoma

Question 30

fibrous labyrinthitis

Answer 30

endolymph/perilymph replaced with fibrous strands mild/decreased post-contrast enhancement

Question 31

labryinthitis ossificans

Answer 31

final stage of labyrinthitis calcified debri where normal endolymph and perilymph is seen best evaluated on CT for calcifications; decreased signal on T2 weighted MRI

Question 32

types of temporal bone fractures

Answer 32

longitudinal and transverse based on axis of temporal bone

Question 33

longitudinal temporal bone fracture

Answer 33

most common; aligned with axis of petrous portion of temporal bone responsible for conductive hearing loss may involve ossicles and facial nerve; risk for development of subsequent acquired cholesteatoma if tympanic membrane disrupted

Question 34

transverse temporal bone fracture

Answer 34

perpendicular to long axis of petrous portion of temporal bone sensorineural hearing loss; involve bony labrinth

Question 35

petrous apex anatomy

Answer 35

medial portion of the temporal bone borders surahyoid neck and intracranial compartment; contains Dorello's canal (CN VI), Meckel's cave (trigeminal ganglion), and petrous portion of ICA

Question 36

cholesterol cyst

Answer 36

foreign body giant cell reaction to cholesterol crystals; expansile mass with internal hemorrhage and fluid that does not suppress on fat suppression

Question 37

apical petrositis/petrous apicitis

Answer 37

rare complication of infectious otomastoiditis; infection extends into pneumatized petrous apex

Question 38

Gradenido triad

Answer 38

otomastoiditis, facial pain from trigeminal neuropathy at Meckel's cave, lateral rectus palsy from CN 6 palsy at Dorello's canal vascular complications include thrombosis of ICA and dural veins

Question 39

petrous apex schwannoma

Answer 39

CN V, VII, VIII smoothly expansile enhanscing mass with bony remodeling; may become cystic or contain fluid levels

Question 40

lancherhans cell histiocytosis/eosinophilic granuloma

Answer 40

neoplastic proliferation of eosinophils and langerhans cells most common site of skull base involvement destructive lesion with nonsclerotic margins

Question 41

chondrosarcoma

Answer 41

malignant neoplasm arises from midline clivus or off midline petroclival synchondrosis ring-and-arc chondroid matrix; lobular cauliflower T2 weighted images

Question 42

chordoma

Answer 42

usually from clivus; may expand laterally to involve petrous apex

Question 43

Petrous apex lesions DDX

Answer 43

ACGMES MC apical petrositis, congenital cholesteatoma, cholesteral granuloma, meningioma, eosinophilic granuloma, schwannoma, mets/myeloma, chondrosarcoma/chordoma