Temporal Bone - EAC - Congenital

Question 1

Congenital Auricle Malformations

Answer 1

• AKA Congenital Auricle Dysplasia
• CT to look for associated temporal bone abnormalities:
• • EAC stenosis or atresia & malformed ossicles
• • ± decreased ME and mastoid pneumatization
• • 1/3 have inner ear malformations
• • Anomalous CN7 canal ± oval window anomaly
• • Congenital or acquired ME cholesteatoma (erosive findings)
• Degree of microtia correlates with underdevelopment of EAC, ME, and mastoid air cells
• Cup-shaped ears are a feature of CHARGE syndrome

Question 2

Congenital External and Middle Ear Malformations

Answer 2

Mild: EAC stenosis (tympanic plate small, TM calcified) ME hypoplasia, ossicle fusions or malformations, maybe stenotic oval window, maybe anomalous course of CN7 tympanic segment

Moderate: EAC stenosis vs atresia, ossicles malformed or rotated or fused “mass”, oval window atresia, anomalous/dehiscent CN7 tympanic, CN7 mastoid more anterior than normal

Severe: EAC atresia, ME tiny or absent, low tegmen tympani, ossicles absent or rudimentary, CN7 anomalous bizarre course

Other findings to look for: congenital cholesteatoma as erosive mass, mastoid pneumatization normal to absent, think syndrome if micrognathia or inner ear anomalies also, duplicated EAC

Question 3

EAC Congenital Cholesteatoma

Answer 3

• Small, nonenhancing, rounded or tubular hypodense mass in medial EAC that causes sharply marginated bony remodeling or erosion.
• Look for an erosion or “hole” in tympanic plate (anterior wall, floor, or lower posterior wall of EAC), b/c failure to excise extension through plate leads to recurrence
• EAC can be normal, stenotic, or duplicated
• May see associated BUT SEPARATE 1st BCC ± sinus tract or fistula to EAC

Question 4

Periauricular 1st Branchial Cleft Cyst

Answer 4

A Branchial remnant that occurs with incomplete obliteration of 1st branchial APPARATUS (which has 3 parts)
• CLEFT (ectoderm) of 1st apparatus → EAC
• Arch (mesoderm) of 1st apparatus →mandible, muscles of mastication, CN5, incus body, malleus head
• Pouch (endoderm) of 1st apparatus → eustachian tube, middle ear cavity, & mastoid air cells

Branchial CLEFT Cyst = no internal (pharyngeal) or external (cutaneous) communication
Branchial CLEFT Sinus Tract = opens only externally or internally (rare), not both, blind ending
Branchial CLEFT Fistula = opens to both and creates communication

By far the most common 1st branchial CLEFT anomalies are isolated cysts (2/3rds), maybe some sinuses, rarely fistulas

1st branchial CLEFT cyst or sinus tract or fistula:
• Well-circumscribed, nonenhancing, or rim-enhancing, low-density mass
• If infected, may have thickened, enhancing rim, adjacent stranding
• Located adjacent to parotid gland, EAC, pinna, or rarely parapharyngeal space
• Work type I:
o Duplication of membranous EAC ONLY (ectodermal (cleft) origin)
o Cyst CLOSER TO THE PINNA - anterior, inferior or posterior to EAC
o May “beak” HORIZONTALLY toward bony-cartilaginous junction of EAC
• Work type II:
o Duplication of membranous EAC AND cartilaginous pinna (ectodermal (cleft) AND cartilage (mesodermal arch) origin)
o Cyst CAN BE LOWER along the superficial soft tissues, parotid space, or PPS, may be as low as posterior submandibular space
o Deep projection may “beak” UPWARD toward bony-cartilaginous junction of EAC
**If you see a LINEAR component coursing somewhere or the patient is having drainage anywhere, think SINUS TRACT or FISTULA

Question 5

Periauricular Venous Malformation

Answer 5

• Think about this if soft tissue mass near ear, grows proportionately with patient
• Lobulated soft tissue “mass” with phleboliths (most specific feature)
• Solitary or multiple
• Circumscribed or trans-spatial &infiltrating
• ± mixed lymphatic or venolymphatic malformation
• Osseous remodeling in adjacent bone
• Fat hypertrophy in adjacent soft tissues
• Variable enhancement pattern (patchy, delayed versus moderately intense) can reflects sluggish vascular flow to & through lesion

Question 6

Periauricular Lymphatic Malformation

Answer 6

• Any H&N location; periauricular lesions may be intraparotid &/or periparotid
• Single space or trans-spatial
• Microcystic or macrocystic
• Unilocular or multilocular
• No more than thin septal and thin peripheral enhancement
• Well defined (macro) or poorly defined (micro)
• Fluid-fluid levels best identified on T2 MR
• Don’t confuse with abscess from mastoiditis!

Question 7

Foramen Tympanicum

Answer 7

• AKA Foramen of Huschke; tympanic bone dehiscence
• Developmental ossification defect in anteroinferior aspect of bony EAC (“tympanic plate”) that is 2-8 mm in diameter (avg 4 mm) that is normal EAC variant seen frequently in peds < 5 yo (5% persist after 5 yo)
• Pathology associated with foramen tympanicum
o Spontaneous herniation of TMJ soft tissues into EAC
o Parotid gland-EAC (sialo-aural) Fistula = Gustatory otorrhea that occurs with eating
o Synovial TMJ fistulas into EAC = decreases in size when opening mouth
o Foramen tympanicum may facilitate ear injury during TMJ arthroscopy