Table of Contents
Introduction
Congenital malformation of external ear
“Micro” = small
“Otia” = ear
Background
Epidemiology
- Ear deformity in 1.1% of births
- Incidence of microtia = 1/7000-8000 births
- Male predominance
- Male:Female = 2-3:1
- Right side predominance
- Right side = 60%
- Left side = 30%
- Bilateral = 10%
- Ethnic distribution
- Hispanic
- Asian
- Pima Indians: incidence = 1/70
Embryology
External ear
- Development occurs during weeks 4 to 8 of gestation
- 1st and 2nd branchial arches, clefts and pouches contribute to development of external and middle ear
- Auricle or pinna
- Develops from 6 mesodermal thickenings (called hillocks) that derive from 1st and 2nd branchial arches
- Development begins during gestational weeks 3 to 6
- Pinna completely formed by week 16
- 1st (mandibular) arch → 3 hillocks
- Becomes superior helix and tragus
- 2nd (hyoid) arch → 3 hillocks
- Becomes antitragus, antihelix, lobule
- Hillocks encircle first pharyngeal cleft
- Hillocks fuse
- Develops from 6 mesodermal thickenings (called hillocks) that derive from 1st and 2nd branchial arches
Inner Ear
- Development begins prior to middle or external ear
- Develop separately from external ear from otic placodes
- Otic placodes develop into otic pits and then into otic vesicles
- Otic vesicles are primordial inner auditory and vestibular systems
Anatomy
Typical Ear Measurements
- Vertical height of ear = between orbital rim and helical root
- Usually 5 to 6 cm
- Ear width = 55% of ear length
- Helical rim
- Protrudes 1 to 2 cm from s