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There
is a wide range of normal variation in the shape of the external ear, and as
such minor variations are often not regarded as abnormalities. It is important to look at the ear structure and determine which components any malformation may involve. The image to the left shows the normal anatomy and structures of the external ear. Ear position is also important, particularly if they are felt to be posteriorly rotated or low-set. |
Click on the image for a larger image |
Microtia is a term used for abnormalities of ear development, ranging
from subtle deviations of ear size, shape, and location of the pinna and
ear canal, through to major malformations of the external ear with only
small nubbins of cartilage and an absent auditory meatus. Anotia
is complete absence of the pinna and ear canal. Microtia-anotia is a rare condition, reported to occur in approximately 1.5:10,000 deliveries 1 (although it may be more common in some populations). About two-thirds of cases are isolated malformations, but it may occur in association with other malformations, and with specific syndromes in 10% of cases such as Treacher-Collins syndrome and Goldenhar (Hemifacial Microsomia) syndrome. Sporadic microtia is most likely to be unilateral; syndromic forms or those associated with other major malformations are more commonly bilateral. Assessment in the neonatal period involves thorough examination for other abnormalities. It is prudent to check that the fetal anatomy scan was normal. Although the parental concern will primarily be whether the ear will look cosmetically normal, the emphasis is initially on ensuring that the child has hearing sufficient for normal speech. Cosmetic repair will not be undertaken for several years, and is often done in combination with the otorhinolaryngology and plastic surgical services (there is a multidisciplinary microtia-anotia clinic at Starship Hospital). 1. Mastroiacovo P, Corchia C, Botto LD, Lanni R, Zampino G, Fusco D. Epidemiology and genetics of microtia-anotia: a registry based study on over one million births. J Med Genet 1995;32:453-7. |
November 21, 2007