||As the external, middle and inner ears differ in both their embryological origins and times of development, there is a wide variation in the types of abnormality that can be encountered.
Patients may be seen who have an absent auricle and external auditory canal and yet have only a minimal deformity of the middle ear and a normal inner ear.
By contrast, some children may have a normal or almost normal external ear and a severe congenital malformation of the underlying middle and inner ears.
Congenital abnormalities of the ear may be unilateral or bilateral and of course may be associated with congenital malformations elsewhere in the body.
These deformities may be the result of a genetic defect, the result of a viral infection or of exposure to ototoxic drugs during the first trimester.