Microtia is the congenital abnormal formation of the pinna of the ear lobe. Microtia is generally divided into 4 grades:
- Grade I: All the subunits of the normal ear are present and identifiable but smaller in size than in normal ear.
- Grade II: Partially underdeveloped pinna with one or more subunits absent.
- Grade III: Absence of all external ear subunits except for small remnants. These ears are sometimes referred to as peanut ears since only a vestigial lobule and pieces of cartilage are present.
- Grade IV: Complete absence of external ear also known as anotia.
Treatment of microtia is dependent on the grade. Generally the treatment is either placement of prostheses which could look as a perfect replica of the opposite ear and very difficult to tell apart from a real ear. The other option is surgical reconstruction which usually requires either a 3 stage surgery using a cartilage rib graft or a two-stage surgery using a synthetic material known as Medpore. It is conceivable that in very near future both of these methods would be replaced with microsurgical implantation of an ear graft developed using patients own stem cells in a culture dish or as a xenograft.
External auditory canal closure is known as atresia when there is no canal present or stenosis when only a very small remnant is still present. This could be either acquired from trauma and similar causes, or congenital which is usually seen with microtia or deformity of the lobule.
In the milder form of this disorder, known as membranous atresia, only the cartilaginous and the soft tissue portion of the ear canal is closed off and the bony portion is open and intact. Treatment of this type of atresia is much less involved than when the bony ear canal has not developed. In the latter case, a wide bony canal is drilled which is then lined by a skin graft. The success of the surgery is dependent on degree of abnormality of the middle ear and presence of room between the wall of the temporomandibular joint and the bone covering the dura or the sac around the brain, as well as the location of the facial nerve. Since in most cases of congenital atresia the inner ear is functional and patients have completely normal nerve hearing, devices such as bone-anchored hearing aid (BAHA) or the Soundbite device could be also used to give patient excellent hearing on that side.
Most of these cases are from trauma, repeat infections, radiation exposure, or surgery of the external ear canal. It usually only affects the cartilaginous and soft tissue portion of the external ear canal. Treatment for this condition is also microsurgery.