Over 90 % of children affected with Microtia have hearing loss.
Depending upon the severity of the Microtia, the inner ear may or may not be developed. If not developed the child will not be able to hear from the ear. If the inner ear is developed then conductive hearing through a bone anchored hearing device (BAHA) is possible. Patients with Microtia will be assessed before the age of 1 at a Microtia clinic with an audiologist, educator, social worker, ENT and Plastic Surgeon and nurse co-ordinator.
Normal hearing requires the function of three structures:
- Outer Ear (External ear and external auditory canal)
- Middle Ear (tympanic membrane, incus malleus and stapes)
- Inner Ear: Cochlea, semi-circular canals and auricular nerve (CN VIII)
The inner ear forms well before the middle ear and external ear, which form at the same time. This important embryological difference is the reason hearing may be possible in those affected with Microtia.
Aural atresia is the underdevelopment of the external ear (auditory) canal, eardrum, and middle ear bones, causing hearing loss and is associated with various forms of Microtia.
While some children may have an ear canal, there is no eardrum and the middle ear is not properly formed. Others may have a very small ear canal with associated hearing loss, called aural stenosis.
A baby born with aural atresia or aural stenosis needs to see an Audiologist for specialized hearing testing and be closely monitored by an Otolaryngologist (Ear, Nose and Throat Surgeon). This is provided at our Microtia/Deafness clinic at the Children’s Hospital at Westmead.
As long as the baby has an inner ear (Cochlea and 8th Cranial nerve) then hearing may be possible in the affected ear by one of two ways:
Which bypasses the abnormal pathology in the external and middle ear and transmits sounds to the inner ear for processing.
Canalplasty is a procedure to surgically create an external auditory canal or widen a narrowed external auditory canal.
A BAHA is the most common method of restoring hearing in isolated Microtia. It is the preference of our Microtia clinic and worldwide preference as detailed in the recent inaugural meeting of the International Society of Auricular Reconstruction. The BAHA can be anchored on babies with a soft headband, and later surgically implanted in children once they reach 5 years of age. Surgery involves placement of a titanium abutment or magnetic plate onto the skull. This connects with the sound processor via a magnet or other attachment. Surgeon). This is provided at our Microtia/Deafness clinic at the Children’s Hospital at Westmead.
Canalplasty or Atresia repair aims to correct the anatomical pathology of no ear canal and middle ear. Atresia Repair is complex surgery to restore hearing in children with unilateral or bilateral atresia. The goal of surgery is to create a healthy skin-lined ear canal with an eardrum (tympanic membrane) and middle ear bones (ossicles) that will allow sound waves to be conducted to the inner ear. Children must have adequate space in the mastoid bone, a normal 8th nerve and inner ear/cochlear for this surgery to be successful. Only 50% of Microtia patients would be candidates for surgery.