Michel aplasia, also known as complete labyrinthine aplasia (CLA), is a congenital abnormality of the inner ear. It is characterized by the bilateral absence of differentiated inner ear structures and results in complete deafness (anacusis). Michel aplasia should not be confused with michel dysplasia. It may affect one or both ears.

Aplasia is the medical term for body parts that are absent or do not develop properly. In Michel aplasia, the undeveloped (anaplastic) body part is the bony labyrinth of the inner ear. Other nearby structures may be underdeveloped as well.

PATHOLOGY

Michel aplasia is thought to result from failure of development of the otic placode, due to developmental arrest at the third week of gestation. The common cavity deformity, a confluence of illdefined cochlea and vestibular organ results from a disruption during the fourth and fifth week. An arrest in fifth or sixth week of gestation result in cochlear aplasia or cochlear hypoplasia respectively.

DIAGNOSIS

Diagnosis is based on clinical findings. 'Clinical findings'

• Profound congenital sensorineural deafness is present
• CT scan or MRI of the inner ear shows no recognizable structure in the inner ear.
• As michel's aplasia is associated with LAMM syndrome there will be Microtia and microdontia present(small sized teeth).

Molecular genetic Testing: FGF3 is the only gene, whose mutation can cause congenital deafness with Michel's aplasia, microdontia and microtia

Carrier testing for at-risk relatives requires identification of mutations which are responsible for occurrence of disease in the family.

TREATMENT

1. enrollment in appropriate early intervention programs for the deaf and hard of hearing.
2. consideration of vibrotactile hearing devices or brain stem implants for individuals with Congenital labyrinthine aplasia
3. Evaluation for cochlear implantation in patients who have cochleovestibular nerve and a cochlear remnant. This is done in children above the age of 12 months having severe or profound hearing loss. Cochlear implants in infant and children is notably contested by the Deaf community, and frequently results in failure and lifelong complications.