Ear Microtia

Excerpt

Ear Microtia Overview

Ear microtia is a congenital hypoplastic malformation of the pinna, ranging in severity from slight auricular diminution to total external ear absence. Anotia is the most severe form, characterized by complete auricular and lobular formation failure. Ear microtia is often unilateral and creates a noticeable asymmetry.

This condition is often associated with congenital syndromes and is thought to be caused by vascular insults or exposure to medications during pregnancy. External ear malformation or absence can cause conductive hearing loss. Additionally, aural atresia—or failure of the middle ear and external auditory canal to form—can exacerbate conductive hearing loss in patients with microtia.

The severity of auricular deformity often correlates with middle-ear deformity. Careful collaboration between plastic surgeons and otologists is required when considering the repair timing if these 2 conditions coexist.

Children born with craniofacial anomalies are at increased risk of low self-esteem and getting bullied. Historically, attempts have been made to restore normal form and function by school age to prevent such social stigma. Management options include observation, treating hearing loss with devices such as bone-anchored hearing aids, applying a prosthetic ear for cosmetic improvement, and reconstructing the auricle with alloplastic implantation or costal cartilage autografting.

As operative techniques have evolved, particularly reconstruction with autologous costal cartilage (ACC), many surgeons can now postpone interventions until the patient is 10 years old. This strategy ensures adequate costal cartilage stock for reconstruction and patient consent and participation in postoperative care. The high-density porous polyethylene (HDPE) implantation procedure may be performed on younger candidates, typically 3 to 5 years. However, the infection and implant extrusion rate in this cohort is higher than in individuals who undergo ACC implantation later. Auricular reconstruction is challenging, often causing complications. The procedure should only be performed by experienced surgery teams.

External Ear Anatomy

Understanding the external ear's anatomy is crucial to microtia evaluation and management (see Image. External Ear). The auricle or pinna is the external ear's visible part, consisting mainly of elastic cartilage covered by skin. The auricle collects and funnels sound waves into the ear canal. The external ear cartilage is the cartilaginous framework that gives shape and structure to the auricle. This cartilage may be underdeveloped or malformed in microtia, leading to external ear deformity.

The helix is the pinna's prominent outer rim. The scapha is a shallow groove on the auricle's outer surface, running parallel to the helix. The antihelix is the pinna's inner curved ridge. The triangular fossa is a small triangular hollow near the helix-antihelix junction. The helical crus is the portion where the helix begins to curve inward toward the ear canal. The superior antihelical crus is the antihelix's upper part, forming a curved ridge on the inner auricular surface. This structure helps define the auricle's shape and structure, contributing to its overall appearance. The inferior antihelical crus is the antihelix's lower portion, extending downward and supporting the auricle's inferior segment.

The tragus is a small, triangular-shaped cartilaginous projection anterolateral to the ear canal. The lobule is the earlobe's soft, fleshy lower part. The antitragus is a cartilaginous prominence lateral to the tragus, above the lobule, and below the helix. The intertragal notch (intertragal incisure or incisura) is a small groove between the tragus and antitragus.

The ear canal (external auditory canal or meatus) is a tube-like structure that extends from the auricle to the tympanic membrane. The ear canal conducts sound waves to the eardrum. The concha is a hollow, bowl-shaped depression located just inside the ear canal. The concha is divided into the superior and inferior conchae, both playing a role in directing sound waves into the ear canal and enhancing sound localization.

The tympanic membrane (eardrum) is a thin, fibrous structure separating the external auditory canal from the middle ear. This membrane vibrates with sound waves and transmits these vibrations to the middle ear.

In microtia, external ear structures may have varying degrees of underdevelopment or absence, leading to a range of deformities. Surgical reconstruction techniques aim to rebuild these structures to improve both the ear's appearance and function. Understanding the anatomy helps surgeons plan and execute reconstructive procedures effectively.