The Causes of External Ear Malformations

External ear variations as well as anomalies are quite frequent and range from mild asymmetries to severe deformities or even complete lack of external ear development. The incidence of outer ear malformations is between 1:6000 newborns to 1:6830 newborns. Severe malformations can be expected in 1:10,000 to 1: 20,000 newborns, gross malformation or aplasia in 1: 17,500 newborns.

The cause of ear malformations may be either genetic or acquired. Congenital malformations of the auricle are the product of a sequence of insults during the embryologic development of auricular cartilage. This is why knowledge on the embryology of the ear is essential in understanding the causes of the variations. Various common anomalies described in the literature include protruding ears, constricted ears, microtia, anotia, aural atresia, preauricular pits and cysts, as well as accessory auricular appendages. These anomalies result in varying degrees of functional impairment and severity, which may or may not necessitate surgical intervention. Some of these anomalies only cause cosmetic imperfections while others can affect the function and physiology of the external ear. In addition, these aberrations can be linked to other congenital syndromes, although they are usually found in isolation. Some examples of congenital syndromes associated with ear malformations include craniofacial dysostosis (e.g. Crouzon syndrome), otofacial dysostosis (e.g. Treacher-Collins syndrome, Goldenhar syndrome) otocervical dysostosis (e.g. Klippel-Feil syndrome, Wildervanck syndrome), otoskeletal dysostosis (e.g. van der Hoeve-de-Kleyn syndrome) and chromosomal syndromes such as trisomy 13 (Paetau syndrome), trisomy 18 (Edwards syndrome), trisomy 21 (Down syndrome) and 18q syndrome.

The acquired ear malformations can originate from injuries during pregnancy or throughout a person’s life. The injury during pregnancy can be due to infections (rubella, cytomegalovirus, herpes simplex virus), irradiation, chemical agents, malnutrition, Rh incompatibility, atmospheric pressure changes, hypoxia as well as noise exposure. Bleeding in the first part of pregnancy and metabolic disturbances like diabetes have to be taken into consideration. Among the chemical agents that can cause ear malformations, medicinal drugs play a predominant role, a notable example being thalidomide, which led to a considerably increased frequency of malformations in the early 1960s. Environmental agents like herbicides, mercury-containing fungicides and lead can also exert teratogenic effects to the external ear. Some of the most common causes of external ear malformations during a person’s life include sports related malformations like the cauliflower ear which is common among wrestlers, split earlobes due to large or heavy earrings as well as traumatic ear deformities resulting from injuries. Furthermore, the cause of various anatomical variations and malformations remain unknown due to inability of thousands of patients to undergo genetic analysis as well as inadequate knowledge on the genetics of many of these variations. In addition, the clinical data and the history regarding the exogenic influences of the patients involved may not be completely clear so no certain cause can be identified.

All in all, regardless of the etiology, variations in the anatomy of the external ear can involve the orientation, position as well as size of the auricle. These variations could only be “cosmetic anomalies”, causing no alarm to physicians regarding the physiology and overall health of the ears, but creating distress and anxiety to the individuals who often seek to correct these imperfections by undergoing otoplasty. Such examples include prominent ears, constricted ears and macrotia; all conditions which do not affect the function of the ears but significantly affect the lives of the people who have them, especially in the younger ages, with many of the kids that have such anatomical variations being victims of bullying and often being singled out from their social circles. Some of the variations however could affect the function of the ear and need to be treated.

Various classifications could be used to describe anomalies of the external ear. Recently, Yotsuyanagi and Hunter divided the anomalies into three grades of dysplasia. Grade I anomalies involve minor variations that do not warrant the use of skin and cartilage to repair the defects. This category includes macrotia, anomalies of the pinna (protruding ear, cryptotia, Darwin’s tubercle, satyr ear, Stahl ear, shell ear, Mozart ear, and lop ear), absent helical cleft, and anomalies of the lobule and tragus. Grade II dysplasia includes anomalies where some normal ear features are detectable and reconstruction requires the use of additional skin and cartilage. This grade covers severely deformed cup ear. In Grade III dysplasia, no normal ear features are detectable and complete reconstruction is required. This category includes microtia (unilateral or bilateral) with EAM atresia, and anotia or complete absence of the ear. The purpose of the following sections is to describe these anatomical variations in detail.