External Ears

GENESIS

Congenital ear anomalies are generally divided into malformations (chondro-cutaneous defects) and deformations (misshaped architectural anomalies of the newborn’s pinna, in which normal auricular components are fully developed yet mechanically distorted). Overfolding of the upper helix and/or other parts of the cartilaginous auricle are common constraint-related deformations, as is flattening of the ear against the head ( Figs. 22.1 and 22.2 ). Prolonged constraint of the external ear may also result in asymmetric overgrowth of the ear. Apparent ear enlargement is commonly observed on the side opposite the muscular torticollis in torticollis-plagiocephaly deformation sequence ( Fig. 22.3 ). On the side of the tightened sternocleidomastoid muscle, the ear is usually measurably smaller, with an uplifted lobe caused by pressure from the shoulder. In nonsynostotic deformational posterior plagiocephaly, the position of the ear is also displaced anteriorly on the side toward which the head is turned (as the occiput on that side becomes flattened with persistent supine positioning). Such ear malposition usually corrects with timely and appropriate treatment of the torticollis-plagiocephaly deformation sequence. Similarly, the vertical position of the ear can be lowered with unilateral coronal or lambdoidal craniosynostosis, and it also improves with timely and appropriate surgical correction ( Fig. 22.4 ). Protrusion of the auricles is also common with positional brachycephaly.

The incidence of ear deformation varies with age and the degree of attentiveness of the observer. The incidence of congenital ear deformities has been documented to be as high as 58% of all newborns. Matsuo studied the ears of 1000 neonates over time and noted that more than 50% of the neonates had external ear shape abnormalities, most of which self-corrected during the first few months. Extrinsic and intrinsic ear muscles play a role in shaping ears and may overcome the impact of fetal head constraint in many instances. For example, Stahl’s ear (third crus) was noted in 47% of neonates but only seen in 7% of the same infants at 1 year of age. On the other hand, protruding ears were only seen in 0.4% of neonates, but 5.5% of the same infants had protruding ears at 1 year of age, usually caused by persistently turning the head toward one side while being maintained in a supine sleeping position. These researchers noted that when constriction was accompanied by a lop ear deformity, it was unlikely to correct spontaneously over time. A lop ear deformity can be defined as a deficient helix and scapha, underdeveloped antihelix, and downfolding of the helix.

Inactivity of the posterior auricular muscles with associated loss of facial nerve function in Möbius syndrome leads to prominent ears, which suggests that some ear deformities result from aberrant neuromuscular function. Maternal relaxing hormones that circulate before parturition can soften the cartilages of the fetus and neonate, making the auricles more susceptible to deforming external forces. Based on this pliability of ear cartilage in the first few days after birth, many ear shape abnormalities can be corrected by splinting the ear into a normal shape with custom molds fashioned from polymer dental compound, thermoplastic materials, or flexible wire splints encased in plastic tubing and taped in place for the first few weeks. Such splinting is much less effective and generally requires longer treatment periods when initiated in older children. In one study by Chen et al. of 173 individuals (274 ears), the mean treatment duration of participants who started ear molding within 14 days of birth was shorter than that of those who started treatment more than 14 days after birth with the same ear deformation. The elasticity of ear cartilages affects successful treatment more than does age, and ear cartilages tend to lose elasticity with age. Many types of congenital auricular deformities are caused by abnormalities in intrinsic and extrinsic ear muscles, with shortened muscles increasing the prominence of cartilages. Thus shortened muscles can be corrected by mechanical stretching with a splint, but stretched muscles are more difficult to shorten by splinting.