11-1
Dentofacial Orthopedics in the Management of Hemifacial Microsomia and Nager Syndrome Cases

Birte Melsen and Athanasios E. Athanasiou

Introduction

Hemifacial microsomia is a congenital disorder of the craniofacial region that affects the development of the lower half of the face and commonly also the ears, facial skin, and mouth. It is called as such because it occurs mainly on one side of the face as the small jaw, but it can be also manifested at both sides of the face simultaneously in 10–15% of patients. Its main etiopathogenic units are the condyle and gonial angle, mostly unilaterally, and the ear abnormalities vary greatly in its external and middle parts (Choi et al. 2015). It presents similar manifestations with the Goldenhar syndrome (additionally, vertebral defects and epibular dermoids) but its etiology is heterogeneous (Tuin et al. 2015). Hemifacial microsomia results from the malformation of the first and second branchial arches (Poswillo 1973). It is considered the second in prevalence syndrome after cleft lip and palatal; it occurs in 1/3500–1/5600 births, and it is not inherited (Tuin et al. 2015). Hemifacial microsomia can present variable signs and symptoms, ranging from the slight asymmetry of face to the complete absence of one ear, small ipsilateral face, facial nerve palsy, and the cleft of the mouth corner (Tuin et al. 2015).

The extent that characterizes the involvement of the temporomandibular joint (TMJ) determines timing and type of treatment that has focused on the possibilities of influencing the growth of the different determinants of mandibular form and size by controlling the quantity and quality of the condylar cartilaginous proliferation. McNamara (1980) reviewed the results of studies on functional appliances performed on animals or based on clinical observations of young children. Also the similar effect of condylar growth by bringing the mandible forward was described many years ago (Weinmann and Sicher 1955) and experiments performed on rats underlined the importance of the treatment timing when trying to generate longer mandibles in these animals (Stutzmann and Petrovic 1979). The influence on growth of the human mandible with a functional appliance was shown to be dependent on the turnover rate meaning the growth potential of the child (Petrovic et al. 1991). The influence of the occlusion and function was the focus of several of the Moyer’s symposia held in Ann Arbor, Michigan, United States, and monograph no. 4 focused specifically on determinants of mandibular form and growth (McNamara et al. 1975), where the influence of function was discussed and demonstrated by Harvold (1975). Later Harvold (1983) published the concept on which the treatment of hemifacial microsomia was based. The treatment principles of hemifacial microsomia have been chosen according to the age. In reference to the use of functional appliances at an early age, there are two benefits. First, depending on the amount that a favorable growth response takes place, the outcome of surgical treatment, if necessary, would be better. Second, any necessary surgical reconstruction would be focused mainly on the osseous components (Proffit and Turvey 1991).

The present chapter will present examples of slow distraction in young children by means of functional appliances (Harvold activator), splints, and pivot appliances, respectively. These case reports illustrate how the relation muscle‐bone interaction will be able to influence the condylar growth in patients with insufficient height of the mandible unilaterally.

Case Reports

Case Report 1

The patient was diagnosed as a hemifacial microsomia without any dental anomalies and affection of ears and tags (Figure 11.1.1a–d). The patient at the age of 4 years referred from the pedodontist who had noted the asymmetric opening pattern. The asymmetry of the face had not been noted until then. The careful clinical examination performed at the Orthodontic Clinic verified a marked deviation of the mandible to the left side, which was significantly exaggerated during maximal opening. The profile evaluation gave the impression of a relative mandibular retrognathism with a rather convex profile. The patient exhibited a complete deciduous dentition with neutral molar relationship on the right side and distal molar relationship on the left side. Both arches were asymmetrical and there was a midline discrepancy of 4 mm.

Evaluation of both the frontal and the panoramic radiographs revealed a pronounced asymmetry of the mandible with the chin deviation to the left (Figure 11.1.1f). Measuring the maximal length from the muscle attachment, the dimension of the right side was 26 mm longer than the left side. Left condyle and ramus were underdeveloped. According to Chierici (1983), the patient presented with a Type II mandibular deformity with missing condylar head and neck. A pronounced pre‐angular notch was also present on both sides (Figure 11.1.1f).

The extraoral photograph of the sagittal view demonstrated a mandibular retrognathism and a convex profile obviously caused by the increased sagittal jaw relationship related to the short‐left side of the mandible. Labial inclination of the lower incisors and lingual inclination of the upper incisors compensated for the increased sagittal jaw relationship resulting in 3 mm overjet. The posterior margins of the ramus deviated 13 mm horizontally at the level of the external cranial base.

The frontal cephalometric radiograph confirmed the marked asymmetry and showed a compensatory inclination of the lower incisors to the right and of the upper incisors to the left. The spina mentalis of the mandible deviated 15 mm from the midline constructed as a perpendicular to the orbital roof through Crista Galli.

When the patient’s parents were informed about the mandibular malformation, they were provided with different approaches to the treatment of their daughter’s problem. They could wait until the end of growth and then perform a surgical‐orthodontic treatment (Kaban et al. 1981), treat during pre‐pubertal and pubertal growth, and finish with surgery, if necessary (Ousterhout and Owsley 1983; Vargervik 1985), or start as soon as possible with the use of functional appliances and still possibly have the need for surgery when reaching adulthood.

The parents selected the third option with the use of a functional appliance (Harvold activator) with a construction bite above the rest position. The principle of this treatment approach is illustrated in Figure 11.1.2 and has been previously described in detail (Melsen et al. 1986).

In this approach, the activator with a construction bite that lowered the condyle on the affected side over the freeway space forcing the mandible into the correct midline by rotating the mandible around the healthy condyle was fabricated and used. The acrylic was removed from occlusal contact which allowed the maxillary teeth in the underdeveloped side to erupt. In the unaffected side, the acrylic was maintained with full coverage. The patient was instructed to wear the activator each night and 1–2 hours a day (Figure 11.1.1e).

After 6 months, the activator was replaced with a new one to stay above the freeway space (Figure 11.1.1g). This was repeated every 6 month, after 4 years a new set of radiographs and photographs were produced (Figure 11.1.1h–l), and the treatment continued. Two years later, the treatment was terminated and at the age of 12 years a new set of diagnostic records was produced (Figure 11.1.1m–q).

At the age of 12 years, the face appeared symmetric and when opening the mouth, the patient performed a symmetric movement of the mandible. The occlusion was normal in all three planes of space and the midlines coincided. Radiographic analysis confirmed that the asymmetry was significantly reduced although the panoramic radiograph demonstrated that the condylar process of the affected side was still underdeveloped and had maintained the Type II deformity classification (Chierici 1983). However, the difference in ramus height between affected and non‐affected sides had been reduced significantly. The spontaneous uprighting of the incisors in the frontal view was obvious. The frontal cephalometric radiograph confirmed the reduction of the asymmetry in all planes of space. The extraoral photograph of the sagittal view demonstrated significant decrease in both the mandibular retrognathism and the convexity of the profile that characterized the patient pre‐treatment.

The conclusion of this treatment confirmed the studies by Harvold (1983).