CC
A 21-year-old male patient with left-sided hemifacial microsomia (HFM) presents for treatment of a persistent facial asymmetry. (HFM may have a male predilection and a higher occurrence on the right side, although some studies have shown an equal laterality and sex distribution.)
HPI
The patient was diagnosed with HFM in early childhood. He was subsequently treated with distraction osteogenesis of the left mandible during childhood; however, his facial proportions have slowly but progressively worsened since the distraction procedure. (Asymmetry in HFM usually progresses with age.) Additionally, the patient has had persistent malar hypoplasia and asymmetry of the left auricle. The patient denies any previous history of facial trauma. (Facial fractures in a growing child, especially to the mandibular condyle, can contribute to growth disturbances.)
PMHX/PDHX/medications/allergies/SH/FH
Noncontributory. The patient is a student in good academic standing at a local college.
Examination
General. The patient is a well-developed, well-nourished male in no apparent distress.
Neurologic. The cranial nerves are intact, specifically the facial (N 0 ), vestibulocochlear, and hypoglossal nerves bilaterally.
Maxillofacial. There are mild deficits in subcutaneous tissue and underlying muscle (S 1 ). There is no perioral or palatal clefting present. There are no distortions in orbital size and no asymmetry in orbital position or dystopia (O 0 ). The left malar eminence is hypoplastic. There is mild hypoplasia of the left ear with significant protrusion of the pinna (E 1 ).
There is hypoplasia of the left mandible; the left condyle is absent, along with a portion of the mandibular ramus. The TMJ articulation is absent, and the zygoma is hypoplastic (M 3 ). There is no posterior stop to the mandible when upward force is directed at the angle. The left gonial angle is underprojected. There is canting of the mandible (upward on the left) with reciprocal canting of the maxilla. The maxillary midline is shifted to the left by 3 mm, and the pogonion is deviated to the left by 5 mm. (Malocclusion is prevalent in HFM, and the degree of malocclusion is proportional to the skeletal deformity. Dental crowding, inclination of the anterior teeth, and unilateral crossbite on the affected side are characteristic findings.)
The patient is not missing any adult teeth, and there is no evidence of enamel hypoplasia. No caries or periodontal disease is evident. (However, patients with HFM are more likely to have missing teeth compared with the general population and frequently have delayed tooth development on the affected side. Dental agenesis and enamel hypoplasia are more likely to occur in those with severe skeletal deformities. Enamel hypoplasia of the primary incisors on the affected side is thought to be an additional early developmental marker for HFM.)
The lips and oral commissure are normal (macrostomia is seen in 35% of patients with HFM). The soft palate, hard palate, and alveolar processes appear normal. (Approximately 7%–15% of patients with HFM present with cleft lip and palate.)
Imaging
A panoramic radiograph is the initial radiograph obtained for evaluating the degree of deformity of the mandible and its articulation with the zygoma. Posteroanterior and lateral cephalometric radiographs may be obtained to evaluate the degree of deformity of the maxillomandibular complex in relation to the cranial base ( Fig. 95.1 A).
Computed tomography (CT) scans (with three-dimensional reformatting) provide the best understanding of the geometry of the hard tissue abnormalities and relationships. Additionally, this information may be used for virtual surgical planning and fabrication of surgical splints.
For the current patient, the Panorex demonstrated significant hypoplasia of the left mandible with absence of the condyle–ramus unit (orbit, mandible, ear, nerve, soft tissues [OMENS] classification of M 3 /Kaban type III).
The CT scan provided further information on the severity of the left zygomatic hypoplasia in addition to the degree of occlusal plane canting and midline discrepancy in relation to the skull base ( Fig. 5.1 B and C).
Labs
Preoperative hemoglobin and hematocrit levels were within normal range for this patient. No other labs are indicated.
Assessment
A 21-year-old male with left-sided HFM; O 0 M 3 E 1 N 0 S 1 or Kaban type III (see OMENS classification system [ Table 95.1 ]).
| Classification | Description |
|---|---|
| O | Orbital distortion |
| O0 | Normal orbital size and position |
| O1 | Abnormal orbital size |
| O2 | Abnormal orbital position |
| O3 | Abnormal orbital size and position |
| M | Mandibular hypoplasia |
| M0 | Normal mandible |
| M1 | Small mandible and glenoid fossa with a short ramus |
| M2 | Short and abnormal shaped ramus |
| M3 | Complete absence of ramus, glenoid fossa, and temporomandibular joint |
| E | Ear anomaly |
| E0 | Normal ear |
| E1 | Mild ear hypoplasia and cupping with all the structures present |
| E2 | Absence of external auditory canal with variable hypoplasia of the concha |
| E3 | Malpositioned lobule with absent auricle |
| N | Nerve involvement |
| N0 | Normal facial nerve |
| N1 | Upper facial nerve involvement (temporal and zygomatic branches) |
| N2 | Lower facial nerve involvement (buccal, mandibular, and cervical branches) |
| N3 | All branches of the facial nerve affected |
| S | Soft tissue deficiency |
| S0 | No apparent soft tissue and muscles deficiency |
| S1 | Minimal muscle and subcutaneous deficiency |
| S2 | Moderate deficiency |
| S3 | Severe deficiency with muscles and subcutaneous tissue hypoplasia |
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