Differential diagnosis of the idiopathic laterally deviated mandible.

Among patients who present for an orthognathic evaluation, a common finding is the presence of a laterally deviated mandible. At times, there is a cause to which the lower face asymmetry can be attributed, such as personal history of trauma to the face, presence of congenital disease known to affect the mandible, or other developmental abnormalities. More commonly, however, the patient is underdiagnosed and the cause of the idiopathic, laterally deviated mandible may be perplexing. The authors review the common causes of lateral deviation of the mandible and discuss how the growth of the mandible is affected and how the correct diagnosis may be ascertained. Among the common diagnoses, there are two major categories of mandibular asymmetry: (1) altered cranial base (e.g., muscular torticollis, unilateral craniosynostosis, and deformational plagiocephaly) and (2) condylar abnormality (e.g., condylar fractures, condylar hyperplasia, juvenile condylar arthritis, and hemifacial microsomia). Proper diagnosis and subsequent treatment of the underlying abnormality of the deviated mandible ensure the patient of the appropriate orthognathic reconstruction and decrease the likelihood of skeletal relapse after surgery.