MR Imaging of the TMJ: A Pictorial Essay

Chris Roth, MD; Robert J. Ward, MD; Scott Tsai, MD; Wendy Zolotor, MD; Richard Tello, MD, MSME, MPH


Appl Radiol. 2005;34(5):9-16. 

In This Article

Developmental Anomalies

Innumerable conditions can affect the normal development of the TMJ, including hereditary and nonhereditary syndromes, postnatal trauma, infection, radiation, and endocrine and dietary disturbances. [2] The uniting feature of these disparate entities is their effect on the growing condyle. The result is a spectrum of abnormalities, ranging from condylar agenesis to condylar hyperplasia.

Condylar agenesis is associated with congenital syndromes, such as otomandibular dysostosis, hemifacial microsomia, and mandibulofacial dysostosis. Depending on the extent of involvement, the condyle, glenoid fossa, coronoid process, ramus, and even the mandibular body may be absent. Deficiencies in the external ear, the auditory canal, and the middle and inner ear may also be present.

Condylar hypoplasia is more commonly the result of a postnatal insult, such as trauma, infection, or radiation. Altered condylar morphology is assocated with a shallow sigmoid notch, a short ramus and mandibular body, and underdevelopment of the glenoid fossa (Figure 8). Soft-tissue abnormalities, such as deficiencies in the external ear, are not a feature of condylar hypoplasia.

A 17-year-old girl with condylar hypoplasia. Sagittal T1- weighted image showing hypoplastic mandibular condyle (black arrow) and a shallow glenoid fossa (white arrow).

Although condylar hyperplasia can result from hereditary syndromes and endocrine disturbances, the most common cause is idiopathic unilateral condylar hyperplasia. The condyle may be morphologically normal, or elongation of the condylar process may be noted. The mandibular ramus and body may be elongated, which will result in chin deviation toward the unaffected side when unilaterial.