Coronoid process hyperplasia: CT studies.

Coronoid process hyperplasia is a disorder that causes restricted jaw movement due to enlargement of the coronoid process of the mandible, which impinges on the zygomatic arch with mouth opening. The cause is unclear. Computed tomographic (CT) findings in three patients with this disorder (two bilateral, one unilateral)--including a 3-year-old boy who may be the youngest patient with this disorder ever reported--include an enlarged coronoid process, with sclerosis and erosion of the zygomatic arch. CT is an effective and rapid method for establishing the diagnosis.