Temporomandibular joint (TMJ) disorders in children are relatively rare. They can be divided into extra-articular and intra-articular types, which can occur alone or together.
PATHOGENESIS, EPIDEMIOLOGY, AND CLINICAL MANIFESTATIONS
Myofascial Pain Dysfunction (MPD)
The most common problem affecting the TMJ is myofascial pain dysfunction (MPD), which is extra-articular in origin. As many as 25% of adults may experience signs of MPD at some point in their lives, and 7% of patients between ages 12 and 18 years will seek treatment for a TMJ-related problem. Patients with MPD often experience pain and decreased jaw function. Related symptoms include headache, ear pain, joint noises, closed or open lock, difficulty chewing, and limited mouth opening.
MPD is characterized by increased tension and spasm of the muscles of mastication for any reason. Risk factors associated with MPD include gender (female), parafunctional habits, psychiatric conditions, unstable dental occlusion, history of facial trauma, and hypermobility syndromes. MPD may be caused by hyperfunction or parafunction, such as nocturnal jaw clenching and teeth grinding (bruxism), or may be a manifestation of psychological stress. TMJs are initially normal in patients with primary MPD, though longstanding MPD may create intra-articular joint problems. Primary intra-articular TMJ dysfunction also frequently leads to MPD.
Intra-articular TMJ disorders result from an abnormal relationship between the mandibular condyle and the cartilaginous intra-articular disk. Intra-articular disorders may present as painless TMJ noises or limited mouth opening. Intra-articular dysfunction is closely tied to MPD, however, as spasm of the lateral pterygoid muscle, which inserts into the disk, can displace the disk anterior and medial to the condyle. Therefore, patients with intra-articular disorders often present with signs and symptoms similar to those with primary MPD.
An anteriorly displaced disk may or may not impair normal mandibular opening depending on the ability for the disk to return to its normal position as the mouth opens. Reduction of the disk is usually associated with a midopening click, which can be audible and/or palpable. Anterior displacement without reduction is often the result of chronic intra-articular dysfunction resulting in tearing and scarring of the retrodiscal tissues. When this occurs, the mandibular condyle can only rotate within its fossa and is unable to translate down the slope of the articular eminence. This results in a limitation of mouth opening to the 25-mm range measured between the incisal edges of the maxillary and mandibular central incisor teeth. Longstanding displacement may result in a change in shape or tearing of the disk.
The TMJs are affected in 39% to 75% of children with juvenile idiopathic arthritis (Chapter 198). It is unusual for TMJ pain and inflammation to be the first presentation of undiagnosed juvenile idiopathic arthritis, but within 5 years of diagnosis, 50% of children ...