Compiled By:
Dakshesh Patel, MD
History:
54 year old female complains of pain when chewing and left side “pops in and out all the time”. She has to hold the left jaw when chewing. The symptoms worsened after a recent MVA.
Exam:
MRI of both temporomandibular joints performed with closed mouth and open mouth.
Findings:
Right: The disc is displaced anteriorly on closed mouth position. With open mouth the disk reduces or captures and the intermediate zone lies between the condyle and eminence.
Left: The disc is displaced anteriorly on closed mouth position. With open mouth the disk does not reduce or capture.
Diagnosis:
Bilateral internal derangement.
Discussion:
Temporomandibular joint (TMJ) is uncommonly imaged joint, particularly for internal derangement which is more often a clinical diagnosis. Understanding the complex joint anatomy and relationship is important for evaluation and is the basis of diagnosis of internal derangement.
TMJ is a diarthrodial joint between squamous portion of the temporal bone and mandibular condyle with intervening disk (meniscus) which divides the joint into superior and inferior recess which do not communicate. The temporal bone articulating surface consists of anterior convex articular eminence and posterior concave glenoid fossa. The articular disk is biconcave and has thin intermediate zone in the middle bounded by thicker anterior and posterior bands. Posteriorly the disk continues with bilaminar zone (or posterior attachment) composed of fibroelastic tissue and collagen fibers with superior and inferior lamina. Anteriorly the disk attaches to the capsule through anterior attachment and anteromedially the superior head of the lateral pterygoid inserts into the disk.
In closed mouth position the condyle rests in the glenoid fossa with the posterior band of the disk intervening at 12 O’clock position. On opening the mouth, the condyle glides forward under the apex of the articular eminence with disk moving forward such that the intermediate zone lies between the two.
The most common pathology of the TMJ is internal derangement, in which there is abnormal relation of the disk to the condyle, glenoid fossa and the articular eminence. It is commonly a disease of young female. The symptoms include headache, earache, pain, tenderness over the joint, clicking and popping and limited opening of the mouth. The disk is in abnormal position when the mouth is closed. Pathologically, there is change in the morphology of the disc which losses its normal shape. The disk becomes thickened and in chronic cases may be fragmented or perforated. Initially as the disk dislocates the bilaminar zone is stretched. Later, with the disk remaining dislocated this zone is remodeled and thickened to form a “pseudodisk” between the condyle and the fossa. It may become perforated. The disc which is dislocated may assume various shapes - globular, crumpled, and folded.
Internal derangement is divided into:
- Anterior displacement with reduction to normal position with open mouth.
- Anterior displacement without reduction to normal position with open mouth.
- Anterior displacement with perforation.
It can also be described by the degree of displacement:
- Mild displacement - posterior band contacts anterosuperior aspect of the condyle.
- Moderate displacement - posterior band lies between condyle and apex of articular eminence.
- Severe displacement - posterior band is at the apex of the articular eminence.
Sequela of chronic internal derangement is degenerative joint disease and perforation, which actually occurs in the retrodiskal tissue and not the disk.
Pearls:
- The thin intermediate zone should interpose between condyle and adjacent temporal bone wherever they are most closely apposed.
- On closed mouth, the posterior band is located at 11 to 12 O’clock position, on top of the condyle.
- On closed mouth, the posterior band may not always be apparent as its signal blends into signal of cortical bone.
- On open mouth, the condyle reaches the apex of the articular eminence.
- On open mouth, the retrodiskal tissue becomes engorged with blood and becomes heterogeneous.
- In internal derangement, the disk is always in abnormal position when mouth is closed.
- In chronic cases, the retrodiskal tissue thickens to give appearance of “pseudodisk”.
- Perforations are not visible on routine MRI. Perforations occur in remodeled retrodiskal tissue and not the disk.
- Thickened disk which has lost its normal configuration and has intermediate signal intensity should be mentioned. Disk shape abnormality itself may not cause limitation of opening of jaw but can affect the type of surgery.
- Always comment if the glenoid fossa and articular eminence are pneumatized. Screws placed in pneumatized fossa and eminence may not hold.
Images:
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Figure 1A:
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Figure 1B:
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Figure 2A:
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Figure 2B:
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Figure 3A:
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Figure 3B:
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Figure 4A:
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Figure 4B:
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Fig. 1A and B: Right TMJ- Open and closed mouth.
Fig. 2A and B: Left TMJ- Open and closed mouth
Fig. 3A and B: Right TMJ- Open and closed mouth: Internal derangement with recapture. On the closed mouth view the disk is abnormal in position. On opening the mouth the disc (arrow) recaptures and lies between the mandibular condyle and the articular eminence.
Fig. 4A and B: Left TMJ- Open and closed mouth: Internal derangement without recapture. On the closed mouth view the disk is abnormal in position. On opening the mouth (arrow) the disc does not recapture and lies anterior to the condyle and the articular eminence.
