MR Imaging of theTemporomandibular Joint

Ashley Aiken, MDa,*, Gary Bouloux, MD, DDSb,c,d,Patricia Hudgins, MDa

KEYWORDS

� TMJ � Temporomandibular joint � Internal derangement � Articular disc � Osteoarthritis � MRI� Synovial joint � Anterior displacement

KEY POINTS

� Internal derangement of the temporomandibular joint (TMJ) is very common.

� MR imaging is the preferred study for evaluating the TMJ.

� Key TMJ features to evaluate include disc position, disc morphology, condylar translation, pres-ence of a joint effusion, and superimposed osteoarthritis.

� Disc position can be classified as normal, anteriorly displaced with recapture, and anteriorly dis-placed without recapture.

� MR imaging is also useful to exclude other diagnoses that may mimic internal derangement,including infection and inflammatory arthritis.

INTRODUCTION overlap with myofascial pain dysfunction, which is

Up to 20% to 30% of the population experiencespain related to the temporomandibular joint (TMJ),and 3% to 7% seek treatment.1–3 TMJ disorder ordysfunction (TMD) is an umbrella term that encom-passes several clinical entities that affect the TMJ,muscles of mastication, or both.4 Internal derange-ment of the disc and joint mechanics is the mostcommon of these various clinical diagnoses.Internal derangement of the TMJ is defined as anabnormal positional and functional relationshipbetween the disc and articulating surfaces.5

Common clinical symptoms include pain and jointsounds (clicking or crepitus), but joint sounds arenonspecific as they are found in up to 35.8% ofasymptomatic persons under 18 years of age.6

However, the clinical evaluation can be unreliableas many symptoms of internal derangement

a Department of Radiology and Imaging Sciences, NeMedicine, 1364 Clifton Road, Atlanta, GA 30322, USA; b

of Medicine, 1364 Clifton Road, Atlanta, GA 30322,Department of Surgery, Emory University School of Med Grady Memorial Hospital, The Emory Clinic ‘B’, 1364 C* Corresponding author.E-mail address: ashley.aiken@emoryhealthcare.org

Magn Reson Imaging Clin N Am 20 (2012) 397–412http://dx.doi.org/10.1016/j.mric.2012.05.0021064-9689/12/$ – see front matter � 2012 Elsevier Inc. All

often a stress-related psychophysiologic dis-order.4,7,8 Therefore, MR imaging has becomepart of the standard evaluation of TMD. Lesscommon entities affecting the TMJ include infec-tion, trauma, neoplasm, and inflammatory arthritis.

MR imaging allows detailed evaluation of TMJanatomy because of its inherent tissue contrastand high resolution using surface coils. MR alsoallows assessment of joint biomechanics throughimaging patients in the closed and open jaw posi-tions. Furthermore, a dynamic study can be ob-tained with cine MR imaging as the patient opensand closes the jaw.4,9–11 Despite the sensitivityand specificity of MR imaging in detecting discposition, results must be interpreted together withclinical findings, because an anteriorly displaceddisc can be seen in up to 34% of asymptomaticpatients, and a normal disc position can be seen

uroradiology Division, Emory University School ofDepartment of Oral Surgery, Emory University SchoolUSA; c Division of Oral and Maxillofacial Surgery,dicine, 1364 Clifton Road, Atlanta, GA 30322, USA;lifton Road, Atlanta, GA 30322, USA

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in up to 23% of symptomatic patients.12–15 Inter-pretation ofMR imaging of the TMJ requires knowl-edge of the normal anatomy and an understandingof normal and abnormal biomechanics.

NORMAL ANATOMY

The TMJ is an unusual synovial joint in that thearticular surfaces are covered with fibrocartilagerather than hyaline cartilage.16 The articularcapsule is attached to the edges of the glenoidfossa, including the articular tubercle, and to theneck of the mandible. The fibrocartilaginous artic-ular disc, or meniscus, lies within the articularcapsule between the mandibular condyle and gle-noid fossa, dividing the synovial cavity into supe-rior and inferior synovial compartments (Fig. 1).The lateral pterygoid muscle inserts anteriorly onthe mandibular condyle at the pterygoid foveaand the anterior band of the disc.17 The articulardisc, or meniscus, is a biconcave avascularconnective tissue structure composed of threesegments: anterior band, intermediate zone, andposterior band.The anterior and posterior bands are triangular

in shape and connected by the thin intermediatezone. The anterior band is attached to the jointcapsule, condylar head, and superior belly of thelateral pterygoid muscle, whereas the posteriorband attaches to the bilaminar zone or retrodiscaltissue, which is a rich neurovascular tissue. The bi-laminar zone, also known as the posterior liga-ment, provides stability to the disc by attachingthe posterior band of the disc to the mandibularcondyle and the temporal bone (see Fig. 1).4

Fig. 1. Normal anatomy of the TMJ. Lateral graphic imagenoid fossa of the skull base. Thenormal bowtie-shapeddisc iseparating the joint space into superior and inferior compthicker anterior and posterior bands and a thinner intermetheanterior band. Theposterior bandattachments are callezone attaches to the posterior mandibular fossa and the in

MR Imaging

On sagittal MR imaging, the normal disc appearsas a biconcave structure with homogenous lowsignal on T1- and T2-weighted imaging. Rarely,bright signal can be seen within the intermediatezone on T2-weighted imaging, resembling a cen-trally hydrated disc.18–21 The fibrofatty bilaminarzone, or retrodiscal tissue, has a higher signalintensity than muscle on proton density and T1-weighted sequences. More fibers of the posteriorattachment with intermediate signal intensity areseen extending from the superior aspect of theposterior band of the disc to attach to the temporalbone, and another band originates from the inferioraspect of the posterior band and attaches to thecondylar neck (Fig. 2).

NORMAL BIOMECHANICS

The TMJ is primarily a hinge and glide articulation,but also allows side-to-side motion. The musclesof mastication are responsible for the openingand closing of the jaw. The temporalis, medial pter-ygoid, andmasseter muscles facilitate jaw closure.The lateral pterygoid contributes to jaw opening. Ina normal joint in the closedmouth position, the discis positioned between the condylar head inferiorly,the glenoid fossa superiorly, and the articulareminence anteriorly. The disc is often sigmoid-shaped and lies in the anterior half of the joint space(see Fig. 2C). In the closed mouth position, thejunction of the posterior band and bilaminar zoneshould lie immediately above the condylar headnear the 12 o’clock position (Fig. 3). The junctionof the posterior band and bilaminar zone should

shows the relationship of the condylar head to the gle-s locatedbetween the condylar headandglenoid fossa,artments (shaded yellow-green). The articular disc hasdiate zone. The lateral pterygoid insertion attaches tod thebilaminar zone. The superior strutof thebilaminarferior strut attaches to the mandibular condyle.

Fig. 2. Normal MR image of the TMJ. (A) Sagittal T1-weighted image in the closed mouth position shows thebiconcave disc with posterior margin at 12 o’clock (arrow). The disc is hypointense on T1, but often the marginsof the disc are not as well defined as on the T2-weighted image. Also note the normal position and T1-hyperintense marrow signal of the mandibular condyle (black asterisk) and articular eminence (white asterisk).(B) Sagittal T1-weighted image in the open mouth position shows adequate opening and normal anterior trans-lation of the disc (arrow) and mandibular condyle (black asterisk) to a position under the articular eminence(white asterisk). (C) Sagittal T2-weighted image in the closed mouth position shows the biconcave disc withposterior margin at 12 o’clock (arrow) and the normal appearance of the articular eminence (white asterisk)and condyle (black asterisk). (D) Sagittal T2-weighted image in the open mouth position shows adequateopening and normal anterior translation of the disc (arrow) and mandibular condyle (black asterisk) to a positionunder the articular eminence (white asterisk). The posterior attachment (bilaminar zone) is also better appreci-ated (arrowhead).

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fall within 10� of vertical to be within the 95thpercentile of normal.13,22,23 However, controversyexists over this definition of normal versus ab-normal, because this definition results in an-terior displacement in a large number ofasymptomatic volunteers (33%).15 Rammelsbergand colleagues24 suggested that a disc should beconsidered anteriorly displaced beyond 30� fromthe vertical. At Emory, the term partial anteriordisplacement is used to describe discs that donot fall within 10� from the 12 o’clock position, butrather lie around the 10 to 11 o’clock position.

During jaw opening, two motions occur at theTMJ. First, rotation occurs around a horizontalaxis through the condylar heads. The secondmotion is anterior translation of the condyle and

disc to a position beneath the articular eminence.Thedisc slides into apositionbetween the condylarhead and articular eminence and takes on a more“bow tie” appearance (see Fig. 2D; Fig. 4). Theloose tissue of the bilaminar zone allows a remark-able range of motion of the disc. In the openmouthposition, the disc rotates posteriorly on the condyleand the entire complex moves anteriorly.

On coronal images, the medial and lateral bor-ders of the disc are aligned with the condylarhead and do not bulge medially or laterally.

MR IMAGING PROTOCOL

MR imaging is the standard imaging choice forevaluating the TMJ for internal derangement.20

Table 1

Fig. 3. Normal range of position of the disc in the closed mouth position. (A) The junction of the posterior bandand bilaminar zone should fall within 10� of vertical to be within the 95th percentile of normal. (B) Because thefirst definition may result in up to 30% false-positives, Rammelsberg and colleagues24 suggested that a discshould be considered anteriorly displaced beyond 30� from the vertical.

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The authors’ TMJ imaging is performed with astandard noncontrast protocol that includes staticand cine imaging in open and closed mouth posi-tions (Table 1). Dual-surface coils are used toprovide excellent detail of the joint with a smallfield of view and high signal-to-noise ratio.Coronal and axial T1-weighted images are

routinely obtained to exclude other pathologies inthe masticator space and to evaluate the contourand marrow signal of the mandibular condyles.Additionally, the coronal images are needed toidentify lateral or medial disc displacement. The

Fig. 4. Normal translation of the mandibular condyleand position of the disc in the open and closedmouth. As the mouth opens, the condyle moves ante-riorly to a position just below the articular eminence.Similarly, the disc moves anteriorly to a positionbetween the articular eminence and the mandibularcondyle in the open mouth.

oblique or parasagittal images are correctedsagittal images (approximately 30� from the truesagittal) that are scanned in a plane perpendicularto the horizontal long axis of the mandibularcondyle. The authors do not routinely use intrave-nous contrast for TMJ imaging, although earlyreports suggested that gadolinium-enhanced T1-weighted images with fat saturation may improvedetection of disruption or injury to the posteriordisc attachment.25 Dynamic information can be

TMJ protocol: without contrast

# Sequence Plane Comment

1 T1: TR 500, TEmin,3 mm, 0.5 skip

COR Closedmouth

2 T1: TR 500, TEmin,2 mm, 0 skip

AX Closedmouth

3 T2 & PD, TR 3500,TE min & 85

Left SAGOBL

Closedmouth

4 T2 & PD, TR 3500,TE min & 85

Right SAGOBL

Closedmouth

5 T2 & PD, TR 3500,TE min & 85

LEFT SAGOBL

Openmouth

6 T2 & PD, TR 3500,TE min & 85

Right SAGOBL

Openmouth

7 T2, TR 1180, TE 64,cine

Left SAGOBL

Dynamic

8 T2, TR 1180, TE 64,cine

Right SAGOBL

Dynamic

Abbreviations: AX, axial; COR, coronal; Min, minimum;OBL, oblique; PD, proton density; SAG, sagittal; T1, T1-weighted; T2, T2-weighted; TE, echo time; TR, repetitiontime.

Box 2Wilkes staging criteria for internalderangement of the TMJ

I. Early stage

Clinical: no significant mechanical symptoms,other than reciprocal clicking

Radiologic: slight anterior displacement, butgood anatomic contour of disc

Surgical: normal anatomic form and slight ante-rior displacement

II. Early/intermediate stage

Clinical: occasional joint tenderness and

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obtained with MR imaging by acquiring staticimages with spin echo techniques at progressiveincrements from closed to open position andthen displaying the images sequentially ina back-and-forth closed cine loop.4,26 Otherauthors have also described using a balancedsteady-state free procession sequence at 3T fordynamic MR imaging of the TMJ.11

Although MR is the preferred imaging study forinternal derangement of the TMJ, CT may becomplementary to MR for evaluating inflammatoryarthritis, infection, or tumors. CT may also becomplementary in the setting of coexistent internalderangement and osteoarthritis (Box 1).

temporal headaches, increase in intensity ofclicking sounds, and beginning transientsubluxations or joint locking

Radiologic: slight anterior displacement andthickening of posterior edge of disc

Surgical: anterior displacement, early anatomicdeformity (slight thickening of posterior edge)

III. Intermediate stage

Clinical: multiple episodes of pain, joint tender-ness, temporal headaches, major mechanicalsymptoms—sustained locking, restriction ofmotion, and pain with function

Radiologic: anterior displacement with signifi-cant anatomic deformity (moderate to markedthickening of posterior edge)

Surgical: marked anatomic deformity withdisplacement, variable adhesions (anterior,lateral, and posterior recesses)

IV. Intermediate/late stage

Clinical: chronic episodic pain, headaches,restriction of motion, undulating course

Radiologic: increase in severity over interme-diate stage with early to

moderate degenerative remodeling of themandibular condyle and glenoid fossa

INTERNAL DERANGEMENT

The most common abnormality of the TMJ isinternal derangement, which is an abnormal rela-tionship of the disc with respect to the mandibularcondyle, articular eminence, and glenoid fossa.The incidence of symptomatic internal derange-ment peaks in the second to fourth decade of life,with a female-to-male ratio of 3:1.27 Patients mostoften present with jaw pain on biting and opening,clicking and locking when opening or closing, anddecreased maximum incisal opening. Headachesand myofascial pain may occur secondarily or beunrelated to the internal derangement. Internalderangement is considered an acquired, progres-sive degenerative process.28 Wilkes29 classifiedvarious stages of internal derangement, progress-ing from an early stage with only reciprocal clickingand no pain, to a late stage characterized by pain,restriction of motion, and grinding symptoms. Inthe earliest stages, only mild anterior displacementof a morphologically normal disc is present in theclosed mouth position, whereas the late stage ischaracterized by anterior displacement withoutrecapture of a thinned disc with perforation andarthritic changes (Box 2). It is important to

Box 1Pathology and primary imaging modalities

� Internal derangement: MR is the primaryimaging modality

� Osteoarthritis (often complication of internalderangement): MR and CT may becomplimentary

� Infection: MR and CT may be complementary

� Tumor: MR and CT may be complementary

� Inflammatory arthritis: MR and CT may becomplementary

� Trauma: CT is the primary imaging modality

Surgical: degenerative remodeling changes ofboth bearing surfaces, osteophytic projections,multiple adhesions, but no perforation of discor attachment

V. Late stage

Clinical: crepitus grinding symptoms, chronicepisodic pain, restriction of motion

Radiologic: anterior displacement, disc perfora-tion with gross anatomic deformity of disc,severe degenerative arthritic changes

Surgical: perforation of posterior disc attach-ments, erosions of bearing surfaces with scle-rosis and flattening of the condyle,osteophytic projections, subcortical cysts

Fig. 5. Partial anterior displacement with recapture. (A) Sagittal T2-weighted image in the closed mouth positionshows anterior displacement of the disc (arrow) in front of the condyle (black asterisk). Notice that on the T2-weighted image, the dark signal of the disc can often appear inseparable from the dark cortical signal of thearticular eminence and condyle (black asterisk). In these cases, the proton density sequence may be helpful tomore accurately assess the position of the disc. (B) Sagittal proton density–weighted image in the closed mouthposition also shows anterior displacement of the disc (arrow) in front of the condyle (black asterisk). However, theproton density shows that the posterior margin of the disc in between 10 and 11 o’clock, and therefore partiallydisplaced. (C) Sagittal proton density–weighted image in the open mouth position shows recapture of the disc(white arrow) between the mandibular condyle (black asterisk) and articular eminence (white asterisk).

Fig. 6. Anterior displacement without recapture. (A) Sagittal T2-weighted image in the closed mouth positionshows anterior displacement of the disc (arrow) in front of the condyle (black asterisk). The condylar eminenceis also shown (white asterisk). (B) Sagittal T2-weighted image in the open mouth position shows adequate ante-rior translation of the condyle (black asterisk) beneath the eminence (white asterisk), and therefore adequateopening, but the disc (arrow) remains displaced anteriorly with no recapture.

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Fig. 7. Medial displacement of disc. Coronal T1-weighted image shows medial displacement of theleft disc (white arrow). Notice the severe degenerativechanges of the mandibular condyles (arrowheads)bilaterally with flattening, loss of joint space, andabnormally dark marrow signal on T1-weightedimage (which could be edema or sclerosis).

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understand the Wilkes staging system, becausemany TMJ surgeons use this system to classifyand treat patients.

At Emory, the average age of patients under-going MR imaging for symptoms of TMD with clin-ical suspicion of internal derangement is 42 years.An overwhelming percentage of patients arefemale (92%) and most proceed to arthroscopy(63%).

Disc displacement may be unidirectional ormultidirectional. Most commonly, it is anteriorand unidirectional. It may also be multidirectionalin an anteromedial direction, or rarely in an

Fig. 8. Severe anterior displacement without recapture, pmotion. (A) Sagittal T1-weighted image in the closed mou(arrow) in front of the condyle (black asterisk). Note the gloof the posterior attachment (bilaminar zone), which iscondyle, suggesting degenerative arthritic changes. TheSagittal T1-weighted image in the open mouth position(black asterisk) in relation to the articular eminence (whiThe disc (arrow) remains displaced anteriorly with no reca

anterolateral direction. Unidirectional transverseand posterior disc displacements are rare.6,28

Although Wilkes describes five stages or levelsof severity, other authors simplify the categoriza-tion of internal derangement on imaging from leastto most severe as follows4:

� Anterior disc displacement with recaptureon mouth opening (Fig. 5)

� Anterior disc displacement without recap-ture on mouth opening (Fig. 6)

� Chronic anterior disc displacement withdisc perforation or disruption of the poste-rior attachment of the disc to the bilaminarzone and features of degenerative jointdisease (Figs. 7–9)

Complications of chronic internal derangementinclude osteoarthritis, bone marrow abnormalities,and avascular necrosis. It is well recognized thatmany cases of osteoarthritis are the result ofinternal derangement. Osteoarthritis is present inup to 20% of patients with internal derangementon initial presentation.30–32 Osteoarthritis alsobecomes more common with longer duration ofinternal derangement. However, the presence ofosteoarthritis does not necessarily impact thedegree of pain and discomfort in patients withinternal derangement. Furthermore, older patientswith osteoarthritis of the TMJ may be completelyasymptomatic.4,33,34

Conservative treatment of internal derangementincludes soft diet, rest, heat, nonsteroidal antiin-flammatory drugs, muscle relaxants, occlusal

erforation of posterior attachments, and restriction ofth position shows far anterior displacement of the discbular morphology of the disc and lack of visualization

disrupted. Also note the chiseled appearance of thearticular eminence is also shown (white asterisk). (B)shows suboptimal anterior translation of the condylete asterisk) in this patient with restriction of motion.pture.

Fig. 9. Severe internal derangement with effusion and osteoarthritis. (A) Sagittal T2-weighted image in theclosed mouth position shows a moderate effusion (arrowhead), flattening and irregularity of the mandibularcondyle with abnormally dark marrow signal (white asterisk), and thinned disc with focal perforation (arrow).(B) Sagittal T2-weighted image in the closed mouth position slightly more lateral also shows the moderate effu-sion (arrowhead) and flattening and irregularity of the mandibular condyle with abnormally dark marrow signal(white asterisk).

Box 3Six key features to evaluate on the TMJ MRI

1. Position of the disc

� Normal

� Anterior displacement

Recapture- seen best on sagittals (Fig. 5)

No recapture- seen best on sagittals (Fig. 6)

� Medial or lateral displacement seen best on coronal T1-weighted image (Fig. 7)

2. Morphology and signal of the disc

� Normal bow-tie appearance (Fig. 2D)

� Thin

� Globular (Fig. 8)

� Perforated: implies focal high signal on T2 weighted image (Fig. 9)

3. Condylar translation

� Normal/ adequate

� Limited (Fig. 8)

� None

4. Masticator space

The axial and coronal T1-weighted sequences will occasionally reveal other causes for TMJ discomfortwithin the masticator space, such as infection or osteochondroma (Fig. 10)

5. Joint Effusion

� No (or trace)

� Yes (Fig. 9)

6. Osteoarthritis: Morphology and signal of mandibular condyle

� Normal

� Flattened, irregular with or without erosions (Fig. 7)

� Abnormal low signal on T1 weighted sequences

� Osteophytyes (Fig. 11)

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Fig. 10. Desmoid tumor or aggressive fibromatosisinvolving the masticator space in a 46-year-old womanwith trismus, initially thought to be related to TMD. (A)Axial T1-weighted image shows an infiltrative isoin-tense mass centered in the right masticator space(white arrow), involving the lateral pterygoid muscleand extending from the ramus to the pterygoid plates.(B) Coronal T1-weighted image post gadolinium showsintense enhancement of this mass (white arrow) andbetter shows its involvementof bothmedial and lateralpterygoid muscles.

Fig. 11. Severe internal derangement with osteoarthritis. (sition shows an anteriorly displaced disc, immediately belthe osteophyte (arrowhead) along the anterior margin ofimage in the open mouth position shows persistent anter

MR Imaging of the Temporomandibular Joint 405

splints, and physical therapy. Surgical interventionis reserved for patients with refractory pain. Discplication and repositioning can be performedeasily with open surgery (arthrotomy), althoughsuccessful disc repositioning with advancedsurgical arthroscopy is also possible. Disc reposi-tioning is typically performed with either resorb-able or nonresorbable sutures, or with the useof mini bone anchors placed in the head ofthe condyle. In patients with morphologicallyabnormal discs or discs that cannot be mobilizedadequately, a simple discectomy with or withouta disc replacement can be performed.

Considerable controversy exists with respect tothe most ideal surgical treatment. Patients withWilkes stage I, II, and early III internal derangement(see Box 2) are the most frequent group treatedwith disc plication. Patients with Wilkes late stageIII internal derangement may be more problematicin terms of disc reposition, and patients in thiscategory may be best treated with discectomy.When discectomy is completed, the decision toreplace the disc is also controversial. The pres-ence of degenerative joint disease (features ofWilkes stage IV and V internal derangement) oftenmandates some form of interposition grafting.Options for disc replacement include temporalismuscle, auricular cartilage, fat, dermis, andtemporary silastic. Preoperative MR imaging ishelpful in staging patients according to Wilkescriteria, allowing a better understanding of discposition and morphology (disease severity), whichcan be helpful in planning for disc repositioning ordiscectomy and the potential need for an interpo-sitional graft. Severe degenerative joint diseaseseen on MR imaging may indicate a potentialneed for alloplastic total joint replacement.

A) Sagittal T1-weighted image in the closed mouth po-ow the articular eminence (white asterisk). Also, notethe condyle (black asterisk). (B) Sagittal T1-weightedior displacement without reduction (arrow).

Fig. 12. Synovitis in a patient with rheumatoid arthritis. (A) Axial T1-weighted image shows abnormal low signalintensity in the left mandibular condyle (arrow). (B, C) Coronal magnetization-prepared rapid gradient-echoimage post gadolinium shows synovial enhancement (arrow).

Fig. 13. Juvenile rheumatoid arthritis (JRA) in a 14-year-old boy with known JRA and joint pain. (A) Coronal T1-weighted image shows irregular flattening of the left mandibular condyle (arrow). (B) Coronal T1-weightedimage post gadolinium shows synovial enhancement and increases the conspicuity of this abnormality (arrow).(C) Sagittal T1-weighted image post gadolinium also shows synovial enhancement (arrow).

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Key MR Imaging Features of InternalDerangement and its Complications

There are six key imaging features or anatomicsubsites to evaluate on every MRI of the TMJ(Box 3). These include the position of the disc,the morphology and signal of the disc, condylartranslation, the adjacent masticator space, thepresence of a joint effusion and signs ofosteoarthritis.

Anterior disc displacement is the most commoninternal derangement of the TMJ. With anteriordisplacement, the posterior attachment (bilaminarzone) is stretched and may be thickened or redun-dant.17 In general, if the disc position is normal inthe closed mouth position, then the position isnormal. If the disc is anteriorly displaced in theclosed mouth position, the next step is to evaluatethe position in the open mouth position to deter-mine if there is recapture. The best sequences to

Fig. 14. Idiopathic condylar resorption in a 17-year-old giSagittal T2-weighted image in the closed mouth positiothe normal condyle. Note the chiseled, pointed appearancmouth position on the left shows complete resorption of ttially empty when scanning through all sagittal images. Ththe eminence (arrow). (C) Axial T1-weighted image showsbilateral mandibular condyles (arrows). The left has been rT1-weighted images are also obtained with the dual surfvisualized.

evaluate anterior disc displacement are the obli-que sagittal PD or T2 weighted sequences. Often,a severely degenerated disc can be difficult toevaluate on the static images. In this scenario,the authors find the dynamic cine images veryhelpful to identify disc position.

Condylar translation refers to the anterior move-ment of the condyle during jaw opening. It is crit-ical to determine whether there has beenadequate jaw opening. If there is adequateopening, there is anterior translation of the condylejust below the articular eminence. The cause oflimited or no normal condylar translation may bepathologic such as a stuck disc or restriction ofmotion or it could be patient cooperation. Stuckor fixed disc may result from intracapsular adhe-sions. MR does not directly visualize the adhe-sions, but the fixed position of the disc issuggestive.35–37 Occasionally, the condyle and

rl with severe bilateral TMJ pain and dysfunction. (A)n on the right shows nearly complete resorption ofe (arrow). (B) Sagittal T1-weighted image in the closedhe left mandibular condyle. The glenoid fossa is essen-e only remnant of the condyle is seen just posterior tothe markedly abnormal morphology and signal of theesorbed to an even greater extent. Note that the axialace coil so that the deeper structures are not as well

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disc may move anterior to the articular eminenceduring maximum incisal opening.A small amount of effusion can be seen in

normal joints, but moderate to large effusions areonly seen in abnormal joints. It has been sug-gested that the presence of an effusion may reflectsynovitis, but a statistical significance has notbeen shown.38

Osteoarthritis in the TMJ, like other synovialjoints, manifests in narrowing of the joint space,articular erosion, eburnation and osteophytosis.

MR IMAGING OF OTHER TMJARTHROPATHIES

A wide range of inflammatory arthropathies canalso involve the TMJ, including rheumatoidarthritis, gout, calcium pyrophosphate dihydratecrystal deposition disease, pigmented villonodularsynovitis (PVNS), and infection.

Fig. 15. PVNS in a 70-year-old male who had an enlargingwith increasing pain on jaw opening. (A) Axial contrassurrounding the left TMJ (arrows) with erosions of the mcalcified loose bodies. (B) Axial T1-weighted image showsthe left TMJ (white arrows), with involvement of the left mgadolinium shows intense enhancement of this mass (whiteacteristic low T2 signal intensity secondary to hemosideriloose bodies on the CT favors PVNS on imaging. (CourtSurgery.)

Rheumatoid arthritis is characterized by bothsoft tissue and bone involvement. Contrast-enhanced MR imaging is most sensitive toevaluate both the soft tissue abnormalities ofsynovial proliferation (Fig. 12) and bone abnormal-ities, such as joint space narrowing, articularerosion, and flattening of the condylar head.37

However, synovial enhancement is not specificfor inflammatory arthritis; it (along with retrodiscalsoft tissue enhancement) has been reported inpatients with internal derangement and osteoar-thritis.25 Contrast-enhanced MR imaging is partic-ularly important for evaluating TMJ involvement inchildren with juvenile arthritis (Fig. 13), becausea delay in diagnosis could compromise normalfacial growth.39 Other inflammatory arthropathies,such as psoriatic arthritis, ankylosing spondylitis,and systemic lupus erythematosus, can also affectthe TMJ and might be radiographically indistin-guishable from rheumatoid arthritis.

left preauricular mass for 1 year. The patient presentedt-enhanced CT shows an enhancing soft tissue massandibular condyle (arrowhead). Note the absence ofan isointense to mildly hypointense mass surroundingandibular condyle. (C) Axial T1-weighted image postarrows). (D) Axial T2-weighted image shows the char-

n deposition (white arrows). The absence of calcifiedesy of Dr Brian Bast of UCSF Oral and Maxillofacial

Fig. 16. Synovial chondromatosis in a 47-year-old man with progressive pain on the left with jaw opening. (A, B)Axial and coronal CT show abnormal widening of the left TMJ with erosions of the mandibular condyle (arrows).However, no calcified loose bodies were seen. The differential considerations included PVNS and synovial chon-dromatosis. (C) At surgery, multiple loose bodies were identified and chondrometaplasia was confirmedhistologically.

Fig. 17. Septic arthritis in a 43-year-old woman withintense leftTMJpain for2weeksandprogressivetender-ness and swelling. Arthroscopic diagnosis and culturegrew streptococcus. Coronal CT shows destruction anderosion of the glenoid fossa and mandibular condyle.

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Idiopathic condylar resorption, also known as“cheerleaders syndrome,” is a poorly understooddisease process that specifically affects the TMJ,usually in teenage girls participating in sports activ-ities. Although the pathogenesis is unknown, theo-ries exist of estrogen hormonemediation leading toan exaggerated response after minor trauma,orthodontics, or orthognathic surgery.40 Althoughmany of the inflammatory arthritides (describedearlier) may also cause condylar resorption, idio-pathic condylar resorption is a separate diseaseentity characterized by loss of vertical height ofthe condyle leading to deformity, TMJ dysfunction,andpain. Expected findings onMR imaging includestriking decreased condylar size and volume, ante-rior disc displacement, and thick retrodiscal softtissue (Fig. 14). The best results are achieved withearly detection and surgical management.40

Other synovial processes, which more com-monly occur in large joints, such as PVNS andsynovial osteochondromatosis, are also rarelyseen involving the TMJ. PVNS is a tumefactivesynovial disease of uncertain origin characterizedby abnormal proliferation of the synovium. OnMR imaging, characteristic areas of low signalintensity on T1- and T2-weighted images arecaused by hemosiderin deposition (Fig. 15).41

Synovial osteochondromatosis is another benigntumor-like disorder that can involve the TMJ. It isthought to be secondary to synovial metaplasia,leading to multiple loose bodies in the joint(Fig. 16). If the loose bodies do not calcify, synovialosteochondromatosis can mimic PVNS on CT and

Fig. 18. Osteochondroma in a 19-year-old man with right TMJ pain mimicking internal derangement. (A) AxialT1-weighted image shows a hypointense, pedunculated mass involving the mandibular ramus and condyle(arrow). (B) Axial CT confirmed characteristic features of an osteochondroma, including continuity with theparent mandibular bone, continuous medullary bone, and uninterrupted cortex.

Fig. 19. Contiguous spread from parotid acinic cell carcinoma. (A) Sagittal T1-weighted image shows abnormalT1-isointense soft tissue surrounding the left mandibular condyle and extending into the TMJ (white arrows).(B) Coronal T1-weighted image, post gadolinium shows a parotid mass (asterisk) invading the TMJ (arrow).Also note the bulky intracranial extension (arrowhead).

Fig. 20. Renal cell metastasis to the mandibular condyle in a patient with TMJ pain. (A) Axial fluid attenuatedinversion recovery (FLAIR) MR image shows focal abnormal signal in the left mandibular condyle (arrow). (B) AxialFLAIR MR image shows multiple additional calvarial metastases.

Aiken et al410

MR Imaging of the Temporomandibular Joint 411

MR imaging. In most cases (70%) the loose bodiescalcify and CT can be helpful to distinguishbetween the two entities when there is overlap ofMR imaging features, becausePVNSvirtually nevercalcifies.

Infectious arthritis of the TMJ is rare. Like septicarthritis anywhere, inoculation can be direct orhematogenous and the clinical course can berapid. Early recognition is key because aggressivejoint destruction can occur, leading to ankylosisand fibrosis of the TMJ (Fig. 17).42

MR IMAGING OF TMJ NEOPLASMS

Osteochondroma is the most common benigntumor that involves the TMJ (Fig. 18).4 Other benigntumors and tumor-like conditions, includingosteoma, giant cell tumor, nonossifying fibroma,and aneurysmal bone cysts, are seen rarely. Mostmalignant neoplasms affecting the TMJ are thesequela of direct spread from a bone primary,such as osteosarcoma or a primary parotid tumor(Fig. 19). Metastases from primary sites such asthe breast, lung, and kidney are more common tothe body of the mandible than to the TMJ (Fig. 20).

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