MR imaging of the temporomandibular joint: a cadaver study of the value of coronal images

Recent studies comparing cryosectional anatomy of the temporomandibular joint (TMJ) to its MR appearance have shown that the assessment of disk displacement is inaccurate when based on the sagittal plane alone. This article describes the MR appearance of the normal and abnormal (positional and osseous changes) TMJ in the coronal plane and compares these findings with their cryosectional anatomy. Twenty-two TMJs from unselected frozen cadavers were embedded in paraffin. Coronal and sagittal MR imaging was performed; specimens were then cut in the same plane as the coronal images. Disk position by cryosection was normal in 14 cases and abnormal in eight cases. Coronal MR images alone correctly depicted the TMJ disk position in 17 cases (77%) (13 normal, four abnormal). Complementary sagittal images were necessary for diagnosing anterior displacement in two cases (9%). MR was inaccurate in three cases (14%) of severe degenerative joint disease. Bone condition was correctly diagnosed on the basis of coronal images alone in all cases. Our study shows that coronal MR imaging alone of the TMJ in cadavers accurately shows disk position in 77% of cases. Complementary sagittal images were of benefit in the diagnosis of an additional 9% with anterior displacement. Disk position was assessed inaccurately in either plane in patients with severe degenerative joint disease. For a full MR assessment of the TMJ for disk position and bone condition, we recommend imaging in both coronal and sagittal planes.     

Temporomandibular joint disk position assessed at coronal MR imaging in asymptomatic volunteers

PURPOSE: To assess the normal position of the temporomandibular joint (TMJ) disk relative to the condyle by using coronal magnetic resonance (MR) imaging in asymptomatic volunteers. MATERIALS AND METHODS: This study was approved by the review committee for human research, and all subjects signed an informed consent form. Thirty symptom-free volunteers without histories of TMJ disorders underwent standardized clinical examinations. Afterward, bilateral sagittal oblique and coronal oblique MR images were acquired with the patient's mouth opened and closed. The coronal oblique opened- and closed-mouth images were analyzed by using computer software. The medial and lateral edges of both the TMJ disk and the condyle were marked for these imaging examinations by using the section through the posterior 3 mm of the disk. To eliminate the effect of different magnifications and/or distortions, the distance between these points was measured automatically and divided by the largest mediolateral dimensions of the condyle. To assess the reliability of the measurements, four observers evaluated the position of the disk in the coronal plane. To assess the changes in position of the posterior 3 mm of the disk in the coronal plane in the closed- and opened-mouth positions, the Wilcoxon signed rank test for matched pairs was used. Interobserver measurement reliability was evaluated by using interclass correlation coefficients (ICCs). RESULTS: Analysis of the coronal closed-mouth disk position revealed a medial position of the TMJ disk relative to the condyle in 11 (21%) of 52 analyzed joints. In the opened-mouth position, the medial location of the disk was more frequent: 29 (85%) of 34 analyzed joints exhibited a medial position of the disk relative to the condyle in this plane. This increasingly medial position of the disk was statistically significant (P < or = .001). Measurement reliability assessment revealed sufficient results (ICC > or = 0.7). CONCLUSION: At both closed- and opened-mouth MR imaging, a medially located TMJ disk seems to be within the normal range of variation. The disk seems to shift even more medially when the mouth is opened.     

Temporomandibular joint after meniscoplasty: appearance at MR imaging

Twenty-five temporomandibular joints (TMJs) were studied in 20 patients who had undergone meniscoplasty. In all patients, preoperative magnetic resonance (MR) images showed anteriorly dislocated disks; all patients underwent a similar postoperative MR examination an average of 6 months after surgery. The results of these studies were correlated with clinical results of surgery, which were classified as poor, fair, good, or excellent at follow-up MR imaging. In 10 TMJs (eight patients [40%]) the clinical results were excellent or good; in 15 TMJs (12 patients [60%]), fair or poor. The position of the disk relative to its preoperative position was a good discriminator in determination of the clinical success of meniscoplasty. After surgery, in all patients with good or excellent results, the disks appeared to be in a normal or an improved position compared with that prior to surgery; in those with poor or fair results, the TMJs had anteriorly dislocated disks that showed no improvement.     

Ligamentum flavum: appearance on sagittal and coronal MR images

The appearance of the ligamentum flavum on sagittal and coronal magnetic resonance (MR) images has not been described in detail in the radiologic literature. The authors reviewed correlative MR images and anatomic sections obtained with a cryomicrotome in 20 cadavers in order to analyze anatomic relationships, variations, and progressive degenerative changes of the ligamentum flavum in the lumbar region. MR imaging showed the ligamentum flavum as an intermediate-signal-intensity structure on images obtained with short and long repetition times (TRs). Sagittal short TR images were effective for evaluating relationships between the ligamentum flavum, spinal canal, and nerve roots. Degenerative changes in the ligamentum flavum appeared as changes in shape or thickness of the ligaments on MR images. Calcification and fat infiltration, which were well depicted on anatomic sections, were not visualized on MR images.     

Temporomandibular joint: multislab, three-dimensional Fourier transformation MR imaging

High-resolution three-dimensional Fourier transformation (3DFT) multislab acquisitions and a specially designed counter-rotating loop surface coil were used to increase the quality and clinical efficacy of imaging of the temporomandibular joint. The results were compared with those of 2D multisection imaging. Multislab 3DFT magnetic resonance imaging combines the advantages of volume imaging for viewing small structures and the clinical efficiency of 2DFT multisection acquisitions. A 3DFT multislab acquisition, coupled with a specially designed coil, yields two slabs of 16 sections each. The thin-section 3D imaging method facilitates the diagnosis of medially and laterally displaced disks and allows a bilateral examination.     

磁共振斜冠状位扫描对正常膝关节前交叉韧带的显示作用

目的 探讨磁共振斜冠状位扫描对膝关节前交叉韧带的显示价值.方法 对60例正常膝关节行常规扫描,包括斜矢状位、冠状位、横断位.所有病例均行在斜矢状位图像基础上平行于前交叉韧带FSE序列斜冠状位薄层无间隔质子密度加权扫描,分析斜冠状、斜矢状、冠状及横断位对前交叉韧带的显示情况.结果 斜冠状可清楚全程显示前交叉韧带于一幅图片上,显示率为100％(60/60),斜矢状位显示率为86.7％(52/60),而横断及冠状位则分段显示前交叉韧带,即不能在一幅图中完整显示前交叉韧带.结论 斜冠状位扫描符合前交叉韧带解剖走向,可明显提高前交叉韧带的完整显示率,有利于其损伤后评价.     

Temporomandibular joint motion: efficacy of fast low-angle shot MR imaging

One hundred temporomandibular joints (TMJs) in 62 symptomatic patients and two healthy volunteers were prospectively examined with T1-weighted spin-echo and fast low-angle shot (FLASH) gradient-echo sequences. FLASH sequences were performed during opening of the mouth and provided a pseudodynamic depiction of TMJ motion. In 49 joints, FLASH sequences provided information that potentially influenced the therapeutic approach to the patient. This information was not available from standard T1-weighted images. The additional information fell into four general categories: (a) determination of the exact time of disk recapture, (b) distinction of normal variants from pathologically displaced disks, (c) clarification of discrepancies found between clinical examination results and T1-weighted images, and (d) elimination of motion degradation of images.     

Temporomandibular joint: MR assessment of rotational and sideways disk displacements

The accuracy of coronal and sagittal magnetic resonance (MR) imaging was examined in the assessment of rotational and sideways displacements of the temporomandibular joint (TMJ) disk. Rotational disk displacement implies a combination of anterior and medial or lateral displacements, whereas sideways displacement implies pure medial or lateral displacement without an anterior component. Multiple 3-mm-thick coronal and sagittal MR images were obtained of 18 fresh TMJ autopsy specimens and compared with the observations in corresponding coronal cryosections. MR imaging correctly delineated the mediolateral position of the disk in 15 joints (83%) and incorrectly delineated it in three joints (17%). Osseous anatomy was correctly assessed in 17 joints (94%). On cryosections, six joints (33%) showed medial disk displacement and two joints (11%) showed lateral displacement. In five of these eight joints the medial or lateral displacement occurred in conjunction with an anterior displacement, that is, rotational displacement. Clinical MR imaging in 37 patients (61 joints with coronal images) showed medial or lateral disk displacement in 16 joints (26%). This study suggests that rotational and sideways displacements of the TMJ disk are an important aspect of internal derangement. The multiplanar capabilities of MR are suitable for an assessment of these abnormalities.     

Temporomandibular joint: MR imaging of internal derangements and postoperative changes

Nineteen abnormal temporomandibular joints (TMJs) imaged with high-field-strength surface-coil MR are presented to illustrate specific changes associated with disk derangement, trauma, and previous surgery. Cases were selected from a series of 248 TMJ MR studies in 144 patients (9-68 year old, 130 females and 14 males) performed during a 5-month period. Surgical findings were available for correlation in 44 of the 248 joints studied. Increased signal caused by myxoid degeneration within the degenerating meniscus was seen, as were pathologic changes including atrophy, fibrosis, and contracture of masticatory muscles occurring with internal derangements. Advantages and limitations of MR are discussed with reference to arthrography and videofluoroscopy. High-resolution and partial-flip-angle images of a normal joint are provided for comparison. In most clinical circumstances, MR is the procedure of choice when examining the TMJ, because it provides contrast resolution of soft-tissue structures superior to that of conventional imaging techniques.     

Limitation of the diagnostic value of MR images for diagnosing temporomandibular joint disorders

OBJECTIVES: Many studies have shown that MRI findings are reliable when experienced calibrated observers work as a group. The hypothesis was that MRI findings can be used as the gold standard also when evaluation is made by single expert observers. Study design: Temporomandibular joint (TMJ) MRIs of 34 patients were evaluated independently by four reviewers with expert knowledge of radiology for the presence of 13 specified pathologic entities, as well as the quality of the images, on a 5-step scale from "Sure Yes" to "Sure No". Intraclass correlation coefficients were calculated to estimate the rating reliability of the examiners. A coefficient of at least 0.8 was deemed good, between 0.60 and 0.80 was deemed acceptable, and less than 0.60 was considered poor. Additionally, weighted kappa statistics were used for pair-wise comparisons across all four reviewers. RESULTS: The hypothesis was not supported by the results. None of the 13 correlation coefficients for comparisons between single examiner evaluations of pathologic entities was good and 8 were poor. CONCLUSION: A diagnosis of TMD based on MRI examination protocols made by a single examiner should not be accepted as a gold standard with regard to TMJ disorders.     

Elbow joint: normal anatomy on MR images

The normal anatomy of the elbow joint in axial, sagittal, and coronal planes was evaluated by comparing 30 magnetic resonance (MR) images of eight healthy volunteers with microtomed cryosections prepared from six cadaver elbows. MR images provided depiction of muscles and tendons, bone marrow, articular cartilage, and neurovascular structures. Cross-referencing of MR images from one plane to another was useful in the evaluation of complicated, obliquely oriented muscle bundles and other soft tissues.     

Temporomandibular joint: improved MR image quality with decreased section thickness.

To determine if the quality of spin-echo magnetic resonance (MR) images of the temporomandibular joint (TMJ) could be improved by reducing section thickness, coronal and sagittal 3.0- and 1.5-mm MR images of the same joints were evaluated. Depiction of the disk, trabecular pattern, and cortex of the condyle was better on coronal 1.5-mm images than on 3.0-mm images (P less than .01), and 1.5-mm sagittal images were better for depiction of the trabecular pattern of the condyle than were 3.0-mm images (P less than .05). The ability of MR imaging with thinner sections to reveal more anatomic details should result in improved diagnostic accuracy.     

Measurement of the normal optic chiasm on coronal MR images.

PURPOSETo develop an objective method for measuring the optic chiasm and to document its normal range in size.METHODSMeasurements of the height and area of the optic chiasm, made on coronal T1-weighted MR images with the use of commercially available region-of-interest software, were obtained in 114 healthy subjects who had a total of 123 MR studies. A normal range and standard deviation were calculated, and the information was broken down by age and sex.RESULTSThe mean area of the optic chiasm was 43.7 mm2, with a standard deviation of 5.21. The mean width was 14.0 mm, with a standard deviation of 1.68.CONCLUSIONThe area and width of the optic chiasm can be measured with the use of commercially available software, which allows an objective estimate of the chiasm''s size. Knowledge of the normal size range of the optic chiasm can be helpful in the early detection of some disorders.     

Temporomandibular joint: morphology and signal intensity characteristics of the disk at MR imaging

Magnetic resonance (MR) imaging has been used in the temporomandibular joint (TMJ) primarily to define the disk position. This report examines altered morphology and signal intensity characteristics of the TMJ disk as they relate to the severity of internal derangement. Two hundred sixteen joints in 133 patients with a history of such derangement. were imaged with MR. Disk position, signal intensity, morphology, and the presence of osteoarthritis were determined for each joint. The normal disk was not anteriorly displaced and had a normal "bow-tie" shape. A grade 1 disk was anteriorly displaced and had a normal shape; a grade 2 disk was anteriorly displaced and had an abnormal shape. Forty (19%) joints were considered normal; none of these exhibited osteoarthritis. One hundred thirty-nine (64%) joints were grade 1; osteoarthritis was found in 17%. Thirty-seven (17%) were grade 2; osteoarthritis was found in 95%. All forty normal joints had high or intermediate signal intensity in the disk. Osteoarthritic joints had a higher percentage of disks with diminished intensity (P less than .0001). Severe or untreated osteoarthritis is known to be a complication of TMJ internal derangements; hence this grading system seems to correlate with the severity of internal derangement.