The usefulness of diagnostic imaging for the assessment of pain symptoms in temporomandibular disorders

The causes of pain symptoms in the temporomandibular joint (TMJ) and masticatory muscle (MM) regions may not be determined by clinical examination alone. In this review, we document that pain symptoms of the TMJ and MM regions in patients with temporomandibular disorders (TMDs) are associated with computed tomography and magnetic resonance (MR) findings of internal derangement, joint effusion, osteoarthritis, and bone marrow edema. However, it is emphasized that these imaging findings must not be regarded as the unique and dominant factors in defining TMJ pain. High signal intensity and prominent enhancement of the posterior disk attachment on fat saturation T2-weighted imaging and dynamic MR imaging with contrast material are closely correlated with the severity of TMJ pain. Magnetic transfer contrast, MR spectroscopy, diffusion tensor imaging, and ultrasonography findings have helped identify intramuscular edema and contracture as one of the causes of MM pain and fatigue. Recently, changes in brain as detected by functional MR neuroimaging have been associated with changes in the TMJ and MM regions. The thalamus, the primary somatosensory cortex, the insula, and the anterior and mid-cinglate cortices are most frequently associated with TMD pain.

Clinical significance of magnetization transfer contrast imaging for edematous changes in masticatory muscle

OBJECTIVE

To evaluate inflammatory changes in masticatory muscles by magnetization transfer contrast (MTC) imaging.

METHODS

Gradient-recalled echo (GRE) and MTC-GRE images of relaxed masticatory muscles in 28 healthy volunteers were obtained before and after exercise. At the same time, muscle stiffness and pain in the masseter muscles were also measured. Magnetization transfer ratios (MTRs) of the muscles were calculated from the GRE and MTC-GRE images. The MTRs of the masticatory muscles in 50 patients with temporomandibular disorder were compared with those in the volunteers.

RESULTS

Immediately after the exercise, the MTRs of the masseter muscles significantly decreased (P < 0.05), whereas muscle stiffness and pain increased in the healthy volunteers. In patients with masseter muscle pain, the MTRs of the masseter muscles were significantly lower than in the healthy volunteers (P < 0.05).

CONCLUSIONS

Magnetization transfer contrast imaging strongly reflects the masticatory muscle edematous changes, possibly leading to masseter muscle pain.

Flexure deformation of the temporomandibular joint disk in pseudodynamic magnetic resonance images

OBJECTIVE

The purpose of this study was to determine correlation of flexure disk deformation during jaw movement with other findings on magnetic resonance images and with clinical signs and symptoms in patients with anterior displacement of the temporomandibular joint disk.

STUDY DESIGN

T(1)-weighted magnetic resonance images and gradient recalled acquisition in steady state magnetic resonance images were obtained in 62 subjects with flexure deformed disk in the jaw opening phase. Each disk deformation observed on a pseudodynamic image during jaw opening was classified as an upward or downward flexure deformation. The relationships between type of disk deformation, clinical signs and symptoms, and other findings on the magnetic resonance images were statistically analyzed by chi(2) test.Results. Of 80 delineated joints, 30 showed upward deformation and 50 showed downward deformation. There were significant differences between the upward and downward deformations in TMJ sound, TMJ pain, restricted jaw opening, extent of anterior displacement, and presence of disk reduction.

CONCLUSIONS

The type of disk deformation appeared to correlate with the clinical signs and symptoms and with the progress of internal derangement.

Applications of magnetization transfer contrast in the musculoskeletal system in children

Magnetization transfer (MT) is a new MR imaging technique which has the potential to create contrast differences between normal and pathologic tissues distinct from T1- and T2-weighted contrast. The technique has been used in adults but received little consideration for pediatric imaging. This article reports the successful creation of MT contrast between normal and abnormal tissues in seven children.