[MRI evaluation of morpho-structural alterations of the retrodiscal tissue in condylo-meniscal incoordination of the TMJ: usefulness of individualised T2-weighted TSE sequences].

PURPOSE: To assess and evaluate morpho-structural alterations of the retrodiscal tissue of the temporomandibular joint (TMJ) that may be seen in chronic trauma of the condylo-meniscal incoordination through magnetic resonance (MR), using T2-weighted TSE sequences. MATERIALS AND METHODS: The study included 40 patients, 6 male and 34 female, age range 12-66 years, mean age 28.5 years. According to the Wilkes classification, TMJs of patients were graded as follows: 10 grade 1 TMJs; 28 grade 2, 16 grade 3, and 26 grade 4. Scans were obtained with a 1.5 T MRI unit, and a dedicated surface coil, using T2-weighted TSE sequences (TR 3000-3500, TE 90-100), 2 acquisitions, 256x256 matrix, 3-mm section thickness, with a 0-mm interval, and 2'30" duration for a single acquisition. Scans were obtained both during opening and during closure of the mouth, on 3 planes: sagittal oblique, perpendicular to the condylar long axis; coronal oblique, perpendicular to the anteroposterior axis of the discs; and axial, perpendicular to coronal scans. Parameters used were the following: presence or absence of retrodiscal fibrosis; morphology of the retrodiscal fibrosis in scans taken during mouth opening in the four grades of the Wilkes classification; dimensions of the retrodiscal fibrosis in scans taken during mouth opening, in the four grades of the Wilkes classification, in an anteroposterior direction, measuring the longest distance on parasagittal planes on a horizontal line touching the outer edge of the disc and the most-distal point of fibrosis, and in a vertical direction, measuring the distance between the highest and lowest points of fibrosis; signal intensity features within the fibrotic area. RESULTS: In all TMJs analysed, it was possible to confirm the presence of retrodiscal tissue fibrosis, which was more or less evident according to the grading of the dysfunction/disease, to the extent of mouth opening, and to displacement with or without reduction of the articular disc. In grade 1 TMJs, fibrosis looked like a truncated cone; in grade 2, fibrosis looked like a cone; in grade 3, it was either shaped like a mushroom placed horizontally, with the stalk towards the disc, or else ribbon-shaped; in grade 4, it had an inhomogeneous, irregular ribbon shape. CONCLUSIONS: MR studies of TMJ dysfunction through T2-weighted TSE sequences allowed us to evidence in all cases the sclerotic alterations of the retrodiscal tissue, and to assess their form and dimensions. Furthermore, it was possible to evidence both the pathognomonic features of retrodiscal tissue fibrosis resembling a mushroom, and the characteristic brace-shape the upper and lower layers take on during mouth opening in TMJs with a disc displacement with reduction.