Temporomandibular joint and masticatory muscle involvement in myotonic dystrophy: a study by magnetic resonance imaging.
OBJECTIVE
The purpose of this study was to evaluate the masticatory muscles and the temporomandibular joint (TMJ) by magnetic resonance imaging (MRI) in myotonic dystrophy (MD) patients.


METHODS
MRI of the masticatory muscles and TMJ was performed in 15 MD patients, 11 male and 4 female, aged 16 to 53 years (mean, 31 years). Many of them had dental malocclusion, especially Angle class III and anterior open bite, and 3 complained of recurrent TMJ dislocation. TMJ and masticatory muscle pain was not observed, and joint sounds were noted in only 1 patient.


RESULTS
The analysis of MRI scans showed masticatory muscle involvement in 13 patients (86.6%). In 11, the involvement was moderate to intense. The main abnormalities observed were increased intramuscular tissue signal on T1 (fatty infiltration) and volumetric reduction of muscles. Regarding the TMJ, articular disk displacement was seen in only 1 patient, but abnormalities of disk shape were common. Mild bone abnormalities were frequently observed, including changes of shape and contour of bone surface, and sclerosis of bone marrow. In 4 patients the condyle moved anterior to the eminence with the mouth opened fully (condylar hyperexcursion).


CONCLUSIONS
This study shows that masticatory muscles are frequently and intensively affected in MD patients. Bone changes are the most consistent abnormalities observed in the TMJ. It is possible that remodeling is caused by biomechanical changes in the jaw as a result of masticatory muscle involvement.
Zanoteli
Edmar
E
Department of Neurology, Universidade Federal de São Paulo-Escola Paulista de Medicina, Brazil. zanoteli@terra.com.br
Yamashita
Helio K
HK
Suzuki
Hideo
H
Oliveira
Acary S B
AS
Gabbai
Alberto A
AA
D000273:Adipose Tissue / Q000473:pathology; D000293:Adolescent; D000328:Adult; D001853:Bone Marrow / Q000473:pathology; D016723:Bone Remodeling / Q000502:physiology; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D004204:Joint Dislocations / Q000209:etiology; D008279:Magnetic Resonance Imaging; D008297:Male; D008310:Malocclusion / Q000209:etiology; D008313:Malocclusion, Angle Class III / Q000209:etiology; D008335:Mandibular Condyle / Q000473:pathology / Q000503:physiopathology; D008406:Masseter Muscle / Q000473:pathology; D008410:Masticatory Muscles / Q000473:pathology / Q000503:physiopathology*; D008875:Middle Aged; D009223:Myotonic Dystrophy / Q000473:pathology / Q000503:physiopathology*; D024343:Open Bite / Q000209:etiology; D010026:Osteosclerosis / Q000209:etiology / Q000473:pathology; D011626:Pterygoid Muscles / Q000473:pathology; D016059:Range of Motion, Articular / Q000502:physiology; D012008:Recurrence; D013701:Temporal Bone / Q000473:pathology; D013703:Temporal Muscle / Q000473:pathology; D019224:Temporomandibular Joint Disc / Q000473:pathology; D013705:Temporomandibular Joint Disorders / Q000473:pathology / Q000503:physiopathology*