Magnetic resonance imaging of masticatory muscles and temporomandibular joint in myotonic dystrophy patients (Steinert's disease)

MAGNETIC RESONANCE IMAGING OF MASTICATORY MUSCLES AND TEMPOROMANDIBULAR JOINT IN MYOTONIC DYSTROPHY PATIENTS (STEINERT'S DISEASE) (ABSTRACT)^*. THESIS. SÃO PAULO, 2000.

EDMAR ZANOTELI ^**

Myotonic dystrophy (MD), or Steinert's disease, is a multisistemic disease with the gene localized on chromosome 19. The muscular involvement is characterized by myotonia, progressive muscular weakness and atrophy, mainly in the neck, facial and distal muscles of the limbs. These manifestations start at second or third decades of life. The masseter and temporalis muscles have already been assessed in these patients by electromyographic and ultrasound imaging studies that confirmed their involvement. This finding has been associated to the malocclusions and craniofacial abnormalities frequently observed in these patients.

The objective of this study was to evaluate the masticatory muscles by MRI in patients with MD, and the effect of this involvement on temporomandibular joint (TMJ). TMJ images (1.5 T Signa) were done in 15 MD patients, 11 males and 4 females, aged 16 to 53 years (medium = 31 years). Many dental malocclusions were observed in these patients, especially Class III and anterior open bite. Three of them referred recurrent TMJ dislocation. TMJ and masticatory muscles pain was not observed, and joint sounds were noted in only one patient.

The analysis of MR images showed masticatory muscles involvement in 13 patients. In eleven, the involvement was moderate to intense. The temporalis was the most affected of the masticatory muscles. The main abnormalities observed were increase of muscular tissue signal on T1 and volumetric reduction of muscles. A unilateral anterior disc displacement with reduction was seen in one patient, but abnormalities of disk shape were common. Mild osseous abnormalities were frequently observed, including irregularities of shape and contours of bone cortical and sclerosis of bone marrow. In four cases, the condyle moved anterior to the eminence with the mouth opened fully; and, in two cases, posterior to the eminence.

In conclusion, in MD patients, masticatory muscles were frequently affected. Osseous changes were the most important abnormalities observed on TMJ. A possible explanation to this finding is the process of bone remodeling caused by changing of biomechanic in the jaw due to masticatory muscles involvement.

KEY WORDS: myotonic dystrophy, temporomandibular joint, masticatory muscles, magnetic resonance imaging.

*

Ressonância magnética dos músculos da mastigação e da articulação temporomandibular na distrofia miotônica de Steinert (Resumo). Tese de Doutorado, Universidade Federal de São Paulo (Área: Neurologia). Orientador: Acary Souza Bulle Oliveira.

Publication Dates

• Publication in this collection
  28 Nov 2001
• Date of issue
  Dec 2001