Use of MRI for the Early Diagnosis of Masticatory Muscle Myositis

Abstract

The medical records of two dogs that were diagnosed with masticatory muscle myositis (MMM) were reviewed. The reported clinical signs included intense pain when opening the mouth and restricted jaw movement. MRI detected widespread, symmetrical, and inhomogeneously hyperintense areas in the masticatory muscle. Electromyography (EMG) demonstrated severe and spontaneous pathologic activity in the temporal and masseter muscles. With early therapeutic treatment, remission of symptoms occurred within 2 mo, and no relapses were observed for the subsequent 2 yr. The gold standard for the diagnosis of MMM is the 2M antibody test, but the purpose of this study was to evaluate the use of MRI as an accurate and efficient diagnostic tool for the initiation of early therapy for the treatment of muscle myositis.

Magnetic resonance imaging of masticatory muscles in basset hounds

“…, Cauduro et al . ). These changes were markedly different from the typical basset hound appearance.…”

“…Masticatory myositis in dogs produces widespread bilateral, heterogeneous T2W hyperintensity and contrast enhancement of all masticatory muscles in the acute stages (Cauduro et al . ) and marked bilateral muscle atrophy in the chronic stage (Shelton ). Trigeminal neuropathy typically leads to unilateral atrophy of the temporalis and masseter muscles with increased signal intensity on T1W images and contrast enhancement of the atrophied muscles (Schultz et al .…”

Clinical presentation and magnetic resonance imaging findings in 11 dogs with eosinophilic meningoencephalitis of unknown aetiology

“…Serum biochemistry and tests for infectious agents were negative, making an infectious aetiology less likely. Further diagnostic tests that could have been performed to further exclude neoplastic or inflammatory/infectious differentials include muscle biopsy and histopathology, 2 M antibody testing and fine-needle aspirates of muscle or nerve (Cauduro et al 2013, Dewey & da Costa 2016.…”

Dynamic exophthalmos and lateral strabismus in a dog caused by masticatory muscle myositis

“…In human medicine, MRI is used as an adjunct diagnostic test for inflammatory myopathy. It may assist with an early diagnosis, assessment of patients' response to treatment, indicate the severity of the disease, and allow determination of an appropriate biopsy site . However, its use in veterinary medicine has not been well described.…”

“…MRI may be a useful adjunct in the diagnosis of myopathy in dogs, for similar reasons as it is in humans. There are two reports on the use of MRI to obtain an early diagnosis of MMM . An early diagnosis is especially desirable, as it preferable to begin treatment with immunosuppressive drugs as soon as possible and these drugs are contraindicated with the other causes of myositis.…”