Bilateral fibrodysplasia ossificans affecting the masticatory muscles and causing irreversible trismus in a domestic shorthair cat

Management of bilateral pterygoid myositis ossificans-like lesion in dogs

Myositis ossificans (MO) and myositis ossificans-like lesions have been rarely described within the veterinary literature, and are even less common in the maxillofacial region. When MO affects the muscles of mastication, it can result in complete or partial inability to open the mouth. As with other conditions resulting in decreased or restricted mandibular range of motion, severe and potentially fatal sequelae such as difficulty with prehension, swallowing, and air exchange are possible. Diagnostic imaging is essential in achieving an accurate diagnosis and in formulating an appropriate treatment plan. In this “method” manuscript, we provide a detailed description of our approach to diagnosis and surgical management of MO-like lesions of the pterygoid muscles and describe our experience with two young French bulldogs.

Case Report: Unable to Jump Like a Kangaroo Due to Myositis Ossificans Circumscripta

A male 10-year-old captive red kangaroo (Macropus rufus) was presented with a chronic progressive pelvic limb lameness and reluctance to jump. The general examination revealed a palpable induration of the lumbar epaxial muscles. Magnetic resonance imaging performed under general anesthesia revealed bilateral almost symmetric, well-circumscribed mass lesions in superficial erector spinae muscles. The lesions had irregular to multilobulated appearance with hyper-, hypo-, and isointense areas in T2- and T1-weighted (w) sequences without contrast enhancement. On computed tomography, a peripheral rim of mineralization was apparent. Histopathological analysis of a muscle biopsy showed osseous trabeculae with rare clusters of chondrocytes indicating metaplasia of muscle tissue to bone. No indications of inflammation or malignancy were visible. The clinical, histopathological, and imaging workup of this case was consistent with myositis ossificans circumscripta. This disorder is particularly well-known among human professional athletes such as basketball players, where excessive, chronic-repetitive force or blunt trauma causes microtrauma to the musculature. Metaplasia of muscle tissue due to abnormal regeneration processes causes heterotopic ossification. The kangaroo's clinical signs improved with cyto-reductive surgery, cage rest, weight reduction, and meloxicam without further relapse.