Primary treatment of most oromaxillofacial tumors in dogs and cats is resective surgery. Management of malignant tumors may be very challenging as wide/radical free-margin surgical removal must be achieved while preserving vital functions. Removal of orofacial tumors may result in large defects exposing the oral cavity or creating a communication with the nasal, pharyngeal, or orbital cavities. Such defects require orofacial reconstruction in order to restore respiratory and manducatory functions. The veterinary surgeon must be familiar with reconstructive techniques in order to prevent the inability of closing the defect, which could lead to an insufficient resection. Small oral defects exposing the nasal cavity are best closed with local random mucosal flaps. Closure of large oral defects may be better achieved with a facial or major palatine-based axial-pattern flap. Small to moderate facial defects can be closed with local advancement or transposition skin flaps. Reconstruction of large facial defects often requires the use of locoregional axial pattern flaps such as the caudal auricular, the superficial temporal, or the facial (angularis oris) myocutaneous axial pattern flaps. Recent publications have shown that the facial (angularis oris) flap is a very versatile and reliable flap in orofacial reconstructive surgery. A surgical decision algorithm based on the size, nature, and location of the defect is proposed.

Case summary An 8-year-old spayed female domestic shorthair cat was referred for trismus of progressive onset, which had started at least 1 month previously. The patient presented with weakness, anorexia, chronic bilateral purulent nasal discharge and concurrent reduced nasal airflow. Upon physical examination, painful mouth opening, bilateral swelling of the temporal areas, with an inability to open and close the mouth completely, were apparent. A vertical mandibular range of motion (vmROM) of 22 mm was noted. Complete blood count, biochemistry, electrolytes and various serology tests were unremarkable. CT revealed multiple mineralised lesions within the masticatory muscles. Histopathological features were consistent with those seen in the human disease fibrodysplasia ossificans progressiva (FOP). Supportive treatment did not improve the vmROM, eventually resulting in a 13 mm open bite, and total inability to close and open the mouth. Cardiac arrest occurred at the induction of an anaesthesia procedure aiming to perform tracheostomy and nasal lavage. Despite emergency tracheotomy and cardiac resuscitation, humane euthanasia was elected by the owners. Post-mortem molecular investigations highlighted a heterozygous deletion, compatible with a splicing site mutation in ACVR1 , which is also associated with FOP in humans. Relevance and novel information This is the first report in the veterinary literature of FOP-like disease selectively affecting the masticatory muscles. This condition is associated with a poor prognosis, as no medical or surgical treatment has currently proven to be of any prophylactic or curative benefit. Although rare, FOP-like disease should be included in the differential diagnosis of trismus in the cat. Any further muscle injury should be avoided.

WRICS can be considered to treat mandibular body fractures in small breed dogs if the fracture is not severely comminuted, and if at least the canine and first molar tooth can be used for anchorage. More severe lesions, such as those with teeth in the fracture line and a shorter fracture surface, are associated with prolonged bone healing.