Suture periostitis

The nasofrontal suture is open at birth, should become less evident over the first six months of life and its obliteration is usually seen by one year of age. A periostitis of the nasofrontal suture, also called suture periostitis or nasofrontal suture exostosis is a rare condition observed in horses and leads to a hard swelling across the dorsal aspect of the head, usually at the level of the rostral aspect of the orbits. More rarely, the nasolacrimal and lacrimomaxillar sutures can also be affected.

Suture periostitis has been rarely reported in the equine literature. Most of these horses do not show distinct clinical symptoms apart from bilateral, firm and non-painful swellings rostral to the eyes. In some cases, if the nasolacrimal duct is occluded, they can develop persistent epiphora.

The diagnosis of suture exostosis is usually made radiographycally.
The most common radiographic finding is a proliferative periosteal reaction along the suture line. Extension and pattern of the proliferative lesions are highly variable and can range from small smooth mounds to florid, irregular, almost nodular projections. In most cases a radiolucent defect in a site compatible with the position of the suture between the frontal and nasal bones is present. Different degrees of soft tissue swellings can be present.

The computed tomography allows an accurate description of the periosteal changes and a precise assessment of the bony structures. On the CT images an irregular new periosteal reaction and proliferation with cloudy appearance can be seen, extending along the suture between the frontal and nasal bone, as well as the suture between frontal and lacrimal bone. The symmetric new bone formation is often visible on both hemispheres, extending to the orbita. The lacrimal duct often shows changes in the CT examination and a partial or complete obstruction can frequently be suspected.

The histologic sample showes, proliferative woven bone and highly differentiated cartilage embedded in abundant fibrous tissue. No inflammatory infiltrates are present. The histological changes are interpreted as callus formation.

Most trauma to the facial region include large impression fractures with multiple large, but also smaller, fragments that are pushed inward by an external force. Like most head fractures in the horse, facial fractures are usually open and frequently large sections of skin are separated from the bone.

As with fractures of other parts of the skull, the extent of involvement of the facial skull is often underestimated without a thorough radiographic or computed tomographic examination. The surgeons are frequently surprised by the actual extent of the traumatic insult depicted by computed tomography and/or encountered during surgery. The prognosis of facial skull fractures, even large ones, is usually very good because of the abundance of vascular supply to the region and the low physical load most bones encounter during mastication.

Fractures of the facial skull must be examined thoroughly for possible involvement of adjacent structures such as the oral and nasal cavities, sinuses, the orbit, eyes and adnexa, as well as the cerebrum and other parts of the nervous system.