Rupture of the longus capitis muscle

From Horse
Lateral radiographic projection of a horse with a basilar skull fracture and rupture of the longus capitus muscle. Note the fracture fragment in the middle of the guttural pouch, resulting from avulsion from the base of the calvarium. The opacity within the guttural pouch is the result of hemorrhage. Courtesy of Dr. Bonnie R. Rush

Traumatic rupture of the longus capitis is the second most common cause (after mycosis) of severe hemorrhage from the guttural pouch.

The longus capitis muscle is one of the ventral straight muscles of the head. It inserts on the basisphenoid bone at the base of the skull. The point of rupture occurs at the insertion of the muscle dorsal to the guttural pouch. Rupture results from traumatic poll injury (rearing over backward) and produces profuse hemorrhage[1].

Clinical signs

Hemorrhage into the retropharyngeal space can cause asphyxia and death.

Diagnosis

Diagnosis is based on history of trauma and epistaxis (nasal bleeding). On endoscopic examination, swelling and hemorrhage can be seen in the most rostral and medial aspects of the guttural pouch by retroflexion of the endoscope. On lateral radiographic examination, an avulsion fracture of the basisphenoid bone may be seen overlying the guttural pouch region. Significant neurologic deficits are often observed with this fracture.

Treatment

Treatment involves stall rest for 4-6 wk; broad-spectrum antibiotics are given for 5-7 days for any infection at the site of muscle rupture. Prognosis for full recovery is good, but persistent neurologic signs or recurrent hemorrhage worsens the prognosis.

References