Vascular air embolisation and expansile sphenopalatine sinus haematoma secondary to a fracture of the rostral skull in a horse

A 13-year-old Thoroughbred gelding presented with acute onset respiratory distress, muscle fasciculations and ataxia during ridden exercise. On physical examination, the horse was extremely distressed and had a markedly increased respiratory rate of 92 breaths/min and heart rate of 82 beats/min. Auscultation of the thorax revealed adventitious sounds throughout the lung fields. A continuous, loud, splashing (‘water-wheel’) murmur was evident on cardiac auscultation. A diffuse, marked interstitial and patchy alveolar pattern was present on thoracic radiographs and comet tail artefacts were found on thoracic ultrasonography. Echocardiography showed air embolisation, with the right ventricle and atrium markedly opacified with air bubbles. The horse deteriorated despite treatment with intranasal oxygen therapy, anti-inflammatories, antimicrobials, diuretics and glycopyrrolate. Post-mortem examination identified an expansile haematoma of the sphenopalatine sinus secondary to a rostral fracture of the skull, a previously unreported differential for vascular air embolism in the horse.