EQUINE VETERINARY EDUCATION / AE / OCTOBER 2014


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contiguous slices of 5mm with detail algorithm). At CT, the vertebral body of C3, including both transverse processes and part of the vertebral arch, showed a mottled, heterogeneous density. The floor of the vertebral canal at the level of C3 was interrupted. The contrast column showed a circumferential decrease in thickness at the mid and caudal aspects of C3 due to extra-dural compression (Fig 3). With CT, discrete, small hypodense foci were also detected at the caudal aspect of the vertebral body of C2. The imaging findings suggest an aggressive bone lesion


involving mainly C3 with a space-occupying lesion in the vertebral canal compressing the spinal cord. Primary or secondary neoplasia and osteomyelitis were considered in the differential diagnosis. Because of the severity of the findings and poor prognosis the horse was subjected to euthanasia.


Fig 1: Left-right lateral projection of the second (C2), third (C3) and fourth (C4) cervical vertebrae. The body and ventral part of the vertebral arch of C3 show several rounded, ill-defined, radiolucent areas (arrows). No abnormalities are detected at C2 and C4.


Post mortem findings and diagnosis At post mortem examination the vertebral bodies of C2–C4 showed osteolysis and several haemorrhagic areas. The dorsal cortex of the vertebral body of C3 showed an indentation of 1.5 cm left to the midline. In this defect a haemorrhagic mass (measuring 1 ¥ 2.5 ¥ 1 cm) was present, filling the epidural space and compressing the spinal cord. Pronounced intramuscular haemorrhage was observed ventral to C3 and C4. The haemorrhagic mass and surrounding bone samples were fixed in formalin (10%) and submitted for histological examination.


Histopathology The formalin-fixed tissue was processed, embedded in paraffin wax, sectioned at 4 mm, stained with haematoxylin and eosin (H&E) and then examined according to standard techniques.


Fig 2: Left-right lateral projection of the second (C2), third (C3) and fourth (C4) cervical vertebrae after injection of contrast medium in the cisterna magna. At the level of C3 the ventral and dorsal contrast columns are thinned and bulging outwards resulting in an image of spinal cord swelling (arrow).


the vertebral arch of C3 (Fig 1). No other radiographic abnormalities were detected on the precontrast radiographs. A cervical myelogram under general anaesthesia (triple drip: combination of a2-agonist, myorelaxans and dissociative anaestheticum) was performed. A puncture of the cisterna magna was performed and the same volume cerebrospinal fluid as the injected volume of contrast medium was removed. Iohexol (Omnipaque 2402, 20 ml/100 kg bwt) was injected. The head of the horse was lifted for approximately 5 min. The cervical myelogram revealed thinning of the dorsal and ventral contrast medium columns at the level of C3 compatible with spinal cord swelling on a lateral projection (Fig 2). CT myelography was performed immediately after the cervical myelogram using a single-slice helical CT scanner3 (image settings: 120 kV; 140 mA; matrix size: 512 ¥ 512;


Immunohistochemistry Paraffin embedded tissues were sectioned at 4 mm, mounted on coated slides4 and allowed to dry for 1 h at 60°C and then overnight at 37°C. Thereafter the sections were deparafinised and incubated with polyclonal rabbit anti-human von Willebrand factor5 (1/200) a marker for endothelial cells. A standard immunohistochemical avidin biotin complex method with diaminobenzidine as chromogen was used (Envision)5. Samples of the spleen and large intestine, used as positive controls, were run concurrently for the antibody tested.


Results


The lesions in the vertebral bodies of C2, C3, C4 and of the mass in the epidural space were consistent with a haemangiosarcoma (Fig 4). It was unclear whether the origin of the mass was in the vertebral body with infiltration in the epidural space or vice versa.


Discussion


Tumours of vascular origin are very rare in the horse. A prevalence of 0.058% is reported in the literature (Kennedy and Brown 1993). Haemangiosarcoma seems to be more frequent than haemangioma and middle-aged to older horses are predominantly affected, although it may appear at any age (6 months to 27 years have been previously reported in the literature) (Johns et al. 2005).


© 2012 EVJ Ltd


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