An 18-year-old Warmblood gelding was presented with a recent, abrupt onset of ataxia. Transcranial magnetic stimulation (TMS) was performed and revealed a delayed response in both thoracic and pelvic limbs. Radiographic examination of the cervical region demonstrated osteolytic lesions in the vertebral body and arch of the third cervical vertebra (C3). A cervical myelogram revealed spinal cord swelling in this region on the lateral projection. Computed tomographic (CT) myelography was performed, which showed osteolytic lesions and circumferential thinning of the contrast column due to extra-dural compression at the cranial cervical region. These findings were compatible with an aggressive bone lesion 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 underwent euthanasia. Post mortem histopathological diagnosis was a haemangiosarcoma involving the cranial cervical vertebrae and epidural space. This report demonstrates the additional value of CT myelography on the extent and exact location of cervical vertebral compressive lesions in the horse. This information can be useful for prognosis, biopsy and/or planned surgery of these lesions.