Thoracic hemivertebra is a rare congenital vertebral malformations in horses resulting in vertebral column deformity with or without neurological signs. A 9-month-old Racking filly was presented with a distinct lump over the back region. This lump was apparent at birth and had been increasing in size. Clinical examination revealed painless kyphoscolio- sis over the thoracic vertebrae with mild hindlimb ataxia and gait abnormality. Plain radio- graphs of the vertebral column showed 13th–16th thoracic hemivertebrae. Myelography was performed under general anaesthesia. The ventral and dorsal aspects of the contrast medium column were narrowed at the level of the 13th–14th thoracic hemivertebrae. The contrast medium was not seen caudally, suggesting spinal cord compression. Little infor- mation about hemivertebra in horses exists, and a better understanding of hemivertebra aetiology is required.

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