Hemivertebrae is a congenital defect in which the vertebrae are deformed, either in such a way that the vertebrae fuse, or that they are wedge-shaped, and cause a twisting of the spine. (show rads of hemivertebrae)
Hemivertebrae is common in brachiocephalic breeds, such as the English Bulldog, French Bulldog, Pug and Boston Terriers. These breeds are famous for having what is called a “screw tail.” The screw tail results from hemivertebrae in the vertebrae of the tail and is characteristic, even desirable, in these breeds. It can also occur in German Shorthair Pointers and German Shepherds.
Hemivertebrae of the tail alone is not of medical concern. However, when it is present in the rest of the spine, it can cause serious clinical signs. Because the deformed vertebrae cause a wedging effect that twists the spine, it can actually cause compression of the spinal cord. Clinical signs include weakness of the hind limbs, pain, urinary incontinence, and fecal incontinence. Signs often progressively get worse, until they plateau at about nine months of age, once the spine stops growing.
Hemivertebrae is relatively easy to diagnose using traditional radiographs. More advanced technologies such as myelograms, CT scans, or MRIs are used to detect spinal cord compression.
Hemivertebrae is a congenital condition, and those breeds that are selectively bred to have “screw tails” are predisposed to the condition. In the case of German Shorthair Pointers and German Shepherds, it is genetically inherited in an autosomal recessive trait.
Many dogs with hemivertebrae show no clinical signs or pain, and do not need to be treated. Rest and anti-inflammatories can be helpful for dogs only mildly affected by the spinal cord compression caused by hemivertebrae. In more severe cases, surgery is necessary to relieve compression on the spinal cord. The procedure used is called a hemilaminectomy, and involves the removal of the intervertebral disc material that is pressing against the spinal cord, followed by stabilization of the spine.
Because hemivertebrae is a congenital condition, the only way to prevent it is through responsible breeding.
Hemivertebrae can vary greatly in severity, from having just one or two abnormal vertebrae and no clinical signs, to having a number of abnormal vertebrae and significant clinical and neurological signs. Prognosis for dogs with hemivertebrae depends on the severity of their case. Decompressive surgery is usually very successful, and most dogs that undergo the procedure regain normal locomotor function.