Hemivertebrae Screening

Hemivertebrae are bones of the spine that are abnormally shaped. Because of their abnormal shape these bones tend not to align correctly with their adjacent bones in the spine. This can lead to instability and deformity of the spinal column, which in turn can lead to the spinal cord or the nerves arising from it becoming compressed and damaged. This causes pain – which can be severe – wobbliness (ataxia) on the hind legs and can also cause loss of hind leg function and incontinence (inability to control passing urine or faeces).

Pain from spinal cord compression can be severe. Affected dogs can also lose function in their hind legs and sometimes lose bladder and bowel control. Not all animals with hemivertebrae develop symptoms, some just have mild signs of ataxia and some have no signs at all.

Dogs with severe clinical symptoms may need major surgical interventions by specialists, which have their own welfare impacts, and, despite this, some may not recover and need to be
euthanised on humane grounds.

Young dogs are most commonly affected when problems associated with skeletal deformities develop as their skeleton grows. The clinical signs associated with the condition can develop rapidly over days, or gradually over weeks and months. Severely affected individuals would, without surgery, have permanent major disability. Even where surgery is possible, some animals may have unacceptable levels of disability necessitating euthanasia.

Therefore this condition can severely limit both the quality and length of life.


Hemivertebrae (HV) – and butterfly vertebrae – are congenital vertebral malformations that result when the vertebrae are not developed properly. HV is seen commonly in small brachycephalic breeds of dogs (screw-tail breeds). In fact the kinked tail can be secondary to HV in the tail vertebrae. Thus, the occurrence of this problem in certain families of dogs suggests the possibility of a hereditary problem. The wedge-shaped vertebrae deformity can lead to secondary progressive spinal cord compression. This may become sufficiently severe to cause marked progressive neurological deficits affecting the pelvic legs. In this case, neurosurgery is the only treatment, but this option is available in only a few specialist neurosurgery centres such as Dick White Referrals.

It is important to remember that Pugs can suffer from many other neurological spinal problems such as slipped disc, spinal cord malformation, spinal cyst, degenerative spinal cord diseases etc. Thus, any Pug with neurological problems, should be assessed by a specialist veterinary neurologist.

This is a very important point and only the results of ongoing research will be able to tell us if this is an hereditary condition. Thus, dogs with any congenital anomaly should not be used for reproduction, even though this carries a risk of losing other good breed qualities. Until further scientific information becomes available, it is advisable to use common sense and caution in the presence of hemivertebrae in Pugs. The HV problem can be in fact be prevented by intelligent breeding practices.

It is necessary ONLY if you wish to breed from your dog.

There is a general feeling that this is a quite wide spread problem in Pugs and many are euthanised due to this, although many breeders report never having seen dogs with it. Only by screening will we be able to assess the prevalence of the condition. Although the condition can be treated surgically, there are very few neurosurgery centres in the UK able to perform the necessary neurosurgery. Dick White Referrals is one of the few.Toggle Content

At the moment there is no DNA test. This congenital malformation is also most likely to be caused by the combination of complex hereditary disorders rather than a simple single DNA abnormality.

To obtain radiographs of diagnostic value, the Pug needs to be positioned perfectly on the radiographic table and this is difficult to obtain in most dogs with sedation alone. Poor quality radiographs can cause difficulty in making a proper diagnosis of presence or absence of HV.

Specialist anaesthetists feel more secure having small brachycephalic dogs  (with possible upper airway problems) anaesthetised, rather than just sedated. Thus most of them are VERY reluctant to sedate any Pug. So whilst anaesthesia is preferred radiographs will be accepted for dogs that have been sedated.