A hemivertebrae French Bulldog diagnosis often turns up on an X-ray taken for something else. These misshapen spinal bones are found in most Frenchies, yet the large majority never show any sign of them. Here is when they matter and what to watch for.
Quick answer: Hemivertebrae are wedge-shaped spinal bones present from birth, found on CT in about 94% of neurologically normal French Bulldogs in one study. Most cause no problems. See a vet promptly for wobbly or weak back legs, back pain or incontinence, and urgently if your dog suddenly can’t walk or urinate.
Key takeaways
- Hemivertebrae are wedge-shaped vertebrae present from birth, linked to the screw tail.
- One CT study found them in 93.5% of French Bulldogs with no neurological signs.
- Most affected Frenchies never have symptoms; the finding is often incidental.
- Wobbly back legs, weakness or incontinence in a young dog need a vet exam.
- Hemivertebrae and IVDD are different conditions, but they can look alike.
What are hemivertebrae?
Each vertebra in the spine normally has a roughly box-shaped body that stacks neatly on its neighbors. A hemivertebra forms when part of that body fails to develop before birth, leaving a wedge-shaped bone. Vets group them with other congenital vertebral malformations, such as butterfly, block and transitional vertebrae. According to the Orthopedic Foundation for Animals (OFA), these anomalies form during embryonic development, are present at birth and do not change shape as the dog grows.
Because the bones are wedge-shaped, a run of them can bend the spine. A forward hunch is called kyphosis and a sideways curve is called scoliosis. In screw-tailed breeds such as the French Bulldog, these malformations are found mainly in the middle of the back (the thoracic spine). In a 2014 radiographic study of 28 screw-tailed dogs that each had at least one malformation, malformations affected 23.5% of the thoracic vertebrae examined, and the seventh thoracic vertebra was the one most often involved (Gutierrez-Quintana et al., 2014).
The link to the screw tail
The short, twisted tail of the French Bulldog is itself made of malformed tail vertebrae. A 2018 genetics study from UC Davis linked the screw tail to a variant in a gene called DVL2. The variant was fixed in French Bulldogs, meaning every French Bulldog tested (79 of 79) carried two copies, and it was associated with both tail and thoracic vertebral malformations. Among French Bulldogs with two copies, 47 of 51 (about 92%) also had thoracic malformations (Mansour et al., 2018).
How common are hemivertebrae in French Bulldogs?
Very common. Two key studies used CT scans taken for other reasons in dogs with no neurological signs, and a genetics study added imaging findings from dogs carrying the screw-tail variant:
| Study | Dogs | Main finding |
|---|---|---|
| Ryan et al., 2017 | Retrospective CT review of 171 neurologically normal screw-tailed dogs, incl. 62 French Bulldogs | Hemivertebrae in 93.5% of French Bulldogs, versus 17.6% of Pugs |
| Inglez de Souza et al., 2018 | 178 French Bulldogs: 101 neurologically normal controls (CT) and 77 with disc extrusion (MRI) | Thoracic malformations in 89% of control dogs; kyphosis in 33% of controls |
| Mansour et al., 2018 | 51 French Bulldogs with two copies of the DVL2 variant and spinal imaging | Thoracic malformations in 47 of 51 (about 92%) |
Ryan and colleagues concluded that thoracic vertebral malformations are common in neurologically normal screw-tailed breeds, and that hemivertebrae appear to be more clinically important in Pugs than in French Bulldogs or English Bulldogs.
Why most hemivertebrae French Bulldog cases cause no signs
A wedge-shaped vertebra only causes trouble if it narrows the spinal canal, makes the spine unstable or bends it enough to press on the spinal cord. In most French Bulldogs the spinal cord has enough room, so the malformation is simply something a vet happens to see on an X-ray taken for another reason. Researchers studying French Bulldogs with disc disease described hemivertebrae with kyphosis as usually an incidental radiological finding, noting that such anomalies rarely cause spinal cord dysfunction on their own, and that even severe kyphosis was sometimes seen in dogs with no obvious neurological signs (Inglez de Souza et al., 2018).
That does not mean they never matter. In the 2014 classification study, MRI showed that dorsal and dorso-lateral hemivertebrae were compressing the spinal cord in 5 of the 12 dogs that had neurological deficits (41.6%), and the number and type of malformations differed between dogs with and without deficits. The type and shape of the malformation seems to influence the risk.
Signs that suggest spinal cord compression
When hemivertebrae do cause problems, the signs usually come from pressure on the spinal cord in the mid-back, so they mostly affect the back legs. In a case series of 13 screw-tailed brachycephalic dogs with symptomatic thoracic malformations, the median age was 6 months, and all of them had wobbly, weak back legs (ataxia and paraparesis) while still able to walk (Wyatt et al., 2018). Signs to look out for include:
- Wobbly, “drunken” or uncoordinated walking in the back legs
- Back legs that are weak, cross over, knuckle or scuff the paws
- Bunny-hopping, trouble with stairs or falling behind on walks
- Back pain: a hunched posture, crying out when lifted, or reluctance to move (see signs a French Bulldog is in pain)
- Leaking urine, or loss of bladder or bowel control
None of these signs is specific to hemivertebrae, so a vet exam is needed to find the cause.
Hemivertebrae vs IVDD
Hemivertebrae and intervertebral disc disease (IVDD) are different conditions. Hemivertebrae are malformed bones present from birth; IVDD happens when a spinal disc degenerates and bulges or ruptures into the spinal canal. In French Bulldogs, disc problems are a much more common cause of back pain and weak back legs, and they usually appear in young to middle-aged adults. Our guide to IVDD and back problems in French Bulldogs covers that condition in detail.
The two can be connected. In the study of 178 French Bulldogs, kyphosis was found in 57.4% of dogs with thoracolumbar disc extrusion compared with 33% of controls, and kyphosis was associated with roughly double the odds of disc extrusion. Because nearly every Frenchie has malformed vertebrae, seeing hemivertebrae on an X-ray does not explain a dog’s signs by itself, which is one reason advanced imaging is so important.
How hemivertebrae are diagnosed
Diagnosis starts with a physical and neurological exam: your vet watches your dog walk, tests reflexes and paw placement, and feels along the spine for pain to locate the problem.
X-rays can show hemivertebrae and spinal curvature, but they cannot show whether the spinal cord is being squeezed. CT gives a more detailed picture of the bones, and MRI shows the spinal cord and discs, so it can tell whether a malformation is causing compression or whether something else, such as a disc, is to blame. MRI and CT usually need general anesthesia, and your vet may refer you to a veterinary neurologist.
Treatment and management options
No signs: a dog whose hemivertebrae were found by chance generally needs no treatment. Keeping your Frenchie lean and fit, using a harness rather than a collar, and limiting jumping off high furniture are sensible for spinal health in general.
Mild or stable signs: conservative management may include restricted exercise, physiotherapy and medication your vet may prescribe for pain or inflammation. Be aware that the evidence here is limited and not encouraging. In the 13-dog case series, every dog managed without surgery showed progression of signs; four were euthanized and two went on to surgery because of worsening neurological function (Wyatt et al., 2018). It was a small study, but it is a good reason for regular rechecks.
Progressive or severe signs: a veterinary neurologist or surgeon may recommend surgery to relieve pressure on the spinal cord and stabilize the affected segment. The right approach depends on your dog’s imaging, age and health; ask about the likely outcome, recovery and costs before deciding.
Emergency signs: when to call the vet now
Contact your vet or an emergency clinic straight away if your French Bulldog:
- Suddenly cannot walk or stand, or drags the back legs
- Has back legs that are getting weaker quickly
- Cannot urinate, or loses bladder or bowel control
- Is in severe pain that does not settle
When moving a dog with a possible spinal problem, keep the back as still and straight as possible, using a flat board, firm tray or carrier, and don’t let your dog walk, jump or twist.
Is hemivertebrae genetic? Breeding and screening
There is no simple way to breed hemivertebrae out of French Bulldogs. The DVL2 variant linked to the screw tail was present in two copies in every French Bulldog tested, so a DNA test cannot separate dogs within the breed. Spine X-rays can show which dogs have malformations: the OFA runs a pilot spine database, set up at the request of the French Bull Dog Club of America, that evaluates radiographs of the whole spine in dogs over 5 months of age. Spine screening is not among the tests the French Bull Dog Club of America requires for its CHIC health program (hips, eyes, patellas and heart). If you are buying a puppy, it is reasonable to ask a breeder whether the parents have had spine X-rays and whether any relatives have had neurological problems; our guide to choosing a French Bulldog breeder has more questions to ask.
Vet note: Hemivertebrae on an X-ray are very common in French Bulldogs and are not a diagnosis on their own. If your dog has wobbly back legs, pain or incontinence, ask your vet whether a neurological exam and MRI are needed to find the actual cause, and whether referral to a neurologist would help.
FAQ
Can hemivertebrae get worse as my Frenchie gets older?
The malformed bones are present from birth and do not change shape during growth. Signs, when they occur, usually appear in young dogs; in one case series the median age was 6 months, and in that series the signs worsened over time in every dog managed without surgery. Any new weakness in an adult is more often caused by something else, such as a disc problem, and needs a vet exam.
Is hemivertebrae the same as IVDD?
No. Hemivertebrae are malformed bones, while IVDD involves a damaged spinal disc. Both can cause weak back legs, and kyphosis has been linked to a higher chance of disc extrusion in French Bulldogs (Inglez de Souza et al., 2018).
Can my French Bulldog live a normal life with hemivertebrae?
Most French Bulldogs with hemivertebrae have no signs at all. Dogs that do develop neurological signs need a vet assessment, and their outlook depends on how severe the compression is and how it is managed. For an overview of other conditions to watch for, see our French Bulldog health guide.
Sources
- Prevalence of thoracic vertebral malformations in French bulldogs, Pugs and English bulldogs with and without associated neurological deficits — The Veterinary Journal (Ryan et al., 2017), via University of Glasgow
- A proposed radiographic classification scheme for congenital thoracic vertebral malformations in brachycephalic “screw-tailed” dog breeds — Veterinary Radiology & Ultrasound (Gutierrez-Quintana et al., 2014), via University of Glasgow
- Evaluation of the influence of kyphosis and scoliosis on intervertebral disc extrusion in French bulldogs — BMC Veterinary Research (Inglez de Souza et al., 2018)
- Whole genome variant association across 100 dogs identifies a frame shift mutation in DISHEVELLED 2 which contributes to Robinow-like syndrome in Bulldogs and related screw tail dog breeds — PLoS Genetics (Mansour et al., 2018)
- Outcomes of nonsurgical treatment for congenital thoracic vertebral body malformations in dogs: 13 cases (2009–2016) — JAVMA (Wyatt et al., 2018), via University of Glasgow
- Spine Database — Orthopedic Foundation for Animals
- Testing Registries (CHIC requirements) — French Bull Dog Club of America
