Equine wobbler syndrome, also known as cervical vertebral stenotic myelopathy (CVSM), is a devastating neurological syndrome resulting from damage to your horse’s spinal cord.

Horses with CVSM exhibit neurological symptoms such as poor balance and stumbling when walking. Wobblers horses can become dangerous to handle and ride if untreated.

An estimated 1.3% of horses are affected by CVSM, with male horses being more likely to have the condition. [1][2] This condition most commonly affects Thoroughbreds, Quarter Horses, and Warmbloods. [3]

Wobblers can be caused by spinal abnormalities, infection or injury. In certain cases, horses with wobblers respond well to treatment and can return to normal work.

However, other forms of wobblers can be permanent and progressive. Early detection and treatment are critical to avoid poor outcomes.

Equine Wobbler Syndrome

Wobblers or cervical vertebral stenotic myelopathy is an umbrella term for many causes of spinal cord compression leading to an uncoordinated gait.

The primary sign of wobblers is ataxia, which is described as impaired coordination of voluntary muscle movement produced by a neurodegenerative disorder.

Wobblers can be caused by malformation, injury, or disease in any part of the spine, including the: [4]

  • Base of the skull
  • Cervical spine
  • Thoracic spine
  • Lumbar spine
  • Sacrum

Horse Cervical Spine

In most cases, CVSM is caused by cervical spinal cord damage. This part of the spine is more susceptible to damage because it is highly mobile.

Cervical Spine

The cervical spine is the area of the spinal cord that lies within your horse’s neck, extending through the seven cervical vertebrae (C1-C7). The spinal cord is the highway through which your horse’s brain sends signals to the rest of the body.

Nerves in the spinal cord transmit signals from the brain to your horse’s muscles to produce movement. Nerves also relay information back to the brain about where the limbs are in space (proprioception).

These nerves are susceptible to damage and do not heal well after injury. When the spinal cord is compressed or otherwise injured, this can interfere with the complex feedback loop that is required to produce movement.

Your horse’s movement may become uncoordinated or imbalanced, resulting in equine wobbler syndrome. [5]

An uncoordinated horse is a dangerous horse, so symptoms of equine wobbler syndrome need to be taken very seriously.

Types of Wobblers in Horses

There are two distinct types of CVSM: cervical vertebral instability and cervical static stenosis.

Cervical vertebral instability is posturally dependent – meaning compression of the cervical spine only occurs when the neck is in a flexed position. This condition is most often diagnosed in horses between 4 and 18 months old, with compression occurring somewhere between C3 and C5.

Cervical static stenosis is characterized by compression of the cervical spinal cord in all neck positions. It is commonly diagnosed in horses between 1 and 4 years old. Cervical spine compression is often seen between C5 and C7. [5][6]

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Causes of Wobblers Syndrome

Equine Wobbler Syndrome most commonly occurs due to:

Possible Genetic Link

Studies indicate that some horses may be genetically predisposed to developing equine wobbler syndrome.

Male horses develop wobbler symptoms 6 times more frequently than female horses. Faster growth rates and lower estrogen levels may result in cervical vertebral malformation. [6]

Equine wobbler syndrome is not breed-specific. However, studies show that Warmbloods and Thoroughbreds are more likely to develop this condition, possibly due to their fast growth rate. [5][6] Wobblers has not yet been identified in miniature horses, who have a slow growth rate.

Genetic traits can contribute to a vertebrae malformation, causing compression of the spinal cord. The spinal cord passes through very small openings in the vertebrae. Any misshaping or small outgrowths within the opening cause compression and impaired coordination.

Most likely, inherence is not based on a single gene but on the interaction between multiple genes (polygenic inheritance). [7]

When mares and stallions diagnosed with wobbler syndrome were bred together, the offspring did not display wobbler symptoms. However, the foals displayed other developmental orthopedic diseases such as osteochondrosis, physitis, and contracted tendons. [7]

Nutritional Causes

Studies on Thoroughbred and Warmblood foals indicate that too much protein and energy in the diet may contribute to equine wobbler syndrome. [8]

Diets that supply excess protein and energy are more likely to result in rapid growth and could lead to developmental issues and cervical vertebral abnormalities.

In one study, researchers fed foals with early signs of wobblers diets that were low in protein and energy, but with balanced vitamin and mineral levels.

Improvements were observed in spinal cord compression. These foals likely would have developed severe neurological symptoms if not for the dietary intervention. [8]

Developmental orthopedic diseases (DOD) are also more likely in horses with vitamin and mineral deficiencies or imbalanced nutrient levels. [8] Weanlings with reduced dietary intake of calcium, phosphorus, zinc and copper have higher rates of developmental disorders. [8][9]

The total intake of these minerals is important, but the ratios between these minerals is also important. For optimal development, horses should be fed zinc and copper in a ratio of between 4:1 and 3:1. The ideal ratio of calcium to phosphorous is 2:1. [10]

Work with a qualified nutritionist to formulate a diet for your growing foal. A nutritionist will help you design a feeding program with appropriate levels of energy, protein, vitamin and minerals to support proper bone development. [8]

Trauma to the Cervical Vertebrae

If your horse is showing signs of wobblers, the first question your veterinarian will ask is whether your horse has recently experienced trauma to their neck.

Physical trauma or injury can result in cervical vertebral instability, such as when a large force is directed on the neck in a twisting motion.

This can occur if your horse rears and flips over, possibly leading to inflammation of the neck, vertebral dislocation, or even vertebral fracture. Swelling and physical damage can interfere with the signal transmission in the spinal cord, producing wobblers’ symptoms. [11]

Infection of the Spinal Cord

Wobblers in horses can also be caused by inflammation of the spinal cord due to protozoal, viral, or bacterial infection.

Viral infection occurs when a virus passes through the protective tissue lining the cervical spinal cord, infiltrating the neurons, and causing swelling and nerve death. [5][6]

Bacterial infection occurs when your horse comes into contact with a pathogen. The most common bacterial infection that can produce wobbler symptoms is Lyme disease – a tick-borne illness that attacks the nervous system.

EPM, or Equine Protozoal Myeloencephalitis, occurs when protozoal parasites attack your horse’s brain and spinal cord. This also results in cell death within the brain and spinal cord. [5][6]

Symptoms

The signs of equine wobbler syndrome are neurological, meaning they are caused by the disruption of signals between the brain, spinal cord and rest of the body. These symptoms include: [12]

  • Stumbling when walking
  • Bunny hopping at the canter – the inability to keep the correct lead behind
  • Dragging of the toes, resulting in abnormal wear on their hooves
  • Weakness in the hind end when their tail is pulled to the side
  • Tightrope walking – bringing the legs too close together when walking
  • Abnormal gait, such as over-exaggerated leg movements
  • Sores on the front heels from over-reaching
  • Stiff neck
  • Excessive spookiness or kicking out due to pain
  • Ataxia – incoordination due to not knowing where their body is in space
  • Muscle atrophy

Early signs of wobblers usually involve poor coordination of the hindlegs. Horses may be able to compensate for poor front leg coordination by seeing where they place those legs. However, they will often stumble due to poor hind leg placement.

In addition, nerves supplying the hindlegs are located outside the spinal cord in the cervical area and are therefore less protected than nerves supplying the forelegs when are within the spinal cord. [15]

When turned in a small circle, these horses often swing their hind legs out. Moving backwards may also be a challenge for horses with wobblers. When asked to walk backwards, they may only move their forelegs back until it becomes awkward after which they hop their hindlegs back.

Horses with wobblers can become dangerous to handle and ride. A horse with neurological problems cannot properly determine where their body is in space and could bump into you or even fall on top of you.

If you notice signs of wobblers in your horse, stop riding them immediately as they are at risk of falling and stumbling at any time. Call your veterinarian right away to perform a thorough neurological exam.

If the findings of this exam are positive, your veterinarian will refer your horse for imaging of the spinal cord.

Diagnosis

Horses are diagnosed with equine wobbler syndrome based on the presence of clinical signs and diagnostic images of your horse’s spinal cord.

Other conditions can also produce discoordination and must be ruled out to confirm a diagnosis of wobblers. Your veterinarian will want to know your horse’s vaccination status to determine whether they have protection against equine herpes virus (EHV), West Nile virus or rabies.

Diagnostic Testing

Your veterinarian will perform several tests to determine the cause of the wobbler syndrome.

A blood test will determine whether your horse’s wobblers is caused by an infection. If the blood test is positive for signs of an infection, you will likely be referred to a veterinary hospital for a spinal tap to sample your horse’s cerebrospinal fluid (CSF).

CSF is the clear fluid that surrounds the spinal cord and brain. This cushions against impact and helps clear away metabolic waste products.

Cerebrospinal fluid samples will be examined for current bacterial, viral, and protozoal load. If a current infection is found in your horse’s nervous system, your veterinarian will treat the infection accordingly. [13]

Your vet may also decide to perform a myelogram which allows visualization of spinal cord compression. This involves inserting a needle into the space between cervical vertebrae, drawing CSF fluid out and injecting an iodine-based fluid. A series of radiographs are then taken to visualize areas of spinal cord compression when the neck is neutral, flexed or extended. [15]

If the spinal tap shows no signs of a current infection, your veterinarian may order full back and neck x-rays to visualize any fractures or bony outgrowths that may be present.

X-rays have limited diagnostic usefulness as they only allow the veterinarian to view the top and side of the spinal column. It is not possible to visualize the spinal cord with x-rays.

Finally, your veterinarian may suggest CT or MRI imaging to identify impingement of the spinal cord. [14] These images allow your veterinarian to view multiple cross-sections of the spinal cord.

Once your veterinarian has identified the point of compression along the spinal cord, they can discuss if treatment is an option.

Treatment of Wobbler Syndrome

The best treatment options for equine wobbler syndrome will depend on the cause of the disorder in your horse.

If the neurological symptoms result from a bacterial infection, treatment with specific antibiotics is likely to relieve or eliminate symptoms.

Steroid medications may be suggested if the spinal cord is inflamed due to trauma without structural damage to the vertebrae.

Steroids can reduce swelling in the spinal cord, potentially alleviating symptoms of wobblers. However, steroids are not always effective and may only partially relieve symptoms. [1]

Drugs such as dimethylsulfoxide (DMSO) and diuretics (mannitol, furosemide) may also be used to reduce pressure on the cranial nerves.

Surgery

If the cause of the spinal cord impingement is a fracture of the vertebrae, surgery may be an option.

Depending on the severity and location of the fracture, the veterinary surgeon may be able to fuse the affected vertebrae to eliminate movement in the area. This could allow the spinal cord to heal, relieving the symptoms.

However, surgery is hard on the horse’s body and not all horses recover; only 50% of horses who undergo surgery return to any meaningful performance. [1]

In cases of wobblers caused by bony outgrowths in the spine, surgery is not an option. If caught early (within their first year of life), your veterinarian may suggest aggressive nutritional intervention and strict stall rest.

However, if caught later in life, wobblers is likely permanent and progressive with symptoms worsening over time. Most veterinarians will suggest euthanasia in this case. [1]

If your horse is exhibiting neurological symptoms, call your veterinarian immediately. If your horse is a wobbler, early diagnosis and intervention can keep your horse comfortable and keep you safe from riding accidents.

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References

  1. Nad, T. et al. Clinical Management of Spinal Cord Injury in a Horse. Intas Polivet. 2012.
  2. Oswald, J. et al. Prevalence of cervical vertebral stenotic myelopathy in a population of thoroughbred horses. Vet Record. 2010.
  3. Camargo, F.J. Wobbler Syndrome in Horses. University Of Kentucky College Of Agriculture. Kentucky Cooperative Extension Service. 2010.
  4. Denoix, J.M., Pailloux, J.P. Anatomy and basic biomechanical concepts. In: Physical Therapy and Massage for the Horse. Manson Publishing Ltd. 2001.
  5. Nout, Y. and Reed, S. Cervical Vertebral Stenotic Myelopathy. Equine Vet Educ. 2003.
  6. Rupanner, R. et al. Equine incoordination. Can Vet J. 1972.
  7. Falco, M. et al. An Investigation into the Genetics of ‘Wobbler Disease’ in Thoroughbred Horses in Britain. Equine Vet J. 1976.
  8. Lawrence, L. and Pagan, J. Nutritional Management Of Developmental Orthopedic Disease In The Equine. Kentuck Equine Research. Proceedings of the 3nd Mid-Atlantic Nutrition Conference. 2005.
  9. Knight, D.A. et al. Correlation of dietary mineral to incidence and severity of metabolic bone disease in Ohio and Kentucky. Proc. Am. Assoc. Equine Pract. 1985.
  10. Fintz, H. and Cymbaluk, N. Nutrition of the Horse. Annual Review of Nutrition. 1994.
  11. Wagner, P. et al. Surgical Stabilization of the Equine Cervical Spine. Veterinary Surgery. 1979.
  12. Wagner, P. et al. Evaluation of Cervical Spinal Fusion as a Treatment in the Equine “Wobbler” Syndrome. Veterinary Surgery. 1979.
  13. Hayes, t. Examination of Cerebrospinal Fluid in the Horse. Vet Clinics of NA: Equine Practice. 1987.
  14. Scrivani, P. Advanced Imaging of the Nervous System in the Horse. Vet Clinics: Equine Practice. 2011.
  15. Grant, B.D. Is He Lame or Is He Neurologic? (Wobbler Syndrome). AAEP. 2016.