Syringomyelia in Cavalier King Charles Spaniels (CKCS)

Syringomyelia (or syringohydromyelia) is also known as Chiari-like malformation (a reference to the human disease), also known as caudal occipital malformation syndrome, is a common disease in dogs. Affected dogs develop a cyst-like lesion in their spinal cord and this causes pain, and movement abnormalities. Cavalier King Charles Spaniels (CKCS) are genetically predisposed to develop this neurological abnormality but it can also be seen in other breeds. The diagnosis of syringomyelia can easily be confirmed using MRI which is now readily available for veterinary patients.

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In the normal dog the brain and spinal cord are bathed in a fluid called cerebrospinal fluid (CSF). The term syringomyelia describes the presence of a fluid-filled cavity (called asyrinx) within the spinal cord. Cavalier King Charles Spaniels (CKCS) have an unusual conformation of the back of the skull (Chiari-like malformation) and it is this that makes them particularly prone to developing the cavity in the spinal cord.

Because of the conformational abnormality, the caudal part of the brain (cerebellum) does not have enough room to develop inside the skull (occipital bone). The cerebellum is therefore pushed through the hole at the base of the skull (where the spinal cord leaves the skull). This creates a pressure point, causing an abnormal flow of CSF from the brain to the spinal cord. With time this flow disturbance can result in the formation of a syrinx. In some dogs, it can also cause a build up of fluid in the brain called hydrocephalus.

Clinical signs can vary widely between dogs and there does not appear to be any relationship between the severity of syringomyelia and the severity of the clinical signs.

Affected animals show twisting of the neck (scoliosis), a stiff front limb gait, scratching of the neck and shoulder region, intermittent neck pain (manifested with yelping episodes for no apparent reason), loss of muscles in the neck, weakness or lameness of the front limbs. Signs typically appear in dogs before 6 years of age and get worse with age. The condition has been reported in puppies as young as 12 weeks.

However it is possible to find the changes of syringomyelia on MRI in dogs that have no clinical signs and similar clinical signs may be seen in dogs that have other neurological diseases.

The best way to diagnose syringomyelia is by means of MRI scanning. The abnormal bone conformation of the skull can be seen well with a CT scan (which is better designed to evaluate bone), but the information about the brain and spinal cord is less likely to show up on CT than with MRI.

There is presently no gold standard treatment for dogs with syringomyelia. Both medical and surgical treatments have been tried, but in people surgical correction is thought to be the best treatment. In dogs, depending on the severity of the neurological signs and the age of the patient, medical management is usually recommended in first instance.

The most common drugs used in the management of the condition are anti-inflammatory drugs, gabapentin, pregabalin or prednisolone. Anti-inflammatory drugs can reduce any inflammation associated with the syrinx. Gabapentin and pregabalin are anti-epileptic drugs used in dogs and humans to treat pain caused by neurological diseases as well as abnormal sensation (like pins and needles). Finally steroids (prednisolone) are used as a last resort and they can have multiple modes of action by reducing CSF production but also any inflammation. If there is no response to any of the drugs then a surgical treatment may be proposed.

At surgery the hole at the base of the skull is enlarged to relieve the pressure and restore a normal flow of CSF between the brain and the spinal cord. If surgery is performed in the early stages of the disease it may be possible to slow, or even stop, the development of the syrinx.

The course of syringomyelia is extremely variable between dogs, but once clinical signs are visible treatment is more likely to stabilize or slow the course of the disease. In general severely affected dogs showing signs before 4 years of age, will have a worse future than those that do not develop signs until later. As the cavity develops it causes damage to the spinal cord. This damage can never be repaired and a complete recovery is unlikely.

Surgery at the back of the skull can improve the clinical signs and subsequently the quality of life, at least short-term, but is unlikely to resolve the clinical signs and long-term medication may be required after surgery. If you are thinking about having surgical management you should ensure your dog is assessed by a specialist neurologist as they will be best placed to advise on the best treatment on an individual basis and explain the risks associated with surgery.

Because this is a genetic problem there is some hope that the disease could be eradicated by careful breeding. Researchers are searching for a genetic test that could identify affected dogs but at present the only diagnostic test available is MRI scanning.