Syringomyelia (SM) is a congenital or acquired intraspinal disease. It is a neurological disorder where a cyst or herniation, known as a syrinx, forms within the spinal cord and cause the flow of cerebrospinal fluid (CSF) to become obstructed and accumulate, causing symptoms which can range in dogs from “air” scratching, pain and limb dysfunction. The syrinx can be located anywhere on the spine but most commonly in dogs at the location of the foramen magnum (where the brain and spinal cord join).
When there is a malformation of the foramen magnum this is referred to as Chiari-like Malformation (CM) and may or may not be accompanied by Syringomyelia. CM refers to caudal fossa crowding a defect that causes a disruption of CSF at that area and have perhaps led to the misleading idea that Cavaliers have “exploding brains”. It is thought that the large majority of Cavalier King Charles Spaniels have the Chiari-like Malformation with only a small number developing and becoming symptomatic for SM; therefore a natural deformity for the breed.
There are other primary conditions which can be accompanied by SM such as hydrocephalus and atlantoaxial subluxation and there are other conditions with similar symptoms that should be ruled out such as PSOM, allergies and other neurological problems.
Syringomyelia can be either acquired or congenital. If acquired, this would occur due to trauma, complications of surgery or disease such as a tumour and the syrinx would develop in the damaged segment of the spine and may expand causing difficulties. It is also possible that a difficult birth may cause damage in the neck/spine area resulting in the acquired form. If congenital, the condition would develop in the womb as a malformation
Both CM and SM were originally considered rare but with more advanced testing and imaging equipment it has been found to be more commonplace in dogs, humans and other species. Originally publicised to be a condition specific to the Cavalier King Charles Spaniel SM is seen more often in small breed dogs such as Brussel Griffons, Pomeranians, Maltese, Poodles (toy and minis), Chihuahua, Mini Dachshund, Bichon Frise, Shih Tzu in addition to the CKCS but has been found in larger breeds such as Bull Terriers, Labrador Retrievers and Weimaraners.
What are the symptoms?
The most common symptom of Syringomyelia in the Cavalier King Charles Spaniel is a hypersensitivity in the neck area resulting in an uncontrolled urge to scratch at the neck and shoulders (aka “air” or “guitar” scratching), quite often to the point that the dog will fall over. This scratching behaviour is quite distinctive and hard to mistake for regular scratching. There is quite often discomfort and pain in the neck and ear areas. There may also be facial paralysis, progressive weakness in the limbs, loss of bladder and bowel control and scoliosis (curvature of the spine). The condition can be aggravated by excitement or stress.
In the congenital form symptoms are usually first seen from 6 to 18 months of age but depending upon the degree affected could manifest at any age. In the acquired form symptoms can be seen any time after the original injury or trauma to the spine.
How is it diagnosed?
Though the condition was recognized symptomatically earlier it has only been due to the advances in advanced imaging techniques through the use of Magnetic Resonance Imaging (MRI) that this disease has been understood and diagnosis been able to be confirmed.
The MRI is the leading diagnostic tool used in determining Syringomyelia. Using the MRI then allows the neurologist to study the spine for the presence of a syrinx or any other abnormality, such as a tumour which might obstruct the flow of the spinal fluid.
Treatment of SM
Mildly affected Cavaliers with the condition may require little to no treatment. More severely affected dogs may require a variety of treatments which can range from medications to relieve the symptoms to surgery.
Oral medications, such as corticosteroids, diuretics and narcotics are used to control swelling, CSF production and pain. Surgery to allow the cerebrospinal fluid to flow normally by placing a shunt may be considered for more severe cases.
The mode of inheritance is unknown though it is suspected that it is polygenic. At present testing for the condition prior to breeding is done through the use of an MRI machine.
Disadvantages of MRI as a testing tool for breeders:
1. The results are speculative. The interpretation of the findings of CM and syrinx are as yet unclear. As the disease is
considered progressive a breedable age dog may be cleared under the current guidelines yet develop the
condition at the later date.
2. The results do not tell if the scanned dog is a carrier and can reproduced the condition in its offspring.
3. Dogs must be under anaesthetic to have the test performed. Anaesthetic/sedation can be dangerous and some dogs
have died having this test performed.
4. Expense – the cost of a single MRI scan in the Netherlands are between 275 euro and 325 euro.
(Animal Practise Dierenkliniek Den Heuvel).
In other countries, the cost of a MRI scan, can be so high, that it’s not affordable for many breeders.
Primary Secretory Otitis Media (PSOM) is a condition of the middle ear which becomes plugged with highly viscous mucus and may cause the tympanic membrane to bulge and rupture. It is similar to the condition known as “glue ear” in children.
This is not caused by an infection and the cause is unknown though it is thought that it might be a dysfunction of Eustachian tube in the Cavalier, where there is an abnormal production of mucus or a decreased drainage of fluid through the Eustachian tube or even a combination of both factors.
Some speculate that there may be a link between the condition PSOM and the brachycephalic anatomy of the breed but at present the condition seems to be primarily reported in the Cavalier King Charles Spaniel, not other brachycephalic breeds. However since some of the symptoms of PSOM mimic symptoms of Syringomyelia, recognition of this condition (PSOM) may be heightened in the Cavalier and merely under-reported in other breeds; much as it happened in the early days of research in Syringomyelia where some researchers considered that condition peculiar to Cavaliers and later research found it commonly in other breeds as well.
Many of the symptoms are similar to those found in dogs with Syringomyelia. They include neck pain, head tilt, scratching at ears, ear itch or pain, facial paralysis, Vestibular disease, crying out in pain, lack of co-ordination, hearing loss, yawning and fatigue.
Diagnosis is usually made by a veterinary neurology or dermatology specialist through use of MRI or CT scans; though other methods of detection may be possible such as a BAER test or ultrasound. In severe cases where the tympanic membrane has bulged or rupture it may even be possible to see this on x-ray.
Treatment for this condition is surgery with a small slit made in the eardrum and then the inner ear is flushed to clean out the mucus. Corticosteroids and antibiotics are then administered to the dog. This procedure may have to be repeated in some cases. Just treating with antibiotics does not seem to work.
The condition is thought to be inherited in the Cavalier King Charles Spaniel; mode of inheritance unknown.