Issue Description Syringomyelia is currently defined as a
condition that results in the development of fluid-containing cavities
within the parenchyma of the spinal cord as a consequence of abnormal
cerebrospinal fluid movement. Other Names Syringomyelia, SM
Causes When there is a blockage or obstruction to the
cerebrospinal fluid flow then a pressure wave will be transmitted down
the spinal cord and cause the formation of one or more cavities. The
most common cause of obstruction is when the cerebellum at the back of
the brain is pushed out of the skull because there is not enough space
within the occipital bone - a common phenomenon in small breeds and
especially in Cavalier King Charles Spaniels, where it is estimated
that at least 50% of the breed are affected. Syringomyelia can be
congenital (primary) or acquired from trauma, infection or neoplasia.
Breeds Affected Syringomyelia is one of the most common spinal
cord disorders of toy breed dogs and has been reported in the Cavalier
King Charles Spaniel, King Charles Spaniel, Griffon Bruxellois,
Yorkshire Terrier, Maltese Terrier, Chihuahua, Miniature Dachshund,
Miniature &Toy Poodle, Bichon Frise, Pug, Shih Tzu, Pomeranian,
Staffordshire Bull Terrier, Boston Terrier, Pekingese, Miniature
Pinscher, and French Bulldog.
Symptoms The most common clinical signs are pain,
scratching at the neck and shoulders and walking difficulty. Not all
dogs with syringomyelia will present with clinical signs but most dogs
will show symptoms of the disease by three years of age.
These include restlessness, increasing reluctance to exercise,
difficulty moving up or down furniture and uncoordinated movements in
the early stages, followed by an uncontrollable urge to scratch the
neck area and shoulders, together with a hypersensitivity of the neck
area. As the diseases progresses, there might be severe pain around
the shoulders, neck and head causing the dog to scream and yelp.
More serious cases result in portions of the spinal cord
being destroyed, so that the dog contorts his neck and cannot eat or
sleep unless its head is held high. In addition, the legs will become
progressively weaker and walking becomes increasingly difficult, with
some dogs deteriorating to the point of paralysis. The rate of
progression varies between individuals - in some, the pain becomes
severely disabling and distressing while in others, the condition can
be managed by medical or surgical intervention.
Diagnosis A vet should be asked to rule out basic causes
of scratching or discomfort such as ear mites, fleas, and allergies,
and then, primary secretory otitis media (PSOM - glue ear), as well as
spinal or limb injuries, before assuming that a dog has SM. PSOM can
present similar symptoms but is much easier and cheaper to treat.
Episodic Falling Syndrome can also present similar symptoms. An MRI
scan is normally done to confirm diagnosis of SM (and also will reveal
Because of the prevalence, SM is increasingly being
considered as important a health issue as mitral valve disease (MVD).
Just as many breeders follow the MVD breeding protocol, many breeders
are now starting to follow breeding guidelines recommended by
international researchers (November 2006), to try to decrease the
incidence and severity of SM in the breed. The guidelines stipulate
that breeding dogs be MRI screened (again, unfortunately, the test is
very expensive and not widely available yet) and graded according to
whether they show the malformation, syrinxes, or both. Neurologists
give scanned dogs a signed certificate noting its grade. At least one
dog in a breeding pair must be graded A (clear of syrinxes). A limited
breeding scheme by a group of Dutch breeders has shown so far that,
encouragingly, AxA matings are consistently producing A puppies.
Treatment Medical ManagementMedical management can help but typically does
not resolve the clinical signs. Signs in mild cases may be controlled
by non steroidal anti-inflammatory drugs (Nsaids) e.g. Rimadyl.
Corticosteroids are very effective in reducing signs partly because of
the effect on reducing CSF pressure and possibly because of a direct
effect on chemicals which mediate pain. Although corticosteroids are
effective in limiting the signs most dogs require continuous therapy
and subsequently develop the concomitant side effects of
immunosuppression, weight gain and skin changes. If there is no
alternative then use the lowest possible dose to control signs. For a
CKCS the typical dose would be 5mg prednisolone or 4mg
methylprednisolone daily/on alternate days. Gabapentin (Neurontin;
Pfizer) is successful in some dogs. This drug, originally patented as
an anticonvulsant, is licensed as a neurogenic analgesic for humans.
Gabapentin, and other anticonvulsants suppress the firing of hyper
excitable damaged nervous system. The canine dose is 10-20 mg/kg
two/three times daily which for a CKCS typically works out at a dose
of 100mg two/three times daily. Gabapentin can also be given in
combination with NSAIDs. Sedation may be seen, especially at higher
does, otherwise the side effects are minimal and on this basis the
preference is Gabapentin over corticosteroids. The main disadvantage
of Gabapentin is that it is expensive and not licensed for dogs. Oral
opioids are also an alternative for example pethidine tablets at 2 ñ
10mg/kg three to four times daily or methadone syrup at 0.1 ñ
0.5mg/kg three to four times daily. Acupuncture appears to help some
Surgical ManagementSM is a surgical disease and the most
appropriate management is to open the foramen magnum by removing a
portion of the occipital bone and usually part of the first vertebrae
(foramen magnum decompression surgery). The aim of surgery is to
reduce the pain improving the dog's quality of life and/or to stop or
reduce further progression. If neurological damage has already
occurred, the surgery may not reverse the damage and most dogs still
have a tendency to scratch.
One must weigh the risks and benefits of surgery versus medication
versus no intervention. Remember, progressive disease means that no
action may enable further deterioration. When measuring the surgery's
success, measure from current condition to the expected further
condition and what the disease would have progressed to, rather than
the current condition only.
When to have surgery?There is more chance of success if the surgery
is done early in the course of the disease before permanent damage has
occurred. Surgery is recommended for dogs with signs at less than 5
years old because progressive disease is likely. In older dogs surgery
is advised if the dog is deteriorating.
What are the risks of surgery?There are major blood vessels in the area and
if traumatised the dog could quickly bleed to death. Although not
actually operating on the brain/spinal cord, it is in close proximity
and there is a risk of permanent neurological injury. In reality
complications from surgery seem to be rare.
Can the disease recur?Signs may recur in a proportion of dogs after
several months/years due to redevelopment of syringomyelia. The newly
created "space" from surgery may fill in with scar tissue. If this
happens, repeat surgery may be indicated; some owners prefer to
continue with medical management e.g. with NSAIDs, Gabapentin or