CM/SM – treatment

 

What drugs are used to treat syringomyelia?
Medical management of syringomyelia is based on anecdotal reports as there has only been one clinical trial assessing the effectiveness of a novel neurogenic painkiller and results from this trial are still being analysed.
Typically the first drugs used for treatment of CM/SM are (unlicensed) drugs that reduce CSF pressure e.g. furosemide, cimetidine or omeprazole.  The principle of this therapy is that reducing CSF pressure reduces the driving force contributing to the syringomyelia. Some owners report a reduction in signs of apparent pain.
If the pet is in pain then a non steroidal anti-inflammatory drug (NSAID) is often prescribed e.g. firocoxib, carprofen or meloxicam. This may be in addition to one of the drugs above.
For dogs with signs of neuropathic pain (e.g. severe pain; increased sensitivity to normally non painful sensation such as touch; and scratching behaviour) an (unlicensed) neurogenic painkiller is more likely to be effective for example gabapentin or pregabalin.
Corticosteroids are an option if pain persists or where available finances prohibit the use of other drugs however as these drugs can have more long term side effects the author prefers to avoid them if possible.

 

Click here for a treatment Algorithm for veterinary surgeons

 

Click here for information on CM/SM for veterinary surgeons

 

Do the drugs have side effects?
All medicines should be given under veterinary guidance.
Furosemide may result in depleted potassium and other electrolytes especially if combined with corticosteroids or other diuretics. Potassium supplementation may be advised. This drug is diuretic, i.e. increases urination, so there is a risk of dehydration. Rare reported side effects are oto(ear)toxicity, gastrointestinal disturbance, anaemia, decreased white blood cells, weakness and restlessness.
Cimetidine - side effects with this antacid are rare even at high doses. Liver and kidney toxicity have been reported so monitoring of blood biochemistry is advised.  In humans cimetidine has been reported (rarely) to be associated with headache. Cimetidine may increase the kidney clearance of gabapentin. 
Omeprazole - This is also an antiacid and in laboratory rodents long term therapy has been reported to result in changes to the stomach lining. However this effect has not been reported in dogs. Reported adverse effects include nausea, diarrhoea, constipation and skin rashes. 
NSAIDS -  NSAIDS can result in vomiting and diarrhoea however an animal that has a bad reaction to one drug will not necessary react to another. Not recommended for animals with kidney disease and there is a very small risk that NSAIDS may precipitate heart failure in animals with pre-existing heart disease. Monitoring of blood biochemistry is advised
Gabapentin / Pregabalin – can result in mild sedation and poor coordination especially when therapy is first started. May increase appetite and increased calorific intake may result in weight gain.  Therapy should not cease suddenly i.e. the drug should be withdrawn slowly. Monitoring of blood biochemistry is advised.
Corticosteroids – can result in vomiting and diarrhoea although typically this is at high doses. These drugs also increase urination (and drinking) and when combined with diuretics can result in potassium depletion. They also increase appetite and increased calorific intake will result in weight gain. Chronic use results in muscle loss, skin changes and poor hair growth. Animals receiving corticosteroids may also be lethargic, weak and heat intolerant. Corticosteroids also delays wound healing and increases susceptibility to infection. Should not be given to patients that are pregnant, have diabetes mellitus or kidney disease. 

 

Are there any alternative therapy options?
Anecdotally, acupuncture and ultrasonic treatments have been reported to be useful adjunctive therapy in some cases. In some cases chartered physiotherapists are able to help alleviate signs. www.acpat.org, acpat@calra.net . Care should be taken however as the response to these treatments is very individual and some dogs may actually be more painful afterwards. Spinal manipulation is contraindicated.

 

CM/SM – surgery

 

What surgical options are there?
The most common surgical management is cranial/cervical decompression (also described as foramen magnum or suboccipital decompression). The principle of this surgery is to allow CSF flow by removing the bone at the back of the skull (supraoccipital bone) and part of top of the first vertebrae. This may be combined with a durotomy (cutting the meninges) with or without patching with a suitable graft material.

A cranioplasty procedure used in human cranial/cervical decompression surgery has also been adapted for use in dogs.  The procedure entails placement of a plate constructed of titanium mesh and polymethylmethacrylate (PMMA) on pre-placed titanium screws bordering the occipital bone defect (Dewey et al 2007).

An alternative method of managing syringomyelia is direct shunting of the cavity. In humans this is not a preferred technique as long term outcome is poor due to shunt obstruction and/or spinal cord tethering.

 

How successful is surgery?
Cranial/cervical decompression surgery is successful in reducing pain and improving neurological deficits in approximately 80% of cases and approximately 45% of cases may still have a satisfactory quality of life 2 years postoperatively (Rusbridge 2007). However surgery may not adequately address the factors leading to syringomyelia and the syrinx appears persistent in many cases (Rusbridge 2007). Much of the clinical improvement is probably attributable to improvement in CSF flow through the foramen magnum.

 

Should my dog have surgery or not?
The cases where surgery is clearly indicated and most likely to be considered successful are dogs that are painful and responding incompletely or not at all to medical management.

 

How long does it take a dog to recover from surgery for syringomyelia?
At Stone Lion Veterinary Centre postoperative dogs are hospitalised until the dog is comfortable enough for injectable painkillers to be discontinued. After discharge it typically takes 1-4 weeks before the dog returns to normal activity levels.

 

Will I need to confine my dog after surgery?
At Stone Lion Veterinary Centre postoperative dogs are not crate/cage restricted after discharge. Exercise is limited to short 5-10 minutes walks 2-4 times daily over the first 2 weeks postoperatively and then, depending on the dog’s progress, gradually increased over the next 4 – 8 weeks.

 

What is the recurrence rate after surgery?
In some cases scaring and fibrous tissue adhesions over the foramen magnum seem to result in re-obstruction and 25% to as many as 50% of cases can eventually deteriorate (Dewey et al 2005,  Rusbridge 2007). This can be as early as 2 months postoperatively.

 

Will my dog need medication after surgery? 
Even after successful surgery it is possible that your neurologist may recommend continuing some medication for example cimetidine or omeprazole to reduce cerebrospinal fluid production or painkillers because the damage to the spinal cord has resulted in a neuropathic pain syndrome.

 

CM/SM – other issues

 

Does syringomyelia progress?
Some dogs with syringomyelia may have no or minimal clinical signs. However syrinxes can progressively expand and a dog which is asymptomatic in early life may eventually become painful. The clinical course may be acute or run an extended course over several months or years. Dogs with a wide syrinx tend to progress more quickly. Scoliosis may slowly resolve despite persistence of the syrinx.

 

What is the prognosis for my dog?
Unlike mitral valve disease, CM/SM is rarely fatal however this does not diminish the importance of this painful disease and a significant number of dogs are eventually euthanatized as a consequence of uncontrolled pain. This is more likely in dogs with a wide syrinx and/or with first clinical signs before 4 years of age. Study of a small case series (14 Cavaliers) managed conservatively for neuropathic pain suggested that 36% were eventually euthanatized as a consequence of uncontrolled pain. However 43% of the group survived to be greater than 9 years of age (average life expectancy for a Cavalier is 10.7 years).  Most dogs retain the ability to walk although some may be significantly tetraparetic and ataxic.

 

What other things can I do to help my dog?
The dog’s activity need not to be restricted but you should understand that your dog may avoid some activities and not tolerate grooming of some body areas (e.g. one ear). Simple actions, for example raising the food bowl and removing neck collars, can help.

 

Can I help the research into this disease? 
 Yes! - by providing information and DNA from your dog.

To help towards breeding healthier cavaliers
Send MRI reports and pedigrees to Dr Sarah Blott CKCS Health Breeding Programme Animal Health Trust, Lanwades Park, Kentford, Newmarket, Suffolk CB8 7UU This can also be done electronically to sarah.blott@aht.org.uk. Click here for more information about this study which aims to calculate estimated breeding values (EBVs) for all Cavaliers, using the health data supplied by owners and breeders.  With EBVs breeders will be able to use a computer programme to match their dogs with suitable mates aiming to select against SM and MVD in a way that does not reduce genetic diversity.
To help find the gene/s that causes CM/SM
The CM/SM genome research team are actively seeking
1. DNA from Cavaliers over five years old that do not have syringomyelia (must have had a MRI scan when 5 years old or older)
2. DNA from Griffon Bruxellois over 2 years old which have had a brain and cervical MRI
3. DNA from other breeds / species with a diagnosis of CM/SM  
If applicable please contact: penny.knowler@ntlworld.com

 

What research is currently being undertaken?
For summaries please click here

 

Why does the genome scan and other research take so long to get results?
Doing research is much akin to trying to get though many concentric brick walls. Much time and effort is spent scaling one wall, you reach the other side and run forwards rapidly only to come up against another brick wall. Many of those walls are the laborious process of securing funding for the research! However progress does continue - click here for update.

 

I want to buy a Cavalier – how do I get a healthy puppy?
It is recommended that breeders screen their stock for syringomyelia and other diseases such as mitral valve disease and eye diseases. A BVA / KC scheme for MRI screening from syringomyelia is proposed.  Current breeding recommendations for Cavaliers concentrate on removal of dogs with early onset syringomyelia (i.e. within the first 2.5 years of life) from the breeding pool  Guidelines for buying a cavalier can be accessed by Clicking Here and Here.