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.
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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, firstname.lastname@example.org . 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.