Dr. Rusbridge has Spoken

Below is the Report from Dr. Rusbridge. She makes very specific recommendations with regard to medical management as well as surgical management, though she stops short of making a recommendation/ endorsement of one route over the other.

Below her report followed by our response to her, followed by her reply back to us. Clearly we have a lot to think over.

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28th February 2010

Dear Dr Ciment

Re: Riley, a 18mth male Cavalier King Charles Spaniel

Thank you for sending me Riley’s medical notes and MRI scan. I was sorry to hear of the difficulties you
have been experiencing with him.

History

Riley was diagnosed with syringomyelia secondary to a Chiari-like malformation on 9th February 2010. You were prompted to obtain an MRI scan after a weekend where Riley had multiple episodes of postural pain. Riley is also having distressing episodes of pain which appear to wake him from sleep and is more tentative about going up and down stairs. Riley has displayed sensitivity to having his ears groomed on the right and also has the characteristic phantom scratching at the right side. However, despite having episodes of acute pain, Riley still has a good exercise tolerance and shortly after these episodes of vocalisation he is willing play with the other dog. The main questions are how much discomfort is he in and whether or not he should be medically or surgically managed.

MRI images

MRI scans of the brain and upper cervical spinal cord are available and they reveal a Chiari-like
malformation (occiptal bone hyperplasia/COMS) with secondary ventricular dilation and extensive
syringomyelia. The syringomyelia extends from C1 to the caudal extent of scanning (C6); it is likely to
extend further down the spinal cord. The maximum measured diameter was 7-8mms. There was
involvement of both spinal cord dorsal horns, but in keeping with the clinical signs, there is more damage on the right.


The phantom scratching behaviour is thought to be part of a neuropathic pain syndrome
relating to a disorder of processing through the spinal cord dorsal horn and generally
signs of scratching are seen with syrinxes which are greater than 5mms. There is
ventriculomegaly of all the ventricles and a small quadrigeminal cyst extending from the
4th ventricle. There is no middle ear disease.

Management

You are right in your assessment that the main treatment objective is pain relief. It is difficult to know what these dogs are feeling. Using my own pain score, I would give him a score of 3 where 0 is normal and 4 are dogs with compromised activity. I enclose details of this pain score (below). Regarding the decision of whether or not to have surgery, this is quite a difficult choice because surgical management at best improves the situation but does not cure it. In Chiari malformation and syringomyelia in humans a foramen magnum decompression will result in syrinx collapse and an improvement of clinical signs in
approximately 80% of cases. The improvement in clinical signs is mostly due to improved cerebrospinal
fluid (CSF) flow through the foramen magnum and patients may still have issues due to the syringomyelia.

In dogs, all of the long-term follow-up studies that I have seen, including my own, have also found an ~ 80% success rate in improvement of clinical signs. However, follow up MRI scans have shown that the syrinx has not collapsed. Also I have found that there is a high recurrence rate. I found that 45% of my cases still had a good quality of life two years post-operatively, however many of these dogs still had signs relating to the syringomyelia and ultimately many dogs will eventually deteriorate - this can be from as early as two months post-operatively. Therefore my general advice is that surgery is the best option if medical management is not sufficient in controlling the dog’s signs of pain or neurological deficits. However, surgery is unlikely to be a lasting solution and medical management may still be required.

However, in Riley’s case you also have to take into consideration his young age and quite severe disease. There is a high chance that his clincial signs will progress and there is an argument that surgery may slow that deterioration. If I was operating on Riley I would seriously consider doing an additional procedure (e.g. interventricular shunt) in conjunction with a foramen magnum decompression, just because I know from experience that a foramen magnum decompression is unlikely to give Riley a lasting quality of life. However I have no experience (yet) whether this will lower the failure rate.

If you decide to opt for medical management in the short or long term then I would advise a combination of a drug which would reduce CSF production in addition to a drug which relieves neuropathic pain and has a site of action at the dorsal horn. Examples of drugs which reduce CSF production are the antacids omeprazole and cimetidine and a diuretics such as furosemide. The drug I more commonly use, although there is no scientific rationale for it (yet), is cimetidine which is dosed at 5-6mg/kg three times daily. I tend to use this drug over omeprazole purely because it is licensed for dogs in the UK (although not for CSF reduction). The dose of omeprazole is 0.5-1.5mg/kg once daily. You don’t give Riley’s weight, but assuming he is approximately 7kg then a 5mg once daily dose of omeprazole seems an appropriate starting dose. If omeprazole has not altered Riley’s signs then you might want to try cimetidine as an alternative otherwise it would suggest either these drugs are ineffective or that a neuropathic analgesic should be given in addition.

The neuropathic analgesic I use most commonly is gabapentin dosed at 10-20mg/kg two to three times daily. I generally start at the lower dose and build up. Pregabalin (Lyrica) can be a better choice for some dogs as it can be a more effective pain relief for syringomyelia with less sedation; however, its considerable downside is that it is more expensive. The dose rate is 5mg/kg twice daily; both pregabalin and gabapentin are unlicensed for treating canine diseases, i.e. there are no published clinical trials although have been used for many years by many clinicians. Potentially they can cause drowsiness and are metabolised through the liver, so that I recommend that liver function is monitored on a six to twelve monthly basis. For some dogs I add a non-steroidal anti-inflammatory drug (NSAID) in addition to the other drugs. I do not have a particular preference at this time, although I am currently evaluating a long-acting drug called Trocoxil and I am quite happy with the early results. I am not sure if this drug is available in the USA. Otherwise any NSAID can be tried; the response to NSAIDs, as you know, can be quite individualistic. Some veterinary neurologists recommend corticosteroids for treating this disease; I tend to use them as the last option because of their long term side-effects, especially in younger dogs. They can be the most effective drug if the dog does have neurological deficits, for example weakness or ataxia (wobbliness).

In summary, I do think from your description that Riley is in pain, however this pain appears to be short
lived and probably relating to impedance of CSF flow through the foramen magnum. Sensitivity to touch
and the scratching is most likely related to the syringomyelia and this sensitivity may become more apparent with time. In my opinion it is worth at least giving a trial of analgesics because it is difficult to know what these dogs are experiencing on a day to day basis and an improvement in demeanour, exercise ability, etc. would suggest that the dog was uncomfortable. If Riley is unchanged or is very sedated then there is an argument for not using these drugs.

With regard to surgery, there is no easy answer. It is likely that if surgery is performed now that the episodes of screaming, etc. will improve. The scratching will continue but may be improved. However, there is a chance that all of the signs will recur before Riley is a middle-aged dog. However, at that time he may be successfully managed medically. The converse argument is that if the signs could be successfully managed medically, is it better to hold off surgery until medical management is no longer successful. I am afraid I do not have that answer to this dilemma which is part of the reason why I work so hard trying to prevent this disease and develop a better surgery/medical management!

I hope that these notes are helpful. Please email me to clarify any further details. I am away from the 5th to the 13th of March.

Yours sincerely,

Clare Rusbridge BVMS PhD DipECVN MRCVS
RCVS and European Specialist in Veterinary Neurology

Stone Lion Veterinary Centre, 41 High Street, Wimbledon, SW19 SAU
Fax 020 8944 0871 (SLVC) 020 8786 0525 (private)
Email: neuro.vet@btinternet.com
http://www.veterinary-neurologist.co.uk/
for information on syringomyelia, FOPS, Lafora’s, epilepsy, spinal disease and more

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Dr. Rusbridge.

Thank you so much for your thoughtful and detailed report. We have have reviewed it twice and just two questions for you.

When we spoke with Dr. Berg, he made the analogy of Syringomyelia to someone who is squeezing a marshmallow. His point was that as long as the Chiari Malformation continues to exert pressure on the Cerebellum and the syrinxes and hydrocephalus persists, there is "pressure". He suggested that if a person were to pinch/squeeze a marshmallow for just a few minutes and then release the pressure, the marshmallow would revert to a more full state. Perhaps it would not revert fully to it's original state, but mostly. Compare that to someone who pinches a marshmallow for hours and hours on end. It is very unlikely that when they release the pressure that the marshmallow would puff up at all. His analogy suggests that the longer we allow the syrinxes to increase pressure in the CSF, the great a risk of permanent nerve damage that would be sustained even after surgery. He stated that he was advocating for surgical management because the sooner we did the FMD, the sooner the pressure would be off the nerves and the less likely that Riley would sustain longer-term nerve damage. Is there, then, an argument that to preserve the integrity of the nerve tissues, the sooner we decompress, the more tissue is salvaged? Clearly, Pregabalin and Gabapentin work to alleviate neurologic symptoms but do nothing to address the longer-term, mechanical injury to the nerves/spinal cord from longer-term compression. Would we be "losing time" and risking further (permanent) nerve damage by exploring medication options which may alleviate symptoms while not addressing the underlying pathology?

With regard to a surgical recommendation, you suggested placing an inter-ventricular shunt in addition to performing an FMD alone. When I asked about this procedure at our original consultation, Dr. Berg recommended against it. He said that he has seen longer-term issues with the shunt not being well tolerated. He said that he's noted it moving around/ slipping, irritating the dog in the longer term. His concern is that an active puppy who will be again running, jumping, etc... is not a great candidate for such a shunt placement. I wondered if you had different longer-term results with your I-V shunts than he? As a surgeon myself, I understand that we all have procedures we're better at than others. Perhaps an I-V Shunt is a procedure that Dr. Berg is not as comfortable with and therefore his outcomes are different? I don't know. Should we decide to follow your surgical recommendation, who would you recommend we see for this kind procedure (i.e., the FMD in combination with the I-V Shunt)? We are willing to travel quite a ways for this, if need be. Certainly within the United States (I'm assuming we couldn't get Riley to the UK for surgery with you due to quarantine laws and the amount of time he would need to be in recovery before taking a long flight home.)

Ethan Ciment
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Yes - there is an argument that the sooner the surgery is performed then the less chance of permanent damage. This makes sense as an argument - I am not sure that is being borne out in clinical practice but this "lack of being sure" is because of the absence of hard data not bad experience.

With regard to the other surgical options - yes shunts are prone to failure and complications. The other problem is that I cannot give you the direct benefit of experience because I have not done this combined procedure yet - which is why I said I would consider it. There are 2 cases similar to Riley that I have ongoing at the moment which I am also considering it for hence my choice of words in the report- the owners have yet to decide. There is a problem being the first and also doing something new when you have already got an established technique. The other option - and probably safer is to do the first surgery and if there is not a substantial improvement then add a shunt.

hope that helps

Dr Clare Rusbridge
http://www.veterinary-neurologist.co.uk/
for info on syringomyelia, FOPS, Lafora's
disease, epilepsy, spinal disease and more