Syringomyelia News 2007 - update from Clare Rusbridge
****Sorry I can't add in the photos, this will be going up in full on http://sm.cavaliertalk.com/ shortly, but thought you may like to read it for now...***
SYRINGOMYELIA NEWS 2007
A research update
By Clare Rusbridge and Penny Knowler
Stone Lion Veterinary Centre, 41 High Street, Wimbledon, London, SW19 5AU
email@example.com (CR) Confidential Fax: 020 87860525
International Neurology Conference November 2006
This meeting was hosted by the Cavalier Club UK and sponsored by Boehringer Ingelheim Ltd
and enabled veterinarians with an interest in syringomyelia to share views and ideas. In addition to
inviting veterinarians from Europe, Canada and the USA, the Cavalier Club UK also included
breed club representatives from across the UK with the aim of disseminating information about
this disease to the wider breeder and dog owning population. Thanks are due to Karlin Lillington
for expertise and hard work in reporting the details of the scientific papers and neurologists’ Round
Table. These are posted on her website http://sm.cavaliertalk.com and
http://www.thecavalierclub.co.uk/ and elsewhere. The outcome of the meeting was very positive
and it is hoped that this co-operation between all the specialists and the breeders will result in the
research being moved forward. There was agreement on confusing terminology and the revision of
the interim breeding guidelines (see websites) The most significant point is that an ‘A’ Grade
should only be given to dogs over 2.5 years of age which do not have a syrinx. A hydromyelia is
acceptable only if it is less than 2mm in C2/3 area (i.e. barely visible with good resolution MRI)
Neurologist’s round table, International Conference RVC
Various ongoing research programmes are outlined in Clare’s PhD thesis p.192-3. The successful
public defence at Utrecht University on February 15th 2007 was really a memorable day made
much more so by the guard of honour from 20 cavaliers and the Cavaliergilde Breeders.
The main conclusions of the thesis were as follows
1) Syringomyelia has a high incidence in the cavalier King Charles spaniel breed and the tendency
for it is suspected to be inherited. Preliminary results from a genome scan suggested some
interesting regions which warrant further investigation
2) Syringomyelia is seen in association with a Chiari-like malformation in this breed however a
definite link between small caudal fossa volume and fluid cavitation within the spinal cord has yet
to be established
3) It is hypothesised that syringomyelia occurs secondary to cerebrospinal fluid obstruction and
abnormal pressure differentials between the spinal cord and subarachnoid space. It is further
hypothesised that the syringomyelic fluid is extracellular rather than cerebrospinal in origin
4) Syringomyelia can result in a neuropathic pain syndrome and this is more likely with a wide
syrinx and damage to the spinal cord dorsal horn.
5) Scoliosis is also likely with a wide syrinx and damage to the spinal cord dorsal horn
6) Medical treatment of syringomyelia associated pain should be directed at agents active at the
level of the spinal cord dorsal horn. Drugs that reduce cerebrospinal fluid pressure may also be
7) Surgical cranial cervical decompression can improve clinical signs of pain however the
syringomyelia is generally persistent.
A summary information sheet has been included in this newsletter called ‘CM_SM Explained’.
Fig 3 –the treatment algorithim has not been updated this time.
Copies of the thesis have been sent to the Chairman/Health Secretaries of the following
Clubs/Libraries for members’ use. If there is any other National Club or Institution that would like
a copy please contact Penny Knowler.
The Cavalier Club UK
CKCSC of USA
CKSC South Africa (Rand)
CKCS Health Foundation
The American Kennel Club Library
Royal College Veterinary Surgeons Trust Library
Glasgow Veterinary School Library
Royal Veterinary Collage Library
Carlson Heath Sciences Library (Davis University)
University Library Guelph (Canada)
Individuals wanting a personal copy
are requested to make a donation to
the ‘Syringomyelia DNA research’
fund accessed by PAYPAL
https://www.paypal.com and email
the address to send the copy. Details
htm or just email Penny.
We would like to take this opportunity to introduce Dr Sarah Blott of the Genetics Department
at the Animal Health Trust who has joined the CM/SM research team and we are extremely
fortunate to have her expertise and experience. Sarah is a geneticist with a particular interest in
developing breeding schemes for companion animals that combines state-of-the-art knowledge in
quantitative genetics with molecular genetic markers. She has an MSc in Animal Breeding and a
PhD in Quantitative Genetics, completed at the Roslin Institute (Edinburgh). Following the award
of a Wellcome Trust Travelling Fellowship, she went to the University of Liège, Belgium to work
with Professor Michel Georges on methods for fine mapping of complex trait loci in dairy cattle.
In 2002 she joined Sygen International plc, one of the world’s leading animal breeding
companies, as a Senior Research Scientist and was responsible for data analysis on several
research projects in the areas of gene mapping and high throughput gene expression analysis. She
has also successfully managed multi-partner European Commission research projects and was a
Visiting Scientist at the University of Cambridge Vet School in 2005.
Syringomyelia DNA Research Fund.
DNA collection for another genome scan is the most challenging aspect of the research to date.
Confidentiality is important because of the reluctance of owners to participate publicly in the
project. This particular fund is held by us and is used to
1) disseminate knowledge about the disease and treatment to vets
2) MRI scanning of particular dogs/family groups (worldwide).
3) facilitate DNA collection
Buccal swabs have been purchased as an easier means of sending in samples from dogs that blood
sampling is not an appropriate option. These can be obtained from Caroline Poulin.
Caroline.Poulin@CRCHUM.qc.ca (North America/Australia) or Penny Knowler (Europe/South
Blood (DNA) samples are still needed from MRI confirmed dogs from breeds other than
CKCS with/without CM. Please contact Caroline Poulin to arrange shipment.
We should like to thank all the cavalier lovers for their generous contributions– not only for the
specific needs mentioned above but for their moral support. In particular the following people and
• Kendall Barker for a fantastic donation of $450 US for the sale of CKCS memorabilia on
• Celestial Rainbow Designs for her imaginative enterprise and donation
• Cavalier Club of Canada. $500C has been sent to CHUM for DVD sales
• South African Cavalier Club of the Rand, although a small club, sent a R4386 donation
• Isabelle Barthes and the FCKC a magnificent. $1,048 donation
2007 International Symposium on Syringomyelia (October 23-26th)
This meeting, taking place at historical setting of Rugby School, England
(www.syringomyelia2007.org, email firstname.lastname@example.org) is a 3 day event with a
veterinary day on the last day (Friday). Abstracts are now being accepted (deadline June 30th and
all abstracts will be published in a neurosurgery journal). Deadline for early bird (reduced)
registration June 30th 2007. Highlights of the meeting include
• A combined meeting between veterinary and human specialists - a unique opportunity to
share ideas and experiences
• A dynamic social program including a Ryder Cup course golf tournament for interested
• A packed scientific program including surgical approaches, pain management, genetics,
hindbrain, post traumatic and idiopathic syringomyelia, pathology, CSF physiology and
• Invited international speakers including Thomas Milhorat, Edward Oldfield, Tatsuya
Nagashima and Ulrish Batzdorf.
Rugby is just 1 hour train journey from London in Shakespeare's county and represents the best of
English Heritage including the birthplace of the sport of Rugby and the site where the traitors
planned the gunpowder plot.
A specific programme for breeders on Friday 26th October is planned (separate “budget”
registration fee) but is dependant on whether enough breeders and dog owners are interested
(please indicate interest to Clare Rusbridge on email@example.com). It is intended to invite
the speakers that present on the Veterinary Programme to also give short talks on their current
research to the dog owners / breeders.
CANINE CHIARI-LIKE MALFORMATION AND SYRINGOMYELIA
© Clare Rusbridge BVMS DECVN PhD MRCVS, European and RCVS Specialist in Neurology
Chiari-like malformation (CM) is a condition characterised by a mismatch between the caudal fossa (skull) volume
and its contents, the cerebellum and brainstem. The neural structures are displaced into the foramen magnum
obstructing cerebrospinal fluid (CSF) movement. A consequence of this is syringomyelia (SM) where fluid filled
cavities develop within the spinal cord (Fig 1). The primary clinical sign of CM/SM is pain, either due to obstruction
of the CSF pulse pressure and/or a neuropathic pain syndrome due to damage to the spinal cord dorsal horn. This
disease has also been referred to as occipital hypoplasia (Rusbridge et al 2006) and caudal occipital malformation
syndrome (COMS) (Dewey et al 2005). CM/SM is sometimes erroneously confused with Arnold Chiari malformation
(cerebellar and medulla herniation associated with myelomeningocoele) and occipital dysplasia (incomplete
ossification of the supraoccipital bone).
Midsagittal T2 weighted MRI of the brain and upper cervical spinal
cord from 3 year old female CKCS with syringomyelia (asterisks)
that first developed signs of pain at 1.7years old. Clinical signs
included shoulder scratching at exercise and when excited. She would
not tolerate her right ear to shoulder area to be touched or groomed.
She frequently screamed and her owners were not able to exercise
without her becoming distressed. She also had mild pelvic limb
weakness. She was managed with a foramen magnum decompression
and despite persistence of the syrinx, made a satisfactory post
operative that was maintained for 1.8years. Following this
deterioration she was managed medically for a further 3.8 years and is
currently 7 years old.
The pathogenesis of canine CM/SM is not fully
understood. An important contributory factor is thought to be that the brain is too big for the skull and early studies
suggest that there is an inappropriately short skull base (basioccipital bone (Fig 1). Cavalier King Charles spaniels
(CKCS) with clinical signs related to syringomyelia are more likely to have a smaller ratio of cauda fossa (i.e. back of
skull) volume to total brain volume compared to unaffected CKCS (Cerda-Gonzalez et al 2006). However it is likely
there are other unidentified anatomical or environmental factors. Studies comparing skull dimensions did not
demonstrate a significant difference between the size of the back of the skull in CKCS with and without syringomyelia
(Curruthers et al 2006, Cerda-Gonzalez et al, 2006).
The precise pathogenetic mechanism of development of syringomyelia is much debated (reviewed by Rusbridge et al,
2006; Greiz, 2006). The most popular theory is that obstruction of CSF flow results in relative increase in spinal cord
pressure and decrease in pressure in the CSF space around the spinal cord, the consequence of which is repeated
mechanical distention of the spinal cord. This in turn results in dilatation of the central canal and accumulation of
tissue fluid which eventually coalesces into cavities.
The CKCS is overwhelmingly overrepresented for cases of CM/SM. There is no colour or sex predisposition. As
shortened skull is a risk factor, any breed with a degree of brachycephalism and/or miniaturization could potentially be
predisposed to CM/SM. To date the condition has been also reported in King Charles spaniels, Brussels griffons,
Yorkshire terriers, Maltese terriers, Chihuahuas, Miniature dachshunds, Miniature/toy poodles, Bichon Frise, Pugs,
Shih Tzus, Pomeranians, Staffordshire bull terriers, a Boston terrier, French bulldogs a Pekingese, a miniature
Pinscher and a couple of cats. Recent studies suggest 35% of SM-affected dogs have clinical signs of the condition.
The youngest reported dogs with SM have been 12 weeks old. Dogs may be presented at any age although the majority
of dogs (approximately 45%) will develop first signs of the disease within the first year of life and approximately 40%
of cases have first signs between 1 and 4 years old. As many as 15% develop signs as mature dogs with the oldest
reported case first developing signs of disease aged 6.8 years. Due to the vague nature of signs in some cases and lack
of awareness about the disease there is often a considerable time period (mean 1.6 years) between the onset of signs
and confirmation of a diagnosis.
The most important and consistent clinical sign of CM/SM is pain however this may be difficult to localise. Owners
may describe postural pain; for example, affected dogs may suddenly scream and/or lie with the head on the ground
between the paws after jumping up or during excitement. It is also common to sleep with the head in unusual
positions, for example elevated. Discomfort often appears worse in the evening and early morning or when excited
and can be associated with defaecation or may vary with weather conditions. Pain is positively correlated with syrinx
width and symmetry (Fig 2); i.e. dogs with a wider asymmetrical syrinx are more likely to experience discomfort, and
dogs with a narrow syrinx may be asymptomatic, especially if the syrinx is symmetrical. Dogs with a wide syrinx may
also scratch, typically on one side only, while the dog is walking and often without making skin contact, such
behaviour is often referred to as an “air guitar” or “phantom” scratching. Dogs with a wide syrinx are also more likely
to have scoliosis. In many cases the scoliosis slowly resolves despite persistence of the syrinx.
SM may result in other neurological deficits such as thoracic limb weakness and muscle atrophy (due to ventral horn
cell damage) and pelvic limb ataxia and weakness (due to white matter damage or involvement of the lumbar spinal
cord by the syrinx). Seizures, facial nerve paralysis and deafness may also be seen; however, no direct relationship has
been proven and this association may be circumstantial.
CM alone appears to cause facial pain in some dogs with owners describing ear and facial rubbing/scratching. It has
been proposed that CM and compression of the brain stem can result a pain syndrome (Thimineur et al, 2002). In this
circumstance it can be difficult to be certain that the CM, as apposed to ear, oral or skin disease, is the cause of the
distress especially as CM is a common incidental finding in the CKCS breed.
FIGURE 2 T2 weighted transverse image through a wide syrinx (asterisks)
demonstrating the asymmetrical involvement of the right spinal cord dorsal
Progression of disease is variable. Some dogs remain stable or deteriorate minimally over years. Other affected dogs
can be severely disabled by pain and neurological deficits within 6 months of the first observed signs.
Magnetic resonance imaging (MRI) is essential for diagnosis and determining the cause of SM (Fig 1). In the instance
of CM/SM the cerebellum and medulla extend into or through the foramen magnum which is occluded with little or no
CSF around the neural structures. The size of the cerebellar herniation is not correlated with severity. There is
typically ventricular dilatation. SM is indicated by fluid-containing cavities within the spinal cord. The upper cervical
and upper thoracic segments are typically most severely affected. Maximum syrinx width is the strongest predictor of
pain, scratching behaviour and scoliosis; 95% of CKCS with a maximum syrinx width of 0.64cm or more will have
associated clinical signs.
CT and radiographs have limited value. In severe cases cervical images may suggest widening of the vertebral canal
especially in the C2 region and/or scoliosis. Flexed and extended radiographs of neck can be used to rule out vertebral
abnormalities such as atlantoaxial subluxation and for an indication of the likelihood of intervertebral disc disease.
Ultrasonography through the cisterna magnum may confirm cerebellar vermis herniation however as CM is so
common in the CKCS this information has limited value. Likewise a syrinx may be identified if within the
cranial/cervical segment; however, failure to detect a syrinx does not eliminate the possibility of one more caudally.
CM/SM does not appear to increase risk of anaesthesia.
The most important differential diagnoses are other causes of pain and spinal cord dysfunction such as intervertebral
disc disease; CNS inflammatory diseases such as granulomatous meningoencephalomyelitis; vertebral abnormities
such as atlantoaxial subluxation; neoplasia; and discospondylitis. When scratching or facial/ear rubbing is the
predominant clinical sign, ear and skin disease should be ruled out. The scratching behaviour for SM is classically to
one distinct area. It is a common incidental finding for CKCS to have a mucoid material in one or both tympanic
bullae and in the majority of cases this is not associated with clinical signs. Some cases with scoliosis appear to have a
head tilt which could be confused with vestibular dysfunction. If in doubt cervical radiographs can confirm scoliosis.
The main treatment objective is pain relief. The most common surgical management is cranial/cervical decompression
(also described as foramen magnum or suboccipital decompression) establishing a CSF pathway via the removal of
part of the supraoccipital bone and dorsal arch of C1. This may be combined with a durotomy (incision of the dura
with/without incision of subarachnoid meninges) with or without patching with a suitable graft material.
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 SM and the
syrinx appears persistent in many cases (Rusbridge 2007). The clinical improvement is probably attributable to
improvement in CSF flow through the foramen magnum. 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. Recently, a cranioplasty
procedure used in human cranial/cervical decompression surgery has 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 2006). An alternative method of managing SM 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. There has been a single report of syringo-subarachnoid shunting in a dog
using an equine ocular lavage tube. However post-operative MRI revealed that SM was still prominent although there
was a clinical improvement in the dog (Skerritt and Hughes 1998).
Due to the persistence of SM and/or spinal cord dorsal horn damage it is likely that the post-operative patient will also
require continuing medical management for pain relief and in some patients medical management alone is chosen
because of financial reasons or owner preference. There are three main drugs used for treatment of CM/SM: drugs that
reduce CSF production; analgesics; and corticosteroids (Fig 3). If the dog’s history suggests postural pain or
discomfort relating to obstruction of CSF flow then a trial of a drug which reducing CSF pressure, e.g. furosemide,
cimetidine or omeprazole, is appropriate. This can also be very useful if it is difficult to determine if the cause of
discomfort is CM versus, for example, ear disease. CSF pressure reducing drugs may be sufficient to control signs in
some dogs, but additional analgesics are likely to be necessary for an individual with a wide syrinx. In this
circumstance we suggest that non steroidal anti-inflammatory drugs are the medication of first choice partly because
there are several licensed products. However, for dogs with signs of neuropathic pain, i.e. allodynia and scratching
behaviour (suspected dysesthesia); a drug which is active in the spinal cord dorsal horn is more likely to be effective.
Because gabapentin has established use in veterinary medicine we suggest that this is the drug of first choice but
amitriptyline or pregabalin may also be suitable. Corticosteroids are an option if pain persists or where available
finances prohibit the use of other drugs. Because the mechanisms of development of neuropathic pain are
multifactorial, appropriate polypharmacy is likely to be more effective than treatment with single agents. Anecdotally,
acupuncture and ultrasonic treatments have been reported to be useful adjunctive therapy in some cases. The dog’s
activity need not to be restricted but owner should understand that dog may avoid some activities and grooming may
not be tolerated. Simple actions, for example raising the food bowl and removing neck collars, can also help.
Prognosis for CM/SM managed medically is guarded especially for dogs with a wide syrinx and/or with first clinical
signs before 4 years of age. Study of a small case series (14 CKCS) 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 CKCS is 10.7 years). Most dogs retain the
ability to walk although some may be significantly tetraparetic and ataxic.
Current breeding recommendations for CKCS concentrate on removal of dogs with early onset SM (i.e. within the first
2.5 years of life) from the breeding pool (for precise recommendations and grading system see
REFERENCES AND FURTHER READING
Carruthers H, Rusbridge C, Dubé, M-P, et al Association between cervical and intracranial dimensions and syringomyelia in the cavalier King
Charles spaniel In: Rusbridge C, Chiari-like malformation and Syringomyelia in the Cavalier King Charles spaniel. ISBN 90-393-4456-6; 978-90-
393-4456-9. 82, 2006
Cerda-Gonzalez S, Olby NJ, Pease TP: Morphology of the Caudal Fossa in Cavalier King Charles Spaniels. J Vet Internal Med 20: 736, 2006
Dewey CW, Bailey KS, Marino DJ, et al. Foramen magnum decompression with cranioplasty for treatment of caudal occipital malformation
syndrome is dogs.
Dewey CW, Berg JM, Barone G et al: Foramen magnum decompression for treatment of caudal occipital malformation syndrome in dogs. J Am Vet
Med Assoc 227: 1270, 2005
Greitz D: Unravelling the riddle of syringomyelia. Neurosurg Rev 29:251, 2006
Levine DN: The pathogenesis of syringomyelia associated with lesions at the foramen magnum: a critical review of existing theories and proposal of
a new hypothesis. J Neurol Sci; 220:3, 2004.
Lillington, K, http://www.cavaliertalk.com/SM - a resource for current information on treatment and breeding recommendations with links to
Chiari-like malformation and syringomyelia discussion and support groups.
Rusbridge C, Greitz D, Iskandar BJ: Syringomyelia: Current concepts in pathogenesis, diagnosis and treatment. J Vet Internal Med 20: 469, 2006
Rusbridge C, Jeffery, NJ: Pain mechanisms and treatment in Chiari malformation and syringomyelia in the dog. In press The Veterinary Journal
Rusbridge C, Knowler SP: Inheritance of occipital bone hypoplasia (Chiari type I malformation) in cavalier King Charles spaniels. J Vet Internal
Med; 18:673, 2004.
Rusbridge C: Chiari-like malformation with syringomyelia in the cavalier King Charles spaniel; long term follow up after surgical management. In
press Veterinary Surgery.
Skerritt GC, Hughes D: A syndrome of syringomyelia in the cavalier King Charles spaniel, and its treatment by syringo-subarachnoid shunting. In
Proceedings from the 12th Annual Symposium of the European Society of Veterinary Neurology, Vienna, 23: 1998..
Smith SR. For the Love of Ollie; a story of compassion and courage Trimatrix Management Consulting Inc, 2047 Pen Street, Oakville, Ontario,
Canada, available though http://www.fortheloveofollie.com, 2006 This book is a valuable resource for owners and their veterinarians and was
written by the owner of 2 CM/SM affected dogs. It describes her journey from first realising that her pet was in pain to the post-operative period.
There are contributions from other CM/SM affected dog owners and a simple explanation of the disease and treatment.
Thimineur M, Kitaj M, Kravitz E et al: Functional abnormalities of the cervical cord and lower medulla and their effect on pain: observations in
chronic pain patients with incidental mild Chiari I malformation and moderate to severe cervical cord compression. Clin J. Pain 18:171, 2002