Canis ISSN: 2398-2942

Chiari-like malformation syringomyelia (CM/SM)

Synonym(s): Chiari I malformation; syringohydromyelia; occipital bone hypoplasia; caudal occiptal malformation syndrome (COMS

Contributor(s): Kyle Braund, Clare Rusbridge, Johnny Plessas

Introduction

  • Syringomyelia is a painful disorder which develops secondary to obstruction of cerebrospinal fluid flow. The most common cause of this in the dog is Chiari-like malformation where foramen magnum is obstructed by herniated cerebellum and medulla. The most common clinical sign is pain and in some cases results in a characteristic paroxysmal shoulder/ear scratching.
  • Cause: Chiari-like malformation is an inherited disorder characterized by a mismatch between brain and skull volume. It is mostly commonly seen in toy breeds, in particular the Cavalier King Charles spaniel, King Charles spaniel and Griffon Bruxellois.
  • Signs: pain; behavioral changes; cervical scoliosis; weakness and muscle atrophy; pelvic limb weakness and ataxia.
  • Diagnosis: clinical signs; MRI.
  • Treatment: medical management; surgery (cranial - cervical decompressions).
  • Prognosis: guarded.

    Print off the owner factsheet Syringomyelia in Cavalier King Charles Spaniels (CKCS) Syringomyelia in Cavalier King Charles Spaniels (CKCS) to give to your client.

Pathogenesis

Etiology

  • Developmental malformation.
  • Chiari-like malformation is an inherited disorder characterized by a mismatch between brain and skull volume. It is mostly commonly seen in toy breeds in particular the Cavalier King Charles spaniel, King Charles spaniel and Griffon Bruxellois.
  • Compared to dogs of similar weight/height the brain is larger and the skull, in particular the caudal fossa, is smaller. There is insufficient space for the brain, which consequently is pushed out through the foramen magnum. The lack of space is aggravated during the systolic pulse when the brain expands with blood.
  • Occlusion of foramen magnum leads to obstruction of CSF pathways and failure to accommodate the systolic pulse pressure. Ultimately this results in development of syringomyelia (fluid filled cavities within the spinal cord).
  • Damage by the expanding syrinx to spinal pathways processing information about pain and sensation results in a neuropathic pain disorder.
  • Pain also occurs due to obstruction of cerebrospinal flow and failure accommodate the systolic pulse pressure.
  • Recent studies suggest Chiari-like malformation is inherited in the Cavalier King Charles spaniel and Griffon Bruxellois. Both of these modern breeds have Toy spaniels in their ancestry (as does the King Charles spaniel).
  • Clinically affected offspring often have affected (clinically or sub-clinically) parents and the disease severity can become worse with an earlier onset with each generation.

Specific

  • Other spinal disease, eg intervertebral disk herniation superimposed on a pre-existing Chiari-like type 1 malformation may play a role in some clinical cases.
  • CKCS is a breed also affected by idiopathic epilepsy Epilepsy: idiopathic, however no association was found between seizures and CM/SM.

Pathophysiology

  • CM/SM is a complex developmental disorders due to occipital bone hypoplasia resulting in a small caudal fossa and overcrowding of the brainstem and cerebellum.
  • The skull is too small and the brain is comparatively large.
  • The vermis of the cerebellum extend through the foramen magnum.
  • The medulla is kinked and also extends through the foramen magnum.
  • Occlusion of foramen magnum leads to obstruction of CSF pathways and failure to accommodate the systolic pulse pressure. Ultimately this results in development of syringomyelia (fluid filled cavities within the spinal cord).
  • Damage by the expanding syrinx to spinal pathways processing information about pain and sensation results in a neuropathic pain disorder.
  • Pain also occurs due to obstruction of cerebrospinal flow and failure accommodate the systolic pulse pressure.
  • Syringomyelia typically more severe and develops first in the cervical spinal cord.
  • Signs of pain can be correlated to maximum syrinx width and damage to the spinal cord dorsal horn.
  • Spinal dorsal column damage can also result in scoliosis due to an imbalance in afferent proprioceptive information from cervical neuromuscular spindles.
  • There is an association between scoliosis and syrinx width - ie more likely with wide syringes.

Timecourse

  • Onset of signs may be acute or insidiously progressive over several weeks, months or years. According to a recent study in CKCS, clinical signs deteriorate in 75%, whereas clinical signs in the other 25% remain stable or improve.
  • Dogs that have a wide syrinx (for a CKCS 5 mm or more) and presenting before 3 years of age are more likely to progressively deteriorate.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Nalborczyk Z R, McFadyen A K, Jovanovik J, Tauro A, Driver C J, Fitzpatrick N, Knower S P, Rusbridge C (2017) MRI characteristics for “phantom” scratching in canine syringomyelia. BMC Vet Res 13 (1),  340 PubMed.
  • Harcourt-Brown T R, Campbell J, Warren-Smith C, Jeffery N D & Granger N P (2015) Prevalence of Chiari-like malformations in clinically unaffected dogs. JVIM 29 (1), 231-237 PubMed.
  • Ives E J, Doyle L, Holmes M, Williams T L & Vanhaesebrouck A E (2015) Association between the findings on magnetic resonance imaging screening for syringomyelia in asymptomatic Cavalier King Charles spaniels and observation of clinical signs consistent with syringomyelia in later life. Vet J 203 (1), 129-130 PubMed.
  • Ortinau N, Vitale S, Akin E Y, Beasley M & Shores A (2015) Foramen magnum decompression surgery in 23 Chiari-like malformation patients 2007-2010: Outcomes and owner survey results. Can Vet J 56 (3), 288-291 PubMed.
  • Plessas I N, Volk H A, Rusbridge C, Vanhaesebrouck A E & Jeffrey N D (2015) Comparison of gabapentin versus topiramate on clinically affected dogs with Chiari-like malformation and syringomyelia. Vet Rec 177 (11), 288 PubMed.
  • Driver C J, Volk H A, Rusbridge C & Van Ham L M (2013) An update on the pathogenesis of syringomyelia secondary to Chiari-like malformations in dogs. Vet J 198 (3), 551-559 PubMed.
  • Driver C J, Chandler K, Walmsley G, Shihab N & Volk H A (2013) The association between Chiari-like malformation, ventriculomegaly and seizures in Cavalier King Charles spaniels. Vet J 195 (2), 235-237 PubMed.
  • Plessas I N, Rusbridge C, Driver C J, Chandler K E, Craig A, McGonnell J M, Brodbelt D C & Volk H A (2012) Long-term outcome of Cavalier King Charles spaniel dogs with clinical signs associated with Chiari-like malformation and syringomyelia. Vet Rec 171 (20), 501 PubMed.
  • Loderstedt S, Benigni L, Chandler K, Cardwell J M, Rusbridge C, Lamb C R & Volk H A (2011) Distribution of syringomyelia along the entire spinal cord in clinically affected Cavalier King Charles spaniels. Vet J 190 (3), 359-363 PubMed.
  • Parker J E, Knowler S P, Rusbridge C, Noorman E & Jeffrey N D (2011) Prevalence of asymptomatic syringomyelia in Cavalier King Charles spaniels. Vet Rec 168 (25), 667 PubMed.
  • Cerda-Gonzalez S, Olby N J, McCullough S et al (2009) Morphology of the Caudal Fossa in Cavalier King Charles Spaniels. Vet Radiol Ultrasound​ 50 (1), 37-46 PubMed.
  • Rusbridge C & Jeffery N D (2008) Pathophysiology and treatment of neuropathic pain associated with syringomyelia. Vet J 175 (2), 164-172 PubMed.
  • Cappello R & Rusbridge C (2007) Report from the Chiari-Like Malformation and Syringomyelia Working Group Round Table. Vet Surg 36 (5), 509-512 PubMed.
  • Rusbridge C, Caruthers H, Dubé M-P, Holmes M, Jeffery N D (2007) Association between spinal cord dorsal involvement and pain in syringomyelia secondary to canine Chiari malformation. JSAP 48 (8), 432-436 PubMed.
  • Rusbridge C (2007) Chiari-like malformation with syringomyelia in the cavalier King Charles spaniel; long term follow up after surgical management. Vet Surg 36 (5), 396-405 PubMed.
  • Rusbridge C, Greitz D, Iskandar B J (2006) Syringomyelia: Current concepts in pathogenesis, diagnosis and treatment. J Vet Intern Med 20 (3), 469-479 PubMed.
  • Dewey C W, Berg J M, Barone G et al (2005) Foramen magnum decompression for treatment of caudal occipital malformation syndrome in dogs. J Am Vet Med Assoc 227 (8), 1270-5 PubMed.
  • Rusbridge C (2005) Neurological diseases of Cavalier King Charles spaniels. JSAP 46 (6), 265-272 PubMed.
  • Rusbridge C, Knowler P, Rouleau G A, Minassian, Rothuizen J (2005) Inherited occipital hypoplasia/syringomyelia in the Cavalier King Charles spaniel experiences in setting up a worldwide DNA collection. J Hered 96 (7), 745-749 PubMed.
  • Rusbridge C & Knowler S P (2004) Inheritance of occipital bone hypoplasia (Chiari I malformation) in Cavalier King Charles spaniels. J Vet Intern Med 18 (5), 673-678 PubMed.
  • Rusbridge C & Knowler S P (2003) Hereditary aspects of occipital bone hypoplasia and syringohydromyelia (Chiari I malformation) in Cavalier King Charles spaniels. Vet Rec 153 (4), 107-112 PubMed.

Other sources of information

  • MRI characteristics for "phantom" scratching in canine syringomyelia. BMCseriesJournals: www.youtube.com/watch?v=uI2hPA7mxSc
  • Lillington K http://sm.cavaliertalk.com/ - a resource for current information on treatment and breeding recommendations with links to Chiari-like malformation and syringomyelia discussion and support groups.
  • Chiari Malformation/Syringomyelia Scheme (http://www.bva.co.uk/Canine-Health-Schemes/CM-SM-Scheme/).
  • Rusbridge C (2007) Chiari-like malformation and Syringomyelia in the Cavalier King Charles spaniel. Doctorial Thesis http://igitur-archive.library.uu.nl/dissertations/2007-0320-201201/index.htm
  • Smith S R (2006) 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. 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.
  • Skerritt G C, Hughes D (1988) 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.
  • Skerritt G C, Hughes D (1988)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.


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