Syringomyelia in dogs


Introduction


Congenital Syringomyelia in dogs is a relatively uncommon malformation of the spinal cord. This malformation results from the incomplete closure or development of the neural tube, the tubular structure in the embryo that differentiates into the brain and spinal cord. This malformation results in cavitation of the spinal cord parynchema or tissue.

Syringomyelia may also occur secondary to oedema (the accumulation of fluid) caused by neoplasms (tumours); spinal cord trauma; vascular compromise or inflammation.

Syringomyelia may occur in isolation, or may also occur in combination with Hydromyelia, that is the dilation of the central canal within the spinal cord. The occurrence of these two conditions in combination is referred to as Syringohydromyelia. These two conditions can often not be distinguished on diagnostic imaging.

Occurrence

Syringomyelia occurs in various breeds ranging from 12 weeks to 12 years in age.  The prevalence of Syringomyelia in a population of 555 Cavalier King Charles spaniels was 25% in dogs aged 12 months, and this incidence increased to 50% in these small dog breeds older than 6 years.

Clinical Signs

 

The clinical signs due to Syringomyelia are variable, depending on the location and severity of the Syringomyelia, as well as the presence or absence of other congenital central nervous system (CNS) malformations.  Other congenital CNS malformations that may occur in combination with Syringomyelia include:

  1. Hydromyelia.
  2. Myelodysplasia
    A bone marrow stem cell disorder resulting in ineffective blood cell formation.
  3. Spina bifida
    A condition where some vertebrae overlying the spinal cord are not fully formed and remain unfused and open.  If the opening is large enough, a portion of the spinal cord may protrude through the opening in the vertebrae.
  4. Sacrocaudal dysgenesis
    The abnormal development of the vertebrae in the sacrocaudal area (area of the sacrum closest to the tail) that is often associated with abnormalities of innervation to the anus, bladder, hind legs and tail.
  5. Meningomyelocele
    The protrusion of the spinal membranes and cord through a defect in the vertebral column.
  6. Hydrocephalus
    The accumulation of cerebrospinal fluid (CSF) resulting in the abnormal expansion of the cavities or ventricles within the brain.
  7. Chiari malformations
    Malformations of the brain.  Syringomyelia malformation associated with Chiari l malformation is most common in small dog breeds, especially the Cavalier King Charles spaniels (CKCS).  Chiari-like malformation in the CKCS is inherited with an estimated incidence of 95%, of which Syringomyelia is present in more than 50% of dogs with Chiari-like malformations.  Approximately 35% of affected dogs exhibit clinical signs.  This condition has also been reported in Pekingese dogs, Maltese Terriers, Miniature Dachshunds, Yorkshire Terriers, and a Saymoyed dog.   Syringomyelia that accompanies a Chiari-like malformation is thought to occur following an abnormal CSF flow at the foramen magnum (a large opening in the occipital bone of the cranium).
  8. Occipital dysplasia
    A congenital malformation of the foramen magnum
  9. Dandy-Walker syndrome
    A congenital brain malformation involving the fluid filled spaces around it.

The onset of clinical signs may be very severe and of very short duration, or it may be progressive of a period of several weeks, months or even years.  Clinical signs may include any of the following:

  • Paraparesis (partial paralysis of the limbs)
  • Tetraparesis (paralysis of all four limbs)
  • Scoliosis (sideways curvature of the spinal column)
  • Torticolis (contracting muscles of the neck causing sustained twisting or frequent jerking)
  • Spinal pain, most commonly localized to the cervical (neck) region
  • Persistent intense scratching over the shoulder / flank / ear / neck / sternum region
  • Muscle atrophy (muscle wasting)
  • Weakness, especially in the front limbs
  • Decreased spinal reflexes
  • Mild dysphagia (difficulty in swallowing)
  • Pelvic (hind) limb proprioceptive deficits (deficits in the awareness of posture, movement and changes in equilibrium)
  • Urinary and faecal incontinence
  • Bunny-hopping gait in the pelvic limbs
  • Progressive ataxia (failure of muscular coordination)
  • May be overly sensitive to touch on one side of the head, the neck, shoulder or sternum

The most consistent clinical sign seen in Syringomyelia affected dogs, is pain localized to the cervical spine, which may be characterised by sudden vocalization after jumping.  This clinical sign is reported in 35% of affected dogs.

 Diagnosis

 

CFS analysis is usually normal.  Electromyography or EMG (an electrical recording of muscle activity) may reveal abnormal spontaneous potentials in cervical epaxial or thoracic muscles.  Myelography (an X-ray of the spine after the injection of a radio-opague substance) may be negative or may reveal diffuse spinal cord enlargement and presence of contrast agent within the central canal.  Magnetic resonance imaging (MRI) and computed tomography (CT) may help outline the extent and location of the lesions.  MRI is however superior in the detection of Syringomyelia and Hydromyelia compared to myelography and CT.  Often Hydromyelia and Syringomyelia can however not be clearly distinguished from one another on MRI images, as both result in focal or regional, usually elongate, accumulations of CSF that appears hypointense on T1 images and hyperintense on T2 images.

 Treatment

 

Medical treatment does not typically resolve the clinical signs, and is therefore aimed at relieving the pain and other neurological signs associated with the condition.  Analgesics (pain killers), drugs targeted at decreasing CSF production, and corticosteroids have shown some benefit depending on the severity of the clinical signs.  The length of treatment depends on the clinical response.  Surgery is also only aimed at relieving the pain and other neurological signs associated with the condition.  the most common procedure is foramen magnum decompression.  81.25% of dogs that underwent this procedure had improvement or resolution of clinical signs.  25% of these dogs however had a recurrence of clinical signs within the follow-up period, presumably because of the scar tissue formation at the surgical site.  In dogs surgery appears to be less successful compared to that in humans.  Until a reliable surgical option is defined, medical treatment is likely to be the mainstay of veterinary therapy.

 Prognosis

 

The prognosis depends on the severity of the clinical signs, and the response to medication. 


For other congenital dog illnesses go to

Dog health conditions - A chart of many inherited dog health conditions

Defects of the vertebral column in dogs - Congenital conditions

Deafness in Dogs

Defects of the Nervous System of Dogs

Dog health conditions - A chart of many inherited dog health conditions

Canine Leukocyte Adhesion Deficiency  - CLAD

Congenital Portosystemic -  Shunts in dogs

Bladder problems - Ectopic Ureter in Dogs

Congenital conditions of the Skin Eyes and Ears of dogs

Dog Hernias

Tracheal Collapse

Return from Syringomyelia in Dogs to Veterinary Articles




Veterinary articles supplied by Dr S Strydom and published with kind permission of DIA Publishing - publishers of KUSA Dogs in Africa Magazine

Dr Sunelle Strydom qualified as a veterinarian in 2004 at the Faculty of Veterinary Science, University of Pretoria.  She has a passion for writing and the sharing of knowledge to promote animal health and welfare.  She has written several articles for KUSA Dogs in Africa as well as for Vra vir Faffa on the Landbouweekblad website at www.landbou.com


References

  1. Vite H C. 2006.  Developmental disorders.  Braund's clinical neurology in small animals: localization, diagnosis and treatment.  Available at www.ivis.org">www.ivis.org as accessed on 13 July 2011.
  2. Baley R S. 2007. Magnetic resonance imaging in the current era of clinical neurology.  Proceedings of the WSAVA 2007.  Available at www.ivis.org">www.ivis.org as at 13 July 2011
  3. Wisner E R. 2009.  Developmental neurological discorder of the dog and cat.  Proceedings of the 62° congresso internazionale multisala SCIVAC.  Available at www.ivis.org as at 13 July 2011
  4. The Merck Veterinary Manual 9th edition [website].  Available at www.merckvetmanual.com as at 13 July 2011
  5. Wolfe C K and Poma R. 2010.  Syringomyelia in the Cavalier King Charles spaniel (CKCS) dog.  Canadian Veterinary Journal 51: 95 - 102
  6. Park C, Kang B-T, Yoo J-H and Park H-M. 2009.  Syrongomyelia in three small breed dogs secondary to Chiari-like malformation: clinical and diagnostic findings.  Journal of Veterinary Science 10(4): 365-367
  7. Parker J E, Knowler S P, rusbridge C, Noorman E and Jeffery N D.  2011.  Prevalence of asymptomatic syringomyelia in Cavalier King Charles spaniels.  Veterinary record 168: 667
  8. Chandler K, Volk H, Rusbridge C and Jeffery N. 2008.  Syringomyelia in Cavalier King Charles spaniels.  Veterinary Record 162: 324
  9. Rusbridge C.  Greitz D and Iskandar B J. 2006.  Syringomyelia: current concepts in pathogenesis, diagnosis and treatment.  Journal of Veterinary Internal Medicine 20: 469 - 479
  10. The Free Dictionary by Farlex [website].  Available from www.medical-dictionary.thefreedictionary.com as accessed as at 13 July 2011

 


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