by Dr. John V. Ioia

Spine & Neurology: Reprinted from AKC Gazette Magazine, March 2015

Syringomyelia (SM) is a disorder in which a cyst or cysts called a Syrinx form within the spinal cord.  SM causes a wide variety of symptoms due to irritation or degeneration of the spinal cord.  Neck pain is the most common presenting sign of this disorder.  In addition to pain, dogs with SM often scratch at one area of the shoulder, ear, neck or sternum, and may have other neurological deficits such as cervical scoliosis, thoracic limb weakness, and pelvic limb ataxia.

While many in the dog community associate SM with Cavaliers, It appears in many breeds. Syringomyelia has been reported as one of the most common spinal cord disorders of Toy Breeds and has been documented in the English Toy Spaniels, Brussels Griffon, Yorkshire Terrier, Maltese, Chihuahua, Miniature Dachshund, Miniature and Toy Poodle, Bichon Frise, Pug, Shih Tzu, Pomeranian, Staffordshire Bull Terrier, Boston Terrier, Pekingese, Miniature Pinscher, and the French Bulldog. The prevalence in mixed breeds is not known. It should also be noted that there are human forms of SM and like the canine variety, the most common presenting sign is neck pain (80% humans, 35% Canines).

Although the cause of SM is unknown, the condition may result from venous or CSF obstruction or distension or may be due to mechanical disruption or shearing of spinal cord tissue planes.

It is impossible to discuss SM without discussing Chiari Malformation (CM).

CM is thought to be similar to Arnold-Chiari-Malformation in humans.  CM is a structural defect that occurs at the junction of the skull and neck.  The opening at the base of the skull or Foramen Magnum (FM) is a funnel-like opening to the spinal canal.  The FM allows the brainstem to exit the skull and join the spinal cord.   Normally, the cerebellum and brain stem sit in a space at the lower rear of the skull, above the foramen magnum.   When part of the cerebellum is located below the foramen magnum, it is called a Chiari Malformation.

CM occurs when the bony space, is smaller than normal, causing the cerebellum and brain stem to be pushed downward into the foramen to the level of the foramen magnum (mild CM) or through the foramen magnum (severe CM) into the upper spinal canal.  Severe CM may be subdivided into Types 1, 2 & 3 based on the amount of cerebellum and brain stem protruding through the FM.  The resulting pressure on the cerebellum and brain stem may affect brain function and block the flow of cerebrospinal fluid (CSF).  Many dogs with CM go on to develop Syringomyelia (SM).  Although it is hypothesized that CM and SM may have several different causes, no clear etiology or genetic markers have been identified.

The most common symptom of Syringomyelia is hypersensitivity in the neck area resulting in an uncontrolled urge to scratch at the neck and shoulders giving the appearance of air scratching while walking.  There is often discomfort and pain in the area of the neck, ears and shoulders, difficulty with collars or leashes.  Progressive limb weakness, balance problems, numbness, loss of coordination and hearing can develop.

While symptoms may suggest SM, the MRI is the imaging procedure of choice.  It is a painless and noninvasive procedure, however your dog will have to be anesthetized which is not always without problem.

Treatment of SM will depend on the severity of involvement and may include the use of non-steroidal anti-inflammatory agents, steroids, neuroleptic agents like gabapentin or Lyrica, drugs to reduce CSF production such as omeprazole, diuretics or even opioids if pain is severe.  Surgical procedures have also been developed.

The real future for SM will be in the elimination of the disease state by identification of a mode of genetic transmission, identification of carriers and a genetic marker.  Responsible breeders are working to remove potential carriers from breeding programs.  The ACKCS Charitable Trust and the AKC/CHF is in the forefront of funding research.  Below is a sampling of research programs funded in whole or in part by ACKCSCS Charitable Trust  and AKC/CHF.

1) 2015: Investigation of Quantitative Trait Loci and Sensory Thresholds in Chiari-like Malformations and Syringomyelia in Cavalier King Charles Spaniels. ACKCSCT Funded

2) 2011: Role of Morphology in clinical Progression and Syringomyelia in CKCS Chiari-like, Funded by the ACKCSCT

3) Evaluation of Objective Structural and Functional Measurements for Predicting Clinical Disease Progression and Assessing Treatment in Cavalier King Charles Spaniel With Caudal Occipital Malformation Syndrome—Ohio State University—Funded by ACKCSCT

4) The Effect of Chiari Malformation on CSF Flow in Cavalier King Charles Spaniels—NC State University, Funded by the ACKCSCCT

5) 2008: Identification of Genes Causing Chiari I Malformation with Syringomelia in the Cavalier King Charles Spaniel. University of Montreal.  Funded by ACKCSCT in cooperation with the AKC/CHF.

6) 2009: Syringomyelia in the Brussels Griffon:  Magnetic Resonance Imaging Findings, Clinicopathology and Prevalence. University of Georgia.  Funded by ACKCSCT in cooperation with AKC/CHF and other Parent Clubs.

7) 2009: Investigation of the presence of Chiari-like Malformation and Syringomelia in Stillborn Cavalier King Charles Foetuses. The Royal Veterinary College, U.K.  Donation by the ACKCSCT

Dr. John V. Ioia is a member of the ACKCS Charitable Trust Board and the Health Committee