Syringomyelia and Chiari-like Malformation
Syringomyelia is a recent hereditary condition first identified in the Cavalier King Charles Spaniel. It has now been diagnosed in other toy breeds including the Griffon Bruxellois, Chihuahua, King Charles Spaniel, Yorkshire Terrier, Pomeranians, Affenpinschers and Pugs. The condition is of a growing concern to breeders and dog owners alike. Syringomyelia and Chiari Malformation in the Cavalier King Charles Spaniel has been known and studied for longer. This has led to a number of informative Cavalier based web sites (see links)
SYRINGOMYELIA (SM) is where the normal flow of cerebrospinal fluid in the brain and the spinal cord is altered or blocked so that cavities develop, called syrinxes. These cavaties/syrinxes filled with the cerebrospinal fluid can cause damage to the spinal cord and function of the nervous system. A syrinx can develop as young as 3 months or more slowly over a period of years. There is no cure, the condition can be managed through medical intervention with high strength analgesics or corticosteroids for pain management and medication to reduce cerebrospinal fluid production
CHIARI-LIKE MALFORMATION (CM) is a malformation or mismatch between the skull size and brain size. In CM the skull is too small and the brain is too big, which leads to the brain being squashed and pushed out the back of the dog’s skull (foramen magnum) into the vertebral canal. This obstructs the flow of cerebrospinal fluid in and out of the brain. CM can be extremely painful and surgery may be an option to relieve pain and suffering and improve the flow of cerebrospinal fluid. Chiari-like malformation is a birth defect where the dog is born with the condition.
Dogs can have chiari-like malformation without syringomyelia or syringomyelia without chiari-like malformation. In many cases chiari-like malformation and syringomyelia are seen together with dogs having both conditions. Chiari-like malformation can present as a precursor to syringomyelia with a dog later developing the condition as they mature. Syringomyelia can be caused by trauma or a tumour. Syringomyelia and Chiari-like malformation particularly in breeds of dogs that are miniaturised are known to be caused through a hereditary link.
What this means for our dogs
CMSM is rarely fatal but can be increasingly painful and debilitating. Suffering is such that affected dogs may need surgery or early euthanasia. Early diagnosis and treatment can help in slowing the progression of the disease. The severity of syringomyelia relates to the width and asymmetry of the syrinx.
Symptoms can vary from dog to dog and not all dogs exhibit all of the same symptoms. Though symptoms may be unnoticeable in some dogs other dogs are quite affected but vary in the way the outward symptoms show. Dogs are usually diagnosed upwards from the age of 6 months. Due to the progressive nature of the condition symptoms may not show themselves until around the age of three or four years or even later as a dog ages and matures. Some badly affected dogs exhibit symptoms from a very young age.
Symptoms include pain or sensitivity to touch around the neck region including ears and shoulders. Scratching in the air without body contact or scratching around the regions of neck, shoulders, head, face and ears .Biting hind quarters or chewing front paws. Sudden yelping or crying out for no obvious reason. Limb weakness, particularly hind legs. Rubbing of eyes, ears, face on to the ground or rubbing on to paws. Slowing down of movement or reluctance to walk due to pain. Reluctance or hesitation to jump on to furniture or climb stairs. Random screaming because of pain which may lead to aggressive behaviour particularly to other dogs. Curving of the spine leading to scoliosis. Seizures.
All symptoms need thorough investigations by an expert (neurologist ) to rule out other causes. Some symptoms are common to other diseases and conditions. A MRI scan is the only conclusive way of confirming a diagnosis of syringomyelia and chiari-like malformation.
The nature of syringomyelia means that a dog may not show any symptoms of the condition but are carriers of CMSM and pass on these genes to their litters. Subsequent litters of pups may show symptoms from an early age or be carriers themselves. Due to the progressive nature and late onset of SM dogs may have sired or bred a number of litters before it is known that they syringomyelia.
For indepth information on all aspects of CMSM check out Dr Clare Rusbridge,BVMS PhD DipECVN MRCVS, very informative website. http:www.veterinaryneurologist.co.uk
A basic CMSMFLYER for downloading and printing