Spinal Dysraphism/Spina bifida/Syringomyelia

Liaison: Jan Young

Spinal dysraphism is the general term for a malformation that affects the spinal column. It results from defective or delayed closure of the neural tube during embryonic development. There are a number of defects and deformities that can arise as a result of spinal dysraphism; spina bifida and syringomyelia are two that have been reported in a Samoyed.

In spina bifida, a portion of the spinal column fails to close. The lining and spinal cord may protrude through the resulting opening and be damaged.
In syringomyelia there are abnormal fluid-filled cavities within the spinal column which may press on the spinal cord and interfere with function.

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Spinal dysraphism is the general term for a congenital (existing at birth) malformation that affects the spinal column. It results from defective or delayed closure of the neural tube during embryonic development. There can be a single defect, or multiple defects in multiple locations along the spinal column. Defects include the following:

Spina bifida: A bony cleft (failure of closure) of the spinal column with protrusion of the meninges (lining of the spinal cord) or meninges and spinal cord tissue. The skin over the defect may be intact or open. Depending on the amount and location of the protruding tissue, there can be involvement of the motor and sensory system, including partial paralysis and loss of bowel and bladder control. The condition can vary wildly in severity, and the degree of impairment depends on the amount of involved nervous tissue. Typically it is nonprogressive (doesn’t get worse with time).
Spina bifida occulta: A bony cleft of the spinal column that does not involve protrusion of any tissue. There is no involvement of the nervous or motor system, but there may be abnormal patterns of hair in the area and in some instances there may be a pilonidal sinus, a dimple in the skin with an opening to the spinal cord. This can be a potential source of infection.
Syringomyelia: A condition where there are abnormal fluid-filled cavities within the spinal column which may interfere with the function of the nervous tissue of the spinal cord. It is often associated with a chiari malformation where the brain is displaced downward, forcing the cerebral spinal fluid (CSF) into the spinal cord and interfering with its flow. Syringomyelia occurs primarily in the neck region because this is the area of the spinal cord closest to where the pressure is coming from.
Hemivertebra: A deformed vertebra which often leads to scoliosis (curvature of the spine)
Tethering of the cord: A situation in which the spinal cord (nerve tissue) is bound to bony tissue. As the dog grows, the cord is stretched and can be damaged. This can be surgically released to prevent further damage. Sometimes tethering is the only manifestation of spinal dysraphism.

Signs and Symptoms

Spina Bifida

When nervous tissue is involved, the primary symptoms of spina bifida are as listed below. These signs and symptoms, when present, are permanent and will not resolve.

Weakness or partial paralysis, most typically of the hindquarters. This may be severe enough that the dog is not able to use the hindquarters. Dogs may have awkwardness of the limbs and often have a wide-based stance to improve balance. Bunny hopping and/or toe walking can be seen as well.
Decreased ability to use the tail.
Loss of bowel and bladder control because of involvement of the nerves controlling these functions. The anus may be flaccid (loose and weak) and pressure over the bladder may cause leakage.
Decreased or absent pain sensation in the affected area, typically the perianal area (around the anus) and sometimes down onto the thighs. Pressure ulcers may result if the dog is not frequently repositioned.
Irritation of the skin in the perianal area from leakage of urine and/or stool.

If there is no nervous system tissue involved (spina bifida occulta), there are no signs. The condition may even go unnoticed until an x-ray taken for an unrelated condition reveals the defect of the spinal column. In some instances there may be minor signs that suggest the diagnosis to the vet:

Hair streaming – an abnormality in the pattern of the hair overlying the defect.
Skin dimple, which may be palpable.

Syringomyelia

Pain is the most common symptom of syringomyelia and is the result of injury to the nerves of sensation.

Typically worse at night. The animal may not like to be touched in the area of the neck or upper chest and may scratch at this area. (Itching is the lowest grade of pain).
Excessive scratching or air scratching because of pain sensation; biting at the rump, again because of abnormal pain sensation.
Yelping with scratching or sometimes for no apparent reason

In more severe cases there can be involvement of motor nerves as well, resulting in weakness of the forelegs or hindlegs with unsteadiness or wobbliness of gait (ataxia).

Symptoms of syringomyelia are often progressive, getting worse with time.

Syringomyelia can also be present in the absence of symptoms.

Causes

Genetics are known to be involved with some breeds such as the Weimaraner (spinal dysraphism) , English Bull Dog (spina bifida) and Cavalier King Charles Spaniels (chiari malformation).

Factors which interfere with prenatal development of the neural tube, including toxins and nutritional or other factors which interfere with blood supply to the developing area, may possibly be involved in the development of spinal dysraphism.

Trauma can be a cause in some cases of syringomyelia.

Risk Factors

No specific risk factors are known for the development of spinal dysraphism in the Samoyed. If seen more than once in a line it would suggest a possible genetic basis. Dogs from such a line should not be bred.

Diagnostic Tests

X-ray of the spine will identify the bony defect.

CT (computerized tomography) and/or MRI (magnetic resonance imaging) will help define the soft tissue involvement, if any.

MRI is the only way to identify the fluid-filled sacs of syringomyelia.

Specialized testing including myelography (injecting dye into the spinal column to help outline the nervous tissue) may be useful on occasions.

Treatment Guidelines

Note: Treatment of animals should only be performed by a licensed veterinarian. Veterinarians should consult the current literature and current pharmacological formularies before initiating any treatment protocol.

Spina Bifida

If nervous tissue (spinal cord or nerves) has not protruded out of the protective bony column, no treatment is necessary and the dog will usually live a normal quality life.

When there is protrusion and damage to nervous tissue, the damage is permanent and there is no effective treatment. Many dogs will have mild enough involvement that they can have quality of life. In more severe cases, the owner and vet may choose to euthanize.

Other than in the instance of tethering, surgical correction of the defect has been generally unsuccessful, mostly because the nervous tissue has already been damaged and surgery cannot allow it to recover. I found one reference to a successful surgical correction with full recovery. This particular case was a very low lesion (sacral) and the nerves involved were not so much damaged as they were bound down by other tissues. They were able to successfully mobilize them in surgery and allow for recovery. The likelihood of this is extremely rare.

Hanna FY, 2008. The successful treatment of a Yorkshire Terrier puppy with spina bifida and myelomeningocele. European Journal of Companion Animal Practice 18:47-50. two bonesrating

Syringomyelia

Analgesics for pain management:

NSAIDS such as Rimadyl and Metacam;
Gabapentin, an anticonvulsant that helps calm excitable injured nervous tissue; or
Opioids such as methadone

Drugs to reduce CSF production or reduce intracranial pressure

Corticosteroids may help with pain reduction but must be used continuously if used, and are subject to many undesirable side effects.

Surgery has been attempted with limited success; signs often recur.

Management

For dogs with mild symptoms, particularly with bowel and bladder control problems, diapering can be helpful but care should be taken to provide good skin hygiene (frequent diaper changes and cleansing of the area).

For some dogs, dietary manipulation to keep the stool firmer will allow better fecal control.

The use of canine assistive devices (such as a canine wheel chair) may be helpful in improving quality of life.

References

Spinal Cord Disorders -Congenital and Inherited Anomalies of the Nervous System. Merck Veterinary Manual, 10th edition. Pp 1125-1126 fourbonesrating

Arias MVB et al, 2008. Spina bifida in three dogs. Brazilian Journal of Veterinary Pathology 1: 64-69. three bonesrating

Vite CH. Developmental Disorders. In: Braund’s Clinical Neurology in Small Animals: Localization, Diagnois and Treatment. 2004. (Link no longer available). four bonesrating