Myelodysplasia (spinal dysraphism)

roblib — Sat, 01 May 2010 23:43:31 +0000

What is ... ?:

Myelodysplasia refers to a number of malformations of the spinal cord that occur as a result of abnormal pre-natal development of the neural tube (which becomes the spinal column). Lesions are most severe in the lumbar (lower back) region. See also spina bifida.

How is ... inherited?:

In the Weimaraner, the mode of inheritance appears to be co-dominant with variable penetrance. The trait is lethal in the homozygous state (ie. a pup inherits the defective gene from both parents).

What breeds are affected by ... ?:

Weimaraner

What does ... mean to your dog & you?:

Clinical signs usually become evident around 4 to 6 weeks when puppies begin to walk around. The signs seen with this condition vary with the severity of the spinal cord malformation. Most commonly you will see a "bunny-hopping" hind limb gait with or without other hind end abnormalities.

The condition is non-progressive (does not get worse) and mildly affected animals - those with a tendency to bunny-hop and a slightly awkward gait - can lead a fairly normal life.

How is ... diagnosed?:

Diagnosis is made based on the clinical signs and by ruling out other possibilities with the aid of tests such as x-rays and cerebrospinal fluid analysis. Diagnosis can also be made on post-mortem, where a veterinary pathologist will find microscopic abnormalities typical of this condition.

How is ... treated?:

There is no treatment. The condition will not get worse.

For the veterinarian:

Definitive diagnosis can only be made by histopathologic examination of the spinal cord. Lesions are most severe in the lumbar region.

Besides the typical bunny-hopping gait, there may be a crouching stance, abduction or overextension of one or both pelvic limbs, decreased pelvic limb conscious proprioception, or scoliosis. Spinal reflexes and pain perception are normal.

Breeding advice:

Affected animals should not be bred.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

LeCouteur, R.A., Child, G. 1995. Diseases of the spinal cord. In S.J. Ettinger and E.C. Feldman (eds.) Textbook of Veterinary Internal Medicine, pp. 629-696. W.B. Saunders Co., Toronto.

Spina bifida

roblib — Sun, 02 May 2010 00:42:42 +0000

What is ... ?:

Normally, the spinal cord is surrounded and protected by the vertebrae of the spinal column. In spina bifida, there is defective fusion of the vertebral arches during embryonic development, so that the vertebrae are incomplete. The abnormalities range from only nonfusion of a small part of one or a few vertebrae, to most of the vertebral arch being absent on several adjacent vertebrae with protrusion of the spinal cord and/or its lining (meninges) through the defect. In the first case the dog will have no medical problems, but with more severe defects there will be clinical signs associated with the area of the spinal cord that is affected. Spina bifida may occur anywhere in the spinal column but is seen most often in the lower back region (caudal lumbar spine).

Both genetic and environmental factors (toxins, nutritional deficiencies during pregnancy) can produce spina bifida.

How is ... inherited?:

The condition is thought to be inherited, but the mode of inheritance has not been identified.

What breeds are affected by ... ?:

What does ... mean to your dog & you?:

Most often, spina bifida occurs in the lower back region (caudal lumbar spine). The clinical signs vary with the extent of the defect. With a mild defect, you will likely never know there is an abnormality unless your dog has x-rays that show the area.

When the spinal cord itself is affected, you will see signs in the hind end ranging from weakness and incoordination to paralysis and urinary and fecal incontinence. With a severe defect (absence of several adjacent vertebral arches with protrusion of spinal cord), signs are generally evident very early, when pups start to walk.

How is ... diagnosed?:

In severe cases in young pups, your veterinarian may recognize the condition on physical examination. Diagnosis is confirmed by x-ray.

With a mild defect, your veterinarian may find this abnormality incidentally when an x-ray is performed.

How is ... treated?:

There is no effective treatment for dogs with spinal cord malformations. No treatment is necessary for dogs in whom spina bifida is discovered incidentally on radiographs. Reconstructive surgery may be helpful for mildly affected animals.

For the veterinarian:

Absence of the vertebral arch or failure of fusion of dorsal spinous processes in one or more vertebrae may be evident on plain radiographs, and may be seen as an incidental finding. Neurological signs may or may not be present depending on the extent of the defect. Most commonly, spina bifida occurs in the caudal lumbar spine, with clinical signs consistent with a transverse myelopathy from L4 to S3 spinal cord segments.

Breeding advice:

Although the mode of inheritance has not been established, it is safest not to breed from families where spina bifida has occurred.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

LeCouteur, R.A., Child, G. 1995. Diseases of the spinal cord. In S.J. Ettinger and E.C. Feldman (eds.) Textbook of Veterinary Internal Medicine, pp. 629-696. W.B. Saunders Co., Toronto.