Wobbler's Syndrome
by
Bruce R. Wittels, D.V.M.
In Great Danes, a true wobbler is usually seen between the ages of 3-12 months of age. The outstanding symptom is a slowly developing, progressive, incoordination and paralysis of the hind limbs. This paresis and/or incoordination is caused by pressure on the spinal cord as it passes thru the vertebrae of the neck, the last three being the most prominent sites. The animal may appear clumsy, "wobbling" or display swaying of the rear legs. On slick surfaces it may be difficult or impossible to walk. The dog may fall when attempting to turn and the toes of the hind feet may drag when walking. The dog usually has its legs spread out as far as possible trying to better balance itself. Initially front leg involvement is minimal or undetectable. As the disease progresses, a characteristic short choppy rolling stride is seen on what appears to be somewhat rigid forelimbs. As the compression of the spinal cord becomes more severe, the front legs can have the same signs as the rear legs. There is usually little or no neck pain but the dog may stand with the neck flexed, which usually alleviates some of the spinal cord pinching. Many dogs will object to neck manipulation and may even collapse when the movement is forced.
On occasion, there can be an acute onset of signs. They are usually more severe than with the progressive type. Forelimb involvement is usually present. There is also a higher incidence of neck pain with the acute onset. This type of wobblers is seen most frequently in five to seven year old Doberman Pinchers and is rarely seen in young Danes. This must be differentiated from similar signs caused by cervical disc protrusion or fractured vertebrae.
The pressure of the spinal cord is due to improper formation of the anatomical parts surrounding the spinal cord during growth. The pressure can be due to one or a combination of the following:
1.Weak ligaments which hold the vertebral bodies in place - this allows irregular movement of the vertebral bodies as the neck is placed in various positions (subluxations) and causes a pinching of the spinal cord.
2.Hyperplasia of the yellow ligaments - normally these are thin loose elastic sheets located between the arches of adjacent vertebrae. Just beneath them is the small epidural space which is immediately above the spinal cord. With enlargement of these ligaments, the epidural space is obliterated and the yellow ligaments push directly on the spinal cord.
3.Malformation of the vertebrae - this can happen in various ways i.e.:
a.Vertibral or spinal canal that is too small for the diameter of the spinal cord
b.Assymetric cartilage defects which cause vertebral subluxations
c.Osteochondrosis of the articular facets which also lead to subluxations
d.Stenosis of the cranial orifices of vertebral foramina which causes a pinching of the nervous system
DIAGNOSIS
This is based on the breed, age, history and results of both a physical
and neurological examination. Diagnosis is confirmed by radiographic examination.
A minimum of three views should be taken: a side view with the neck in
normal position, a side view with the neck in a flexed position (head pointed
towards the feet), and a side view with the head in a skyward position.
A subluxation of one or more vertebrae may be the only causative agent
and is often only seen when the neck is in and extended or flexed position.
At times, a view of the neck from top to bottom must be taken. A myelogram
might be needed to properly determine the exact compression sites. Other
disease entities which can cause similar symptoms that must be differentiated
from are: disc protrusions, infectious, neoplastic, vascular, or traumatic
disorders of the spinal cord. Other bone disorders common to the giant
breeds can cause gait abnormalities but are usually presented with a lot
of pain and do not show any nervous system involvement.
CAUSES
The exact reasons why the aforementioned vertebral abnormalities occur
are unknown. There is probably a genetic factor that comes into play. This
is determined by a high incidence of Canine Wobblers seen in certain families
of Danes. It is difficult to separate the genetic from the environmental
factor (nutrition, management and activity) as most of these families are
kept in the same environments because many breeders keep the pups for three
to four months thus keeping the family under a similar environment. Deformity
and displacement of the cervical vertebrae secondary to a long neck, large
head and rapid growth has been proposed. (Weight et al 1973).
A vertebral canal that is too small for the diameter of the spinal
cord could easily be caused by nutritional hypercalcitonism. As discussed
in my second article, Nutrition of the Newly Born and Growing Individuals
(GDR Jan/Feb '85). Calcitonin is released from the thyroid gland when
the animal is fed a diet high in calcium. Its function is to retard bone
reabsorption and thus decrease blood calcium levels. Remember, calcium
is kept within strict limits in the blood stream. In normal growth, expansion
of the spinal canal must be perfectly synchronized with growth of the spinal
cord. Expansion is achieved by resorption of bone inside the vertebral
canal. With hypercalcitonism, the retarded rate of bone resorption prevents
proper expansion of the canal - therefore the diameter of the spinal canal
is decreased and has an irregular contour. The spinal cord grows independently
of the surrounding bone and is thus pinched by the nonresorbed bone therefore
causing Cervical Spondylopathy.
Nerves leave the spinal cord, to go to other parts of the body, through
spaces formed by notches is the vertebrae called foramina. A narrowness
in these spaces will cause a pinching of the nerves leaving the spinal
cord which in turn causes inflammation and swelling of the spinal cord
itself thus causing wobblers syndrome. Hypercalcitonism causes narrowness
in the vertebral canal can also yield a stenosis of the cranial orifices
of the vertebral foramina due to its effect of slowing bone resorption.
Hyper or overnutrition can also give the same results as an increased growth
rate without proper mineralization and body controls can cause enlarged
or asymmetric bone formation of the vertebrae in the neck as well as in
any other bone in the body. This could easily result in pinching of the
nerves as an overabundance of bone can yield improper notch formation.
Although the vertebrae may not be as flexible as other joints in the
body - they do move and have joint surfaces as do other bones. The joint
surfaces called "articular facets" are lined with a cartilage the same
as those of other joints. Improper formation of these surfaces can cause
the vertebrae to move improperly and cause luxation or subluxation which
can cause pinching of the spinal cord. A mechanism that can cause such
a situation is Osteocondritis Dessecans (OCD). For now, let's describe
OCD as a disturbance of endochondral ossification (one type of bone formation)
which leaves the joint cartilage thicker than normal. It is therefore further
away from the blood supply leaving it more susceptible to injury and cell
death which will cause poor rotation of the joint and hence subluxation.
This can happen at all or only one of the facets in the cervical spine.
Again the last three vertebrae are most commonly affected. Osteochondrosis
will be more thoroughly discussed in the next issue of the Reporter. The
main cause of OCD is overnutrition or ad-lib feeding. Hedhammer et all
(1974) studied the relation between overnutrition and skeletal disease
in growing Great Danes. In general - dogs fed ad libitum had smaller than
cervical vertebral foramina (notches) with subsequent spinal cord compression
as well as asymmetric vertebral articular facets. There was also OCD in
the facets displayed as defects in the cartilage covering the facets. They
concluded that "excessive intake of food rich in protein, energy, calcium
and phosphorous accelerates growth and can induce various skeletal changes
including changes in the cervical vertebrae that result in the wobbler
syndrome."
TREATMENT
The treatment of cervical spondylopathy depends on the severity of
the neurological involvement and the longevity of the disease process.
Treatment is directed at stopping further cord trauma and at decreasing
the current neurological deficits.
The acute form of canine wobbler syndrome is truly a medical emergency.
The dog is very often quadriplegic and immediate veterinary attention must
be sought in order for the spinal cord to be saved. Generally the veterinarian
will treat the animal with diuretics (i.e. mannitol) and high dose steroids
to decrease the swelling and inflammation in the cord as well as ascorbic
acid to protect the myelin sheath that surrounds the nerves. This treatment
may last as long as 2 to 3 days. Depending on the degree of improvement,
decompressive surgery is usually required to prevent further trauma to
the cord. If via rigorous medical treatment, the animal regains full neurological
function, surgery may be delayed from one to three weeks with the animal
probably kept in a neck brace. If, however, little or no improvement is
rendered via medical care - surgery must be done within a few days in order
to preserve the integrity of the spinal cord. The more time that passes
with the spinal cord compressed and therefore without nutrients and oxygen,
the higher the likelihood of some degree of permanent paralysis. The two
most used surgical techniques are Dorsal Laminectomy (where the top of
the spinal canal is removed thus allowing the spinal cord to rise out of
the confining environment) and Ventral Decompression which removes ulcerated
disc material as well as certain ligaments under the spinal cord and some
of the vertebral body that may be compressing the cord. Choice of surgical
technique is made by the orthopedic surgeon or by someone that has had
much experience with spinal surgery as well as the special instrumentation
needed for this complicated procedure. Even with the correct facilities
and techniques there are always possibilities of post operative complications.
Dogs with slowly progressive signs of Wobblers Syndrome often respond
well to a combination of cage rest and corticosteroid therapy. I usually
apply a neck brace as well to provide some stabilization of the neck and
at the same time some traction as well. This is only if the syndrome is
caught in the early stages. Remember that the above will only alleviate
the effects of compression of the cord and does not and will not correct
the vertebral and ligamentous changes. The IMMEDIATE thing to do is to
reduce the protein level of the diet. A protein level not to exceed 22-24%
should be fed. Any and all mineral supplements should be discontinued.
All food and water must be elevated to further reduce neck tension. Ball
playing or any action where the head is dipped down to snatch up an object
is to be eliminated. A very concerted effort to restrain this dog from
exercise is to be instituted as this can easily yield an increase in the
likelihood of vertebral subluxation or further damage to the spinal cord.
It is a known fact that signs of joint instabilities are less severe in
animals kept in a sedentary environment than those allowed unrestricted
exercise. Hopefully if this is discovered early and the diet is changed
while the bones are still forming and little recurrence of cord trauma
occurs, the remaining formation of bone will be normal and the condition
can stabilize itself to the point that surgery will not be needed. Surgery
for the slowly progressive form of cervical spondylopathy may not be as
rewarding as with the acute form, if it is discovered late since the damage
to the spinal cord may be permanent. It may however, prevent further damage
to the cord.
What can we do to prevent canine wobblers syndrome? My own observations
and present studies indicate a probable genetic factor that may predispose
certain lines or individuals to producing wobbler offspring. You as breeders
must strongly consider the use of these lines or individuals for breeding
purposes. You must answer to your own conscience and morals. The goal of
breeders and the purpose of breeding is to strive to ever better the breed
and those of you in breeding solely for the monetary gain must seriously
reconsider this motive!!!
One thing that we all must do is to refrain from that archaic urge
to supplement the excellent commercial foods available as the main cause
of growing bone disparities in the giant breeds is hypernutrition.. For
those of you who have found that one or two pups out of every litter or
every other litter have shown signs or have developed into wobblers, I
recommend that you do your very best to eliminate the environmental elements
that might encourage or enhance the pups' chances of developing into a
wobbler. This would entail feeding the entire litter the adult form of
the high quality food (22%-24% protein) starting at weaning time. Don't
use Iams puppy food or A.N.F. 30 for instance. The extra calcium and protein
in these foods could easily cause signs of the above. I would feed a multiple
vitamin and absolutely no additives. Perhaps a little canned food to increase
the palatability. Each litter must be treated individually. Don't equivocate
your litter to your friend's. Don't ignore the possibility that your dogs
might be more efficient in digesting foods and utilizing a higher percentage
of available nutrients than someone elses. This could give the same effect
of overfeeding without the addition of any supplements. Periodic radiographs
may be advantageous to early detection of wobbler development. Again it
is very important to put as little stress on the necks of these pups -
directions to be followed as previously described.
SUMMARY
There is no cut and dry answer or definition as to why or where this
disease entity originates - this is a fairly new area of veterinary science.
We are finding strong evidence suggestive to a genetic entity in this syndrome
and have found definite proof that nutrition plays a major role in the
development of wobblers and other bone disorders in the giant breeds. Again
this is due to our wanting only the best for our dogs and knowing that
the giant breeds need more nutrition than average dogs. Where we tend to
go wrong is in the belief that if a little more is good, than a lot more
must be better. Take an honest look at your own feeding program and look
for areas where you might be able to improve the lives of your dogs
