This is the first in a series
of articles that will discuss specific disease entities of bone caused, in
part, by improper or over nutrition. Some of the information to be presented
in this and future articles will have been discussed previously but will
be put into specific consideration to the disease entity covered. It is my
desire to provide an understanding of the total picture of proper nutrition
and a well balanced and strong skeleton upon which these modern day giants
are to support their massive bodies. If the foundation of any structure is
weak, then the weight which is born by it will cause this foundation to break
and fall.
The principal breed affected with Wobbler's Syndrome is the Great Dane.
Cervical Spondylopathy or Canine Wobblers Syndrome as the lay person knows
it, consists of any in coordination or lameness caused by pressure on the
spinal cord as it travels through the neck (at any age for any reason).
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 through 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 over nutrition
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 over nutrition or ad-lib feeding. Hedhammer et all
(1974) studied the relation between over nutrition 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 hyper nutrition.. 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 else's. 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.
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