DEGENERATIVE DISC DISEASE
What is a disc, and what is its
cord is one of the most important and sensitive organs in the body.
If it is damaged, the nerve cells do not regenerate but are replaced
with fibrous or scar tissue. Spinal cord injuries usually result in
permanent damage. Therefore, the spinal cord is protected in a very
special fashion. It goes through a bony canal within the spine and
is surrounded by protective bone everywhere except the junction of
two vertebrae. These junctions are filled by rubber-like cushions
called intervertebral discs. They allow the back to move up
and down and sideways without allowing contact between the bones of
the spinal column. This extreme protection of the spinal cord
reflects its importance and fragility.
What does it
mean for a disc to rupture, and how does it happen?
The disc is
composed of two parts. The outer covering is much like a thick
shell. It is comprised of tough fibers that protect and contain the
central part. The disc is thinnest at the top. This thin area is
located just below the spinal cord. The central part of the disc is
much softer than the outer part and has the consistency of thick
outer shell degenerates, it allows the central part of the disc to
escape. This is called a disc rupture or a "slipped" disc. Since the
disc is thinnest near the spinal cord, disc material that escapes
through the tear usually goes upward, putting pressure on the spinal
cord. Because the spinal cord is encased within its bony canal, it
cannot move away from the pressure and it becomes “pinched”.
disc disease causes spontaneous degeneration of the outer part of
the disc, resulting in disc rupture. It may not be related to
injury, although trauma is a common cause. It is also not related to
age. Most dogs with degenerative disc disease are 3-7 years old. It
is a sudden event most likely due to genetic factors. Certain
breeds, especially the Dachshund, Poodle, Pekinese, Lhaso Apso,
German Shepherd, Doberman and Cocker Spaniel have a high incidence
of disc disease.
report that a disc rupture occurred following some kind of traumatic
event, such as a relatively small jump or fall. Although this act is
frequently blamed for the disc rupture, the injury actually occurred
due to chronic disc degeneration.
How does a
slipped disc affect the spinal cord?
cord is like a telephone cable carrying thousands of tiny wires.
When it is crushed, transmission of information through the wires is
slowed or stopped. When the disc degenerates and ruptures, a similar
event in the spinal cord occurs. The central part is forced upward,
putting pressure on the spinal cord and the nerves that leave the
spinal cord over the discs (i.e. spinal nerves). Pressure on the
spinal nerves results in pain. Pressure on the spinal cord results
in pain and/or loss of information transmission causing partial or
ruptures occur in the middle to lower part of the back. However,
they may also occur in the neck. Back injuries often cause paralysis
without severe pain while neck injuries usually cause severe pain
without paralysis. If paralysis affects all four legs, the disc
rupture must be in the neck. Due to the way nerve tracts are
arranged in the spinal cord, disc ruptures in the neck may affect
the rear legs first and may not involve the front limbs.
How fast do
discs degenerate and rupture?
degeneration usually occurs relatively slowly, usually over several
days or weeks. The dog often experiences pain and becomes reluctant
to move. It may lie around for a few days allowing the body to try
to heal the injury, often without the owner being aware that a
problem existed. However, discs may also rupture very acutely. Some
dogs will go from normal walking to total paralysis in less than one
How is a
slipped disc diagnosed?
presumptive diagnosis of disc disease is made based on the dog's
history of neck or back pain, uncoordinated walking, or paralysis
when there is no history of trauma. The physical examination will
indicate that the problem originates from the spinal cord, giving
further evidence to disc disease. Another important factor is the
breed. If the dog is one of the high incidence breeds, the diagnosis
is even more likely.
cases, plain radiographs (x-rays) may assist the diagnosis, but they
may also be normal since neither the disc nor the spinal cord is
visible on an x-ray. If the diagnosis is in doubt or if surgery is
to be performed, a myelogram may be done. This procedure
involves injecting a special dye around the spinal cord while the
dog is anesthetized. When radiographs are taken, the dye will be
seen outlining the spinal cord. A break in the dye column means that
there is pressure on the spinal cord at that point.
How do you
know if the pressure on the spinal cord is due to a disc or
possible that the pressure is due to a blood clot or tumor. Both are
possible but rare, especially when compared to disc ruptures. If the
patient is a high-risk breed and there has been a sudden onset
without trauma, there is an approximately 95% chance that a disc
rupture is causing the clinical signs. However, the diagnosis is not
definite until the time of surgery.
Are all disc
ruptures treated with surgery?
necessarily. Treatment is based on the stage of the disease.
Stage I disc disease produces mild pain and is usually
self-correcting in a few days. Stage II disc disease causes
moderate to severe pain in the neck or lumbar (lower back) area.
Stage III disc disease causes partial paralysis (paresis) and
results in the dog walking in staggering or uncoordinated movements.
Stage IV disc disease causes paralysis but the ability to
feel is present. Stage V disc disease causes paralysis and
loss of feeling. These stages tend to overlap in some dogs, and dogs
may move from one stage to another over a period of hours to days.
Stage II and III disease are usually treated with anti-inflammatory
drugs, pain relievers, and restriction from exercise. Surgery may be
considered if the pain or lack of coordinated movements persists
after 4-7 days of treatment or if the neurological status declines
from one day to the next. The time of confinement will vary based on
each patient’s condition.
Stage IV disease should have surgery, although a small percentage
will recover without it. Dogs with Stage V disease should have
surgery immediately. The sooner that surgery is done, the better the
prognosis. Ideally, these dogs should be operated on within the
first 24 hours of the onset of paralysis.
What is the
purpose of surgery?
The goal of
surgery is to remove pressure from the spinal cord. If the disc
rupture occurs in the lower back, a window is made in the side of
the vertebral bone to expose the spinal cord. This window allows
removal of disc material and relieves pressure from the cord. If the
disc rupture occurs in the neck, a window is made in the bone
exposing the spinal cord. This may be done either from the top or
the bottom, depending on the situation and the veterinarian’s
What is the
success rate for treating disc disease with and without surgery?
Surgery Recovery with Surgery
I: up to
to 3 days <
3 days <
V: up to
24 hours <
24 hours <
When will we
know if the surgery is successful?
Unfortunately, success cannot be determined immediately. The return
of neurological function, walking ability and relief from pain may
not occur for several days to weeks after surgery.
When can my
dog go home?
surgery, your dog will be hospitalized for several days. Bladder and
bowel control are often lost when the dog is paralyzed. Once control
of these functions has returned, we will begin discussing discharge
from the hospital. It is generally better not to extend
hospitalization beyond seven days because regaining the ability to
walk partly depends on exercise and motivation. Since motivation is
such an important part of the recovery process, visitation is often
encouraged starting a few days after surgery. Your veterinarian will
discuss visitation with you.
was present before surgery, your dog may not be able to walk when it
is discharged from the hospital. You will be given detailed
instructions on the procedures that should be performed. Recovery is
dependent on four factors: whether or not permanent damage was done
before surgery, if the surgery relieved the pressure quickly enough,
physical therapy performed at home, and the motivation of your dog.
Can my dog
slip a disc again?
is "yes". However, more than 95% of degenerated discs will heal
without surgery. So the chance of your dog requiring a second
surgery is less than 5%.
What if the
myelogram is normal?
of the myelogram is to identify pressure on the spinal cord. If the
myelogram is normal, there is no pressure on the spinal cord. This
has several important implications. First, it means that surgery
will generally not be appropriate. Second, it means that one of the
following conditions is likely to exist.
This is a
temporary loss of spinal function that is generally associated with
trauma. It occurs suddenly and is somewhat like a concussion of the
brain. It may leave permanent damage or full recovery may occur.
Recovery from spinal shock generally occurs within a few hours to a
condition, a small amount of disc material ruptures and gets into
one of the blood vessels leading to the spinal cord. As the vessel
narrows, the disc material obstructs it, depriving a certain segment
of the spinal cord of its blood supply. Without proper blood supply,
that segment of the spinal cord dies, resulting in paralysis.
Surgery will not help these dogs because there is no pressure on the
spinal cord. Often, paralysis involves only one rear leg, or one
rear leg is more severely affected than the other. Complete recovery
may occur in a few days to weeks, or there may be permanent damage
to a portion of the spinal cord. Diagnosis of fibrocartilaginous
embolism is based on the correct clinical signs and a normal
myelogram. Definitive diagnosis can only be made after death by
performing a spinal cord biopsy.
This is a
condition where the spinal cord is slowly dying. It results in
progressive paralysis that begins with the dog dragging its rear
feet as it walks. This is called "knuckling over" and results in the
toenails of the rear feet being worn because they drag the ground
with each step. It progresses to weakness of the rear legs, then
paralysis. It generally takes several weeks before paralysis occurs,
and generally occurs in large breeds of dogs, especially German
Shepherd dogs. It is often referred to as “German Shepherd Dog
Disease” or “Alsatian Disease”. There is no treatment and ultimately
causes loss of urine and bowel control.
degenerative myelopathy is based on clinical signs, breed and a
normal myelogram. Confirmation requires a biopsy of the spinal cord
at time of death.
A normal myelogram in a dog with slowly progressive paralysis is
very frustrating because the two most likely diseases,
Fibrocartilaginous Embolism and Degenerative Myelopathy, cannot be
confirmed without an autopsy.