CANINE INTERVERTEBRAL DISK DISEASE
by Leslie Manis , Health/Genetics Chairman, ASTC
(Originally published in The Barks, 2003)
[Every effort has been made to ensure accuracy of information. However,
this is not a substitute for prompt veterinary care. Any similarity
to other publications is unintentional. Published online at Sealyhealthguard.org,
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Intervertebral disk disease (or IVD for short) is the degeneration
or rupture of one or more disks (rubber-like cushions)
between the vertebrae. Several breeds are prone to IVD.
They are called chondrodystrophic (meaning faulty development or
nutrition of the cartilage) due to the shape of their bones from
breeding. These include the Dachshund, Welsh Corgi, Lhasa Apso,
Cocker Spaniel, Bulldog, Beagle and Pekinese. Some of these breeds
have disproportionately short and angulated limbs.
Back problems are said to have been a minor problem in the past
for some lines of Sealyhams, but less so today. According to our
last health survey, out of 30 respondents (which included all previous
Sealys owned), six Sealys had calcified disks, one had a herniated
disk and two had a slipped disk.
COMPOSITION OF THE DISKS
The spinal cord goes through a bony canal
within the vertebrae. The disks between the vertebrae
allow the back to move up, down and sideways without
allowing any contact between the vertebrae. The disk is composed
of two parts: the outer covering is a thick shell consisting of
tough fibers that protect and contain the central part, and the
central part has the consistency of thick toothpaste. The disk is
thinnest at the top.
DEGENERATION CAN CAUSE PARALYSIS
Degenerative disk disease causes
spontaneous degeneration of the outer part of the disk, resulting
in escape of the central part. This is called a ruptured disk. Since
the shell is thinnest near the spinal cord, disk material that escapes
almost always goes upward, putting pressure on the cord. Because
the spinal cord is encased within the vertebrae, it cannot move
away from the pressure and becomes pinched. Pressure on the spinal
nerves results in pain; pressure on the spinal cord results in pain
and/or full or partial paralysis.
TRAUMA SOMETIMES BLAMED
It is not related to injury, although trauma
can cause disks to rupture. Many owners report that a disk rupture
occurred following some traumatic event, such as a relatively small
jump or fall. Although this act is frequently blamed for the disk
rupture, if the disk had not already been degenerating, the rupture
would not have occurred. Most dogs with degenerative disk disease
are 3-7 years old. It is most likely controlled by genetic factors.
Biochemical differences between chondrodystrophoid and non-chondrodystrophoid
disks are apparent shortly after birth and explain the differences
in the types of degeneration that occur. In the former, degeneration
takes place rapidly and begins as early as six month of age.
A dramatic and rapid increase in collagen content is seen between
6 and 12 months of age. Total glucosaminoglycan content with be
30 to 50 percent lower than age-matched nonchondrodystrophoid dogs
within the first 3 years, resulting in a great loss of water content
in the inner part of the disk. It no longer acts as an efficient
shock absorber. Eventually the hyaline cartilage which forms calcifies
leading to almost complete loss of elasticity.
TYPE I AND TYPE II HERNIATIONS
Disk herniations are classified as
Type I, in which there is a large tear allowing a large quality
of the inner paste-like material to escape, and Type II, in which
there are several small tears gradually over time, resulting in
bulges with only occasional escapes of inner material. Normally,
the previously mentioned breeds get the Type I IVD, and larger dogs
get the Type II starting at about 5 years of age. The classifications
do not always apply in every case.
DAMAGE TO THE NERVOUS SYSTEM
When a disk herniates, it causes damage
to the nervous system in several ways. The spinal cord and/or nerves
can be compressed. Blood supply can be compromised, causing a decrease
in oxygen and glucose supply. Vascular compromise can lead to the
release of destructive chemicals from the blood of the by-products
of nervous tissue breakdown. If this chain reaction cannot be stopped
in time, nervous tissue will liquefy, an irreversible state called
myelomalacia. There can be secondary damage if the dog's body mounts
an immune response against the presence of disk material in an abnormal
Most disk ruptures occur in the middle to lower part of
the back often near the junction of the last few thoracic vertebrae
and the first few lumbar vertebrae. Symptoms vary from mild to severe,
depending on type, which vertebrae are involved and how long the
problem has been present. They include crying, poor appetite, muscle
spasms, reluctance to move, lameness, incoordination, paralysis,
tense abdomen, hunched appearance, and incontinence.
AGGRESSIVE, PROMPT ATTENTION REQUIRED
Aggressive, prompt medical
therapy is recommended in any form of spinal cord trauma. Diagnosis
is made using symptoms, exam, x-rays and sometimes a myelogram,
in which a special dye is injected around the spinal cord while
a dog is sedated. When an x-ray is then taken, a break in the dye
column means there is pressure on the spinal cord. If a myelogram
is inconclusive, an MRI can provide valuable information. X-rays
can determine if a dog's pain or paralysis is due to IVD or another
cause, such as trauma tumors, cysts, or infections of the vertebrae.
Dogs with IVD might have calcified disks, collapsed disks, even
calcified disk material in the spinal canal.
TESTS TO DETERMINE IVD
During the exam the veterinarian may perform
one or more of the following tests: he may check some reflexes to
help localize the problem and verify that the problem is IVD. Panniculus
is a test in which the skin is poked gently with a needle, to see
if the muscles beneath that area "crawl" to identify the
affected nerve root. It will usually be 1-2 vertebrae in front of
the spot where the skin crawls.
Proprioceptive reflex is a postural reflex that tests the ability
of a dog to recognize the placement of one of its limbs (i.e. the
foot is placed so it is bearing weight on the wrong surface - the
knuckle rather than the pad) without actually seeing it. The dog
should return its foot to a normal position immediately. Other diseases,
like a broken leg, can cause this problem.
The knee jerk reflex tests the ability of the spinal cord to react
to the stretching of the patellar tendon. If absent or diminished,
it indicates a potential problem with the nerve root. If exaggerated,
it indicates a potential problem with the spinal cord. Tendons other
than the knee can be checked for this reflex. In deep pain (withdrawal)
reflex, when a toe is pinched, the dog will withdraw its limb away
from the painful stimulus. It occurs independent of whether or not
the pain is perceived at the brain level. A dog with a problem in
its spinal cord will have the reflex, but will not realize it is
painful because the nerves that travel along the spinal cord to
the brain are injured. Dogs that show no reaction are considered
to have severe spinal cord injury and have poor prognosis for recovery.
This is a subjective test though, and needs to be performed numerous
times for proper interpretation. Some dogs don't consciously shows
signs of pain, so this critical test can be misinterpreted.
Treatment depends upon the severity and type of the problem.
In many cases, if caught early, conservative therapy can be beneficial.
Total cage rest is the most important treatment short
of surgery. Crate confinement may be recommended for several weeks
for an adequate outcome. The dog must be monitored carefully in
case its condition worsens.
MEDICATIONS CAN CONTROL IT
Anti-inflammatory and analgesic medications
are used routinely in Type I disease to minimize pain and inflammation.
Strict cage rest is imperative for a dog on this medication to prevent
more damage due to the dog resuming normal activity. Corticosteroids
are the first line of attack in handling any acute spinal
The currently preferred corticosteroid is methylprednisolone sodium
succinate. It has far better sparing effects on the spinal cord
while causing fewer side effects. In severe cases, hyperomolar agents
such as mannitol or glucose can be useful in reducing some of the
spinal cord swelling. Muscle relaxants can be used to minimize spasms
that accompany back problems. The goal is to give just enough pain
medication to make the dog more comfortable, yet not so much that
it resumes its normal activity.
WHEN DRUGS ARE NOT ENOUGH
Surgery is the treatment of choice for
recurring problems, dogs that have not improved with conservative
therapy, or those that have neurologic deficits. Dogs that are paralyzed
in the back legs need immediate surgery to relieve pressure on the
spinal cord. This is one by removing a piece of the vertebral body
or cleaning out the disk material that is putting pressure on the
cord. Post-operative care is important and may involve hydrotherapy,
manual expression of their bladders and controlled walking with
assistance (using a towel as a sling beneath the dog), massaging
the affected limbs and later "bicycling" the limbs to
encourage muscular resistance.
ACUPUNCTURE OR VOM WHEN ALL ELSE FAILS
Acupuncture is a relatively
new treatment. It can be helpful in dogs that are not paralyzed
or in those where anesthesia or surgery are contraindicated. It
is important to remember that it does not always work and the prolongation
should not be undertaken due to the severe and potentially irreversible
nature of this disease.
VOM, or veterinary orthopedic manipulation, is a relatively new
treatment method in which a spinal accelerometer fires a very fast
and concise force to subluxated vertebrae, in 4 milliseconds. It
cannot be used in dogs that are paralyzed.
CATCH IT EARLY
IVD is a serious and potentially crippling disease.
If caught early, the outcome is usually satisfactory. Care should
be taken with a short-legged breed such as the Sealy to avoid excessive
stress to the back, such as repeated jumping off the couch and always
be alert to any problems. But I would like to repeat what I said
at the beginning: this has occasionally been a problem In Sealyhams,
but less so today than in the past.
Sources: AKC Gazette "Surviving Spinal Cord Injuries",
Christine Wilford, DVM