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Epidermal Inclusion Cyst
Issue Description
The sinus is caused in the embryonic stage of
development. In normal development, the neural tube from which the
spine develops separates from the skin. In the case of a dermoid
sinus, this separation has not fully taken place. The result is that
in some cases, the dermoid sinus remains connected to the animal's
spinal cord; in other cases, the sinus terminates in a "blind sac"
that is less dangerous to remove.
Other Names
Dermoid Sinus, DS, Dermoid Cyst, Dermoid
Inclusion Cyst, African Cyst, Hair Cyst, Trichiasia
Spiralis
Causes
The dermoid sinus gene is believed by some to
be recessive, meaning that the animal must receive one defective gene
from each parent in order to develop the condition. Where one parent
carries the gene and the other does not, the offspring remain carriers
and can continue to pass the defective gene on to their offspring in
turn. Others believe that the dermoid sinus condition is more
appropriately characterized as polygenic, involving multiple genes. In
any case, because of the genetic nature of this potentially dangerous
condition, most breeders and veterinarians advise against breeding
animals that have a dermoid sinus, or have a parent that is known to
carry the gene.
Breeds Known To Be Affected
Rhodesian Ridgeback
Thai Ridgeback - in which it is hereditary
Kerry Blue Terriers
Shih Tzus
Boxers
Symptoms
It can appear as single or multiple lumps on
the dorsal midline. The D.S. is generally found on the midline of the
neck, back, and tail along the spinal column. Although rarely found in
the ridge there have been several cases noted. Dermoid sinuses have
also been noted on ridgeless puppies.
Diagnosis
To find the D.S. you must palpate along the
midline of the spine, starting at the top of the head close to the
occiput (bump) bone. To do this you may pick the pup up and hold it in
the cup of your hand or palpate as the pup is sleeping. Take the other
hand and envision yourself picking up a baby kitten by the scruff of
the neck with your thumb and forefinger. Exert enough pressure to
feel, but not enough to bruise. Use your whole hand as one unit,
pulling first up toward the nose and then down toward the tail. The
skin will stretch quite a bit in both directions. Do not roll the skin
through your fingers. The fingers remain exactly where you placed them
on the skin. The D.S., being attached on the top to the skin and at
the base to the spinal cartilage, will slip through your fingers. A
large D.S. will feel like a wet noodle and a finer D.S., like a small
string. Reposition your fingers on the neck just below the starting
spot and repeat this process. Continue to work your way down the neck
and back to the tail.
At the tail it is very difficult to
raise enough skin to palpate effectively. It is best to use your thumb
in this area. With fingers underneath the pup supporting it, place the
flat of your thumb over the spinal column at the pelvic area. Push
skin first to one side and then back to the other side. Again,
remember that the D.S. is attached and will slip under your thumb.
This will feel like a squiggly noodle on a larger, longer D.S., or
just an area that simply will not move at all on a shorter D.S. If you
do not feel anything by sliding the skin from side to side, try
sliding the skin toward the nose and then back to the tail, taking
care to slide the skin, not your thumb.
As you palpate the
area over the shoulders, you may feel connective tissue that holds the
skin to the shoulder area. The tissue is heavier in this area than in
the other areas of the spinal column. It will feel flat and you will
not be able to trace it from the area close to the muscle all the way
to the skin, whereas the D.S. is easily traced from the muscle to the
top of the skin and feels round.
The D.S. can be visually
detected by looking for a group of hairs that protrude straight up out
of the hair coat of the pup. When you see this, the pup should be
palpated for a D.S. The hair can also be shaved at this site and upon
examination, a small dimple will be revealed. By moving the skin back
and forth, the dimple will become more apparent as the anchor of the
D.S. will pull the skin down more.
Treatment
The D.S. can be surgically removed. It is
advised that a vet be contacted that is familiar with this condition
and has performed this operation before. Dermoid sinuses are not alike
in their makeup and it is impossible to tell which ones are easily
removed or which ones go to the spine. They can wrap around or enter
the area of the spinal cord, which makes them almost, if not
impossible, to remove. In cases such as this some success has been
achieved by folding the D.S. over and tying it off, but some have had
regrowth. Since there is no way to detect which type of D.S. that the
pup has, instructions to the vet should include that if the D.S. is
not completely removable, the pup be put to sleep. D.S. pups should
not be promised to a new home until after the surgery.
The
healing process can be as traumatic as the operation itself. In the
simple cases that remove easily, there will be little or no serum
build-up in the surgical area. In the more complicated surgeries,
where the tissue damage has been more severe, the serum will start
building up as soon as the surgical site heals over on the top of the
skin. Usually this will be on the fourth or fifth day. This requires
aspiration with a large guage needle and syringe, sometimes three or
four times daily, to remove the serum build-up. This can last for
three to 10 days after surgery.
Pups that have had surgery
must be removed from the litter to prevent damage to the surgical
site. As puppies play, they grab and shake areas of skin on the other
pups. If they were to grab and shake over or near the surgical site,
damage would occur and the serum buildup would become a bigger
problem.
Dermoid sinuses have been detected on other parts
of the body, but are not as commonly seen as on the midline of the
spine. A few have been noted on the head, attaching to the skull or
the base of the ear. Another area of note is on the neck under the ear
or on the front of the neck. Sometimes these can be dermoid sinuses
and sometimes they are skin tabs.
Post Surgery
Limit your dog's activity. While your dog is
recovering from surgery, activity should be limited. Keep him indoors
except for bathroom breaks. While your dog is outside, leash him to
avoid excess activity.
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