Issue Description A brain tumor is an abnormal growth of cells
within the brain or inside the skull, which can be cancerous or
non-cancerous (benign). Other Names Brain Tumors, Canine Brain Cancer, Brain Cancer
Causes Brain tumors can be primary or secondary
(metastasis from other sites). Primary brain tumors are usually
solitary, the most common ones in the dog being gliomas and
meningiomas. In cats, the most common type are meningiomas and these
can occur at multiple locations.
Secondary tumors in dogs
include extension of a nasal tumor, metastases from breast, lung or
prostate cancer, hemangiosarcoma or extension of a pituitary gland
tumor. Nerve sheath tumors and skull tumors have also been reported.
Secondary tumors in cats include pituitary gland tumors, metastatic
carcinomas, local extension of nasal tumors, skull tumors and middle
ear cavity tumors.
Symptoms Symptoms of brain tumors will depend on the
size of the tumor and its location. Signs may range from moderate to
severe. The best thing to do is to report any change of behavior to
your veterinarian. A neurological examination, and possibly an MRI
might help discover the cause.
Here are common changes you may notice:
Gait - In general, you might notice that your dog's legs seem
weaker. He may find it hard to jump on the couch or climb a flight of
stairs. He may run more slowly, stumble or walk as though he was
drunk. You may notice a shake or quiver in his limbs, and they may
sometimes give out from under him.
Personality - His personality may change, perhaps becoming
aggressive, perhaps becoming docile or puppy like. He may become less
affectionate or develop obsessive behaviors, like barking or a
compulsion to eat.
Mental ability - He may forget commands, or not recognize familiar
people. He might forget to how find his way around the house or yard.
A dog with a brain tumor can become lost in a corner, or under a
coffee table, and can't find their way back out. Your dog may also
seem "dazed and confused" or "out of it". Maybe for just a moment, but
possibly for longer periods of time.
Housebreaking accidents - A dog with a brain tumor will probably
have a harder and harder time maintaining his house training, even if
he was formerly reliable. Try not to get mad or punish him. In
contrast to the mischief of his younger days, this time he really
can't help it. You might notice that he can't hold his bladder as
long, or he might forget how to go out. For suggestions on how to
cope, please see our section on potty management for sick dogs.
Appetite - You dog may lose his desire to eat. On the other hand,
he may become ravenous. The seizure medications and steroids your dog
receives can also make him feel hungrier. See our feeding suggestions
for dogs with brain cancer for ways to help keep him feeling full.
Senses - Some dogs lose their sight, or their hearing or even
their sense of smell. If sight is affected, your dog may bump into
things, or become frightened if removed from a familiar environment.
Dogs with hearing loss may not react to noises around them, or hear
you when you call.
Seizures - This might be your first clue that something is
seriously wrong. Seizures generally become worse as the tumor gets
larger. Cluster seizures (several seizures one after another in a
short period of time) may develop. A dog cannot breathe during a
seizure and the brain does not get oxygen until the seizure stops. A
grand mal seizure that continues more than three or four minutes can
cause brain damage, or even death. That's why it is important that a
dog who has seizures be placed immediately under a veterinarian's
care. Your veterinarian can prescribe medication that can help to
control the seizures, at least for a time. Seizures become more and
more difficult to control as the disease progresses.
Pain - Your dog may whine, whimper or even yipe without apparent
reason. He may shake or scratch his head or rub it against objects. He
may seem restless, or have trouble sleeping. He might give up his soft
bed so that he can rest his head on the solid, secure floor. If your
pet appears to be hurting, tell your veterinarian.
Difficult breathing - This is an important sign if it happens
while your dog is sleeping. His breathing may stop and start, or his
breathing may seem labored. His rib cage might rise and fall like an
old accordian. This means that the tumor is putting pressure on the
mid-brain, affecting the involuntary breathing reflexes.
Diagnosis The first step for a veterinarian is to take a
thorough history of all of the clinical signs, and when they
developed. This is followed by a full general clinical examination and
a full neurological examination.
Blood - Blood should be taken for routine haematology and
biochemistry profiles. This is to look for any disease outside the
brain. Results will be normal for brain tumors, with the possible
exception of some pituitary gland tumors.
Radiography - Plain skull radiographs (xrays) under general
anesthetic have little value in detecting a brain tumor, but they can
be useful if there is a tumor in the nasal cavities or the middle ear
which could extend into the skull. On rare occasions, they can
identify bony changes in the skull which can accompany a brain tumor,
or mineralization within the tumor itself. Radiographs and ultrasound
of the chest and abdomen are useful to look for a tumor elsewhere in
the body, in cases where the brain tumor is a secondary metastasis.
MRI and CT Scans - Confirmation of a brain tumor can is usually
only achieved using the advanced imaging techniques, CT scans or MRI.
Both of these have pros and cons when compared to one another. CT is
better for bony changes, while MRI is better for soft tissue
definition, for the detection of many of the knock on effects of brain
tumors such as edema, cysts and bleeding. MRI is the preferred option
for diagnosing primary brain tumors.
Biopsy - This is the only way to definitively diagnose a brain
tumor. The advanced imaging techniques above offer much information,
but they can occasionally confuse a tumor with a non cancerous mass or
a cyst, and they also do not tell us the exact type of tumor present,
and therefore the appropriate treatment and prognosis. The best type
of biopsy is the CT guided stereotactic brain biopsy system, which is
rapid, accurate and quite safe.
Since exploratory surgery is high risk, it is not usually
attempted unless there is a reasonable chance of removing the whole
tumor with minimal collateral damage. Many brain tumors in cats and
dogs are not categorized on a cellular level until post mortem.
Cerebrospinal Fluid (CSF) Analysis - CSF analysis is useful for
ruling out inflammatory causes of the symptoms, but tumor cells are
rarely identified here. Increased levels of white blood cells and
increased protein levels may be present in the CSF with many brain
tumors, though this is not diagnostic. This test can be high risk when
intracranial pressure is increased, as brain herniation can occur.
Treatment Treatment is aimed at being either curative or
palliative. Curative treatment eradicates the tumor or reduces its
size, whilst palliative therapy reduces the surrounding cerebral edema
and slows down the growth of the tumor. Palliative therapy also
involves administering antiepileptic drugs, if seizures are occurring
as a result of the tumor.
Surgery - Whether this is an option depends on the general health
of the animal, and the precise location, size, extent, invasiveness
and nature of the tumor. Tumors such as meningiomas in cats can be
removed successfully by surgery. However, surgery to remove tumors in
certain locations such as the brainstem can be extremely dangerous,
possibly resulting in death. Even partial removal can benefit the
animal though, particularly if the tumor is slow growing.
Radiotherapy - This is probably the most widely used form of
treatment for brain tumors. Radiation therapy can be used alone or in
combination with other treatments. It is also useful in the treatment
of secondary brain tumors. The aim is to destroy the tumor without
harming the normal tissue too much.
Chemotherapy - The main problem with chemotherapy for brain tumors
is that many drugs do not cross the blood brain barrier. In addition,
the tumor may only be sensitive to high doses, doses which are toxic
to normal brain tissue and therefore unsuitable for use. However,
several drugs have been used for this purpose that can cross the blood
brain barrier with reported success, including cytosine arabinoside,
lomustine and carmustine.
Prognosis Studies of animals that receive palliative
treatment (corticosteroids) for brain tumors show a survival range
post diagnosis of 64 to 307 days. This demonstrates the inability to
accurately predict life expectancy in these cases. What is certain is
that the survival times significantly increase with surgery,
radiotherapy or chemotherapy. Radiation therapy seems to offer the
best results, alone or in combination with other treatments.
Generally, the more severe the symptoms, the shorter the life