Though relatively uncommon, a brain tumor has always made a grim prognosis for any unfortunate animal that is diagnosed with one. Traditionally they were often assumed but seldom confirmed, but since MRI and CT scanning has become more mainstream they can be diagnosed correctly. Here we discuss the different types of brain tumor that affect dogs and cats, the clinical investigations that can be performed, the treatments available and the likely outcomes.
Brain tumors seem to be more common in dogs than cats, and certain breeds are over represented such as Boxers, Golden Retrievers, Dobermans, Scottish Terriers and Old English Sheepdogs.
Primary vs Secondary
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.
What causes a brain tumor?
The cause of brain tumors is not known. Diet, environment, chemical, genetic, viral, immunologic and trauma have all been considered. In cats with meningiomas, because they often occur in very young animals, a genetic element is suspected.
Benign vs Malignant
The terms benign and malignant must be used with care when referring to brain tumors. Normally these terms apply to various characteristics on a cellular level, but on a biological level, even benign brain tumors can kill the animal due to the secondary effects like increased intracranial pressure or cerebral edema. In short, any brain tumor can kill.
What are the symptoms?
There can be huge variety here. Many animals will present with vague signs, such as one or several of the following:
1.Loss of trained habits 2.Decreased levels of activity 3.Decreased frequency of purring in cats 4.Disorientation 5.Confusion
More specific symptoms are dependent upon where exactly the tumor is located within the brain, the size of the tumor and how quickly it is growing. As a tumor enlarges, symptoms tend to become more severe. These can include:
6.Seizures (often indicate a tumor in the cerebral cortex) 7.Facial paralysis (may indicate a brainstem tumor) 8.Tremors (may indicate a tumor in the cerebellum) 9.Wobbliness (may indicate a tumor in the cerebellum) 10.Full or partial blindness (may indicate tumor in hypothalamus or optic nerve) 11.Loss of smell (may indicate tumor of olfactory system)
The physical presence of the tumor can cause knock on effects due to inflammation and edema of the surrounding area. This can cause symptoms such as:
12.Changes in behaviour or temperament (irritability, lethargy) 13.Compulsive walking 14.Circling 15.Pressing head against a wall or hard surface
Animals can sometimes carry brain tumors for several years before presenting to a veterinary clinic, if the tumor is slow growing. In these cases the symptoms develop gradually, and the owner tends to get used to them so that by the time the animal is examined, the tumor has reached a considerable size.
How is a brain tumor diagnosed?
History and Clinical Examination
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.
Bloods
After that, 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.
Probable Outcome
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 expectancy.
With advances in veterinary medicine, more complex surgical procedures are being performed on our beloved pets. Thus, there is an increased need for blood bank programs to supply life-saving blood components. In the past, Veterinarians had to use their own dogs, dogs owned by their staff, or even dogs borrowed from their clients as blood donors in the absence of animal blood banks.
Animal blood banks depend solely on animal blood donors. Animal blood is specific to certain specie, dogs can receive dog blood only, and similarly, cats can only receive cat blood. Moreover, dogs have blood types just like humans. Among the eleven different blood groups of dogs, the most important one is the A1/A2 system. Canines with A negative blood types are considered universal donors.
Dogs rarely have isoantibodies against other blood types, so in most cases, it is practically safe to give a dog a blood transfusion without blood typing the donor and recipient or crossmatching prior to the transfusion. Despite this, it is still recommended that all recipients be crossmatched prior to receiving a blood transfusion (especially dogs which have received a previous blood transfusion).
There are two types of cross-matching tests: the major and minor cross matching. For major cross-matches, red cells from the donor are mixed with serum from the recipient. Then it is observed to see if there is a reaction; the recipient may attack donor cells and not accept them. If you have a major cross-match incompatibility you shouldn't do a transfusion, unless you're really desperate. In a minor cross-match test, the recipient's red cells are compared with the donor's serum. In minor incompatibilities, parts of the donor's blood can be given to the recipient but not the blood in its entirety.
A healthy animal with no history of metabolic or heart disease or seizures, has lean body weight (greater than 50 kg), and is 1-7 years of age is a potential donor. In addition, they should not be on any medication (except heartworm and parasite meds), have a good temperament, have been neutered and nulliparous, have jugular veins that are easily visualized and palpated and should have constant vaccinations. The Greyhounds are ideal blood donors due to their amenable disposition and high PCV.
As with human donors, screening is done to the animal donor's blood for metabolic and infectious diseases after blood type determination. The following labs are done: CBC, biochemical profile, U/A, fecal exam, von Willebrand's factor, and testing for Dirofilaria immiti, Ehrlichia canis, Babesia canis, B. gibsoni, Brucella canis (in intact or previously bred dogs), and Bartonella.
There is no preparation before going to the donation center and no fasting is required. Donor dogs are not sedated and the donation itself takes less than half an hour. The dog is welcomed in and lifted onto a table. Blood is taken from the jugular vein, which is a large vein in the neck. A small patch of hair on the neck is shaved to expose the skin right over the vein. The area is then swabbed with alcohol and a needle is inserted into the vein. Blood goes into the needle, through a tube, and then into the collection bag. After the blood is collected, pressure is applied to stop any bleeding and the donor is then lifted off the table. There might be a mild bruising at the site.
Water and food are offered to replace nutrients. The dog's system starts to replace the blood immediately after the donation. Blood volume will then be back to normal in a day and the red blood cell count in 2 to 3 weeks. Strenuous activity should be discouraged for the next 24 hours after donating, just as it is with human blood donors. Also similar to human donors, there must be a waiting period of at least two months before blood can be collected again.
Dogs are compensated as soon as they have made their donation. In addition to hugs and belly rubs, they're rewarded with gifts and treats that vary from program to program. After the first donation, a dog often gets a tag, which identifies him or her as a blood donor. Edible rewards might include dog biscuits and bottled water, a jar of baby food, or a can of dog food. Some donors may even get brand new toys. At some blood banks, dogs go home wearing cool donor bandanas. In a number of programs, they also receive a large bag of dog food with each donation. This is obviously a great benefit for their owners as well.
Blood banks collect blood from a donor and then separate the blood into components - either red blood cells, platelets or plasma. Red cells are given to a recipient that may be anemic due to trauma or due to a treatable disease. Plasma is used to build up blood volume when the animal is not making enough or is losing too much protein. Platelet-rich plasma is for those recipients whose platelets are depleted or dysfunctional.
Now, there several animal blood banks that supply blood products to Veterinary hospitals. Fortunately, dog owners have a positive response to the plea for blood donations. Every year, the animal blood bank processes roughly 2,000 units of blood donated by dogs. The donated blood is then brought in to the bank at the Veterinary hospital and to the bank's bloodmobile, which visits Veterinary clinics and kennel clubs.
Other regional blood banks depend entirely on the generosity of caring people who enroll their dogs in canine blood donor programs and take them to scheduled appointments to donate. Canine blood banks hold drives to find new volunteer donors, just like the Red Cross and other health organizations do to encourage human blood donations.
If you would you like your pet to be a life-saver of other pets, and that they fit the requirements to be a volunteer donor, check out the where regional blood banks for dogs and cats or the list of Veterinary Hospitals and University Veterinary Medical Centers are located and contact the one nearest you. You can also inquire about animal blood donor programs during your next visit to the veterinarian.
Both Matthew Homfray & John Bear are contributors for EditorialToday. The above articles have been edited for relevancy and timeliness. All write-ups, reviews, tips and guides published by EditorialToday.com and its partners or affiliates are for informational purposes only. They should not be used for any legal or any other type of advice. We do not endorse any author, contributor, writer or article posted by our team.
Matthew Homfray has sinced written about articles on various topics from Pets, Cats and Thanksgiving. Dr Matthew Homfray is one of the veterinary pet experts at . Our dedicated community of caring pet experts are waiting to offer you advice, se. Matthew Homfray's top article generates over 12100 views. to your Favourites.
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