Though relatively uncommon, a brain tumor has always made a grim diagnosis for unfortunate animal that is diagnosed with one. Traditionally they were often assumed but seldom confirmed, but since Mri and Ct scanning has come to be more mainstream they can be diagnosed correctly. Here we discuss the different types of brain tumor that influence 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 confident breeds are over represented such as Boxers, Golden Retrievers, Dobermans, Scottish Terriers and Old English Sheepdogs.
Brain Cancer Stages
Primary vs Secondary
Brain tumors can be primary or secondary (metastasis from other sites). primary brain tumors are normally 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 many locations.
Secondary tumors in dogs include prolongation of a nasal tumor, metastases from breast, lung or prostate cancer, hemangiosarcoma or prolongation 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 prolongation 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 varied 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 collection here. Many animals will present with vague signs, such as one or some of the following:
1. Loss of trained habits
2. Decreased levels of activity
3. Decreased frequency of purring in cats
5. Blurring More specific symptoms are dependent upon where exactly the tumor is settled within the brain, the size of the tumor and how speedily it is growing. As a tumor enlarges, symptoms tend to come to be more severe. These can include:
6. Seizures (often indicate a tumor in the cerebral cortex)
7. Facial dullness (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 corporal nearnessy 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
15. Pressing head against a wall or hard surface
Animals can sometimes carry brain tumors for some years before presenting to a veterinary clinic, if the tumor is slow growing. In these cases the symptoms compose gradually, and the owner tends to get used to them so that by the time the animal is examined, the tumor has reached a important size.
How is a brain tumor diagnosed?
History and Clinical Examination
The first step for a veterinarian is to take a accepted history of all of the clinical signs, and when they developed. This is followed by a full normal clinical test and a full neurological examination.
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 potential exception of some pituitary gland tumors.
Plain skull radiographs (xrays) under normal 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 expand into the skull. On rare occasions, they can recognize 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 normally only achieved using the industrialized imaging techniques, Ct scans or Mri. Both of these have pros and cons when compared to one another. Ct is best for bony changes, while Mri is best 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 favorite option for diagnosing primary brain tumors.
This is the only way to definitively diagnose a brain tumor. The industrialized 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 accepted rehabilitation and prognosis. The best type of biopsy is the Ct guided stereotactic brain biopsy system, which is rapid, literal, and quite safe. Since exploratory surgical operation is high risk, it is not normally attempted unless there is a inexpensive opportunity 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 diagnosis 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 is aimed at being either healing or palliative. healing rehabilitation 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 effect of the tumor.
Whether this is an option depends on the normal health of the animal, and the literal, location, size, extent, invasiveness and nature of the tumor. Tumors such as meningiomas in cats can be removed successfully by surgery. However, surgical operation to take off tumors in confident locations such as the brainstem can be highly dangerous, perhaps resulting in death. Even partial discharge can advantage the animal though, particularly if the tumor is slow growing.
This is probably the most widely used form of rehabilitation for brain tumors. Radiation therapy can be used alone or in blend with other treatments. It is also useful in the rehabilitation of secondary brain tumors. The aim is to destroy the tumor without harming the normal tissue too much.
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, some drugs have been used for this purpose that can cross the blood brain fence with reported success, including cytosine arabinoside, lomustine and carmustine.
Studies of animals that receive palliative rehabilitation (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 confident is that the survival times significantly growth with surgery, radiotherapy or chemotherapy. Radiation therapy seems to offer the best results, alone or in blend with other treatments. Generally, the more severe the symptoms, the shorter the life expectancy.Brain Cancer Stages :Brain Tumors in Dogs and Cats