| Though relatively uncommon, a brain tumor
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| | Radiography
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| has always made a grim prognosis for any
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| | Plain skull radiographs (xrays) under
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| unfortunate animal that is diagnosed with
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| | general anesthetic have little value in
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| one. Traditionally they were often
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| | detecting a brain tumor, but they can be
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| assumed but seldom confirmed, but since
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| | useful if there is a tumor in the nasal
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| MRI and CT scanning has become more
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| | cavities or the middle ear which could
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| mainstream they can be diagnosed
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| | extend into the skull. On rare occasions,
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| correctly. Here we discuss the different
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| | they can identify bony changes in the
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| types of brain tumor that affect dogs and
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| | skull which can accompany a brain tumor,
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| cats, the clinical investigations that
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| | or mineralization within the tumor
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| can be performed, the treatments
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| | itself. Radiographs and ultrasound of the
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| available and the likely outcomes.
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| | chest and abdomen are useful to look for
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| Brain tumors seem to be more common in
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| | a tumor elsewhere in the body, in cases
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| dogs than cats, and certain breeds are
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| | where the brain tumor is a secondary
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| over represented such as Boxers, Golden
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| | metastasis.
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| Retrievers, Dobermans, Scottish Terriers
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| | MRI and CT Scans
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| and Old English Sheepdogs.
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| | Confirmation of a brain tumor can is
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| Primary vs Secondary
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| | usually only achieved using the advanced
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| Brain tumors can be primary or secondary
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| | imaging techniques, CT scans or MRI. Both
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| (metastasis from other sites). Primary
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| | of these have pros and cons when compared
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| brain tumors are usually solitary, the
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| | to one another. CT is better for bony
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| most common ones in the dog being gliomas
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| | changes, while MRI is better for soft
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| and meningiomas. In cats, the most common
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| | tissue definition, for the detection of
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| type are meningiomas and these can occur
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| | many of the knock on effects of brain
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| at multiple locations.
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| | tumors such as edema, cysts and bleeding.
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| Secondary tumors in dogs include
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| | MRI is the preferred option for
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| extension of a nasal tumor, metastases
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| | diagnosing primary brain tumors.
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| from breast, lung or prostate cancer,
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| | Biopsy
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| hemangiosarcoma or extension of a
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| | This is the only way to definitively
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| pituitary gland tumor. Nerve sheath
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| | diagnose a brain tumor. The advanced
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| tumors and skull tumors have also been
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| | imaging techniques above offer much
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| reported.
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| | information, but they can occasionally
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| Secondary tumors in cats include
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| | confuse a tumor with a non cancerous mass
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| pituitary gland tumors, metastatic
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| | or a cyst, and they also do not tell us
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| carcinomas, local extension of nasal
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| | the exact type of tumor present, and
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| tumors, skull tumors and middle ear
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| | therefore the appropriate treatment and
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| cavity tumors.
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| | prognosis. The best type of biopsy is the
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| What causes a brain tumor?
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| | CT guided stereotactic brain biopsy
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| The cause of brain tumors is not known.
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| | system, which is rapid, accurate and
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| Diet, environment, chemical, genetic,
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| | quite safe.
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| viral, immunologic and trauma have all
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| | Since exploratory surgery is high risk,
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| been considered. In cats with
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| | it is not usually attempted unless there
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| meningiomas, because they often occur in
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| | is a reasonable chance of removing the
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| very young animals, a genetic element is
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| | whole tumor with minimal collateral
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| suspected.
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| | damage. Many brain tumors in cats and
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| Benign vs Malignant
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| | dogs are not categorized on a cellular
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| The terms benign and malignant must be
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| | level until post mortem.
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| used with care when referring to brain
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| | Cerebrospinal Fluid (CSF) Analysis
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| tumors. Normally these terms apply to
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| | CSF analysis is useful for ruling out
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| various characteristics on a cellular
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| | inflammatory causes of the symptoms, but
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| level, but on a biological level, even
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| | tumor cells are rarely identified here.
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| benign brain tumors can kill the animal
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| | Increased levels of white blood cells and
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| due to the secondary effects like
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| | increased protein levels may be present
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| increased intracranial pressure or
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| | in the CSF with many brain tumors, though
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| cerebral edema. In short, any brain tumor
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| | this is not diagnostic. This test can be
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| can kill.
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| | high risk when intracranial pressure is
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| What are the symptoms?
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| | increased, as brain herniation can occur.
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| There can be huge variety here. Many
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| | Treatment
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| animals will present with vague signs,
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| | Treatment is aimed at being either
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| such as one or several of the following:
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| | curative or palliative. Curative
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| 1. Loss of trained habits
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| | treatment eradicates the tumor or reduces
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| 2. Decreased levels of activity
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| | its size, whilst palliative therapy
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| 3. Decreased frequency of purring in cats
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| | reduces the surrounding cerebral edema
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| 4. Disorientation
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| | and slows down the growth of the tumor.
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| 5. Confusion
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| | Palliative therapy also involves
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| More specific symptoms are dependent upon
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| | administering antiepileptic drugs, if
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| where exactly the tumor is located within
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| | seizures are occurring as a result of the
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| the brain, the size of the tumor and how
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| | tumor.
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| quickly it is growing. As a tumor
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| | Surgery
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| enlarges, symptoms tend to become more
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| | Whether this is an option depends on the
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| severe. These can include:
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| | general health of the animal, and the
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| 6. Seizures (often indicate a tumor in
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| | precise location, size, extent,
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| the cerebral cortex)
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| | invasiveness and nature of the tumor.
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| 7. Facial paralysis (may indicate a
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| | Tumors such as meningiomas in cats can be
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| brainstem tumor)
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| | removed successfully by surgery. However,
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| 8. Tremors (may indicate a tumor in the
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| | surgery to remove tumors in certain
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| cerebellum)
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| | locations such as the brainstem can be
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| 9. Wobbliness (may indicate a tumor in
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| | extremely dangerous, possibly resulting
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| the cerebellum)
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| | in death. Even partial removal can
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| 10. Full or partial blindness (may
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| | benefit the animal though, particularly
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| indicate tumor in hypothalamus or optic
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| | if the tumor is slow growing.
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| nerve)
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| | Radiotherapy
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| 11. Loss of smell (may indicate tumor of
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| | This is probably the most widely used
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| olfactory system)
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| | form of treatment for brain tumors.
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| The physical presence of the tumor can
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| | Radiation therapy can be used alone or in
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| cause knock on effects due to
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| | combination with other treatments. It is
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| inflammation and edema of the surrounding
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| | also useful in the treatment of secondary
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| area. This can cause symptoms such as:
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| | brain tumors. The aim is to destroy the
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| 12. Changes in behaviour or temperament
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| | tumor without harming the normal tissue
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| (irritability, lethargy)
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| | too much.
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| 13. Compulsive walking
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| | Chemotherapy
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| 14. Circling
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| | The main problem with chemotherapy for
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| 15. Pressing head against a wall or hard
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| | brain tumors is that many drugs do not
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| surface
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| | cross the blood brain barrier. In
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| Animals can sometimes carry brain tumors
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| | addition, the tumor may only be sensitive
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| for several years before presenting to a
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| | to high doses, doses which are toxic to
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| veterinary clinic, if the tumor is slow
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| | normal brain tissue and therefore
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| growing. In these cases the symptoms
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| | unsuitable for use. However, several
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| develop gradually, and the owner tends to
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| | drugs have been used for this purpose
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| get used to them so that by the time the
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| | that can cross the blood brain barrier
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| animal is examined, the tumor has reached
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| | with reported success, including cytosine
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| a considerable size.
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| | arabinoside, lomustine and carmustine.
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| How is a brain tumor diagnosed?
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| | Probable Outcome
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| History and Clinical Examination
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| | Studies of animals that receive
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| The first step for a veterinarian is to
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| | palliative treatment (corticosteroids)
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| take a thorough history of all of the
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| | for brain tumors show a survival range
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| clinical signs, and when they developed.
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| | post diagnosis of 64 to 307 days. This
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| This is followed by a full general
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| | demonstrates the inability to accurately
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| clinical examination and a full
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| | predict life expectancy in these cases.
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| neurological examination.
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| | What is certain is that the survival
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| Bloods
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| | times significantly increase with
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| After that, blood should be taken for
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| | surgery, radiotherapy or chemotherapy.
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| routine haematology and biochemistry
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| | Radiation therapy seems to offer the best
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| profiles. This is to look for any disease
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| | results, alone or in combination with
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| outside the brain. Results will be normal
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| | other treatments. Generally, the more
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| for brain tumors, with the possible
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| | severe the symptoms, the shorter the life
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| exception of some pituitary gland tumors.
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| | expectancy.
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