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Central Nervous System Neoplasia (view source)

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==Neoplasia==
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* Particularly affects older animals.
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* Signs may occur acutely, or be progressive and reflect
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** The primary parenchymal damage by the tumour
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** Sequelae such as haemorrhage or oedema.
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==Primary==
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===Meningioma===
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[[Image:meningiomaleftfrontallobe.jpg|thumb|right|150px|Meningioma - left frontal lobe. Image couretsy of BioMed Archive]]
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[[Image:meningiomabrain.jpg|thumb|right|150px|Meningioma. Image couretsy of BioMed Archive]]
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* Meningioma is most frequently seen in cats and dogs, and is the most common primary brain tumour in these species.
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** Dolicocephalic dog breeds are predisposed. [[Image:meningiomahisto.jpg|thumb|right|150px|Meningioma, histological view. Image couretsy of BioMed Archive]]
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* Tumours arise from arachnoid cap cells ion the arachnoid layer of meninges.
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* Meningiomas are usually benign, and therefore seldom invade. [[Image:meningiomainfiltrating.jpg|thumb|right|150px|Infiltrating meningioma, histological view. Image couretsy of BioMed Archive]]
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** Spread to the lung has, however, been reported.
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* The main effects of the tumour is due to its action as a compressive, space-occupying lesion.
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* Meningiomas may become mineralised. <br><br>
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<center>
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{| border="1" cellpadding="7"
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!'''Feature'''
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!'''Dog'''
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!'''Cat'''
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|-
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| '''Lesion Number'''
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| Solitary
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| Multiple
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|-
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| '''Infiltration to Cortical Parenchyma'''
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| More infiltrative
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| Less infiltrative
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|-
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| '''Encapsulation'''
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| Poorly encapsulated
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| Well encapsulated
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|-
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| '''Metastatic Potential'''
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| Low
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| Low
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|}
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</center>
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[http://w3.vet.cornell.edu/nst/nst.asp?Fun=F_KSsrch&kw=MENINGIOMA View images courtesy of Cornell Veterinary Medicine]
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====Treatment====
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* Chemotherapy
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* Radiation therapy
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* Surigcal resection.
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** Better results in cats (as encapsulated and clearly distinguished from normal brain).
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*** Survival is 22-27 months following resection.
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===Glioma===
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* Due to their origin, gliomas are found within the intraaxial neuroxis.
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* Brachycephalic breeds are predisposed.
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* Glial tumours rise from cells of the brain parenchyma.
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** Astrocytes - '''Astrocytoma'''
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** Oligodendrocytes - '''Oligodendroglioma'''
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** Ependymal cells - '''Ependymoma'''
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** Choroid plexus cells - '''Choroid plexus tumours'''
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====Astrocytoma====
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[[Image:astrocytomagross.jpg|thumb|right|150px|Astrocytoma. Image courtesy of BioMed Archive]]
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* The most common of the glial tumors
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* Brachycephalic breeds are predisposed.
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** E.g. boxer, bulldog.
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[[Image:astrocytomahisto.jpg|thumb|right|150px|Astrocytoma: histological view. Image courtesy of BioMed Archive]]
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=====Gross=====
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* Astrocytomas are firm, solid tumours.
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* Colour tends to be grey-white.
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** This may sometimes be mottled with red due to areas of necrosis and haemorrhage.
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[http://w3.vet.cornell.edu/nst/nst.asp?Fun=F_KSsrch&kw=ASTROCYTOMA View images courtesy of Cornell Veterinary Medicine]
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====Oligodendroglioma====
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* Oligodendroglioma is most commonly found in dogs.
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* As for astrocytomas, there is a predilection for brachycephalic breeds.
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=====Gross=====
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* Oligodendrogliomas are soft in texture, and often gelatinous.
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* Colour ranges from grey to pink/red.
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[http://w3.vet.cornell.edu/nst/nst.asp?Fun=F_KSsrch&kw=OLIGODENDROGLIOMA View images courtesy of Cornell Veterinary Medicine]
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====Ependymoma====
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* Ependymomas are found in dogs, cats, [[Hindgut Fermenters - Horse - Anatomy & Physiology|horses]] and cattle.
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* They occur mainly in the ventricles.
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** The lateral ventricle is most often affected.
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* The tumours may spread withing the ventricular system via the cerebrospinal fluid.
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* Growth is generally expansile, but it can be invasive and destructive.
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[http://w3.vet.cornell.edu/nst/nst.asp?Fun=F_KSsrch&kw=EPENDYMOMA View images courstesy of Cornell Veterinary Medicine]
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====Choroid Plexus Tumours====
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* Choroid plexus tumours are rare.
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* They are mainly found in dogs.
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* Choroid plexus tumours are found in areas where the choroid plexus is concentrated, i.e.:
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** Lateral ventricle
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** Third ventricle
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** Fourth ventricle
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** There is a particular predilection for the fourth ventricle.
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* This association with the ventricular system makes hydrocephalus a common sequelae.
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* The tumours may metastasis via the CSF and ventricular system.
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* Chroid plexus tumourc contain an increased concentration of blood vessels.
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** Contrast administration may therefore aid in their identification.
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====Treatment of Gliomas====
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* The usual modes of anti-cancer therapy may be used to tackle gliomas:
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** Radiation therapy
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** Chemotherapy
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** Surgery
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* However, surgery is less ideal as the tumours are located within the parenchyma.
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==PNETs==
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* PNETs stands for Primitive NeuroEctodermal Tumors.
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* These are tumors of primitive germ cell origin.
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* They are rare.
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==Secondary==
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* May arise from:
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** '''Metastasis'''
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*** Numerous tumours of older animals may metastasise to the brain:
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**** Haemangiosarcoma
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**** Lymphoma
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**** Mammary gland carcinomas
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**** Other carcinomas
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*** Tumours which metastasise to the lungs may be more likely to metastasise to the brain.
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*** Incidence is underestimated, as the brain is not routinely examined at necropsy.
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*** The white-grey matter junction is the most frequently affected area.
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*** Brainstem and spinal cord metastasis are less common than forebrain metastasis.
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*** Choroid plexus tumours and ependymomas may metastasise via the CSF.
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** Extenstion from extraneural sites, e.g.
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*** Skull
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*** Nasal cavity
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**** Signs of extenstion may preced signs of nasal disease.
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*** Frontal sinuses
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