Central Nervous System Neoplasia

()Map NERVOUS SYSTEM (Map)

Neoplasia

• Particularly affects older animals.
• Signs may occur acutely, or be progressive and reflect
  • The primary parenchymal damage by the tumour
  • Sequelae such as haemorrhage or oedema.

Primary

Meningioma

Meningioma - left frontal lobe. Image couretsy of BioMed Archive

Meningioma. Image couretsy of BioMed Archive

• Meningioma is most frequently seen in cats and dogs, and is the most common primary brain tumour in these species.
  • Dolicocephalic dog breeds are predisposed.
    

    Meningioma, histological view. Image couretsy of BioMed Archive
• Tumours arise from arachnoid cap cells ion the arachnoid layer of meninges.
• Meningiomas are usually benign, and therefore seldom invade.
  

  Infiltrating meningioma, histological view. Image couretsy of BioMed Archive
  • Spread to the lung has, however, been reported.
• The main effects of the tumour is due to its action as a compressive, space-occupying lesion.
• Meningiomas may become mineralised.
  
  

Feature	Dog	Cat
Lesion Number	Solitary	Multiple
Infiltration to Cortical Parenchyma	More infiltrative	Less infiltrative
Encapsulation	Poorly encapsulated	Well encapsulated
Metastatic Potential	Low	Low

View images courtesy of Cornell Veterinary Medicine

Treatment

• Chemotherapy
• Radiation therapy
• Surigcal resection.
  • Better results in cats (as encapsulated and clearly distinguished from normal brain).
    • Survival is 22-27 months following resection.

Glioma

• Due to their origin, gliomas are found within the intraaxial neuroxis.
• Brachycephalic breeds are predisposed.
• Glial tumours rise from cells of the brain parenchyma.
  • Astrocytes - Astrocytoma
  • Oligodendrocytes - Oligodendroglioma
  • Ependymal cells - Ependymoma
  • Choroid plexus cells - Choroid plexus tumours

Astrocytoma

Astrocytoma. Image courtesy of BioMed Archive

• The most common of the glial tumors
• Brachycephalic breeds are predisposed.
  • E.g. boxer, bulldog.

Astrocytoma: histological view. Image courtesy of BioMed Archive

Gross

• Astrocytomas are firm, solid tumours.
• Colour tends to be grey-white.
  • This may sometimes be mottled with red due to areas of necrosis and haemorrhage.

View images courtesy of Cornell Veterinary Medicine

Oligodendroglioma

• Oligodendroglioma is most commonly found in dogs.
• As for astrocytomas, there is a predilection for brachycephalic breeds.

Gross

• Oligodendrogliomas are soft in texture, and often gelatinous.
• Colour ranges from grey to pink/red.

View images courtesy of Cornell Veterinary Medicine

Ependymoma

• Ependymomas are found in dogs, cats, horses and cattle.
• They occur mainly in the ventricles.
  • The lateral ventricle is most often affected.
• The tumours may spread within the ventricular system via the cerebrospinal fluid.
• Growth is generally expansile, but it can be invasive and destructive.

View images courstesy of Cornell Veterinary Medicine

Choroid Plexus Tumours

• Choroid plexus tumours are rare.
• They are mainly found in dogs.
• Choroid plexus tumours are found in areas where the choroid plexus is concentrated, i.e.:
  • Lateral ventricle
  • Third ventricle
  • Fourth ventricle
  • There is a particular predilection for the fourth ventricle.
• This association with the ventricular system makes hydrocephalus a common sequelae.
• The tumours may metastasis via the CSF and ventricular system.
• Chroid plexus tumourc contain an increased concentration of blood vessels.
  • Contrast administration may therefore aid in their identification.

Treatment of Gliomas

• The usual modes of anti-cancer therapy may be used to tackle gliomas:
  • Radiation therapy
  • Chemotherapy
  • Surgery
• However, surgery is less ideal as the tumours are located within the parenchyma.

PNETs

• PNETs stands for Primitive NeuroEctodermal Tumors.
• These are tumors of primitive germ cell origin.
• They are rare.

Secondary

• May arise from:
  • Metastasis
    • Numerous tumours of older animals may metastasise to the brain:
      • Haemangiosarcoma
      • Lymphoma
      • Mammary gland carcinomas
      • Other carcinomas
    • Tumours which metastasise to the lungs may be more likely to metastasise to the brain.
    • Incidence is underestimated, as the brain is not routinely examined at necropsy.
    • The white-grey matter junction is the most frequently affected area.
    • Brainstem and spinal cord metastasis are less common than forebrain metastasis.
    • Choroid plexus tumours and ependymomas may metastasise via the CSF.
  • Extenstion from extraneural sites, e.g.
    • Skull
    • Nasal cavity
      • Signs of extenstion may preced signs of nasal disease.
    • Frontal sinuses