Brain: neoplasia

i canis

Contributor(s):

Rodney Bagley

William Brewer Jr

Synonym(s): Brain tumor

Introduction

Neoplasia secondarily involves the brain via metastasis or via direct extension from extraneural sites.
Primary tumors within the skull, nasal cavity or frontal sinuses can extend directly into the brain.
Often, signs of intracranial extension such as seizures, occur prior to or without other signs of nasal disease.
May be primary or secondary.
Usually unilateral, giving an asymmetrical picture with deficits contralateral to the side of the lesion.
Secondary effects, eg brain edema and herniation, may cause rapid progression of signs.
Cause:
- Meningioma.
- Gliomata (various).
- Pituitary macroadenoma.
- Others.
Signs: circling, cranial nerve deficits, related to space occupying lesion, eg seizures, depression, ataxia.
Higher incidence in older individuals and in brachycephalic breeds.
Diagnosis: confirmation of diagnosis is best carried out using computed tomography.
Treatment: depends on nature of tumor but may include surgical resection, chemotherapy, radiotherapy and medical control of secondary effects, eg using corticosteroids.
Prognosis: depends on tumor type and location.
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Primary brain tumors

Meningiomas Meningioma.
Glial tumors, eg astrocytoma Astrocytoma , oligodendrogioma, choroid plexus papilloma Brain: neoplasia - choroid plexus tumor , ependymoma Brain: ependymoma , medulloblastoma, etc.

Secondary brain tumors

Local infiltration from, eg skull or primary nasal tumors.
Metastasis from other sites.
Pituitary adenomas Pituitary adenoma.
Numerous tumors of older animals metastasize to the brain including hemangiosarcoma Hemangiosarcoma , lymphosarcoma Lymphoma , mammary gland Mammary gland: neoplasia , and other carcinomas.
The incidence of intracranial metastasis is often underestimated as the brain is not always examined during a routine necropsy.
Tumors that readily metastasize to the lungs may be more likely to metastasize to the brain.
The cortical gray/white junction is a common area of metastasis due to the increased vascularity, with brain stem and spinal cord metastasis less frequent.
Choroid plexus tumors may metastasize through the CSF to other areas in the brain or spinal cord ('drop-lets').
In some instances, spinal signs from choroid plexus metastasis may be the first sign of the presence of the tumor.

Secondary effects

Tumors often occupy >1 anatomic division of brain and so may result in signs suggestive of multifocal disease.

Secondary effects of brain neoplasia

Tumor may disrupt the blood-brain barrier, causing local accumulation of fluid mostly in the white matter. This vasogenic brain edema may develop rapidly and is the most significant of the secondary effects, giving an acute clinical picture.
Rigid cranium does not allow expansion of contents (blood, CSF and brain tissue), so brain edema causes an increase in intracranial pressure. Raised intracranial pressure usually leads to brain herniation.

Types of brain herniation

Subfalcine.
Caudal transtentorial.
Foramen magnum (can cause respiratory depression).
Rostral transtentorial.
Clinical signs may be localized or multifocal depending upon the number and location of metastasis and associated pathophysiologic sequelae such as hemorrhage and edema.
Infarction and hemorrhage are common with CNS metastasis.