Signs: usually unilateral, giving an asymmetrical picture with contralateral deficits if affecting a cerebral hemisphere, ipsilateral if affecting the brainstem. Secondary effects, eg brain edema and herniation, may cause rapid progression of signs. Higher incidence in older individuals.
Diagnosis: confirmation of diagnosis is best carried out using computed tomography or MRI scanning.
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.
Distant metastasis of primary intracranial neoplasia (meningioma) is rare. Print off the owner factsheet Brain tumor or cancer to give to your client.
Presenting signs
Unilateral clinical signs, eg circling, proprioceptive defects and some cranial nerve deficits .
Ataxia and behavioral changes.
Visual deficits.
Seizures.
Geographic incidence
3.5 per 100,000.
Age predisposition
Older individuals.
75% of cats with meningioma >9 years.
Young individuals.
Sex predisposition
Male - meningioma.
Cost considerations
Surgical resection (meningioma in particular amenable to surgery).
Radiotherapy .
Corticosteroids .
Anticonvulsants.
Osmotic diuretic, eg mannitol .
Special risks (e.g. anesthetic)
Collection of cerebrospinal fluid (CSF) samples can predispose brain herniation in cases of increased intracranial pressure.
General anesthesia
Hypoxia due to seizure activity and compromise of the airway will lead to cytotoxic brain edema and possibly raised intracranial pressure, therefore oxygen supply should be monitored carefully.
Local infiltration from, for example, the skull or primary nasal tumors.
Metastasis from other sites.
Pituitary adenomas.
Secondary effects
Brain edema.
Brain herniation.
Pathophysiology
Increased pressure.
Brain herniation.
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
Subfalcal.
Caudal transtentorial.
Foramen magnum (can cause respiratory depression).
Rostral transtentorial.
Timecourse (incubation, duration)
Slow and progressive development of signs, though may present with acute onset or acute deterioration of signs.
Usually unilateral with deficits contralateral to side of lesion.
Progressive deterioration of mental state, locomotion, gait and posture, pupillary light reflexes and the oculovestibular response are all indicative of brain herniation.
Visual deficits.
Seizures .
Diagnostic investigation Radiography
Cats with meningioma may have evidence of lysis or hyperostotic bone adjacent to tumor, but may be difficult to see on skull radiographs. Calcification may be radiographically visible within a neoplasm.
Other
Computed tomography:
Magnetic resource imaging.
To identify presence of space occupying lesion.
Contrast venography:
Abnormal pressure within the cranium may cause deviation of vascular pattern.
Fluid/aspirate analysis - CSF analysis. Collection of CSF is hazardous where there is increased intracranial pressure due to the potential for brain herniation.
Also, abnormal CSF findings are relatively non-specific.
Gross autopsy findings
Intracranial mass .
Differential diagnosis
Other causes of intracranial disease (including metabolic encephalopathies).
Oxygen by mask or endotracheal tube. Do not administer oxygen by nasal catheter as it can cause sneezing increase intra-cranial pressure.
Brain edema/herniation
Corticosteroids, eg IV dexamethasone or methylprednisolone succinate in acute situations and maintenance with prednisolone .
Osmotic diuretic - mannitol (0.25-2.0 g/kg in a 20% solution IV over a period of one hour). Mannitol may cross the blood-brain barrier into the brain parenchyma, causing rebound edema by drawing fluid into the brain tissue. Also, must not be given to a hypovolemic animal.
Furosemide given 15 min before the mannitol will enhance the response. Urinary output should be monitored.
Seizures
Diazepam (up to 1 mg/kg IV).
Phenobarbital .
Pentobarbital (4-20 mg/kg IV).
Standard treatment
Surgical removal or reduction of the tumor. Even if resection is not possible, craniotomy can achieve decompression of the brain and make tissue available for histopathological examination.
Radiotherapy .
Surgical resection followed by radiotherapy to reduce recurrence.
Chemotherapy . (Palliative only. Blood-brain barrier limits drugs that can be used.)
Photodynamic therapy.
Brachytherapy.
Immunotherapy.
Monitoring
Urinary output when using diuretics to treat brain edema.
Subsequent management
Treatment
Radiotherapy following surgical resection may help to prevent recurrence.
Tumor type and location within the brain. A readily accessible tumor may be resected. If resectable, ~80% of cats did not have recurrence of a range of follow-up times from 18-47 months.
Severity of secondary effects. Brain herniation carries a grim prognosis.
Neurological status of animal at presentation. Advanced stages with severe neurological deficits carry a grim prognosis.
Improvement in general demeanor and neurological dysfunction should occur within 48 hours to 1 week after surgery.
Print off the owner factsheet Brain tumor or cancer 
Collection of CSF 
increase intra-cranial pressure.