Brain tumours occur in approximately 7-21 persons per 100 000 per year. They are responsible for 2% of cancer deaths and 2% of reported neoplasms.
WHO Classification of intra-cranial tumours (Kleihus & Cavenee, 2000) is based on their tissue of origin.
Tumours of Neuroepithelial Tissue
- Astrocytomas are the most common primary brain tumours. They are classified into 4 grades (see table).
N.B. Grade IV tumours (GBM) are the most malignant type and have a poor prognosis. Patients usually die within several months.
- Oligodendrogliomas are usually slow-growing, sharply defined tumours that originate from oligodendrocytes.
Tumours of the Nerve Sheath
Germ Cell Tumours
Tumours of the Sellar Region
- Pituitary adenomas are benign tumours and often secrete pituitary hormones:
- Craniopharyngiomas arise from the embryonic remnants of Rathke’s cleft and lie in close proximity to the pituitary stalk. They are usually nodular tumours with cystic areas containing greenish fluid and cholesteatomous material
Tumours of the Meninges
- Raised intracranial pressure (ICP)
- Focal neurological deficit
- Usually relentlessly progressive
Posterior Fossa Tumours
- Never present with seizures
- Focal deficits
- Relentless progression
- Obstructive hydrocephalus causes symptoms of raised ICP, which may develop rapidly.
- Focal neurological deficit
- Hydrocephalus from compression of the third ventricle from below
- CSF leak
- Pituitary apoplexy (resulting from either acute haemorrhage or ischaemic necrosis)
- Endocrine presentation; panhypopituitarism, amenorrhoea, impotence, acromegaly (adults), gigantism (paediatrics), Cushing’s disease
Paediatric brain tumours are not covered in depth in this article. They are almost always in the posterior fossa and may be one of the following:
They present with failure to thrive, developmental delay and hydrocephalus.
Management is with surgery followed by radio- and chemotherapy.
The following tests may confirm the presence of a brain tumour and find its location:
• CT scan - will detect >90% of tumours. However, it is not very sensitive for:
• Gadolinium-enhanced cranial MRI - preferred study for the initial anatomic evaluation of CNS tumours. Most tumours are hypointense on T1-weighted images and hyperintense on fluid-attenuated inversion recovery, T2-weighted, and proton-weighted images.
• Biopsy of the tumour during surgery or CT-scan may confirm the type of tumour
• EEG - used primarily to complement CT and MRI by evaluating functional changes in the patient's condition. It demonstrates aspects of brain physiology that are not reflected in structural neuroimaging.
• CSF analysis - Lumbar puncture contraindicated in many patients with brain tumours, but may be useful in some where it may show cancerous changes.
Many other imaging techniques (see table below), including MR spectroscopy, diffusion and perfusion imaging, single photon emission computed tomography (SPECT) and positron emission tomography (PET) may help to identify foci of high-grade tumour prior to surgery, thereby improving the accuracy of histopathological evaluation.
The aims of management is diagnosis, symptomatic relief and tumour control (with minimal morbidity for malignant disease and maximal aggression for benign disease).
- Immediate introduction of palliative care may be appropriate when there is no doubt regarding diagnosis and if the patient is in extremis.
- Asymptomatic lesions may be left alone, especially in the elderly and in surgically difficult spots.
- Watch and wait with serial imaging for:
- Corticosteroids (Dexamethasone) for ↑ ICP (reduces vasogenic oedema). Steroids may also temporarily improve focal neurological deficits by treating brain oedema.
- Anti-epileptic drugs for epilepsy. Carbamazepine, lamotrigine, oxcarbazepine, sodium valproate, and topiramate are the drugs of choice for partial (focal) seizures.
- Prolactinomas respond well to dopamine agonists and these are the treatment of choice. Acromegaly can be treated with Octreotide and Pegvisomant.
- Postsurgical radiation is the standard treatment for high-grade gliomas.
- Stereotactic radiosurgery used to palliate small, well-demarcated recurrent glioblastoma multiforme and as a boost after conventional external beam radiotherapy.
- Interstitial radiotherapy (brachytherapy) involves surgically implanting radioactive material directly inside the tumour.
- Combining Temozolomide therapy with radiation improves survival in patients with high-grade gliomas.
- Irinotecan and targeted agents such as Bevacizumab, which inhibits vascular endothelial growth factor; and Gefitinib, Erlotinib, and Imatinib, which inhibit the epidermal and platelet-derived growth factor receptors, have shown some promise in the treatment of recurrent malignant gliomas.
Most patients with intracranial tumours require one of the following surgical approaches (as shown in the diagram):
The surgical procedure may involve biopsy, debulking/cytoreduction or complete removal of the tumour. However this depends upon the nature of the tumour and its site.
It is important to note, that if any of the tumour tissue is overlooked, or if fragments remain attached to deep structures, recurrence may be seen.
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