Brain Tumors

 

• Background

  Definition

  A primary intracranial tumour affecting the brain, meninges, pituitary gland, pineal gland, and/or cranial nerves.

  Classification

  • Low-grade. Grade 1 doesn't spread, while grade 2 sometimes spreads slowly and may recur if removed. Roughly synonymous with 'benign brain tumour', though this is a misnomer for some as their mass effects mean they can still be harmful.
  • High-grade (grade 3 and 4): malignant tumours which spread to other tissues and tend to recur if removed.

  Epidemiology

  • Lifetime risk of any primary brain tumour: 1/75. 50% are malignant (high-grade), so 1/150 risk.
  • Annual incidence: 1/10,000.
  • Commoner in men.

• Signs and symptoms

  • ↑ICP: headache, nausea and vomiting, papilloedema
  • Focal signs: seizures, visual symptoms, cerebellar signs, personality changes.
  • Onset is typically progressive and subacute, with 60% diagnosed in emergency departments.

• Low-grade brain tumours

  Also note that any of these tumour types can occasionally be high-grade/malignant.

  Meningioma

  • 25% of primary brain tumours.
  • Commoner in women.
  • 80% 5 year survival.

  Pituitary adenoma

  • 15% of primary brain tumours.
  • May cause endocrine symptoms e.g. ↑prolactin, Cushing's, acromegaly.

  Acoustic neuroma

  Background

  • 5% of primary brain tumours.
  • Benign tumour of CN8 Schwann cells. Aka vestibular schwannoma.
  • Associated with neurofibromatosis type 2.

  Signs and symptoms

  • Gradual onset of unilateral sensorineural deafness and pressure in one ear.
  • Followed by unilateral face numbness and absent corneal reflex (due to CN5 compression), vertigo, and nausea and vomiting.

  Management

  • Slow growing, so small tumours can be monitored with annual MRI.
  • Otherwise, remove with surgery or Gamma Knife radiosurgery.

  Craniopharyngioma

  • Bimodal onset: age 5-15 and 65-75.
  • Arise in pituitary stalk. May affect hypothalamus and pituitary.
  • Signs and symptoms: ↑ICP, bitemporal hemianopia, hydrocephalus, endocrine symptoms.

• High-grade brain tumours

  Glioma

  Epidemiology:

  • 50% of primary brain tumours in adults.
  • Commoner in men.

  Astrocytoma is the commonest type:

  • Includes glioblastoma (aka glioblastoma multiforme, GBM), the commonest malignant tumour in adults (mean onset 55 years), with a life expectancy of 1 year.
  • Also includes pilocytic astrocytoma (PCA), the commonest benign tumour in kids (<20 years old), with a 95% 5 year survival.

  Other types are ependymomas and oligodendrogliomas.

  Medulloblastoma

  • Commonest malignant tumour in kids.
  • Tumour of cerebellar neurons. A type of primitive neuroectodermal tumour (PNET).
  • Often causes hydrocephalus and cerebellar signs such as abnormal gait and coordination.
  • 70% 5 year survival.

  Primary CNS lymphoma

  • Usually diffuse large B-cell lymphoma.
  • Most commonly seen in HIV.

• Investigations

  • MRI/CT with contrast. Often first detected on CT due to wider availability, but MRI is the diagnostic modality of choice. Tumour type can often be determined with reasonable accuracy by radiological features.
  • Histology from biopsy or resection.

• Management

  • Surgical resection for most.
  • Radiotherapy (external beam or stereotactic) is an alternative (low grade) or adjunct (high grade) to surgery.
  • Chemotherapy is an additional adjunct available for some types of high grade tumours e.g. temozolomide for glioma.

• Brain metastases

  Pathophysiology and epidemiology

  • Brain metastases are 3x commoner than primary brain tumours.
  • Most commonly from the breast, lung, melanoma, or kidneys.

  Presentation and imaging

  As for primary brain tumours, with features of ↑ICP and/or focal neurology, and diagnosis with CT/MRI plus contrast.

  Management and prognosis

  Untreated, median survival is 1 month.

  The following may provide symptomatic relief and add 3-6 months of life, with a very small minority achieving sustained remission:

  • Dexamethasone (IV or PO) provides rapid relief by reducing vasogenic oedema.
  • Surgery and/or radiotherapy for a single brain metastasis.
  • Chemotherapy or whole brain radiotherapy for multiple brain metastases, depending on the primary.