Brain tumours originate from neoplasms that have arising within the central nervous system (CNS) or from systemic cancers that have spread to the central nervous system. Lung cancer, melanoma and breast cancer are systemic cancers that are most likely to metastasise to the CNS.
Local brain invasion, compression of adjacent structures and increased intracranial pressure (ICP) are ways in which symptoms of brain tumours are presented. Clinical manifestations of brain tumours can also arise as a result of the functional area of the brain that is involved. Any patient with a suspected brain tumours necessitates a detailed history, neurological examination and diagnostic neuroimaging.
In the United States, approximately 29 per 100,000 persons have suffered from primary brain and nervous system tumours in adulthood. Two-thirds of all primary brain tumours are accounted for by meningioma’s and glial tumours.
Age is used as determinant for tumour types and grades. For adolescents and young adults, low grade gliomas are predominate with primary brain tumours are more common than metastatic tumours. The likelihood of metastatic brain tumours becomes more prevalent for adults above the age of 30 to 40 years. In adulthood generally, glioblastoma is the most common of malignant brain tumour. Sixty-four years is the median age for this type of brain tumour.
There are no identifiable risk factors for most primary brain tumours and they are sporadic.
Brain tumours can present as generalised or localised to particular areas of the brain. Patient’s may experience symptoms or they could be asymptomatic. For high-grade gliomas and metastatic tumours, symptoms may arise over days and weeks, however for low grade gliomas and idle tumours, the progression of symptoms may take months to years. Low-grade tumours or small lesions on the brain may result in an absence of symptoms.
The most common symptom that arises from a brain tumour is a headache and this is seen in up to half of patients. Despite this, only a small proportion of headaches in general medical practice are due to brain tumours. Increased intracranial pressure (ICP) and meningeal irritation often results in more severe headaches, while generally the severity of headaches progresses over time.
Patients with brain tumours often complain about muscle weakness. This may be subtle in appearance depending on which motor neurons are implicated by the tumour. Tumours that are near the motor cortex resulting in muscle weakness often respond to glucocorticoids. Tumour removal or resection may help to relieve the muscle weakness however this option is not curative.
Patients with tumours located in the primary sensory cortex, sensory deficits can develop. The type and extent of the deficit experience is dependent on the location and severity of the tumour.
Tumours located in the language-dominant left hemisphere may result in varying degrees and types of aphasia. Presenting symptoms can include the occasional hesitation finding the correct word or severe expressive or comprehension aphasia. Tumours located near Broca’s area in the frontal lobe usually cause expressive aphasia, where tumours located near Wernicke’s area in the temporal lobe usually cause difficulties with language comprehension.