Brain tumours

Several thousand people are diagnosed with brain tumours in the UK each year. Brain tumours originate from the brain and its surroundings (called primary brain tumours), or arise as secondary deposits of other cancers developing elsewhere in the body (called metastases). Whereas primary brain tumours can arise pretty much from every cell type existent in the brain (with different occurrence rate), only certain cancers are associated with brain metastases.

A detailed list of brain tumours and their classification that can be found here

This is generic term that refers to a large group of tumours deriving from cells that exist within the brain. Depending on the cell of origin, gliomas are called astrocytomas, oligodendrogliomas, ependymomas etc. The cellular origin of gliomas defines their clinical manifestation, radiological appearance and prognosis. Despite these differences gliomas are similar in their ability to invade the brain parenchyma, and as a result, they do not have well defined margins to separate them from the brain. During operations, even if we can see visible margins of these tumours under the microscope, we do know that tumour cells extend well beyond these visible tumour margins. This common feature of gliomas is important when surgical strategies and postoperative oncological treatments are decided.

Apart from the cell type they originate from; the prognosis of gliomas is also defined by the WHO grade of the tumour. Brain tumours and so gliomas are classified by the World Health Organisation (WHO) in 4 grades on the basis of how aggressively they behave. The higher the grade the more aggressive a brain tumour is.

Gliomas of a lower grade (WHO II) have an inherent potential of transforming to higher grades and become malignant (WHO III or IV). For this reason, it is now common practice for these tumours to be treated proactively early after diagnosis. The prognosis of gliomas also depends on their size and location of the tumour at the time of diagnosis (which dictates the surgical management), the clinical performance of the patient (age, general health, level of consciousness, cognitive function, mobility), and the genetic profile of the tumour.

Gliomas are still incurable tumours. However, advances in surgery, neuro-anaesthesia, brain imaging, and neuro-oncology have led to a better overall prognosis. 

Meningiomas are tumours that originate from the covering membranes of the brain. In their majority (around 80%) are benign tumours (WHO I). If benign meningiomas are completely removed surgically they have a very low risk of recurrence. 15 -18% of meningiomas (figure depending on the series) can be what we call atypical meningiomas (WHO II).

These are tumours that may recur even if completely removed. Patients with atypical meningiomas may need several operations for recurrences and even radiotherapy. The benefit of radiotherapy in preventing recurrences of atypical meningiomas is currently being assessed in clinical trials. Rarely meningiomas (1-2%) are cancerous and incurable tumours. These are called malignant meningiomas (WHO III). Malignant meningiomas are treated with surgery and postoperative radiotherapy, but remain incurable. 

Metastases are secondary tumour deposits originating from primary cancers elsewhere in the body. They develop in the brain when malignant cells travel in the blood stream and invade the brain. Certain cancers like lung, breast, malignant melanomas, renal, and some gastrointestinal cancers, are well known to be associated with brain metastases. The overall prognosis of patients with brain metastases depends on the stage of the primary cancer, the clinical state of the patient, whether or not treatment options are available for the primary cancer, and the number and location of the brain metastases.

The recurrence rate of resected brain metastases is known to be relatively high and for this reason the combination of surgery with postoperative Gamma Knife is very important. In recent years, there are many oncological treatments available for metastases, and also widely available stereotactic radiosurgery treatments such as Gamma Knife.

The posterior fossa is a relatively small compartment of the cranial cavity at the back of the head. It contains important structures of the brain that support vital functions of the human body (brain stem), the cerebellum which supports balance and coordination of movements, and a relatively large brain fluid cavity called 4th ventricle. If a relatively large tumour grows in this crowded compartment of the brain, it can cause significant symptoms (unsteadiness, headache, nausea, vomiting) or even a rapid neurological deterioration (drowsiness, coma).

If remained untreated large posterior fossa tumours can be potentially life threatening because of acute hydrocephalus (due to blockage of the circulation of brain fluids) and/or brain stem compression. Tumours in this part of the brain can be either primary (usually benign and in younger patients) or metastases (usually older patients).

Treatment of tumours in this part of the brain is dictated by well-established priorities. The general principle is elimination of the life-threatening factors first (e.g. accumulation of brain fluids under high pressure, called hydrocephalus) before deciding the definite management of the main pathology.