The Different Types of Brain Tumours and What Causes Them

Brain tumours are abnormal growths that develop in the brain or the surrounding tissues. Brains are enclosed in rigid skulls, so any unnatural growth occurring inside the restricted space can cause serious problems that require prompt medical attention. Tumours of the brain can be either cancerous (malignant) or noncancerous (benign) – Whatever the type, they can cause your skull's pressure to increase when they grow. In severe cases, this can cause brain damage and possibly even lead to death.

Today, we will explore what brain tumours are, what are its different types, and the stages of brain tumour development.

Primary Brain Tumours

Brain tumours can be primary or secondary. Primary brain tumours originate in the brain, whereas secondary brain tumours develop when cancer spreads from another part of the body to the brain. Primary brain tumours include gliomas, meningiomas, and pituitary adenomas.

Gliomas are the most common type of brain tumour, accounting for about 80% of all brain tumours. They develop from the glial cells that surround and support the neurons in the brain. There are several types of gliomas. The most talked about ones include astrocytomas, oligodendrogliomas, and ependymomas.

a)    Astrocytomas: Apparent glial cell tumours formed from cells inside connective tissue called astrocytes are the most common kind of primary brain tumour in the axial region, accounting for about half of all primary brain tumours in the axial region. Most of them reside in the cerebrum (the large, outer region of the brain), but some are also found in the cerebellum (located at the base of the brain). 

It is possible for both adults and children to develop astrocytomas. High-grade astrocytomas, called glioblastomas multiforme, are the most malignant brain tumours. Symptoms of glioblastoma are often similar to those of other gliomas. The pilocytic astrocytoma is a low-grade cerebellar glioma commonly found in children. Cerebral astrocytomas are more common in adults. 

b)    Oligodendrogliomas: These tumours are formed from oligodendrocytes, brain cells that support the cerebrum. Approximately 2 percent to 4 percent of primary brain tumours are oligodendrogliomas. These diseases tend to affect young and middle-aged adults, more often men. The most common symptom of these gliomas is seizures, along with headaches, weakness, or speech problems. Most oligodendrogliomas have a better prognosis than other types of gliomas. 

c)     Ependymomas: Due to ependymal cells lining the ventricles or spinal cord, ependymomas develop. Only 2 percent to 3 percent of primary brain tumours are ependymomas. However, children younger than 10 are more likely to develop these tumours, which represent 8-10 percent of all brain tumours. In children, ependymomas tend to develop near the cerebellum, where the tumour can block the flow of cerebrospinal fluid and increase pressure inside the skull (obstructive hydrocephalus.) As a result of this, the tumour may spread to the brain or spinal cord (drop-metastases).

Meningiomas are tumours that develop in the meninges, the thin membranes that cover the brain and spinal cord. They are usually benign, and they account for about 20% of all brain tumours. Often, meningiomas are slow-growing tumours that don't cause noticeable symptoms until they are quite large. Meningiomas may remain asymptomatic for a lifetime or be detected unexpectedly during a brain scan for an unrelated symptom. The signs and symptoms of a tumour vary according to its size and location. Some of the symptoms of meningiomas may include headaches, seizures, confusion, drowsiness, muscle weakness and hearing loss.

Several factors can make diagnosing meningiomas difficult. Symptoms of meningiomas can be so subtle that a patient and/or doctor may think they are normal signs of ageing because of the gradual growth. Some of the symptoms associated with meningiomas can also be caused by other medical conditions, which further adds to the confusion. It is not uncommon to make a misdiagnosis, and it may take several years before the correct analysis is made.

There are 4 major types of meningiomas.

a)    Posterior Fossa Meningioma: An abnormal growth on the back of the brain.

b)    Sphenoid Meningioma: This is located near the sphenoid bone, behind the eyes.

c)     Spinal Meningioma: Can be found in the spine, sometimes directly against the spinal cord.

d)    Suprasellar Meningioma: Found near the pituitary gland in the skull.

Pituitary adenomas are tumours that develop in the pituitary gland, a small gland located at the base of the brain. They are usually benign, but they can cause hormonal imbalances if they grow large enough to put pressure on the surrounding tissues. The pituitary gland controls the secretion of most hormones in the body, which is why it is often called the ‘master gland’. Pituitary glands are about the size and shape of kidney beans and weigh less than 1 gram.

An analogy can be drawn between the pituitary and a household thermostat. As the thermostat continuously measures the temperature in the house, it sends instructions to the heater so that it can keep a steady, comfortable temperature. Similarly, the pituitary constantly monitors bodily functions and sends signals to remote organs and glands to maintain a stable body temperature.

Microadenomas are tumours less than 10 millimetres in diameter that secrete anterior pituitary hormones. Adenomas that are smaller and functional are usually detected earlier because hormone levels increase, causing abnormal changes in the body. The majority of pituitary adenomas are diagnosed when they are smaller than 5 millimetres. Usually, macroadenomas do not secrete hormones when they exceed 10 millimetres in size. Often, these tumours are discovered because they cause symptoms by compressing nearby brain or cranial nerves.

Secondary Brain Tumours

In addition to these primary brain tumours, there are secondary brain tumours that result from the spread of cancer from another part of the body. These tumours are named based on the type of cancer that originated elsewhere in the body. For example, if a person has breast cancer that has spread to the brain, they will have a secondary brain tumour called a metastatic breast tumour.

Stages of Brain Tumour Development

The stages of brain tumour development are graded from I to IV, with grade I being the least aggressive and grade IV being the most aggressive. The grading system is based on the microscopic appearance of the tumour cells, as well as the tumour's location and size.

Grade I brain tumours are usually slow-growing and non-invasive. They are often successfully treated with surgery alone, and they rarely recur after treatment. 

Grade II brain tumours are more aggressive than grade I tumours, but they are still considered relatively slow-growing. They may require additional treatment, such as radiation or chemotherapy, in addition to surgery.

Grade III brain tumours are more aggressive than grade II tumours, and they are more likely to recur after treatment. They require aggressive treatment, such as surgery followed by radiation and chemotherapy.

Grade IV brain tumours are the most aggressive type of brain tumour, and they require the most aggressive treatment. They are often invasive and difficult to remove completely, and they are more likely to recur after treatment.

Conclusion

Treatment options for brain tumours vary, depending on the type and stage of the tumour. However,  they usually involve a combination of surgery, radiation, and chemotherapy. As with any health condition, early detection and treatment are key to improving outcomes for people with brain tumours.

Park Hospital's Neurosciences Department specializes in brain and spine surgery, offering the latest in advanced medical technology and treatment options. Our team of experienced neurosurgeons provides personalized care to each patient, ensuring the best possible outcomes. Contact us today to learn more about our services.