Neuro-oncology is the subspecialty of oncology concerned with the diagnosis and treatment of tumours arising from or involving the central nervous system (CNS) that includes the brain and spinal cord and the peripheral nervous system (PNS), including the nerve roots, peripheral nerves, and nerve sheaths. The field sits at the intersection of neuroscience, oncology, and neurosurgery, and represents one of the most clinically and scientifically complex domains in all of medicine.

Tumours of the nervous system are unique in several fundamental respects. The brain and spinal cord are enclosed within rigid bony structures, the skull and vertebral column, meaning that even relatively small tumours can produce devastating neurological consequences through compression, oedema, and disruption of the highly specialised neural circuits governing movement, sensation, language, cognition, vision, and consciousness.

A brain tumor is different from a brain lesion. A lesion is usually the area of damaged tissue so not all lesions are tumors.

Primary brain tumors usually arise in the brain, and rarely do they break away and spread to other regions. Secondary/Metastatic brain tumors are those that are malignant tumors that have originated elsewhere in the body but have spread to the brain.

Metastatic brain tumors are four times more common than primary brain tumors, and they tend to spread and grow aggressively. Some common cancers that spread to the brain include kidney, lung, skin and colon cancer along with breast cancer.

Unlike most other organs, brain and nervous system CNS has an extremely limited capacity for regeneration - damage to neural tissue from tumour invasion, surgical resection, or treatment-related injury is often permanent. And the blood-brain barrier, a highly selective physiological interface between the systemic circulation and the CNS, restricts the entry of many systemic therapies, creating unique pharmacological challenges.

Brain tumours collectively account for approximately 330,000 new cases annually worldwide, making them among the most lethal of all cancer diagnoses when high-grade primary tumours are considered.

All brain cancers are tumors but not all brain tumors are cancerous.

Primary Brain Tumours

Gliomas are the most common primary brain tumours, arising from glial cells — the supportive cells of the CNS. They are further classified based on the cell of origin and molecular characteristics:

Glioblastoma (GBM)

The most common and most aggressive primary brain tumour in adults that account for approximately 50% of all primary malignant brain tumours.

Meningiomas

The most common primary intracranial tumour overall, accounting for approximately 37% of all primary brain tumours. They arise from the arachnoid cap cells of the meninges (membranous coverings of the brain and spinal cord) rather than from brain tissue itself, and are therefore extra-axial (outside the brain parenchyma). The vast majority are benign, slow-growing, and often curable with complete surgical resection. Grade 2 (atypical) and Grade 3 (anaplastic) meningiomas carry higher recurrence rates and may require adjuvant radiotherapy.

Pituitary Tumours

These are common benign tumours of the anterior pituitary gland. They are classified as functioning (secreting excess hormones such as prolactin, growth hormone, TSH) or non-functioning (causing symptoms through mass effect alone). Functioning adenomas produce characteristic endocrine syndromes like acromegaly (GH excess), Cushing's disease, and hyperprolactinaemia. Large adenomas (macroadenomas >1cm) can compress critical parts of the visual system and cause characteristic loss of the outer visual fields of both eyes. Pituitary carcinomas, true malignancies with CSF or systemic metastases are rare.

Secondary Brain Tumours

Brain metastases are significantly more common than primary brain tumours, occurring in approximately 20-40% of all cancer patients, most frequently from lung cancer (~40-50% of all brain metastases), breast cancer (~15-25%), melanoma (~5-20%), renal cell carcinoma, and colorectal cancer.

Symptoms

As brain tumor can occur at different parts of the brain, the symptoms also vary based on thier location. Some common symptoms are:

Risk Factors

Though the exact risk factors have not been proved, but these are few that increase one’s predisposition:

Treatment

The most common treatment for brain tumor is surgery. These are usually performed by craniotomy or endoscopically. Chemotherapy and radiation therapy are also used to shrink and slow down its growth or prevent it from recurring.

When the tumor is lodged close to the area which controls speech or movement, the physician may suggest awake craniotomy to monitor the function of different parts of the brain during surgery. Partial tumor removal surgeries may also be performed to alleviate the symptoms of patients.

The pituitary gland is situated in the hollow area in the back of the skull. The surgeries which are done to remove these tumors typically involve accessing the typically involve accessing the transsphenoidal route, and via this the tumor or damaged tissues are removed. These also help in alleviating other symptoms such as hormone imbalances or vision issues.

In some cases, neuroendoscopy or key-hole brain surgery, is a minimally invasive procedure that uses high-definition endoscopy to treat aneurysms, tumors and vascular conditions without damaging the nearby healthy tissues.