Central Nervous System (CNS) tumours

The central nervous system includes the brain and spinal cord. The brain consists of 3 main parts: the cerebrum, cerebellum and brainstem, and are each responsible for important neurological functions. The cerebrum consists of the two cerebral hemispheres, and is responsible for motor and sensory function, cognitive function, memory, language and personality. The cerebellum controls involuntary actions, including body balance and coordination. The brainstem governs many vital functions of life, such as consciousness, blood pressure, heart rate, and breathing. It also serves as a centre of signal conduction, in which all information relayed from the body to the cerebrum or cerebellum (and vice versa) passes through.

CNS tumours are formed from abnormal growth of cells in the brain or spinal cord. They may originate from the CNS (primary tumours), or spread from cancers that originate in other parts of the body (secondary tumours). 

Primary CNS tumours are generally named after the type of cells they are developed from, and are either benign or malignant. Benign tumours are relatively slow growing, and have distinct boundaries. Examples include pituitary adenoma, schwannoma, and meningioma with good cellular differentiation. They have relatively low risk of recurrence after definitive treatment, and are associated with good prognosis. In contrast, malignant CNS tumours grow quickly, have irregular boundaries, and may invade or press on surrounding tissue, causing neurological damage. The common types of malignant primary CNS tumours include glioblastoma and astrocytoma. They are associated with high rates of recurrence and poorer prognosis.

Secondary CNS tumours are those that have spread to the CNS from cancers that originate in other parts of the body, typically via the bloodstream. Common cancer origins include the lung and breast. Occasionally, they may be detected long after the initial diagnosis or treatment of the primary cancer.

The cause of primary CNS tumours is uncertain. However, there are a number of factors that may increase the risk of developing them. They include:

• Age: CNS tumours may occur at any age, but they are more common in those over 45 years of age. Certain types of brain tumours, such as medulloblastoma, occur almost exclusively in children.
• Gender: CNS tumours are more common in men than women.
• Family history: People with family members who have gliomas may be more likely to develop this disease.
• Exposure to radiation or to certain chemicals at work, such as formaldehyde, vinyl chloride and acrylonitrile.

Doctors are not sure of the exact cause of CNS tumours. Only a few cases indicated that they might be inherited or caused by chemicals. Hence, there is no known way to prevent them. To date, there is no evidence of any association between the use of mobile phones and the development of brain tumours. On the other hand, early awareness of tumour-related symptoms could prompt early diagnosis and treatment.
 

The symptoms of CNS tumours depend on their location, type and size. Since different areas of the brain and spinal cord are responsible for different neurological functions, tumours arising from different positions could result in corresponding neurological symptoms. Some common symptoms include:

• Seizures
• Headaches, dizziness, tinnitus
• Nausea or vomiting
• Weakness or loss of sensation of arms or legs, imbalance, or partial paralysis.
• Reduced vision or double vision
• Numbness or tingling of facial muscles
• Speech problems, difficulty in language comprehension or expression
• Confusion, personality changes or memory loss
• Bladder or bowel incontinence

 
Tumours in the brain can also cause an increase in intracranial pressure. Symptoms may include headache (which may be worse with coughing, sneezing or straining), vomiting, and clouding of consciousness. Tumours located in the pituitary gland may lead to disorders of excessive or impaired hormone secretion.
 

Aside from clinical history and physical examination, common investigations for CNS tumours include:

• Computer Tomography (CT): to visualise the size and location of the tumours.
• Magnetic Resonance Imaging (MRI): provide high-resolution imaging to make radiological diagnosis of the type of tumour, and facilitate the planning of surgery or radiotherapy.
• Positron Emission Tomography (PET) scan: particularly useful in secondary CNS tumours, to detect and delineate the primary cancer origin.
• Pathological diagnosis: the gold standard to confirm the diagnosis, subtyping, and inform on the prognosis for many CNS tumours. Pathological diagnosis may be made at definitive surgery, or obtained by tissue biopsy.

Treatment for CNS tumours can involve surgery, radiation therapy or chemotherapy, depending on the type of tumour. Many patients require a combination of treatment modalities. Doctors will tailor treatment to individual tumour and patient characteristics such as age, comorbidities, tumour location, and associated treatment risks. In general, primary and secondary CNS tumours are different in treatment approach.
 
Primary CNS tumours
Treatment options include:
Surgery
Surgery is the definitive treatment for most patients if feasible. It aims to remove as much tumour as possible or safe. As minimally invasive surgery techniques are increasingly refined, neurosurgeons are able to remove the tumours more effectively and safely, increasing the chances of recovery and minimising the side effects. In some cases, where tumours are located near sensitive areas of the brain or surgical risk is high, surgery may not be possible and other forms of treatment may be required.
 
Radiation therapy
Radiation therapy refers to the use of high-energy rays to kill tumour cells. It is commonly used as an adjuvant treatment after surgery, and may be combined with chemotherapy in some tumour types. In recent years, there is significant improvement in radiotherapy techniques, such as the availability of intensity-modulated radiation therapy (IMRT), image-guided radiation therapy (IGRT) and stereotactic radiosurgery (SRS). These techniques improve treatment accuracy, allowing the delivery of a high dose of radiation to eradicate tumour cells while minimising the dose to normal tissues and the risk of neurological complications.
 
Chemotherapy
Chemotherapy refers to the use of drugs to kill cancer cells, and may be given in oral or intravenous route They are commonly combined with radiotherapy. Chemotherapy is also indicated where curative treatment is not possible. In these situations, the aim of treatment is for tumour control, relief of symptoms, and improve quality of life.
 
Secondary CNS tumours
CNS-directed local treatment, such as radiotherapy or surgery (as described above) are common treatment options. In addition, systemic anti-cancer treatment of the underlying primary cancer for overall disease control is usually required. These include chemotherapy, targeted therapy and immunotherapy, and the choice of treatment depends on the underlying cancer type.
 

Possible side effects or complications vary with different treatment modalities. Examples include:

• Surgery: there may be impairment in neurological function, such as impaired mobility or weakness of limbs, sensory deficit, decline in cognition or memory, and impaired language or swallowing function. Some of these complications may also be related to the effects of the tumour. Other surgical complications may include bleeding, infection, and wound problems.
• Radiation therapy: possible side effects include fatigue, scalp irritation, hair loss, nausea/ vomiting, headaches, and long-term memory and cognitive decline. High dose radiation therapy may also result in a small risk of necrosis of the normal brain tissue.
• Chemotherapy: side effects may include fatigue, mouth sores, nausea/ vomiting, poor appetite, diarrhoea, hair loss, and weakened immune system.

• Being prepared: patients and their caregivers should be aware of the relevant disease and treatment information. Better understanding and being prepared in advance helps to facilitate the treatment process and positive coping.

• Treatment and follow-up: attend to necessary treatment and regular follow-up for monitoring of the disease progress and potential treatment-related side effects.

• Rehabilitation: patients with CNS tumours often have impaired neurological function, such as mobility, language and swallowing ability. Attendance to structured rehabilitation programs tailored to individual patient needs, such as physiotherapy, occupational therapy, and speech therapy, could facilitate gradual training and improvement in neurological function.

• Taking care of dependent patients: patients with CNS tumours are often physically dependent on their care-givers for activities of daily living such as feeding, toileting, bathing, etc. Support from family members is a key element to the patient’s treatment and rehabilitation process. Advice from the medical team, assistance from medical social workers, and support from the community are available based on individual patient and care-giver needs.

• Healthy lifestyle: adequate rest, avoid over-exertion, and maintaining a balanced diet and appropriate exercise are recommended. Cancer treatment such as chemotherapy might weaken the immune system. Immunocompromised patients are advised to avoid intake of raw or undercooked meat, poultry, eggs, seafood, raw or unpasteurized dairy products, and ready-to-eat raw vegetables.

• Mental health: emotional support and positive disease coping are crucial for CNS tumour patients and care-givers to navigate emotional challenges in the disease and treatment journey. Advice from mental health professionals, including clinical psychologists, psychiatrists, and medical social workers can help to alleviate stress and anxiety through supportive counselling or other strategies.