Q1. What are the brain tumours in children?
Brain tumours are the second most common tumour in children. There are about 30 to 40 new cases in Hong Kong every year. Brain tumours develop in the brain, and can be either benign or malignant. The most common types include glioma, medulloblastoma and germ cell tumour.
Q2. What causes brain tumours? When do they occur in children?
Similar to other tumours, brain tumours mostly result from genetic changes or mutations in the cells within the body. These mutations are not necessarily inherited, but occur during growth and development. Any malfunction in genetic materials or genes in different cells can contribute to the development of various types of tumours. Due to the presence of different types of tissues in the brain, there can be various kinds of brain tumours.
The age at which brain tumours occur depends on the tumour type. Some brain tumours, such as germ cell tumours, can happen to children at different ages, ranging from infancy to adolescence. Certain types of brain tumours, however, are more commonly diagnosed in children under the age of five, such as medulloblastomas. There are exceptional cases, as certain specific types of brain tumours may develop during adolescence.
Q3. What are the common symptoms of brain tumours?
The symptoms vary with tumour location. As the two of the most common brain tumours, medulloblastomas and germ cell tumours are characterised by obstructive hydrocephalus and affected flow of cerebrospinal fluid. It is similar to a clogged sink that cannot drain water properly. When the brain cavities called “ventricles” are under the pressure of excessive cerebrospinal fluid, the most obvious symptoms are vomiting and headache.
The vomiting pattern is quite distinctive. Affected children are more likely to vomit when they wake up in the morning or from an afternoon nap, often without recurrence in the following days. And it tends to repeat more frequently after the second vomiting episode, with shorter intervals in between subsequent episodes. Parents often misinterpret this intermittent vomiting pattern as stomach problem or other conditions, resulting in delayed medical consultation.
As for headaches, children under the age of five may not be able to express themselves, or they can only complain that the head hurts or feels heavy, being unable to describe the pain. Both vomiting and headaches are the most common early symptoms of paediatric brain tumours.
Q4. Why is it difficult for parents to notice the symptoms?
As mentioned earlier, those symptoms may not necessarily be associated with brain conditions. For example, when it comes to vomiting, most people would usually think of gastrointestinal problems or food-related causes, rather than brain-related issues. The facts that headaches are common, and children are less able to express their pain or discomfort, also add to the difficulty.
The impacts on the nervous system with any neurological presentations are also difficult to notice. For example, children with germ cell tumours that grow on the pineal gland may have difficulty looking upward. Also their pupils do not respond to light. These symptoms are less likely to be noticed by common people. Children with tumours in the cerebellum may stumble, a symptom even less noticeable among those aged below five. While some may write in larger and larger characters due to a brain tumour, one’s writing may be normal if only the right side of the brain is affected, the right cerebral lesion will affect the functions of left side extremity only. Therefore, it is often not reliable to make assessment solely based on the dysfunction related to the nervous system.
Q5. How to diagnose brain tumours?
Brain tumours are often diagnosed by clinical examinations and imaging investigations, including computed tomography (CT scan) and magnetic resonance imaging (MRI). Diagnosis is important as the doctor needs to assess the nature of the detected tumour. In recent years we have significant advancements in pathological diagnosis. In addition to the study of tumour morphology, molecular biology analysis can identify both the specific molecular targets in tumours for targeted therapy as well as the tumour origin by monitoring changes in the methylation pattern of the tumour.
Q6. What are the treatment methods for brain tumours?
Common treatment methods, such as surgery, chemotherapy and radiotherapy, are also adopted in brain tumour treatment. Treatments vary with tumour types. In case of germ cell tumours, chemotherapy and radiotherapy are the mainstay treatments. For ependymomas, surgery and radiotherapy are the major treatment options. The treatment approach depends on the brain tumour types, the conventional cancer management methods remains the main stream approaches.
In recent years, there have been significant advancements in treatment options, such as targeted therapy and immunotherapy. For patients with certain specific types of brain tumours, e.g. infants with rapidly growing high-grade gliomas, targeted therapies show great promises in clinical outcomes. Furthermore, tumours with chromosomal instability can be managed with immune checkpoint inhibitors. In addition to conventional treatment methods, we witness new approaches that give us advantage over specific types of brain tumours in recent years.
Q7. What type of discomfort will children with brain tumours experience during treatment?
Conventional treatment methods such as chemotherapy and radiotherapy have various known side effects. As chemotherapy targets the rapidly-dividing cells, hair loss may occur. It may also cause damage to the mucous membranes from the mouth to the gastrointestinal tract. As the haematopoietic stem cells in bone marrow are suppressed, chemotherapy can lead to anaemia, low platelet count, or low white blood cell count. Low platelet count can increase the risk of bleeding, while low white blood cell count can make individuals more prone to infection.
As regards conventional radiotherapy, there are also concerns over damage to the tissues surrounding the treatment site, i.e. the normal brain tissues. With recent advancement in treatment options, namely proton therapy, comparable efficacy can be achieved with far less impact on the surrounding normal tissues in the affected area.
Q8. What should I beware of after recovery?
Brain tumours differ from other cancer types such as leukaemia, of which post-therapy remission after cured means full recovery, while survivors of post-treatment brain tumours have a certain degree of damage to the brain tissues. The damaged brain tissues after treatment make it necessary for post-recovery rehabilitation. For example, patients with tumuors in the cerebellum may experience impact on balance and other related functions. Therefore, upon completion of cancer treatment, it is important for patients with impaired functions to undergo exercises and training for adaptation. Some patients may have tumours arising in the sellar region, i.e. the pituitary gland below the optic nerves, and affect the endocrine function. Doctors need to give hormonal replacement to compensate for their impaired functions, e.g. growth hormone. In case of deficiency in sex hormones, hormonal replacement therapy may be needed. For others such as thyroid and adrenal glands, the post-therapy recovery follow-ups depend on where the tumour grows.
Some patients have brain tumours in the motor cortex region, affecting their physical functions and limb movement. They need to receive physiotherapy or use assisted devices.
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