Brain Tumours in Children
Pediatric Brain Tumours
According to Cancer Council NSW, brain tumours happen to be the most common solid cancer that occurs in children, with approximately 75 children under 15 diagnosed in Australia each year. They occur almost as often as lymphopblastic leukaemia and are more likely to cause death (accounting for one third of cancer deaths in this age bracket).
Based on these statistics, it has been suggested that an early diagnosis of paediatric brain tumours is crucial to saving a patient’s life as it will allow treatment to be initiated while the tumour is still small. However, although paediatric brain tumours have a much better prognosis than adults due to the widespread availability of CNS imaging, they can often be misdiagnosed or diagnosed late. Hence, children who experience a long symptom interval associated with brain tumours are more likely to experience life-threatening complications, greater cognitive deficits, and irreversible neurological deficits (i.e. vision loss and endocrinopathies) than those who are diagnosed rapidly.
Symptoms and Signs of Paediatric Brain Tumours
Although some types of tumours may occur more frequently than others, they all have similar manifestations which are most commonly caused by increased intracranial pressure:
- Behaviour changes
- Gait and balance disorders
Repeated frequent headaches, that become worse with associated nausea and vomiting, indicate the possibility of a brain tumour. According to Albright (1993), this is still valid even if the neurologic examination does not show signs of abnormality, and a family history of migraines exists.
Diagnosis of Brain Tumour in Children
As soon as an intracranial lesion is suspected, a complete neurological examination becomes essential for diagnosing brain tumours. These include: MRI and Biopsy.
MRI – Magnetic resonance scans, according to research, have become the preferred diagnostic study for paediatric brain tumours. This is because it avoids irradiation and provides far better definition of parenchymal tumors as opposed to computed tomography (CT) scans. Furthermore, it detects tumours within the posterior fossa, subarachnoid spaces, arachnoid and pia mater.
Biopsy – A biopsy is usually required in order to confirm the diagnosis as well as determine tumour type and grade. Definitive diagnosis is made using a histologic evaluation of biopsy specimen or entire resected tumour. Once confirmed, the patient undergoes a staging process which is followed by:
- MRI of the entire spine
- Lumbar puncture for CSF cytology
- Postoperative MRI to assess for any residual tumour
In order to determine the risk of the tumour diagnosed, pathologists usually use a grading system which designates grades I and II as low grade tumours and III and IV as high grade tumours. Risk assessment is based on age, degree of residual tumour as well as evidence of disease spread.
Paediatric Brain Tumour Classification
There are many differences that exist between adults and children in terms of location and type of brain tumour encountered. Among children, brain tumours typically originate in the posterior cranial fossa, are more diverse by type and are more likely to be histologically atypical. The most common types of pediatric CNS brain tumours include:
Astrocytomas are CNS tumours that develop from a particular kind of glial cell, which are star-shaped brain cells located in the cerebrum known as astrocytes. According to researchers, this type of tumour can occur anywhere in the brain or spinal chord, but it is most common in the cerebellum. Astrocytomas range from two broad classes which have been recognized in literature: low-grade indolent tumours (which are the most prevalent) to malignant high-grade tumors.
Medulloblastomas are the most common type of paediatric malignant brain tumour that develop in the posterior fossa (containing the brain stem or cerebellum). Unlike most brain tumours, Medulloblastomas are non-invasive rapidly growing brain tumours that spread through the CSF (cerebrospinal fluid). The etiology is unknown in most patients, however, it may occur with certain syndromes such as Turcot syndrome or Gorlin syndrome.
Ependymomas are slow growing CNS tumors which arise from the ependymal lining of the ventricular system. In pediatric cases, the location of this type of tumour is usually intracranial (i.e. the fourth ventricle), whereas in adults it occurs in the spinal chord. Based on research, 70% of pediatric Ependymomas occur in the posterior fossa, where both high grade and low grade tumours tend to spread locally to the brain stem.
Treatment of Paediatric Brain Tumour
Since most treatments vary according to histology, it is necessary to conduct an operation to make tissue diagnosis and eradicate some if not all of the tumour. According to researchers, prognosis for certain tumours is correlated with the extent of resection. After the tumour is removed through surgery, the patient undergoes radiation therapy, chemotherapy, or both are usually required.