Optic pathway glioma
Childhood optic pathway glioma is a type of brain tumour which is usually benign (non-cancerous) and slow growing. It is also called a low grade glioma. Gliomas are tumours that originate from brain cells called astrocytes.
An optic pathway glioma occurs along the nerves that send messages from the eye to the brain (the optic pathway) and can occur anywhere along its path.
Who gets optic pathway glioma?
Although the cause of most brain tumours is not known, we do know that a genetic condition called neurofibromatosis (type 1) can lead to these particular tumours. If the child is young (under five years of age) it may not be obvious to anyone that the child has this condition until the time of diagnosis of the optic pathway glioma.
Neurofibromatosis type 1 (NF-1) can be inherited from a parent, but half the time the child will be the first affected in the family. The condition varies widely but the following problems can occur throughout life:
- tendency to develop both benign and occasionally cancerous tumours
- skin lesions (several types from lesions like freckles to large lumps in the skin (neurofibromata)
- skeletal problems (for example, curvature of the spine or scoliosis)
- behavioural and learning difficulties (ranging from none to severe).
A child or family with NF-1 will be offered specialist counselling and be followed up by a paediatrician with an interest in the condition.
Signs and symptoms
The first problems a child may suffer from are usually related to vision such as:
- reduced vision
- flickering eyes
- eye protruding forward
- double vision
- head tilt
- blind spots.
If there is increased pressure in the head (raised intracranial pressure), symptoms will also include:
- nausea and vomiting (most common)
- lethargy and irritability
These symptoms may show up as problems in school, apparent clumsiness and sitting closer to watch television. Part of the brain that helps to control the hormones in the body (hypothalamus) is sometimes affected by optic pathway tumours. This can lead to hormonal problems such as early puberty or weight problems (either loss or gain).
Tests / investigations
We will need to carry out some tests to find out as much as possible about the type, position and size of the tumour. This will help us to decide on the best treatment for your child. These tests include:
- CT scan – it is likely a CT scan of your child’s brain was the first specific test carried out at your local hospital. Although MRI scans are usually the best way of seeing the tumour and the effects of treatment, sometimes CT scans are also useful.
- MRI scan – this scan allows us to see the brain and spine in great detail and is used regularly to diagnose and follow the effect treatment is having on your child’s tumour.
- Ophthalmic assessment – a full assessment of your child’s vision will need to be recorded at the time of diagnosis, during and after treatment. This is painless but sometimes difficult for young children.
- Endocrine assessment – if there is evidence of the tumour pressing the hypothalamus or pituitary gland a full test of your child’s hormones will be needed. This usually involves simple blood tests.
Staging is a measure of how far the tumour has spread beyond its original site.