Optic pathway glioma
Childhood optic pathway glioma is a type of brain tumour which is usually benign (non-cancerous) and slow growing.
In this section
Optic pathway glioma 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.
If a child’s symptoms are very mild (children with known NF-1 will have visual screening to pick up early problems) and the optic glioma is small and growing very slowly, observing the tumour only is an option. Optic pathway gliomas associated with NF-1 can be very benign and can occasionally stop growing, or even shrink without treatment. However, regular eye checks and brain scans are necessary for observation.
Surgery may be considered after the diagnosis of an optic pathway glioma. The purpose of this may be a simple biopsy to confirm the type of tumour or to try and remove part of the tumour to relieve pressure. As the main aim is to preserve vision, it is rare for a neurosurgeon to try and remove all of the tumour, as this operation could damage the nerves supplying the eye.
Chemotherapy and radiotherapy
Both chemotherapy and radiotherapy can be used to treat the tumour with the aim of stopping the growth so that any further loss of vision is halted (sometimes vision is improved). The age of the child and how fast the tumour is growing are important in deciding whether the child needs further treatment and which type of therapy will be used.
In older children radiotherapy will be considered as a first treatment. It lasts up to six weeks as an outpatient and is very effective at controlling the tumour but does have some potential significant long-term side effects.
Chemotherapy is usually given as an outpatient and continues for up to 18 months. It is usually given by injections and drips into a vein (intravenous infusion). If your child takes part in a clinical trial, the treatment is explained in more detail in the specific trial information sheet. You will be given an outline of the treatment in the form of a ‘road map’.
Clinical trials are medical research trials involving patients that are carried out to try and find new and better treatments. In cancer, clinical trials are most commonly used to try and improve different forms of treatment such as surgery, radiotherapy or chemotherapy.
The treatment being tested may be aimed at:
- improving the number of people cured (for example: trying new types of surgery or chemotherapy)
- improving survival
- relieving the symptoms of the cancer
- relieving the side effects of treatment
- improving the quality of life or sense of well-being for people with cancer.
Clinical trials may also involve research aimed at understanding more about the tumour’s biology. You may be asked to allow us to do research on the tumour sample removed at surgery, or on blood samples.
Well-run clinical trials have led to a significant improvement in the treatment of children with cancer. You can find more general information on clinical trials in the separate information sheet. If you are asked to consider entering your child into a clinical trial you will be given specific information about the trial before deciding whether to take part.
Optic pathway gliomas are not usually life threatening (although aggressive tumours which grow quickly can be) and the aim is to preserve function. In up to half of children although controlled at first optic pathway gliomas can grow back and need further treatment.
General side effects of chemotherapy
Bone marrow suppression (myelosuppression)
Chemotherapy drugs decrease the production of blood cells by the bone marrow for a variable period of time. This results in low red blood cells (anaemia), low white blood cells (neutropenia) and platelets (thrombocytopenia). Your child may need blood or platelet transfusions and will be at increased risk of infections. The doctors and nurses caring for your child will tell you more about these side effects.
Nausea and vomiting
Some of the chemotherapy drugs used may make your child feel sick or vomit. We will give anti-sickness drugs at the same time to stop nausea and vomiting. These are usually very effective.
Sore mouth (mucositis)
Some of the chemotherapy drugs make the lining of the mouth and throat very sore and ulcerated. We will give your child painkillers for this, and explain how to care for your child’s mouth during treatment.
Temporary hair loss is common.
For details of the side effects of individual drugs please see Macmillan specific drug information leaflets.
What are the possible long-term effects of treatment?
A child may become blind or visually impaired needing help for their disability including suitable educational support. They may need hormone replacement therapy throughout their lifetime. They may develop learning difficulties as a result of the tumour or its treatment.
Children with NF-1 may have other problems over and above those from the tumour and these can impact on schooling.
All children are followed up after treatment is finished in the long-term brain tumour follow-up clinic. Your child will be seen at regular intervals in this clinic, indefinitely, so that we can help with any long-term effects of the treatment