Optic nerve glioma, also known as optic gliomas, are a rare type of brain tumoura tissue mass that forms from groups of unhealthy cells that develop from the glial (or supportive) cells in the central nervous system (CNS). More specifically, they develop from a type of glial cell called astrocytes, a star-shaped cell that has a variety of functions, including regulating blood flow and regulating and maintaining synapses.
The brain is a complex organ that is responsible for controlling all functions of the body. It has five main portions: the cerebrum, cerebellum, brainstem, pituitary gland, and hypothalamus. The cerebrum is the biggest part of the brain, and consists of the frontal, parietal, temporal, and occipital lobes. This part of the brain is responsible for voluntary movement, intelligence, and memory. The cerebellum is a small part of the brain located at the back of the head, and regulates posture and balance. The brainstem is a small, stalk-like structure towards the bottom of the brain that connects the brain to the spinal cord. It regulates many vital bodily processes, such as swallowing, breathing, and heart rate. The pituitary gland is a pea sized organ located behind the eyes, and is responsible for the production and secretion of hormones in the body. The hypothalamus is located deep within the brain, and has many important functions, such as producing and secreting different hormones, regulating temperature, and controlling appetite.
The optic nerve, which is also known as the second cranial nerve, is responsible for transmitting visual information from the eyes to the brain. It also has a role in regulating your 24-hour internal body clock, also known as the circadian rhythm. In most cases, tumours that develop on the optic nerve are either pilocytic astrocytomas or fibrillary astrocytomas, however other types of tumours may occur, such as gangliogliomas.
Optic nerve gliomas are generally diagnosed equally among the sexes, and are often diagnosed in children under 10. However, anyone can develop this disease.
Treatment
When cancers are detected, they are staged and graded based on size, metastasiswhen the cancer has spread to other parts of the body, also known as mets, and how the cancer cells look under the microscope. Staging and grading helps your doctors determine the best treatment for you. However, brain cancers are rarely staged, as they rarely spread to other parts of the body. Instead, they are generally graded from I-IV.
In most cases, optic nerve gliomas are categorised as gradea description of how abnormal cancer cells and tissue look under a microscope when compared to healthy cells I tumours. Grade I (low grade) tumours have cellsthe basic structural and functional unit of all living things that present as slightly abnormal, and are usually slow growing.
Once your tumour has been graded, your doctor may recommend genetic testinga procedure that analyses DNA to identify changes in genes, chromosomes and proteins, which can be used to analyse tumour DNA to help determine which treatment has the greatest chance of success, which analyses your tumour DNA and can help determine which treatment has the greatest chance of success. They will then discuss the most appropriate treatment option for you.
Treatment is dependent on several factors, including location, age, stage of disease and overall health.
Treatment options for optic nerve gliomas may include:
- Chemotherapya cancer treatment that uses drugs to kill or slow the growth of cancer cells, while minimising damage to healthy cells.
- Radiation therapya treatment that uses controlled doses of radiation to damage or kill cancer cells.
- Surgerytreatment involving removal of cancerous tissue and/or tumours and a margin of healthy tissue around it to reduce recurrence (limited).
- Shunt insertiona procedure to relieve build-up of cerebrospinal fluid (CSF) in the brain.
- Watch and waitthe close monitoring of a cancer without giving treatment until symptoms appear or worsen.
- Targeted therapymedication that targets specific molecular features of cancer cells.
- Clinical trialsresearch studies performed to test new treatments, tests or procedures and evaluate their effectiveness on various diseases.
- Palliative carea variety of practices and exercises used to provide pain relief and improve quality of life without curing the disease.
Risk factors
While the cause of optic nerve gliomas remains unknown, the development with these tumours has been associated with a genetic condition known as neurofibromatosis type 1 (NF1).
Not everyone with these riskthe possibility that something bad will happen factors will develop the disease, and some people who have the disease may have none of these risk factors. See your general practitioner (GP) if you are concerned.
Symptoms
Optic nerve gliomas may appear asymptomatic in the early stages of disease. As the cancera disease where abnormal cells split without control and spread to other nearby body tissue and/or organs progresses, some of the following symptoms may appear dependent on the tumours location within the brain:
- Decreased vision.
- Proptosisbulging or protrusion of one or both of the eyes out of the eye sockets, also known as exophthalmos.
- Nystagmus.
- Hydrocephalusa build up of cerebrospinal fluid (CSF) in the brain, causing pressure and potentially damaging brain tissue, which carries its own set of symptoms:
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- Headaches.
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- Nausea and/or vomiting.
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- Difficulties with eye movement.
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- Difficulties with balance.
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- Difficulties with walking.
- Polyuriafrequent urination.
- Polydipsiaabnormal or escessive thirst.
- Precocious (early) puberty.
- Changes in alertness.
- Changes in energy levels.
- Hormonal deficiencies.
- Unexplained weight loss or weight gain.
Not everyone with the symptoms above will have cancer, but see your general practitioner (GP) if you are concerned.
Diagnosis
If your doctor suspects you have an optic nerve glioma, they may order the following tests to confirm the diagnosisthe process of identifying a disease based on signs and symptoms, patient history and medical test results and refer you to a specialist for treatment:
- Physical examinationan examination of your current symptoms, affected area(s) and overall medical history.
- Neurological examinationan assessment of sensory and motor functions, such as vision, balance and coordination.
- Genetic testing.
- Eye tests.
- Blood teststesting done to measure the levels of certain substances in the blood.
- Imagingtests that create detailed images of areas inside the body tests, potentially including:
- MRI (magnetic resonance imaging)a type of medical imaging that uses radiowaves, a strong magnet and computer technology to create detailed images of the body.
- CT (computed tomography) scana type of medical imaging that uses x-rays and computer technology to create detailed images of the body.
- Biopsyremoval of a section of tissue to analyse for cancer cells (if possible).