Optic nerve glioma (or optic glioma), a form of

glioma A glioma is a type of tumor that starts in the glial cells of the brain or the spine. Gliomas comprise about 30 percent of all brain tumors and central nervous system tumours, and 80 percent of all malignant brain tumours. Signs and symptoms ...

which affects the

optic nerve In neuroanatomy, the optic nerve, also known as the second cranial nerve, cranial nerve II, or simply CN II, is a paired cranial nerve that transmits visual system, visual information from the retina to the brain. In humans, the optic nerve i ...

, is often one of the

central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all par ...

manifestations of neurofibromatosis 1. Optic gliomas are usually pilocytic tumors, and can involve the

optic chiasm In neuroanatomy, the optic chiasm, or optic chiasma (; , ), is the part of the brain where the optic nerves cross. It is located at the bottom of the brain immediately inferior to the hypothalamus. The optic chiasm is found in all vertebrate ...

. Optic gliomas are usually associated with

neurofibromatosis type 1 Neurofibromatosis (NF) is a group of three conditions in which tumors grow in the nervous system. The three types are neurofibromatosis type I (NF1), neurofibromatosis type II (NF2), and schwannomatosis. In NF1 symptoms include light brown sp ...

in 30% of people with the condition. Optic nerve gliomas have low mortality but extremely high prevalence of vision loss & eye-bulging

exophthalmos Exophthalmos (also called exophthalmus, exophthalmia, proptosis, or exorbitism) is a bulging of the eye anteriorly out of the orbit. Exophthalmos can be either bilateral (as is often seen in Graves' disease) or unilateral (as is often seen in ...

) in children. As of 2014, approximately 1000 cases had been reported.

Diagnosis

Optic nerve gliomas are diagnosed using

magnetic resonance imaging Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio wave ...

(MRI) and CT scans. The tumor adopts a

fusiform Fusiform means having a spindle-like shape that is wide in the middle and tapers at both ends. It is similar to the lemon-shape, but often implies a focal broadening of a structure that continues from one or both ends, such as an aneurysm on a b ...

appearance, appearing wider in the middle and tapered at the ends. Enlargement of the optic nerve along with a downward kink in the mid-orbit is usually observed. While CT scans allow for optic nerve evaluation, MRI allows for intracranial evaluation to observe if the tumor has extended to other regions such as the

hypothalamus The hypothalamus () is a part of the brain that contains a number of small nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrine system via the pituitary gland. The hypothalamu ...

Treatment

The main goal of treating optic gliomas is to preserve vision for as long as possible. The tumor’s slow & self-limiting growth indicates that it is not immediately problematic in most benign cases, with long-term studies showing that people with optic glioma may still have stable functional vision without intervention. As a result, the first & preferred course of action is usually observation of optic glioma over time. Once the first signs of visual deterioration and/or tumor progression are observed, interventional treatments will then commence. These include

radiation therapy Radiation therapy or radiotherapy, often abbreviated RT, RTx, or XRT, is a therapy using ionizing radiation, generally provided as part of cancer treatment to control or kill malignant cells and normally delivered by a linear accelerator. Radia ...

chemotherapy Chemotherapy (often abbreviated to chemo and sometimes CTX or CTx) is a type of cancer treatment that uses one or more anti-cancer drugs (chemotherapeutic agents or alkylating agents) as part of a standardized chemotherapy regimen. Chemotherap ...

and surgical excision. While being the most effective therapy, radiation has shown damaging effects on the already compromised intellect as well as an increase in vascular issues & second tumor formation in children with neurofibromatosis 1. However, fractionated

stereotactic radiation therapy Stereotactic radiation therapy (SRT), also called stereotactic external-beam radiation therapy and stereotaxic radiation therapy, is a type of external radiation therapy that uses special equipment to position the patient and precisely deliver rad ...

(FSRT) is gaining traction as the most preferred interventional treatment for optic nerve glioma due to its combination of the therapeutic efficiency of radiation therapy without the negative side effects. Chemotherapy has also been shown to be a safer alternative to most radiation therapies & surgery for very young children (under the age of 3). However, the optimal chemotherapeutic therapy has not been defined, with risks of different toxicities still observed in older children. Surgery is considered the final choice of treatment, due to the high risk of blindness & damage to the affected eye. It is considered in only certain scenarios, such as relieving a cosmetically unappealing bulging eye (

), removing an enlarging and/or expanding tumor or a combination of both.

Prognosis

Optic gliomas alternate between periods of inactivity and growth, making their clinical presentation variable & clinical course unpredictable. Once the optic chiasm is involved, the prognosis for life & vision worsens.

References

External links

* {{Central nervous system tumors Nervous system neoplasia