Optic nerve glioma classification
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: {{Simrat]]
Overview
Classification
Optic pathway gliomas (OPGs) are classified by whether or not they are associated with neurofibromatosis type 1 (NF1, von Recklinghausen's disease) and by anatomic location. According to their location along the optic pathway, the two major categories are: Location — Low-grade gliomas may involve the anterior visual pathway of the optic nerve (25 to 35 percent of cases) or the posterior visual pathways (chiasmal and postchiasmal).
Anterior visual pathway — Anterior tumors can be subdivided into:
- Orbital
- Intracanalicular
- Intracranial prechiasmal lesions.
Most of anterior visual pathway tumors are classified as pilocytic astrocytomas and they occur most frequently in prepubertal children.
Posterior visual pathway — Posterior tumors may arise in the
- Optic chiasm
- Hypothalamus
- Anterior third ventricle
Most of posterior visual pathway tumors are classified histologically as pilocytic astrocytomas, and occasionally gangliogliomas. Hypothalamic and chiasmal lesions present at a mean age of about three years. Optic nerve gliomas can involve one or both optic nerves. About 10% of optic pathway tumors are located within an optic nerve, one third of the tumors involve both optic nerve and chiasm, another one third involves predominantly the chiasm itself, and one fourth involves predominantly the hypothalamus. 5 5% of optic nerve gliomas are multicentric. In approximately 50% of patients, an OPG occurs in isolation, without any known chromosomal aberration; however, in the remaining 50% of patients, a diagnosis of von Recklinghausen disease is seen. Von Recklinghausen disease, also known as Neurofibromatosis Type I (NF1), is an autosomal dominant disorder with an incidence of one in 3000-5000 births, but approximately 50% of cases are spontaneous mutations. When associated with NF1, most OPGs are benign, and can be multifocal and bilateral in nature and usually confined to the optic nerves. If a child has bilateral tumors, then it is very likely that the child has NF-1. OPGs are the most common central nervous system tumors associated with NF1. If all children underwent screening, estimates indicate that OPGs would be found in 15 percent of those with NF1 [7,8]. NF1 tumors more commonly involve the anterior visual pathway, while tumors in NF1 negative children are more frequent in the posterior visual pathway [9]. OPGs have also been described in patients with NF2 25-40% of optic gliomas occur in children with NF-1, and of children with NF-1, about 10% develop optic gliomas.
This classification correlates highly with:
The appropriate treatment for the disease Symptoms associated with the tumor Patient prognosis