<unk>  is a slow-growing brain tumor that arises in or around the<unk>  nerves.<unk>  may extend into the<unk>  chiasm or hypothalamus.  The majority of the<unk> s are benign but malignant<unk> s of the<unk>  nerve can occur.<unk> s are rare. The majority of<unk> s occur in children. They are usually slow-growing and noncancerous and almost always occur before age 20.<unk>  may be classified into several subtypes based on microscopic histopathology, anatomic location, and association with neurofibromatosis type 1.<unk>  pathway<unk> s are classified according to WHO classification into two subtypes: pilocytic astrocytoma and fibrillary astrocytoma.<unk> s may be classified according to anatomic location into two subtypes: anterior visual pathway tumors and posterior visual pathway tumors. Based on whether or not they are associated with neurofibromatosis type 1, they may be classified into two subtypes:<unk> s associated with neurofibromatosis type 1 and<unk> s not associated with neurofibromatosis type 1. Genes involved in the pathogenesis of<unk>  include BRAF-KIAA, tumor suppressor genes and chromosomes 7q34 and 17q. On gross pathology, smooth and fusiform intradural lesions are characteristic findings of<unk> . On microscopic histopathological analysis, low grade spindle shaped pilocytic astrocytes & glial filaments with the presence of numerous Rosenthal’s fibers are characteristic findings of<unk> s. There is no established cause for<unk> .<unk> s affects females and males equally.<unk> s commonly affects individuals younger than twenty years of age. There is no racial predilection to the<unk> .<unk> s affects girls and boys equally. There are no established risk factors for<unk> s. Symptoms of<unk>  include proptosis, unilateral or bilateral visual impairment, nystagmus, squinting, obstructive hydrocephalus and diencephalic syndrome. On head and neck CT,<unk>  is characterized by variably enlarged and elongated<unk>  nerve with kinking or buckling. On head and neck MRI,<unk>  is characterized by isointense to hypointense mass on T1-weighted MRI, and hyperintense mass on T2-weighted MRI. The mainstay of therapy for<unk>   is chemotherapy and radiation therapy. Chemotherapy is used in children to delay radiation therapy, and to reduce the severity of radiation therapy induced side-effects. Radiation therapy is not generally used in children less than five years of age and usually avoided in children between five and ten years of age. Radiation therapy is delayed in young children to reduce the risk of significant side- effects such as developmental and neurocognitive delay. Chemotherapy using vincristine, actinomycin D, bevacizumab, etoposide, and other agents has also been reported to be effective in patients with progressive hypothalamic/chiasmal<unk> s.  Surgery is not the first-line treatment<unk> n for patients with<unk> . Surgical excision is usually reserved for patients with either progressive proptosis, blindness, exophytic chiasm tumor causing mass effect, hydrocephalus, or with increased intracranial pressure.
Optic nerve glioma
Optic nerve sheath meningioma
Intraocular lymphoma
Graves ophthalmopathy
Labyrinthitis
Kjer's optic neuropathy
Lacrimal gland tumor
Vestibular tumor