Primary tumors of the optic nerve are uncommon. Optic nerve gliomas (ONG) represent approximately 4% of all orbital tumors, 4% of all intracranial gliomas, and 2% of all intracranial tumors.<sup>2 Alvord E.C., Lofton S. Gliomas of the optic nerve or chiasm: Outcome by patients' age, tumor site and treatment J Neurosurg 1988 ;  68 : 85-98  [cross-ref]

Cliccare qui per andare alla sezione Riferimenti</sup> They account for 66% of all primary optic nerve tumors. The main differential diagnosis for an ONG is an optic sheath meningioma.<sup>25 Thompson C.R., Lessell S. Anterior visual pathway gliomas Int Ophthalmol Clin 1997 ;  37 : 261-279  [cross-ref]

Cliccare qui per andare alla sezione Riferimenti</sup> Gliomas are 4:1 more common than meningiomas. The peak age of occurrence ranges from 2 to 8 years old, with a girl to boy predominance of 3:2. Seventy-five percent of gliomas are diagnosed in the first decade and 90% are diagnosed in the first two decades.<sup>3 Aoki S., Barkovich A.J., Nishimura K. , e al. Neurofibromatosis types 1 & 2: Cranial MR findings Radiology 1989 ;  172 : 527-534

Cliccare qui per andare alla sezione Riferimenti</sup> They can be solitary or a component of neurofibromatosis-1 (NF-1). If bilateral, they are considered to be pathognomic of NF-1. Ten percent to 38% of patients with ONG have NF-1 and 15% to 40% of patients with NF-1 have optic pathway gliomas.<sup>1 Alshail E., Rutka J.T., Becker L.E. , e al. Optic chiasmatic-hypothalamic glioma Brain Pathol 1977 ;  7 : 799-806

Cliccare qui per andare alla sezione Riferimenti</sup> Fifty percent to 85% of all optic pathway gliomas involve the chiasm or the hypothalamus.<sup>27 Weber A.L., Klufan R., Pless M. Imaging evaluation of the optic nerve and visual pathway Neuroimaging Clin North Am 1996 ;  6 : 143-177

Cliccare qui per andare alla sezione Riferimenti</sup> Eighty percent of patients with NF-1 have optic nerve gliomas confined to the optic nerve alone.

This article discusses the anatomy of the optic pathway and the imaging and clinical manifestations of ONG. Other neoplasias, which mimic ONG, are discussed elsewhere in this issue.