Tumors and Masses of the Optic and Perioptic Nerve Fibers

Although MRI plays a major role in the diagnosis of these lesions of the optic nerve, ultrasound is useful too, especially combining B-mode, standardized A-mode and color-Doppler imaging (CDI). Optic pathway gliomas occur mainly in children and are frequently associated with neurofibromatosis type 1. When involving the orbital optic nerve, there is an enlarged fusiform optic nerve, with a possible angulation when posteriorly located and a subsequent dilation of the subarachnoid spaces around the anterior optic fibers. The lesion is well delineated, homogeneous, with sometimes small cystic areas; on CDI, the lesion is most often weakly vascularized. Meningiomas affect especially women from 40 to 60 years of age. On ultrasound, the optic nerve may be coarse and uneven or fusiform, with the optic nerve fibers generally seen inside the mass, more or less eccentric, with an optic disc swelling, or a flattening of the posterior pole and the visibility of calcified nodules (psamomas). On CDI, the tumor is generally quite vascularized. Hemangioblastoma, associated with von Hippel-Lindau disease, most often involves the orbital optic nerve and is very vascularized, with low resistive flows. Lymphoid lesions may be related to optic nerve lymphomas or optic perineuritis; they appear as low reflective, well-limited lesions, which are vascularized with low resistive (RI < 0.70) vessels. The search for an extension of an ocular tumor to the optic nerve involves MRI. Ultrasound would only be able to reveal large lesions, fortunately rare. Cysts may be related to optic nerve coloboma or to pseudocysts, which are small, retrobulbar, superiorly located and incidentally discovered when exploring a normal tension glaucoma.