Plexiform neurofibromatosis of the orbit: CT evaluation

Seven patients with orbital plexiform neurofibromas (PNFs) were evaluated by computed tomography (CT). These lesions are pathognomonic of von Recklinghausen disease and manifest a spectrum of radiologic abnormalities ranging from thickening of the eyelid and periorbital soft tissues to enlargement of the bony orbit and extensive infiltration of the orbital soft tissues. In analyzing the CT features of orbital PNF, three findings that have not been previously reported were identified. Increased density of the intraconal fat present in four of seven patients was believed to represent PNF involvement of small intraconal nerves. Three patients demonstrated enhancing, irregularly nodular thickening of the optic nerve sheath complex thought to be caused by PNF of the posterior ciliary nerves surrounding the optic nerve. Three patients with buphthalmos and congenital glaucoma demonstrated thickening and enhancement of the uveal/scleral layer believed to represent PNF of these structures. Involvement of the choroid and sclera, posterior ciliary nerves, and small intraconal nerves has been recognized pathologically but has not been previously identified by CT.