Neurofibromas are tumors composed chiefly of proliferating Schwann cells within the nerve sheaths. Axons, endoneural fibroblasts, and mucin are also noted on histologic examination. Plexiform neurofibromas consist of diffuse proliferations of Schwann cells within nerve sheaths, and they usually occur in cases of neurofibromatosis 1 (NF1). They are well-vascularized infiltrative lesions, making complete surgical excision difficult. Discrete neurofibromas are less common than the plexiform type and can usually be excised without recurrence. In either instance, surgery is limited to tumors that compromise vision or produce disfigurement.
Patients with neurofibromas are evaluated for neurofibromatosis. Also known as von Recklinghausen disease, NF1 is inherited through an autosomal dominant gene with incomplete penetrance. Because NF1 is characterized by the presence of hamartomas involving the skin, eye, central nervous system, and viscera, it is classified as a phakomatosis. NF1 is the most common phakomatous disorder; its significant orbital features include plexiform neurofibromas of the lateral aspect of the upper eyelid resulting in an S-shaped contour of the eyelid margin (Fig 5-10), pulsatile proptosis (Video 5-1) secondary to sphenoid bone aplasia, and optic nerve glioma. See BCSC Section 6, Pediatric Ophthalmology and Strabismus, for further discussion of neurofibromatosis and other phakomatoses.
Figure 5-10 Neurofibromatosis 1 presenting with a plexiform neurofibroma of the right upper eyelid in S-shaped configuration.
(Courtesy of Bobby S. Korn, MD, PhD.)
Patient with NF1 presenting with pulsatile proptosis from sphenoid wing aplasia. Courtesy of Bobby S. Korn, MD, PhD.
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Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.