Optic nerve sheath meningioma

Optic nerve sheath meningioma (ONSM) is a rare type of meningioma that forms around the optic nerve, which transmits visual information from the eye to the brain. These tumors are benign but can cause significant visual impairment due to their location. ONSM can affect one or both eyes and is more common in women than in men. The condition is most frequently diagnosed in adults, although it can occur at any age.

Symptoms

Symptoms of optic nerve sheath meningioma include, but are not limited to, progressive and painless loss of vision, visual field defects, and proptosis (bulging of the eye). Some patients may also experience optic disc swelling and, less commonly, diplopia (double vision).

Diagnosis

Diagnosis of ONSM is primarily based on magnetic resonance imaging (MRI) with contrast, which can delineate the tumor's extent and its effect on the surrounding structures. Computed tomography (CT) scans may also be used, especially to visualize calcifications, which are more common in meningiomas. A thorough ophthalmologic examination is essential for assessing visual function and identifying characteristic signs of the disease.

Treatment

Treatment options for optic nerve sheath meningioma vary depending on the size and location of the tumor, as well as the patient's symptoms and overall health. Observation is sometimes recommended for small tumors that do not affect vision. For symptomatic tumors, treatment options include surgery, radiation therapy, and, less commonly, chemotherapy. Surgical removal can be challenging due to the risk of damaging the optic nerve and other nearby structures. Radiation therapy, including stereotactic radiosurgery, offers a non-invasive alternative with promising outcomes in terms of tumor control and preservation of vision.

Prognosis

The prognosis for patients with optic nerve sheath meningioma largely depends on the tumor's size, location, and response to treatment. While the tumor is benign and slow-growing, its impact on vision can significantly affect quality of life. Early detection and treatment are crucial for preserving vision and preventing further complications.

Epidemiology

Optic nerve sheath meningioma accounts for approximately 1-2% of all meningiomas. The incidence of ONSM is higher in individuals with neurofibromatosis type 2 (NF2), a genetic disorder characterized by the growth of multiple nervous system tumors.