Schwannomas

Description of Orbital Schwannomas

• Schwannomas are slow-growing, benign tumors that develop within the outer covering of peripheral and sympathetic nerves formed by Schwann cells, called the nerve sheath. They are sometimes referred to as neurilemmomas and often involve sensory and motor nerves supplying the orbital region. Schwannomas are rare tumors and constitute about 1% of all orbital tumors and 35% of peripheral nerve tumors within the orbit.
• They primarily affects individuals between 20 and 60 years old, with 10-15% of cases accompanied by neurofibromatosis.

Pathophysiology of Orbital Schwannomas

Orbital schwannomas are rare and mostly benign peripheral/sympathetic nerve sheath tumors. Typically, they reside in the orbital muscle cone or the superior temporal region. Tumor growth puts pressure on the eyeball, pushing it forward and downward. They are different from neurofibromas, which impact nerve fibers. Orbital schwannomas are separated into Antoni A type areas, Antoni B type areas and Verocay body. Antoni A type areas are solid growths of tumor cells, Antoni B type areas are loose cystic spaces with no axons, and Verocay bodies involves tumor nuclei in acellular zones.

Symptoms and Signs of Orbital Schwannomas

Orbital schwannoma is slow-growing and is marked by painless proptosis. It is progressive and can take years or decades to produce symptoms. Patients may experience edema of the eyelids, eyeball dystopia, exophthalmos, ocular motility impairment, vision loss or disturbance, and optic disc changes.

Diagnosis of Orbital Schwannomas

At Idaho Eyelid and Facial Plastic Surgery, orbital schwannomas are suspected through clinical observation and patient history of symptoms. This suspicion may be confirmed by the presence of an encapsulated mass, using either CT scans or MRIs of the orbital area.

Treatment of Orbital Schwannomas

It is recommended to completely remove orbital schwannomas. Surgical excision is straightforward given their encapsulation. The risk of malignancy and recurrence is low. After the tumor is removed, histologic diagnosis can show Antoni A or Antoni B areas, Verocay bodies and positivity for the S-100 immunohistological stain.