• stereotactic irradiation
• optic nerve sheath meningioma

The role of conventional external beam radiotherapy in the management of optic nerve sheath meningiomas (ONSM) has been controversial because of limited radiation sensitivity of these tumours and radiation damage to surrounding tissues.¹ Recently, in a study of 64 patients with ONSM managed with observation, surgery, radiotherapy, or surgery and radiotherapy, Turbin and colleagues² found that patients treated by (conventional) radiotherapy alone demonstrated the best long term visual outcome, and suggested fractionated external beam radiation (5000–5500 cGy) as the initial treatment in selected cases, when preservation of visual function is a reasonable goal.

The collateral damage secondary to conventional radiotherapy may be minimised by better focusing and shaping of the radiation beams, as in stereotactic radiotherapy (SRT).^3–5 We report on a woman whom we treated with fractionated SRT for a biopsy proved, large ONSM.

In April 2000 a 41 year old woman was referred with a 1 month history of proptosis of her left eye (Fig 1, top left). She had been treated for a presumed orbital “pseudotumour” with oral prednisone (initial dose 90 mg/day) without effect.