Management of sight-threatening optic nerve sheath meningioma with fractionated stereotactic radiotherapy

Background: Previous management of optic nerve sheath meningioma included conservative observation, surgery, radiosurgery and conventional radiotherapy. All carried significant risk, either of visual loss or damage to adjacent structures. Fractionated stereotactic radiotherapy appears to have few side-effects and may preserve or improve vision. To date only three groups have published their experience with this modality. Methods: A retrospective review of patients with optic nerve sheath meningioma treated with stereotactic radiotherapy in an academic complex was conducted. Patients with greater than 18 months follow up and no previous related surgery were eligible for inclusion. Patients received an average of 43.5 Gy to the tumour in 26 fractions. Case records from the treating institutions as well as those of the referring ophthalmologist were analysed. The limited literature on the subject was reviewed in order to draw conclusions relevant to contemporary patient management. Results: Four patients had undergone follow up for over 18 months. Prior to treatment all had exhibited progressive loss of visual function. In all cases visual function remained stable or improved at the last assessment. Side-effects included radiologically detected cerebral changes in one patient and transient hair loss in one patient. Conclusions: This treatment modality represents a promising refinement of previous treatment options. It may be offered to patients who demonstrate progressive loss of visual function caused by optic nerve sheath meningioma. It offers significant advantages over other currently available therapeutic options but its use should be tempered by the knowledge that long-term side-effects are yet to be determined.