Management of the optic canal invasion and visual outcome in spheno-orbital meningiomas.

OBJECTIVE: Spheno-orbital meningiomas often present with visual deficit due to invasion of the optic canal by the tumor. This study discusses the reasons of visual impairment, the choice of the surgical approach according to the type of optic canal involvement, and the factors correlated to the visual outcome in patients harboring a spheno-orbital meningioma.
MATERIALS AND METHODS: A surgical series of 60 spheno-orbital meningiomas is reviewed. The preoperative visual symptoms, the involvement of the optic canal in both neuroradiological studies and surgical descriptions, the different surgical approaches are reviewed. These data are correlated with the postoperative visual outcome.
RESULTS: The 60 spheno-orbital meningiomas were classified in 4 types according to the intraorbital tumor localization: type I, supero-lateral (18 cases); type II, inferomedial (8 cases); type III, orbital apex (22 cases); type IV, diffuse (12 cases). Thirty-six of the 60 patients (60%) had variable decrease of the visual acuity on the tumor side. Forty-three patients (71.6%) had tumor extension into the optic canal on imaging studies. On the whole, 36 patients among 43 with invasion of the optic canal (83.7%) had preoperative visual dysfunction; on the other hand, none among 17 patients without tumor invasion of the optic canal had visual dysfunction. The surgical approaches according to the tumor location were as follows. A supraorbital-pterional approach was used in the 8 inferomedial tumors, in the 22 orbital apex tumors, and in 9/12 diffuse tumors; these last two types had concentric involvement of the optic canal. Three diffuse tumors with significant extension in the infratemporal fossa were operated on via a frontotemporal-orbitozygomatic approach. A wide decompression of the optic canal was performed in all cases, excepting in two inferomedial tumors without optic canal invasion. The 18 patients with lateral tumors were approached via a lateral orbitocranial approach, including removal of the sphenoid wing and lateral orbital wall without bone flap; the resection of the lateral aspect of the optic canal was performed in the 3 cases with canal invasion. Postoperative improvement of the visual function was observed in 18 of 36 cases with visual dysfunction (50%). The rate of visual improvement was significantly higher in cases with lateral involvement (3/3 or 100%) than in those with concentric involvement of the optic canal (11/27 or 40.7%).
CONCLUSION: The invasion of the optic canal by the tumor is the main reason of visual dysfunction in patients with spheno-orbital meningiomas. A wide opening of the optic canal must be performed routinely in patients with orbital apex and diffuse orbital tumors, where there is concentric invasion of the optic canal wall. In these cases the supraorbital-pterional approach is the technique of choice. In selected cases with lateral intraorbital tumors and invasion of the lateral aspect of the optic canal the complete tumor resection coupled with good decompression of the optic nerve may be achieved via a less invasive lateral orbitocranial approach without craniotomy.