Surgical unroofing of the optic canal and visual outcome in basal meningiomas

Abstract

Background: To define from a series of surgically treated suprasellar, anterior clinoid, and sphenoid wing meningiomas, an unequivocal criterion for performing optic canal deroofing in patients with basal meningiomas with deteriorated vision.

Methods: One hundred-fifty consecutive patients with suprasellar and parasellar meningiomas (44 tuberculum sellae, 46 clinoidal, and 60 spheno-orbital) who underwent surgery between 1988 and 2008 are retrospectively analyzed. The rate of preoperative visual deficit, the incidence of optic canal involvement, the related surgical management, and its influence on visual outcome are reviewed in all tumor localizations.

Results: All 44 patients with tuberculum sellae meningiomas had variable preoperative visual impairment. All were operated on by transcranial approach. Unroofing of the optic canal was performed in the two cases with intracanalar tumor extension. Postoperatively, the visual function improved in 27 patients (61.4 %) and was unchanged in 17 (25 %). Among 46 patients with clinoidal meningiomas, visual dysfunction was found in 30 (65.2 %). The first 32 patients were operated on by classical pterional approach, with selective opening of the optic canal in six cases (group A), whereas all the last 14 underwent routine anterior clinoidectomy and opening of the optic canal (group B). The visual function improved postoperatively in 17 among 30 patients (56.7 %), with a significantly higher rate in group B cases (80 % versus 45 %). Among 60 patients with spheno-orbital meningiomas, 36 (60 %) had visual dysfunction and 43 (71.6 %) involvement of the optic canal. The visual function improved in 18 cases (50 %), was unchanged in 13 (36 %), and worsened in 5 (14 %). Lateral tumors had the lowest rate of optic canal involvement and a 100 % rate of visual improvement; on the other hand, all orbital apex and diffuse tumors had concentric invasion of the optic canal with a 18.6 % rate of visual worsening.

Conclusions: UOC seems to be a safe procedure not associated with immediate postoperative impairment of the vision. We recommend routine deroofing of the optic canal coupled with extradural anterior clinoidectomy in all clinoidal meningiomas in order to obtain early and complete exposure of both intradural and extradural segments of the optic nerve. For tuberculum sellae meningiomas, we advise to open the optic canal only in cases with intracanalar tumor extension. Finally, for spheno-orbital meningiomas, we recommend UOC through a cranio-orbital approach in almost all cases, except for lateral meningiomas, where the involvement of the lateral wall of the optic canal is rare and may be successfully managed through a lateral orbitotomy without craniotomy.