Neurology India, Vol. 59, No. 3, May-June, 2011, pp. 461-463
Letters to Editor
Optic nerve fenestration in sphenoid wing meningioma
PP Panciani, E Crobeddu, D Garbossa, A Ducati, M Fontanella
Department of Neuroscience, Division of Neurosurgery, University of Turin, Italy
Correspondence Address: P P Panciani Department of Neuroscience, Division of Neurosurgery, University of Turin Italy firstname.lastname@example.org
Date of Submission: 15-Dec-2010
Code Number: ni11131
Fenestrations of the optic nerve have been described in association with aneurysms of the internal carotid artery. ,,,,,, Only one case of de novo fenestration has been described.  We report a case of splitting of the optic nerve in a patient operated for a middle sphenoid wing meningioma, probably the first report of such case.
A 46-year-old man presented with decreased vision in his left eye of 2 weeks duration. Goldman perimeter fields demonstrated an enlargement of central scotoma. Brain magnetic resonance imaging (MRI) showed middle sphenoid wing meningioma [Figure - 1]. The patient was taken for a left pterional craniotomy. The first step of the procedure was the un-roofing of the optic canal and the falciform ligament cutting. Microsurgical dissection and excision of the tumor was completed. A reddish mass was observed through the optic nerve [Figure - 2]. At a high magnification the anomaly was recognize as a possible splitting of the optic nerve [Figure - 3]a. The indocyanine green video angiographic study revealed a vessel below the fenestration [Figure - 3]b. Postoperative cerebral angiography showed the absence of vascular malformations [Figure - 4]. The postoperative course was uneventful and his visual acuity deficit remained unchanged at the 6-month follow-up examination.
Sphenoid wing meningiomas frequently encase or displace the internal carotid artery and its branches, as well the optic nerve and chiasm. Visual dysfunctions, both defective acuity and visual fields, are often the presenting symptoms. Moreover, a risk of up to 20% of visual deterioration after surgery is reported.  In our patient, a defective visual acuity due to an enlarged central scotoma was the initial symptom. We performed an early optic canal unroofing and falciform ligament cutting in order to avoid visual impairment. Intraoperatively, a splitting of the optic nerve was observed [Figure - 3]a. The indocyanine green video angiographic study showed an artery below the fenestration [Figure - 3]b. The postoperative angiography excluded the presence of aneurysms [Figure - 4]. There as no visual deterioration postoperatively.
The presence of a penetrating aneurysm was reported in seven cases with optic nerve fenestration. ,,,,,, In the case reported by House  the patient presented multiple aneurysms not related to the fenestration [Table - 1]. A vascular anomaly is generally proposed to explain the splitting. An embryological vascular remnant or perforating vessels supplying the optic apparatus could be involved in the development of a fenestration in the bundle of nerve fibers.  In our patient the angiography excluded vascular diseases. In cases of sphenoid wing and tuberculum sellae meningiomas, the optic nerve frequently shows a discolored band representing the area where it had been squeezed against the proximal edge of the optic canal and falciform ligament.  In patients with a congenital predisposition, the pressure point may result in the splitting of the nerve. Intraoperative damage can be avoided through an early nerve decompression. Congenital fenestrations of the optic nerve are extremely rare. In our patient, high pressure below the falciform ligament could explain the splitting of the optic nerve. Early optic canal un-roofing and falciform ligament cutting are recommended to avoid worsening of visual functions.
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