Combined epi- and subdural approach to carotid ophthalmic aneurysms

Abstract

Surgery of carotid ophthalmic aneurysms, which was until recently a very demanding procedure, has become much safer and easier to perform by employing the combined epi- and subdural approach [8]. In this procedure a standard pterional craniotomy [55, 56] is used, following this is removal of the orbital roof together with the sphenoid wing and the ACP. Then the proximal, medial, and lateral part of the wall of the optic canal are removed to give the operative exposure of the ON from the dura to the entry point into the intraorbital tissue, in its entire segment in the optic canal. The orbital roof is removed on the anterior side of the SOF, as well as on its dorsal side. For this type of aneurysm it is enough if the anterior loop of the ICA in the anteromedial triangle is exposed. Therefore, it is not necessary to explore the ICA in the carotid canal in the petrous bone through the posterolateral triangle. The dissection of the ICA in the anteromedial triangle is essential and must be completed before the dissection of the aneurysm itself is commenced. With this type of aneurysm it is important that the dura is not damaged while operating epidurally and removing the bone. In addition, this is imperative when dealing with large or giant carotid ophthalmic aneurysms which are not thrombosed. Equally important is that the intradural pressure is not lowered by lumbar drainage which is contraindicated in this type of surgery. Maintaining the normal cerebrospinal fluid quantity and pressure by preserving the intact dura is the best protection of the underlying aneurysm, the brain, and the neural structures from mechanical injury during the drilling of the ACP. Care must be taken because the ACP is tightly attached to the dura.