Direct neck clipping of cavernous internal carotid aneurysm is very difficult and hazardous. This is because of the deep location of such lesions for the pterional approach and their close anatomical relationship with the carotid artery, optic nerve and bony structures of the frontal base.
When ruptured, an aneurysm of this location can be presented as a subarachnoid hemorrhage, carotid cavernous fistula or epistaxis depending on the extent of development of the cavernous sinus and the sphenoid sinus and on the correlative pathway of the internal carotid artery.
The authors report two cases of internal carotid aneurysm located between the cavernous sinus and the branching of the ophthalmic artery. In both cases, the aneurysm was treated by aneurysmal neck clipping through the contralateral pterional approach, and after the operation, both patients were discharged in good condition. Case 1 was presented as recurrent massive epistaxis, and to the authors' knowledge, this is probably the first report of successful neck clipping of an internal carotid aneurysm ruptured into the sphenoid sinus. In Case 2, the aneurysm was discovered incidentally. It might have been presented as subarachnoid hemorrhage if it had ruptured before discovery.
The operation was started with the usual craniotomy for the pterional approach using a small skin incision, and the sylvian fissure was sufficiently dissected in order to obtain an adequate operative field. The tuberculum sellae, planum sphenoidale and anterior clinoid process were then drilled using a microsurgical drill which led to unroofing of the optic canal and opening of the bony wall of the sphenoid sinus. The internal carotid artery was then dissected in the proximal direction until the aneurysmal neck came in sight, retracting the optic nerve of the aneurysmal side laterally in a gentle manner, and the lateral wall of the sphenoid sinus was removed piece by piece as deemed necessary. For this process, the mucous membrane of the sphenoid sinus was detached from the bony wall and pushed downward with great attention not to injure it. When the neck of the aneurysm was secured, a clip was applied. After the clipping, the opened sphenoid sinus was filled with the fascia of the temporal muscle and fibrin glue.
In both cases, we could clip the aneurysm directly through the contralateral pterional approach because the aneurysm was small and projected medially. In our two cases, we believe, it would have been impossible to clip the aneurysm through the ipsilateral pterional approach. This is because the ipsilateral optic nerve and the distal internal carotid artery would have obstructed the vision of the aneurysm.
Generally, in the face of a cavernous internal carotid aneurysm, the possibility of direct neck clipping through the contralateral pterional approach should be considered. For the evaluation of this possibility, preoperative examinations such as angiography, angiotomography, CT cisternography and cavernous sinography are necessary to obtain precise anatomical knowledge concerning the aneurysm and surrounding structures.
