Subclinoid aneurysms

The falciform ligament: Anatomical study with microsurgical implications

OBJECTIVES

The current study aims to increase awareness of the falciform ligament and its anatomical and surgical relationships, for the benefit of the neurosurgeon.

PATINENTS AND METHODS

Twenty-four sides from twelve Caucasian cadaveric heads (all fresh-frozen) were used in this study. The length and thickness of the falciform ligament were recorded. The relationship of the falciform ligament to the optic nerve was also observed and documented. Finally, the force needed to avulse the falciform ligament was recorded.

RESULTS

In all specimens, the ligament was identified as a continuation of the outer dural layer, forming a roof at the entrance of the optic canal. The mean medial-to-lateral length, anteroposterior length, and thickness of the falciform ligament were 7.97 mm, 2.12 mm, and 0.26 mm, respectively. The mean distance from the medial attachment of the ligament to the midline was 5.54 mm. For the undersurface of the falciform ligament, the optic nerve occupied the middle third in 50.0 %, the lateral third in 44.4 %, and the medial third in 5.6 % of sides. The mean optic nerve diameter at the entrance of the optic canal was 4.20 mm. The mean failure force was 2.47 N.

CONCLUSION

The anatomical measurements and relationships provided in this description of the falciform ligament serve as a tool for surgery selection and planning, as well as an aid to improving microsurgical techniques, with the final goal being better patient outcomes.

Long-term surgical results with aneurysms involving the ophthalmic segment of the carotid artery

Object

Because of the anatomical complexity of the paraclinoid region, the surgical treatment of aneurysms arising in the C6 segment of the internal carotid artery is extremely challenging. The authors' aim in this study was to describe the extended clinical follow-up and assess the short-term and long-term effectiveness of surgical treatment for these aneurysms, focusing on the clinical outcome and degree of aneurysm occlusion and recurrence.

Methods

The authors retrospectively analyzed the clinical records for patients treated surgically between 1973 and 2004 at the University of Rome, “La Sapienza.” Aneurysms were classified into the following 3 groups according to the site where they arose: the anteromedial, anterior or anterolateral, and posteromedial wall of the C6 segment.

Results

Of the 108 aneurysms in 104 patients treated, 63 (58%) were large or giant. Eighty-eight aneurysms in 84 patients were clipped, 16 underwent a high-flow bypass, 2 were trapped, 1 was wrapped, and 1 was left untreated. The mean follow-up was 126 months; 47 patients had a follow-up of > 10 years. Of the 88 aneurysms that were clipped, 6 (6.8%) had an incomplete occlusion that required an immediate reoperation in 1 case and at 2 years in another. Overall 6 patients (5.8%) had surgery-related permanent complications.

Conclusions

Mortality and morbidity rates depend mainly on the patient's preoperative Hunt and Hess grade subarachnoid hemorrhage, whereas surgical morbidity principally reflects excessive manipulation of the optic nerve or ischemic problems due to excessive temporary trapping undertaken without adequate neuroprotection. In expert hands, surgery (clipping and bypass procedures) is a definitive treatment for C6 aneurysms and has an acceptable complication rate.

BLISTER-LIKE ANEURYSMS OF THE ANTERIOR COMMUNICATING ARTERY

OBJECTIVE

Blood blister-like aneurysms are small hemispherical bulges from the dorsomedial wall of the internal carotid artery that resemble berry aneurysms but differ in their clinical and surgical features. On the basis of our literature review, blister-like aneurysms have been reported to occur only at nonbranching sites of the dorsomedial internal carotid artery. In this report on our series of five patients, we describe blister-like aneurysms of the anterior communicating artery (AComA) and discuss important diagnostic and therapeutic aspects unique to them.

METHODS

In our retrospective review of 719 patients with nontraumatic subarachnoid hemorrhage admitted to our service from 1998 to 2003, 181 (25.17%) patients harbored AComA aneurysms. Five (2.76%) patients (four women, one man) had blister-like aneurysms that were recognized at the time of surgery.

RESULTS

Initial digital subtraction angiography was diagnostic in only one patient. A second digital subtraction angiogram was diagnostic in one patient but failed to reveal an aneurysm in the remaining three patients; these were eventually diagnosed by computed tomographic angiography. All aneurysms were clipped. At the time of surgery, the aneurysms arose from the horizontal portion of the AComA without any involvement of the branches of the anterior cerebral artery. All presented as blister-like aneurysms that were thin-walled and lacking a surgical neck. On dissection, two of the lesions ruptured. All lesions were treated with straight fenestrated clips through the A1–AComA junction, thus remodeling the AComA. No delayed rupture was noted at the time of the last follow-up evaluation. At the time of discharge, outcomes were good in two patients, fair in two, and poor in the remaining patient.

CONCLUSION

Blister-like aneurysms constitute technically challenging lesions that may occur at the AComA. Computed tomographic angiography is valuable in diagnosis. Blister-like aneurysms should be suspected when digital subtraction angiography findings are negative for subarachnoid hemorrhage.

Intrasellar rupture of a paraclinoid aneurysm with subarachnoid hemorrhage: usefulness of MR imaging in diagnosis

Characterization of paraclinoid aneurysms may be difficult because of the complexity of anatomic structures involved, and differentiation between intradural and extradural lesions is crucial. We report a case of a patient with a unique presentation of a paraclinoid aneurysm with intrasellar hemorrhage in which the presence of intrasellar blood and the relationship of the paraclinoid aneurysmal neck and sac to the dural rings were elegantly demonstrated on MR imaging and were critical in choosing the target lesion for treatment.

Optic Strut as a Radiographic Landmark in Evaluating Neck Location of a Paraclinoid Aneurysm

OBJECTIVE:

The optic strut (OS) is a candidate landmark in computed tomographic (CT) angiographic scans for the discrimination of intradural and extradural/intracavernous aneurysms involving the paraclinoid segment of the internal carotid artery. The goal of this study is to examine and confirm the qualifications of the OS as a landmark in CT angiographic scans for the preoperative evaluation of aneurysms in this region.

METHODS:

Seventeen consecutive patients with 18 unruptured paraclinoid aneurysms who underwent preoperative CT angiography scans and direct surgery between 1998 and 2005 were evaluated retrospectively. We focused on the relationships of the necks of aneurysms to the OS in CT angiographic scans and that of the necks to proximal dural rings during intraoperative examinations.

RESULTS:

Direct surgery revealed that 14 aneurysms, the necks of which were distal to the OS on CT angiographic scans, arose distal to the proximal dural rings. All aneurysms were clipped, except one exhibiting calcification of the neck. Three aneurysms, for which the neck was proximal to the OS on CT angiographic scans, revealed only a portion or nothing of their domes instead of their necks through the proximal dural rings after dissection of the distal dural rings. Dome coating with fibrin glue and a piece of muscle tissue or mere exploration was performed. Another aneurysm, of which the neck straddled the OS on CT angiographic scans, was found to arise across the proximal dural ring. Clipping of the neck was performed after dissection of the proximal dural ring. Of the source images of CT angiographic scans, the axial images were the most useful in evaluating the relationship of the neck of an aneurysm to the OS.

CONCLUSION:

On CT angiographic scans, the OS is a precise identification of the proximal dural ring that forms the superior border of the cavernous sinus. The aneurysms whose necks arise obviously distal to the OS on CT angiographic scans are able to be clipped without dissection of the proximal dural ring.

Aneurisma paraclinóideo: técnica cirúrgica e resultados em 51 pacientes

Analisam-se 51 pacientes portadores de 55 aneurismas paraclinóideos (APC) submetidos a tratamento cirúrgico. Em decorrência de tratar-se de procedimento de alta complexidade, descrevemos em pormenor os seus aspectos técnicos. O processo clinóideo anterior foi removido por via extradural após secção da duplicação dural da tenda da fissura orbitária superior e/ou por via intradural. Conseguiu-se exclusão do APC nos 51 pacientes. Em dois casos a clipagem foi parcial e, em três, ocorreu oclusão da ACI. Em 42 (82%) pacientes ocorreu bom resultado; em 5 (10%), incapacidade moderada; em 1 (2%), incapacidade grave e três (6%) faleceram por infarto cerebral. Sete (13,7%) pacientes tiveram lesão adicional do nervo óptico, sendo parcial em 4 (7,7%) e total em 3 (6%).