Surgery for paraclinoidal carotid artery aneurysms

Endovascular embolization of superior hypophyseal artery aneurysms

OBJECTIVE

Internal carotid artery aneurysms arising from the superior hypophyseal artery are frequently termed paraophthalmic or paraclinoid aneurysms, but they constitute a distinct anatomic entity. They are particularly amenable to endovascular treatment.

METHODS

Between 1991 and 1995, we attempted treatment in 11 patients with superior hypophyseal artery aneurysms with Guglielmi detachable coil embolization and were successful in 10. Surgical exploration in seven of the patients was unsuccessful, three patients were considered to be at high risk for surgery or to have poor likelihood of surgical success by the referring neurosurgeon, and one patient refused operative clipping. Two aneurysms were giant (> 25 mm), three were large (10-25 mm), and six were small (< 10 mm). Of the six small aneurysms, two had wide necks (> 4 mm) and four had narrow necks (< or = 4 mm).

RESULTS

There were no technical or clinical complications related to embolization. Immediate complete aneurysm obliteration was obtained in five aneurysms, all of which were small. Four of the remaining five aneurysms had obliteration of the dome and body, leaving only a small remnant neck. The remaining semifusiform aneurysm represented our single treatment failure. Recanalization occurred in only one patient; that patient had a giant aneurysm. Nine of the 10 patients for whom embolization was successful had good or excellent clinical outcomes; there were no clinical deteriorations attributable to embolization.

CONCLUSION

We conclude that Guglielmi detachable coil embolization of superior hypophyseal artery aneurysms is an excellent treatment alternative, especially for smaller lesions.

Cerebral aneurysms unrelated to arterial bifurcations

The majority of saccular cerebral aneurysms arise at arterial branchings; those arising elsewhere are rare. Among 557 saccular cerebral aneurysms surgically treated between 1983 and 1994, 29 (5.2%) were unrelated to arterial divisions. These cases were retrospectively analysed. The ages of the subjects ranged from 6 to 80 years (mean 57); 17 (59%) were female, and 12 (41%) male. Twenty-four (83%) presented with subarachnoid haemorrhage. Seventeen (59%) had a history of hypertension, and ten (34%) had multiple cerebral aneurysms. The most common site was the internal carotid artery (45%), followed by the middle cerebral artery (28%), the vertebrobasilar arteries (17%), and the anterior cerebral artery (10%). The aneurysms were classified in relation to arterial curvature into three groups: dorsal curvature (41%), ventral curvature (10%) and non-curvature (49%). During surgery, sclerotic changes were noted in the arterial wall adjacent to the aneurysms in 14 patients (48%). Five cases (17%) had small thin walled (blister-like) aneurysms, four of which ruptured during surgery resulting in poor clinical outcomes. We suggest that arteriosclerotic changes in the arterial wall, carotid siphon, and/or local haemodynamic forces are important factors in the development of this type of aneurysms. At surgery, one should bear in mind the possibility of sclerotic or blister-like aneurysms which require special attention to deal with them.

Segments of the internal carotid artery: a new classification

This study proposes an anatomically based nomenclature for the internal carotid artery (ICA) that can be applied by all disciplines. In 1938, Fischer published a seminal paper describing five segments of the ICA that were designated C1 through C5. These segments were based on the angiographic course of the intracranial ICA rather than its arterial branches or anatomic compartments. Subsequent attempts to apply modern nomenclature to these numerical segments failed to recognize Fischer's original intent of describing patterns of arterial displacement by tumors and, therefore, resulted in a nomenclature that was anatomically inaccurate. Fischer's system was further limited, because segments were numbered opposite the direction of blood flow and the extracranial ICA was excluded. The authors propose a new classification, which includes the entire ICA, uses a numerical scale in the direction of blood flow, and describes the segments of the ICA according to a detailed understanding of the anatomy surrounding the ICA and the compartments through which it travels. Twenty cadaveric specimens with intravascular injection of silicone rubber were used for microscopic dissection and 20 dry skulls were inspected. Histological sections in critical areas were examined. The authors' classification has the following seven segments: C1, cervical; C2, petrous; C3, lacerum; C4 cavernous; C5, clinoid; C6, ophthalmic; and C7, communicating. This classification is practical, accounts for new anatomic information and clinical interests, and clarifies all segments of the ICA.

Cranio-orbital approach for the paraclinoidal and anterior communicating aneurysms

Aneurysms arising at the proximal intracranial carotid artery (between cavernous sinus and posterior communicating artery) and at the anterior communicating complex may present with technical difficulties regarding appropriate access without excessive brain retraction. In a series of 15 patients the authors show the use of the cranio-orbital approach, formerly designed in the access of skull base tumors, for these subgroups of aneurysms. They discuss the advantages of a basal avenue in minimizing brain retraction, better anatomical orientation, obviation of tissue ressection and easier extra-dural bone removal. It was not identified any complication due to the described approach.

A case of acute vertigo with incidental aneurysms

It is essential to decrease the risk to the patient to an absolute minimum when prophylactic procedures are offered against a relatively unpredictable (for the individual patient) natural history risk. Very careful preoperative planning and intraoperative execution are mandatory to maximize the chances of the patient for a successful outcome.