Three-dimensional blood flow analysis in a wide-necked internal carotid artery-ophthalmic artery aneurysm

OBJECT: The aim of this study was to evaluate axial and secondary flow structures in a wide-necked internal carotid artery-ophthalmic artery aneurysm, one of the most common locations for endovascular coil placement. METHODS: A clear acrylic aneurysm model was manufactured from a three-dimensional computerized tomography angiogram. Intraaneurysm blood flow analysis was conducted using an acrylic aneurysm model together with laser Doppler velocimetry and particle imaging velocimetry. The maximal axial blood flow velocities in the inflow and outflow zones at the aneurysm orifice were noted at the peak systolic phase, measuring 46.8 and 24.9% of that in the parent artery, respectively. The mean size of the inflow zone during one cardiac cycle was 44.3 +/- 9.8% (range 35.6-58.7%) the size of the axial section at the aneurysm orifice. In the lower and upper planes of the aneurysm dome, the mean size of inward and outward flow areas were 43.3 +/- 6.7% and 43.8 +/- 6.8% the size of the axial cross-sectional plane, respectively. The axial flow velocity structures were dynamically altered throughout the cardiac cycle, particularly at the aneurysm orifice. The fastest secondary flow at the opening was also noted at the peak systolic and early diastolic phases. Axial blood flow velocity was slower in the upper axial plane of the aneurysm dome than in the lower one. Conversely, the secondary flow component was faster in the upper plane. CONCLUSIONS: The side-wall aneurysm in this study did not demonstrate a simple flow pattern as was previously seen in ideally shaped experimental aneurysms in vitro and in vivo. The flow patterns of inflow and outflow zones were very difficult to predict based on the limited flow information provided on standard digital subtraction angiography, even in an aneurysm with a relatively simple dome shape.     

Bilateral internal carotid artery aneurysms.

Two patients were treated for bilateral internal carotid artery aneurysms. One had resection and restoration of continuity on the right side nine years after ligation of the left internal carotid artery. The second had sequential resection and reconstruction of both vessels. Complications of carotid aneurysms include embolization, rupture, and thrombosis. Preferred treatment is resection with reconstitution of the flow. Patients with carotid aneurysms should be investigated for similar lesions on the opposite side. Patients who have had one carotid aneurysm treated should be followed up for the possible occurrence of a contralateral aneurysm.     

Surgical treatment of extracranial internal carotid artery aneurysms

PURPOSE: Extracranial internal carotid artery aneurysms (EICAs) can be treated by carotid ligation or surgical reconstruction. In the consideration of the risk of stroke after internal carotid artery (ICA) occlusion, the aim of this study was to report the results of reconstructive surgery for these aneurysms, including lesions located at the base of the skull. METHODS: From 1980 to 1997, 25 ICA reconstructions were performed for EICA: 22 male patients and 3 female patients (mean age, 54.4 years). The cause was atherosclerosis (n = nine patients), dysplasia (n = 12 patients), trauma (n = three patients), and undetermined (n = one patient). The symptoms were focal in 15 cases (12 hemispheric, three ocular), nonfocal in three cases (trouble with balance and visual blurring), and glossopharyngeal nerve compression in one case. Six cases were asymptomatic, including three cases that were diagnosed during surveillance after ICA dissection. In nine cases, the upper limit of the EICA reached the base of the skull. A combined approach with an ear, nose, and throat surgeon allowed exposure and control of the ICA. RESULTS: After operation, there were no deaths, one temporary stroke, two transient ischemic attacks, and 11 cranial nerve palsies (one with sequelae). The ICA was patent on the postoperative angiogram in all but one case. During follow-up (mean, 66 months), there were two deaths (myocardial infarction), one occurrence of focal epileptic seizure at 2 months, and one transient ischemic attack at 2 years. In December 1998, duplex scanning showed patency of the reconstructed ICA in all but one surviving patient. CONCLUSION: Surgical reconstruction is a satisfactory therapeutic choice for EICA, even when located at the base of the skull.     

Carotid cave aneurysms of the internal carotid artery

In a series of 32 surgical cases of carotid-ophthalmic artery aneurysm, seven of the lesions were located in the "carotid cave." This special type of aneurysm is usually small and projects medially on the anteroposterior view of the angiogram. At surgery, it is located intradurally at the dural penetration of the internal carotid artery (ICA) on the ventromedial side, appears to be buried in the dural pouch (carotid cave), and is often difficult to find, dissect, and clip. The aneurysm extends into the cavernous sinus space, and the parent ICA penetrates the dural ring obliquely. An ipsilateral pterional approach was used in all 32 cases, and ring clips were used exclusively because the aneurysms were located ventromedially. Clipping was successful in five cases. All patients returned to their preoperative occupation, although vision worsened postoperatively in two cases. The technical steps required for successful obliteration of this aneurysm are summarized as follows: 1) exposure of the cervical ICA; 2) unroofing of the optic canal and removal of the anterior clinoid process; 3) exploration of the ICA around the dural ring and opening of the cavernous sinus; 4) direct retraction of the ICA and optic nerve; and 5) application of multiple ring clips to conform to the natural curvature of the carotid artery; a curved-blade ring clip is especially useful. The relevant topographic anatomy is discussed.     

Gradual carotid artery occlusion in the treatment of inaccessible internal carotid artery aneurysms

The authors discuss 21 cases of large or surgically inaccessible internal carotid artery aneurysms treated with gradual occlusion of the cervical portion of the internal carotid artery. Eighty-five per cent of the patients experienced relief or marked improvement of their symptoms after treatment. Two early cases developed postligation ischemic deficits that partially resolved. After the introduction of expansion of circulating blood volume and induced hypertension as adjuncts to graded carotid occlusion, no ischemic complications occurred.     

Characteristics of aneurysms of the internal carotid artery bifurcation

Summary Background. Arterial bifurcations are sites of maximal hemodynamic stress, where cerebral aneurysms commonly develop. However, in our experience with endovascular treatment for aneurysms of the internal carotid artery (ICA) bifurcation, we often experienced that the aneurysmal neck did not necessarily exist only at the ICA bifurcation (ICBi). In this study, we have retrospectively evaluated characteristics of aneurysms at the ICBi. Methods. Ten ICBi aneurysms in 10 consecutive patients were studied retrospectively. The size of the aneurysms, the angles formed between the ICA and the anterior cerebral artery (ACA) and middle cerebral artery (MCA), and the diameter of the ICA, ACA and MCA were measured. Furthermore, to study the relationship between the location of the aneurysmal neck and the bifurcation of the ICA, the distance between the midline of the aneurysmal neck and of the ICA was measured. Results. The average aneurysm size was 6.3 ± 3.2 mm and the average neck was 3.1 ± 1.2 mm. The average ICA-ACA angle was 57.3 ± 16.5 degrees, and the average ICA-MCA angle was 128.9 ± 24.1 degrees. The average diameters of the ICA, ACA and MCA were 2.9 ± 0.5 mm, 1.9 ± 0.4 mm and 2.5 ± 0.4 mm, respectively. The average distance between the midline of the aneurysmal neck and the ICA was 1.6 ± 0.6 mm, and all aneurysmal necks of the ICBi arose from the side of the ACA. Conclusion. ICBi aneurysms were deviated to the side of the A1 segment of the ACA, where the artery might suffer higher hemodynamic stress.     

Management of high cervical-intracranial internal carotid artery traumatic aneurysms

The successful surgical management of a patient with a traumatic aneurysm of the internal carotid artery (ICA) at the base of the skull and a second traumatic aneurysm of the ipsilateral superficial temporal artery is described. EC-IC bypass was not necessary, and graded occlusion of the ICA was employed. Direct repair was not chosen because of its high risk of distal embolization. Electrophysiologic monitoring techniques are helpful in predicting hemispheric ischemia.     

The hemodynamic effects of internal carotid artery stenosis and occlusion

The purpose of this study was to determine in subhuman primates whether hemodynamic mechanisms (as compared with embolic mechanisms) contribute to cerebral ischemia following carotid artery occlusion or stenosis. Following carotid artery occlusion there was loss of cerebral autoregulation: cerebral blood flow (CBF) measured with the xenon-133 technique became passively dependent upon the mean arterial blood pressure (MABP) over an MABP range of 30 to 110 mm Hg. By contrast, autoregulation was preserved in normal animals and in animals with a 90% carotid artery stenosis. Regional CBF was measured with carbon-14-labeled iodoantipyrine autoradiography in normotensive baboons, in hypotensive animals, and in hypotensive animals with carotid artery occlusion or stenosis. With carotid artery occlusion and hypotension, reduced levels of local CBF were seen ipsilaterally in the boundary zones between the anterior and middle cerebral arteries with 35% of the area of an anterior section through the hemisphere displaying a CBF value of less than 20 ml/100 gm/min. Comparable values with hypotension were 21% with carotid artery stenosis, 20% with no proximal vascular lesion, and 1% in normotensive animals. These areas of reduced CBF corresponded with areas of boundary-zone ischemia seen with light microscopy. The study suggests that while hemodynamic ischemia develops with carotid artery occlusion, it does not occur with even a 90% carotid artery stenosis or in normal animals.     

Radiometric analysis of paraclinoid carotid artery aneurysms

OBJECT: Classification of paraclinoid carotid artery (CA) aneurysms based on their associated branching arteries has been confusing because superior hypophyseal arteries (SHAs) are too fine to appear opacified on cerebral angiograms. The authors performed a retrospective radiometric analysis of surgically treated paraclinoid aneurysms to elucidate their angiographic and anatomical characteristics. METHODS: A retrospective analysis was made of 85 intradural paraclinoid aneurysms in which the presence or absence of branching arteries had been determined at the time of surgical clipping. The lesions were classified as supraclinoid, clinoid, and infraclinoid aneurysms based on their relation to the anterior clinoid process on lateral angiograms of the CA. The direction of the aneurysms were measured according to angles formed between the medial portion of the horizontal line crossing the aneurysm sac and the center of the aneurysm neck on anteroposterior angiograms. Branching arteries were associated with 68 aneurysms, of which 28 were ophthalmic artery (OphA) lesions (32.9%) and 40 were SHA ones (47.1%); associated branching arteries were absent in 17 aneurysms (20%). Twenty-five aneurysms (29.4%) were located at the supraclinoidal level, 46 (54.1%) at the clinoidal, and 14 (16.5%) at the infraclinoidal. The majority of aneurysms identified at the supraclinoidal level were OphA lesions (44%) or those unassociated with branching arteries (48%), with mean directions of 57 degrees or 67 degrees, respectively. At the clinoidal level, the mean directions of aneurysms were 76 degrees in six lesions unassociated with branching arteries (13%), 43 degrees in 16 OphA lesions (35%), and -11 degrees in 24 SHA ones (52%). All aneurysms at the infraclinoidal level arose at the origin of the SHAs, with a mean direction of -29 degrees, and most of these were embedded in the carotid cave. CONCLUSIONS: Aneurysms arising from the SHA can be distinguished from those not located at an arterial division by cerebral angiography, because SHA lesions are usually located at the medial or inferomedial wall of the internal carotid artery at the clinoidal or infraclinoidal level. Their distribution correlates well with the reported distribution of SHA origins. The carotid cave aneurysm is a kind of SHA lesion that originates at the most proximal intradural CA.     

Aneurysms at nonbranching sites in the surpaclinoid portion of the internal carotid artery: internal carotid artery trunk aneurysms

OBJECTIVE: Aneurysms at nonbranching sites in the supraclinoid internal carotid artery (ICA), known as blood blister-like aneurysms or ICA anterior or dorsal wall aneurysms, are not well understood. To clarify this clinical entity, 7408 patients with subarachnoid hemorrhage who were treated during a 5-year period were analyzed. METHODS: Forty-eight patients had aneurysms that were intraoperatively confirmed to be located at a nonbranching site in the supraclinoid portion of the ICA. Neuroradiological and clinicopathological features and outcomes were studied. RESULTS: The aneurysms were divided into the "blister type," with a blood blister-like configuration and fragile walls, and the "saccular type," with a saccular configuration and a relatively firm neck, like ordinary berry aneurysms. The most frequent origin was the anteromedial wall for both types. ICA dissection was associated only with the blister type, and hypertension was more frequent with the blister type (P = 0.0978). The preoperative conditions of the patients were the same, but the outcomes for patients with blister-type aneurysms were worse, because of frequent intra- and postoperative aneurysmal bleeding. Saccular-type aneurysms were safely clipped. Treatment of blister-type aneurysms by clipping on wrapping material achieved good results, but ICA trapping (P = 0.0952), clipping (P = 0.0146), and wrapping (P = 0.0110) were associated with much worse results. CONCLUSION: Blister-type and saccular-type aneurysms have different shapes and wall characteristics. The saccular type can be treated by clipping, whereas the blister type requires clipping on wrapping material. ICA trunk aneurysms may be a better designation to express the diversity of these aneurysms, rather than ICA blood blister-like or anterior or dorsal wall aneurysms.     

Treatment of ruptured and unruptured internal carotid artery aneurysms.

A consecutive series of 95 patients with a total of 131 intracranial cerebral aneurysms came under observation from 1972-1978. Of these, 78 patients had operations for 106 aneurysms. Over half of the patients (41) had operations for an aneurysm of the intracranial internal carotid artery; there were 16 incidental "asymptomatic" aneurysms also found. There was no surgical mortality in this group. Medical treatment, including bed rest, antihypertensive treatment and administration of epsilon amino caproic acid followed by microsurgical obliteration of the aneurysm offers the best results for the treatment of ruptured and unruptured aneurysms.