Histological change in permanently clipped or ligated cerebral arterial wall. Part II: Autopsy cases of aneurysmal neck clipping

Histological changes of vascular clipping in Wistar rats

Background

During aneurysm microsurgery, the aneurysmal sac is excluded from circulation by placing one or more clips at the base of the aneurysm. In some cases of complex aneurysms or subarachnoid hemorrhage history, transient clipping before definitive clipping is necessary. The closing force of the transient clip is less than the permanent clip; however, it is sufficient to stop circulation to the aneurysmal sac. The aim of the following work is to analyze and describe histological changes caused by transient and permanent clipping of the abdominal aorta in Wistar-type rats, to study the correlation between the closing force of the clip and the time, it remains on the vascular tissue structures.

Methods

Six groups were formed, with 10 rats each, whereby temporary clipping of the abdominal aorta was performed with subsequent sampling of the site where the vascular clip was placed. The groups were: control and temporary clipping with: 2, 5, 10, and 15 and permanent clipping with 5 min.

Results

Resection samples of the 3 μm thick aorta were obtained through the routine histological technique and special histochemical techniques (Masson's Trichrome and orcein) from the six groups. Transmural changes were found from Group II-VI.

Conclusion

There is a vascular histological effect after both transient and permanent clipping. The sum of time and strength of the clip induce vascular changes visible at 5 min.

Cell-mediated allergy to cerebral aneurysm clip causing extensive cerebral edema

The authors report the first case of vasogenic cerebral edema due to a cell-mediated hypersensitivity reaction to a nickel-containing aneurysm clip. The patient initially presented for elective clipping of a right middle cerebral artery aneurysm, and on long-term follow-up she demonstrated relapsing-remitting cerebral edema. Four years post–aneurysm clipping, she underwent an exploratory craniotomy given unsuccessful conservative management of her headaches and imaging evidence of cerebral edema with mass effect. During surgery, gross parenchymal edema and inflammatory nodules were observed. Histopathology was consistent with a cell-mediated (Type IV) hypersensitivity reaction. Concerns regarding nickel allergy are often reported in the cardiac literature. This case highlights the possibility of nickel hypersensitivity when using nickel-containing aneurysm clips, especially in patients with known nickel allergies.

Assessment of the clipping efficacy of intracranial aneurysms: analysis of the employed methodology in relation to case difficulty

OBJECTIVE

To assess intracranial aneurysms clipping efficacy (CE) employing different angiographic techniques in relation to the case difficulty.

METHOD

In the past 6 years, 152 patients harboring 179 aneurysms who underwent surgical clipping in our department were angiographically examined to confirm aneurysm occlusion. Intraoperative angiography (IA), post-operative conventional (PCA) and three-dimensional angiography were single or sequentially performed based on the surgeon's concern about case difficulty. The percentage of visualized angiographic abnormalities (PVAA) assessing CE and their impact on corrective treatment were retrospectively analysed.

RESULTS

The PVAA of IA was 67.8% (19 of 28 aneurysms). Eighteen of them (eight aneurysm remnants, four parent vessel stenosis, two distal branch occlusions and five clip slippage phenomena) underwent immediate corrective treatment (clip reposition in 11 cases, complementary clipping in three cases and combined treatment in four cases). The impact on corrective treatment was 94.7%. The PVAA of PCA was 18.4% (33 of 179 aneurysms). Fifteen patients presented aneurysm remnants, six presented parent vessel stenosis, five presented distal branch occlusions and seven presented clip slippage phenomena. The impact of this technique on corrective treatment was 15.1% (five of 33 angiographic abnormalities). In only one case, PCA demonstrated an aneurysm remnant which was missed on IA. Twenty patients were additionally examined with three-dimensional angiography. The impact on corrective treatment of three-dimensional angiography was 25% (five of 20 examined patients with angiographic abnormalities).

CONCLUSION

In pre-selected difficult cases, IA provides high PVAA and increased impact on corrective treatment. In non-selected patients, PCA shows low PVAA and reduced impact on corrective treatment. The complementary assessment with multiplanar three-dimensional angiography increases the impact on corrective treatment and facilitates decisions about the final case management.

Histological analysis of clipped human intracranial aneurysms and parent arteries with short-term follow-up

BACKGROUND

Surgical clipping of intracranial aneurysms is the gold standard for the prevention of rupture. However, the biological processes that occur following clipping are poorly understood. To better understand these effects, retrieved and clipped human intracranial aneurysms were examined histologically.

METHODS

At autopsy, 17 aneurysms from 10 patients were retrieved 3-21 days after clipping. The tissues were embedded in paraffin, and microtome sections were stained using hematoxylin-eosin and Movat pentachrome. Using light microscopy, clip placement relative to the internal elastic lamina of the parent artery, endothelialization of the aneurysm neck, thrombus organization inside the aneurysm sac, inflammation in the sac, wall, and parent artery, and atherosclerotic changes were determined.

RESULTS

Despite complete reconstruction of the artery with the clip, diseased vessel wall was frequently observed outside the clip. By 10 days postsurgery, the beginnings of endothelialization and neointima formation were observed at the neck. However, the neck coverage was variable and incomplete at these early time points. Thrombus organization inside the aneurysm sac was rarely observed, and inflammatory cells were not present inside the aneurysm sac. Inflammatory cells were commonly observed in the aneurysm wall, and atherosclerotic change was present in each sample.

CONCLUSIONS

Complete aneurysm exclusion and apposition of healthy arterial wall occurred infrequently in our series. Endothelialization and neointima formation at the aneurysm neck take some time to complete and are often incomplete. The effectiveness of aneurysm clipping is related to the mechanics of aneurysm exclusion rather than the processes of endothelialization and neointima formation.

SUMMARY

Complete aneurysm exclusion and apposition of healthy arterial wall occurred infrequently in our series. Endothelialization and neointima formation at the aneurysm neck take some time to complete and are often incomplete. The effectiveness of aneurysm clipping is related to the mechanics of aneurysm exclusion rather than the processes of endothelialization and neointima formation.

Bare, bio-active and hydrogel-coated coils for endovascular treatment of experimentally induced aneurysms. Long-term histological and scanning electron microscopy results

Endovascular treatments of cerebral aneurysms with bare platinum coils have a higher rate of recurrence compared to surgical clipping. This may be related to failed vessel wall reconstruction since histological and scanning electron microscopy results following embolization failed to demonstrate neoendothelialization over the aneurysm neck. The present study tried to elucidate whether the use of modified coils resulted in a better rate of reconstructing the vessel wall over the aneurysm neck in experimental aneurysms. Aneurysms were created in 20 rabbits by intraluminal elastase incubation of the common carotid artery. Five animals each were assigned to the following groups: untreated, bare platinum coils, bioactive coils with polyglycolic/polylactic acid coating, and hydrogel-coated platinum coils. After 12 months, angiography, histology and scanning electron microscopy was performed. No neoendothelial layer was visualized in the bioactive and bare coil groups with a tendency to an increased layering of fibroblasts along the bioactive coils at the aneurysm fundus. However, at the aneurysm neck perfused clefts were present and although a thin fibrinous layer was present over some coils, no bridging neointimal or neoendothial layer was noted over different coils. Following loose Hydrogel coiling, a complete obliteration of the aneurysm was present with neoendothelialization present over different coil loops. The study demonstrates that with surface coil modifications complete and stable aneurysm obliteration may become possible. A smooth and dense surface over the aneurysm neck may be necessary for endothelial cells to bridge the aneurysm neck and to lead to vessel wall reconstruction.

A novel endovascular clip system for the treatment of intracranial aneurysms: technology, concept, and initial experimental results

Object

The authors describe a novel device for the endovascular treatment of intracranial aneurysms, the endovascular clip system (eCLIPs). Descriptions of the device and its delivery system as well as the results of flow model tests and the treatment of experimental aneurysms are provided.

Methods

The eCLIPs comprises a flexible hybrid implantable device (an anchor and a covered leaf) and a balloon catheter delivery system, designed to be positioned and activated in the parent vessel in such a way that the covered portion will abut the aneurysm neck. The eCLIPs was subjected to testing in glass, elastomeric, and cadaveric flow models to determine its navigability, orientation, and activation compared with commercially available stents. In a second experiment, 8 carotid artery sidewall aneurysms in swine were treated using eCLIPs. The degree of occlusion was observed on angiography immediately following and 30 days after device activation, and a histological analysis was performed at 30 days.

Results

The device could navigate tortuous glass models and human cadaveric vessels. Compared with commercially available stents, the eCLIPs performed well. It could be navigated, oriented, and activated easily and reliably. With regard to the 8 porcine experimental aneurysms, immediate postactivation angiograms confirmed complete occlusion of 4 lesions and near occlusion of the other 4. Angiographic follow-up at 30 days postactivation showed occlusion of all 8 aneurysms and patency of all parent vessels. Histopathological analysis revealed aneurysm healing, with smooth-muscle cells growing across the lesion neck to allow reendothelialization.

Conclusions

Aneurysm occlusion with a single extrasaccular endovascular device has potential advantages. The authors believe that eCLIPs may prove to be a useful tool in the endovascular treatment of cerebral aneurysms. The system should reduce risks associated with coiling, procedure time, costs, and radiation exposure. The device satisfactorily occluded 8 experimental sidewall aneurysms. The observed healing pattern is similar to that seen after microsurgical clipping.

Long-term histological and scanning electron microscopy results of endovascular and operative treatments of experimentally induced aneurysms in the rabbit

OBJECTIVE

Treatment strategies of cerebral aneurysms include surgical clipping and endovascular therapies. To determine the long-term results of these therapeutic strategies, the vessel wall reaction close to the former aneurysm was studied according to the assumption that an intact endothelial layer over the former aneurysm neck constitutes complete vessel wall reconstruction and stable aneurysm obliteration.

METHODS

Aneurysms were created in 40 rabbits by intraluminal elastase incubation of the common carotid artery. Five animals each were assigned to the following groups: untreated, porous stents, polyurethane covered stentgrafts, porous stents with subsequent coiling. Ten animals were treated with coils alone, 10 with clips. After 6 months, angiography, histology, and scanning electron microscopy was performed.

RESULTS

Porous stents did not obliterate the aneurysm, whereas stentgrafts did; in-stent stenosis of up to 60% was present because of neointimal multilayer proliferation. After coiling, the aneurysm dome was occluded with fibrinous and collagenous material, whereas the aneurysm neck was not covered by an endothelial lining. Coil loops lay bare within the vessel, with fresh thrombus material on their surface. After clipping, a thin layer of endothelial lining bridging the two attached vessel walls was present, thereby completely obliterating the aneurysm and reconstructing the vessel wall.

CONCLUSION

This study demonstrates complete and stable aneurysm obliteration with vessel wall reconstruction after clipping, a sufficient obliteration of the aneurysm dome using endovascular techniques, but a failed healing response of the aneurysm neck that might correlate to its associated higher risk of rebleed. Whether or not this is counterbalanced by the better immediate outcome after endovascular treatment remains a matter of debate.

Management of giant intracranial aneurysms

Based on an own material of 64 cases a survey is given on the management of giant intracranial aneurysms. Essential investigations are as well CT and Magnetic Resonance Scanning as detailed angiographic studies. With regard to the operative handling the following questions are discussed: approach; use of temporary vascular occlusion and related monitoring; preparation of the aneurysm neck for occlusion. In cases without recent subarachnoid haemorrhage morbidity and mortality were less than 10%. It was 15% in cases where recent haemorrhage had occurred.

Intracranial aneurysms in India--microsurgical approach

This is a retrospective study of 100 cases of intracranial aneurysms, treated in an Indian hospital, reflecting the special situation and experiences in our country. The incidence of subarachnoid haemorrhage due to ruptured aneurysm has been more or less the same as is reported from other parts of the world. The cases of recurrent haemorrhage resulting in poor clinical status are more common in our situation. Delayed referral and diagnosis were responsible for recurrent haemorrhage, increased morbidity and mortality. Forty two percent developed cerebral vasospasm within two weeks after the bleed. The use of a temporary clip on the parent vessel prevented the intraoperative rupture of the aneurysm while dissecting round about the aneurysm. Operative mortality was eight percent in the present series.

Symptomatic arterial luminal narrowing presenting months after subarachnoid hemorrhage and aneurysm clipping

The authors describe three cases of clinical cerebral ischemia associated with angiographic evidence of cerebral arterial luminal narrowing presenting 7, 14, and 52 weeks after subarachnoid hemorrhage (SAH) and aneurysm clipping. Delayed vasospasm, in its usual time setting 1 or 2 weeks after hemorrhage, did not occur symptomatically in these patients. No evidence for aneurysm clip migration or rebleed was present. All patients responded favorably to volume expansion and elevation of blood pressure. This unusual occurrence of a very delayed vasospasm may further the understanding of the vasospastic process. The symptomatic onset of arterial luminal narrowing months after SAH may suggest that a proliferative vasculopathy more accurately explains the observed vessel narrowing, rather than conventional active constriction of vascular smooth muscle.

Temporary vascular occlusion during aneurysm surgery

Premature rupture of a cerebral aneurysm during operation is a serious hazard. Direct pressure and suction may not always be effective in controlling the hemorrhage, and hasty dissection under such circumstances can cause serious injury to vital structures. In facing this risk, elective temporary arterial occlusion of parent vessels can be an advantage. Temporary clipping also may be helpful in the case of a giant aneurysm when the lesion must be opened and evacuated, or in the case of a thin-walled fundus tightly adherent to perforating vessels. Reduction of tension in the aneurysmal sac can be a valuable aid to safe dissection. The authors reviewed a total of 185 cases of intracranial aneurysm operated upon (L.S.) in the 5-year period between January 1980 and January 1985. Sixty-six patients (35.7%) underwent temporary arterial occlusion during the operations. Clinical outcome was excellent in 65.2% of the patients, good in 13.6%, fair in 12.1%, and poor in 3%. The mortality rate was 6.1%. No significant difference was found by comparing the 66 patients with temporary arterial occlusion with the 119 patients without occlusion. The longest occlusion time for the patients with excellent outcome was 23 minutes for bilateral A1 segments, 40 minutes for middle cerebral artery, 27 minutes 44 seconds for internal carotid artery, and 13 minutes 30 seconds for basilar artery. This study suggests that temporary arterial occlusion does not necessarily increase the overall mortality and morbidity in aneurysm surgery. When justified and used with caution it can be a valuable adjunct for the neurosurgeon.

A clinico-experimental study on various wrapping materials of cerebral aneurysms

In this paper, we discuss the results of a systemic study of various materials so far used for wrapping, using the intracranial arteries of 43 mongrel dogs. The findings obtained are: Muscle, fascia and dura observed began to show necrotic and absorbable change within 1 to 2 months after operation, suggesting their unreliability. Bemsheet was superior in this study in adhesiveness to the vascular wall, highly contributory to constructing a firm reinforced wall by proliferating collagen fibres in the space of stereo-reticular structure of cotton fibre. No change occurred in the cotton fibre itself with the passage of time. Lyodura had a poor adhesiveness to the vascular wall with detectable gap; in addition, it showed necrosis and absorption in the bending site. Coating with Aron alpha A had a relatively poor adhesiveness to the vascular wall and seemed to crack and disappear with time.