De novo basilar tip aneurysm. Case report and literature review

Residual lesions in patients who underwent microsurgical clipping of cerebral aneurysms

Microsurgical clipping is currently the main method of treating cerebral aneurysms, even with the improvement of endovascular therapy techniques in recent years. Treatment aims at complete occlusion of the lesion, which is not always feasible. Although appearing superior to endovascular treatment, microsurgical clipping may present varying percentages of incomplete occlusion. Such incidence may be reduced with the use of intraoperative vascular study. Some classifications were elaborated in an attempt to standardize the characteristics of residual lesions, but the classification criteria and terminology used in the studies remain vague and poorly documented, and there is no consensus for a uniform classification. Thus, there is also no agrément on which residual aneurysms should be treated. The aim of this study is to review the literature on residual lesions after microsurgery to treat cerebral aneurysms and how to proceed with them.

Cerebral arterial infundibula are preaneurysmal lesions caused by direct flow impact

PURPOSE

To investigate whether arterial infundibular widening is a preaneurysmal lesion or not.

METHODS

Two hundred and nine patients with cerebral angiography were enrolled. The morphology, size and location of infundibula and cerebral aneurysms were studied in two-dimensional angiography and three-dimensional software space. Computational fluid dynamics (CFD) analysis was performed.

RESULTS

234 infundibula and 129 infundibulum-like aneurysms (IFAs) were detected. In two-dimensional space, the typical morphology of an infundibulum was a symmetric dilatation at the arterial branch origin with a small vessel branch emanating from the tip and a wide base connecting the parent artery. In three-dimensional space, the infundibulum was dissymmetric with always one side longer than the other side. Furthermore, the infundibulum tilted upstream rather than downstream, with the longer side located downstream and the shorter side upstream in all cases. All the 129 IFAs occurred on the distal wall of the vessel branch origin, and no IFAs grew from the proximal wall of the branch origin. The possible development process of an infundibulum to an IFA was described in four development stages. The CFD analysis revealed that these lesions were associated with direct flow impingement in all cases. All the hemodynamic parameters on the distal wall of infundibula and IFAs were significantly (P<0.0001 or P<0.05) decreased compared with on the distal wall after virtual lesion removal.

CONCLUSION

The infundibulum is a preaneurysmal lesion associated with high total pressure and high wall shear stress resulted from direct flow impingement and will progress to an aneurysm with time.

Endovascular treatment of carotid-cavernous vascular lesions

Objective:

to evaluate the endovascular treatment of vascular lesions of the cavernous segment of the internal carotidartery (ICA) performed at our institution.

Methods:

we conducted a descriptive, retrospective and prospective study of patients with aneurysms of the cavernous portion of the ICA or with direct carotid-cavernous fistulas (dCCF) undergoing endovascular treatment.

Results:

we included 26 patients with intracavernous aneurysms and ten with dCCF. All aneurysms were treated with ICA occlusion. Those with dCCF were treated with occlusion in seven cases and with selective fistula occlusion in the remaining three. There was improvement of pain and ocular proptosis in all patients with dCCF. In patients with intracavernous aneurysms, the incidence of retro-orbital pain fell from 84.6% to 30.8% after treatment. The endovascular treatment decreased the dysfunction of affected cranial nerves in both groups, especially the oculomotor one.

Conclusion:

the endovascular treatment significantly improved the symptoms in the patients studied, especially those related to pain and oculomotor nerve dysfunction.

Objetivo:

avaliar o tratamento endovascular de lesões vasculares da artéria carótida interna (ACI), segmento cavernoso, realizado na Santa Casa de São Paulo.

Métodos:

estudo descritivo, retrospectivo e prospectivo, de pacientes com aneurisma da porção cavernosa da ACI ou com fístulas carótido-cavernosas diretas (FCCd) submetidos a tratamento endovascular.

Resultados:

foram incluídos 26 pacientes com aneurismas intracavernosos e dez com FCCd. Todos os aneurismas foram tratados com oclusão da ACI. Os com FCCd foram tratados com oclusão, em sete casos, e com oclusão seletiva da fístula nos outros três. Houve melhora da dor e proptose ocular em todos os pacientes com FCCd. Nos pacientes com aneurisma intracavernoso, a incidência de dor retro-orbitária caiu de 84,6% para 30,8% após o tratamento. Após o tratamento endovascular houve uma melhora importante da disfunção de nervos cranianos afetados em ambos os grupos, sobretudo no nervo oculomotor.

Conclusão:

o tratamento endovascular trouxe melhora para os pacientes deste estudo, especialmente nos critérios dor e acometimento do nervo oculomotor.

Hypertension and Estrogen Deficiency Augment Aneurysmal Remodeling in the Rabbit Circle of Willis in Response to Carotid Ligation

Increased cerebral blood flow has been shown to induce pathological structural changes in the Circle of Willis (CoW) in experimental models. Previously, we reported flow-induced aneurysm-like remodeling in the CoW secondary to flow redistribution after bilateral common carotid artery (CCA) ligation in rabbits. In the current study, we tested the hypothesis that loading rabbits with biological risk factors for vascular disease would increase flow-induced aneurysmal remodeling in the CoW. In the same series as the previously-reported bilateral CCA-ligation-alone (n  = 6) and sham surgery (n = 3) groups, eight additional female rabbits (the experimental group in this study) were subjected to two risk factors for intracranial aneurysm (hypertension and estrogen deficiency) and then bilateral CCA ligation. Upon euthanasia at 6 months, vascular corrosion casts of the CoW were created and analyzed by scanning electron microscopy for morphological changes and aneurysmal damage. In rabbits with hypertension and estrogen deficiency, arterial caliber increased throughout the CoW, similar to rabbits with CCA ligation alone. However, aneurysmal remodeling (i.e., local bulging) in the CoW was significantly greater than in CCA-ligation-only rabbits and was more widespread, presenting in regions that did not show aneurysmal changes after CCA ligation alone. Furthermore, hypertension and estrogen deficiency caused greater increases in vessel length and tortuosity. These results suggest that hypertension and estrogen deficiency make the CoW more vulnerable to flow-induced aneurysmal remodeling and tortuosity. We propose they do so by lowering the tolerance of vascular tissue to hemodynamic forces caused by CCA ligation, thus lowering the threshold necessary to incite vascular damage.

Endothelial nitric oxide synthase and superoxide mediate hemodynamic initiation of intracranial aneurysms

Background

Hemodynamic insults at arterial bifurcations are believed to play a critical role in initiating intracranial aneurysms. Recent studies in a rabbit model indicate that aneurysmal damage initiates under specific wall shear stress conditions when smooth muscle cells (SMCs) become pro-inflammatory and produce matrix metalloproteinases (MMPs). The mechanisms leading to SMC activation and MMP production during hemodynamic aneurysm initiation are unknown. The goal is to determine if nitric oxide and/or superoxide induce SMC changes, MMP production and aneurysmal remodeling following hemodynamic insult.

Methods

Bilateral common carotid artery ligation was performed on rabbits (n = 19, plus 5 sham operations) to induce aneurysmal damage at the basilar terminus. Ligated animals were treated with the nitric oxide synthase (NOS) inhibitor LNAME (n = 7) or the superoxide scavenger TEMPOL (n = 5) and compared to untreated animals (n = 7). Aneurysm development was assessed histologically 5 days after ligation. Changes in NOS isoforms, peroxynitrite, reactive oxygen species (ROS), MMP-2, MMP-9, and smooth muscle α-actin were analyzed by immunohistochemistry.

Results

LNAME attenuated ligation-induced IEL loss, media thinning and bulge formation. In untreated animals, immunofluorescence showed increased endothelial NOS (eNOS) after ligation, but no change in inducible or neuronal NOS. Furthermore, during aneurysm initiation ROS increased in the media, but not the intima, and there was no change in peroxynitrite. In LNAME-treated animals, ROS production did not change. Together, this suggests that eNOS is important for aneurysm initiation but not by producing superoxide. TEMPOL treatment reduced aneurysm development, indicating that the increased medial superoxide is also necessary for aneurysm initiation. LNAME and TEMPOL treatment in ligated animals restored α-actin and decreased MMPs, suggesting that eNOS and superoxide both lead to SMC de-differentiation and MMP production.

Conclusion

Aneurysm-inducing hemodynamics lead to increased eNOS and superoxide, which both affect SMC phenotype, increasing MMP production and aneurysmal damage.

Aneurysmal remodeling in the circle of Willis after carotid occlusion in an experimental model

Carotid occlusions are associated with de novo intracranial aneurysm formation in clinical case reports, but this phenomenon is not widely studied. We performed bilateral carotid ligation (n=9) in rabbits to simulate carotid occlusion, and sham surgery (n=3) for control. Upon euthanasia (n=3 at 5 days, n=6 at 6 months post ligation, and n=3 at 5 days after sham operation), vascular corrosion casts of the circle of Willis (CoW) were created. Using scanning electron microscopy, we quantified gross morphologic, macroscopic, and microscopic changes on the endocasts and compared findings with histologic data. At 5 days, CoW arteries of ligated animals increased caliber. The posterior communicating artery (PCom) increased length and tortuosity, and the ophthalmic artery (OA) origin presented preaneurysmal bulges. At 6 months, calibers were unchanged from 5 days, PComs further increased tortuosity while presenting segmental dilations, and the OA origin and basilar terminus presented preaneurysmal bulges. This exploratory study provides evidence that flow increase after carotid occlusion produces both compensatory arterial augmentation and pathologic remodeling such as tortuosity and saccular/fusiform aneurysm. Our findings may have considerable clinical implications, as these lesser-known consequences should be considered when managing patients with carotid artery disease or choosing carotid ligation as a therapeutic option.

De novo aneurysms in long-term follow-up computed tomographic angiography of patients with clipped intracranial aneurysms

OBJECTIVE

This study was undertaken to evaluate de novo aneurysm formation in the long-term follow-up of patients with clipped aneurysms.

METHODS

Of 459 patients who underwent clipping of ruptured cerebral aneurysms at our institution between 1997 and 2008, 119 patients were available in good condition and agreed to undergo 64-detector row computed tomographic (CT) angiography. In addition, eight patients underwent CT angiography for new subarachnoid hemorrhage.

RESULTS

The mean ± standard deviation interval from surgery was 7.2 ± 2.3 years for CT angiography controlled patients. De novo aneurysms were detected in 5 of 119 (4.5%) patients and 4 of 8 patients with new subarachnoid hemorrhage. A history of multiple aneurysms was associated with de novo aneurysm formation (P < 0.001).

CONCLUSION

The risk of de novo aneurysm formation in patients with clipped aneurysms is significant in long-term follow-up. CT angiography can be used as a noninvasive method for detection of de novo aneurysms in these patients.

De novo large fusiform posterior circulation intracranial aneurysm presenting with subarachnoid hemorrhage 7 years after therapeutic internal carotid artery occlusion: case report and review of the literature

BACKGROUND AND IMPORTANCE

Although the use of proximal artery occlusion, or hunterian ligation, for the treatment of intracranial aneurysms has decreased greatly over the past decades, this approach still finds use for certain giant and complex aneurysms. The main risks of artery sacrifice are ischemic complications but also, although rare, de novo aneurysm formation. We present here a case of de novo formation of a large fusiform basilar artery aneurysm 7 years after internal carotid artery occlusion.

CLINICAL PRESENTATION

A 17-year-old male patient with a history of a giant right cavernous aneurysm treated 7 years earlier with right-sided endovascular internal carotid artery occlusion presented to our institution with a thunderclap headache. At the time of initial evaluation, the patient was neurologically intact and imaging revealed a 22 × 10-mm fusiform aneurysm of the distal basilar artery with mass effect on the adjacent pons as well as a small amount of subarachnoid and intraventricular blood. Complete occlusion of the right internal carotid artery was demonstrated with retrograde filling of the right middle cerebral artery from the enlarged right posterior communicating artery. The patient was subsequently treated with hunterian occlusion of the basilar artery below anterior inferior cerebellar arteries. A superficial temporal artery to middle cerebral artery bypass was performed on the right side before this occlusion.

CONCLUSION

Further studies on the epidemiology of de novo aneurysms after carotid artery occlusion are warranted. Patients at higher risk of the development of intracranial aneurysms should be followed aggressively after hunterian ligation, and the possibility of an extracranial-intracranial bypass should be discussed.