Risk factors for intraoperative in-stent thrombosis during stent-assisted coiling of paraclinoid aneurysms

Objectives

To identify independent risk factors for intraoperative in-stent thrombosis (IST) in paraclinoid aneurysms (PAs).

Methods

172 PA patents undergoing stent-assisted coiling (SAC) were divided into an IST group (n = 12) and a non-IST group (n = 160). Clinical characteristics, aneurysm morphologies, and laboratory parameters were measured. We performed independent t tests (for normally distributed data) or non-parametric tests (for non-normally distributed data) to compare continuous parameters. Multivariate logistic regression analysis with a stepwise forward method was conducted to determine independent risk factors. Receiver operating characteristic curves were generated, and the Delong test was employed for comparisons.

Results

Independent risk factors for IST included size ratio (SR) (p < 0.001, odds ratio [OR] = 3.909, confidence interval [CI] = 1.925-7.939), adenosine diphosphate (ADP) inhibition (p = 0.028, OR = 0.967, CI = 0.938-0.996), and reaction time (R) (p = 0.006, OR = 0.326, CI = 0.147-0.725). The combined factors (SR, ADP inhibition, and R) exhibited area under the curves of 0.870, 0.720, 0.716, and 0.697, with cutoff values of 2.46, 69.90%, and 4.65, respectively.

Conclusion

The SR, ADP inhibition, and R values were independent risk factors for the IST in the PAs undergoing SAC. For PAs with a large SR, surgeons could prepare for long-term dual antiplatelet therapy before SAC.

Clipping of Bilateral Ophthalmic Artery Aneurysms Through a Single Craniotomy

Bilateral ophthalmic aneurysms are rare and involve two aneurysms in the ophthalmic arteries, one on each, leading to potential symptoms such as vision loss and headaches. The treatment options for aneurysms, ranging from surgery and endovascular embolization to observation, depend on various factors, including aneurysm size and the patient's health. Microsurgery, while presenting complexities due to the intricate anatomy of the anterior clinoid region, offers potential advantages such as enhanced decompression rates and reduced aneurysm recurrence. The presented surgical video illustrates the treatment of bilateral ophthalmic artery aneurysms via a single craniotomy. This method reduces surgical duration and trauma, facilitating quicker patient recovery. However, this method bears potential risks, especially to both optic nerves. As underscored in the video, the utmost anatomical understanding in the anterior clinoid area is pivotal for successful outcomes and reduced complications.

Endoscopic endonasal approach for simultaneously treating a pituitary adenoma coexisting with a paraclinoid aneurysm: illustrative case

BACKGROUND

There is a certain incidence of pituitary adenomas coexisting with intracranial aneurysms, but a concurrent therapeutic strategy of tumor removal and aneurysm clipping via endoscopic endonasal approach is rarely reported. The indications and limitations of endoscopic endonasal approach surgery for this type of lesions are worth discussing.

OBSERVATIONS

The case of a pituitary tumor coexisting with a paraclinoid aneurysm was reviewed. Using an endoscopic endonasal approach, the pituitary adenoma was completely excised with extrapseudocapsular separation technique, the aneurysm was clipped at the same time, and the skull base defect was reconstructed in multilayer fashion. No tumor recurrence was found, and aneurysm clipping was complete at the 6-month follow-up after surgery.

LESSONS

For patients harboring a pituitary adenoma with a selected paraclinoid aneurysm, simultaneous tumor resection and aneurysm clipping via endoscopic endonasal approach are feasible. This strategy has the advantages of saving medical resources, promoting the patient’s rapid postoperative recovery, and reducing possible antiplatelet therapy after interventional therapy. However, surgery needs to strictly follow the indications in experienced hands, and the therapeutic effect needs to be verified by more cases and longer follow-up results.

Increased Carotid Siphon Tortuosity Is a Risk Factor for Paraclinoid Aneurysms

Background

Geometrical factors associated with the surrounding vasculature can affect the risk of aneurysm formation. The aim of this study was to determine the association between carotid siphon curvature and the formation and development of paraclinoid aneurysms of the internal carotid artery.

Methods

Digital subtraction angiography (DSA) data from 42 patients with paraclinoid aneurysms (31 with non-aneurysmal contralateral sides) and 42 age- and gender-matched healthy controls were analyzed, retrospectively. Morphological characteristics of the carotid siphon [the posterior angle (α), anterior angle (β), and Clinoid@Ophthalmic angle (γ)] were explored via three-dimensional rotational angiography (3D RA) multiplanar reconstruction. The association between carotid siphon morphology and the formation of paraclinoid aneurysms was assessed through univariate analysis. After this, logistic regression analysis was performed to identify independent risk factors for aneurysms.

Results

Significantly smaller α, β, and γ angles were reported in the aneurysmal carotid siphon group when compared with the non-aneurysmal contralateral healthy controls. The β angle was best for discriminating between aneurysmal and non-aneurysmal carotid siphons, with an optimal threshold of 18.25°. By adjusting for hypertension, smoking habit, hyperlipidemia, and diabetes mellitus, logistic regression analysis demonstrated an independent association between the carotid siphons angles α [odds ratio (OR) 0.953; P < 0.05], β (OR 0.690; P < 0.001), and γ (OR 0.958; P < 0.01) with the risk of paraclinoid aneurysms.

Conclusions

The present findings provide evidence for the importance of morphological carotid siphon variations and the likelihood of paraclinoid aneurysms. These practical morphological parameters specific to paraclinoid aneurysms are easy to assess and may aid in risk assessment in these patients.

Hybrid Anterior Clinoidectomy in the Clipping of Paraclinoid Aneurysms: Technique, Utility and Case Illustration

BACKGROUND

Anterior clinoidectomy for aneurysm clipping is generally performed intradurally. Despite obvious advantages, accidental drill slippage or indirect damage from heat and bone dust remain major drawbacks.

OBJECTIVE

To demonstrate the surgical technique and utility of a combined extra- and intra-dural clinoidectomy in the clipping of dorsal wall paraclinoid internal carotid artery aneurysm.

MATERIAL AND METHODS

A case of dorsal wall paraclinoid aneurysm which was stuck to the anterior clinoid process on preoperative angiogram is presented. The surgical technique is shown stepwise, and the intricacies of the technique are described.

RESULTS

The hybrid clinoidectomy allowed for proper delineation of the aneurysm, mobilization of the optic nerve and intracranial proximal control on the clinoidal segment by dint of "apparent" intracranial ICA lengthening. This allowed the aneurysm to be clipped successfully and the patient made an uneventful recovery.

CONCLUSION

Hybrid clinoidectomy is a useful technique and must be learnt.

Late complications of visual impairment and hydrocephalus after flow diverter-assisted coil embolisation for intracranial large aneurysm: a case report and literature review

Large or giant paraclinoid aneurysms typically have good indication for flow diverter (FD) treatment. Here, we report a very rare case of a patient with an unruptured supraclinoid large aneurysm who underwent FD deployment with coil embolisation that resulted in delayed visual field defect (VFD) and hydrocephalus. A 75-year-old woman with a large right supraclinoid aneurysm presented with severe hemianopia in the right eye. She underwent FD deployment with coil embolisation of the aneurysm. However, permanent left visual field loss occurred four months after surgery. Magnetic resonance imaging (MRI) showed severe oedema surrounding the aneurysm along the optic tract. Inflammation led to postoperative hydrocephalus, requiring ventriculoperitoneal shunt placement. To the best of our knowledge, this is the first report of both a delayed VFD and hydrocephalus following FD treatment. In cases of FD treatment with coil embolisation for large paraclinoid aneurysms, clinicians should keep in mind that postoperative visual impairment or/and hydrocephalus may occur.

Paraclinoid Segment Aneurysms of the Internal Carotid Artery: Surgical Clipping

Background

Paraclinoid segment aneurysms arise from the internal carotid artery (ICA) between the distal dural ring and the origin of the posterior communicating (PComm) artery.

Objective

This pictorial study presents videos showing clipping of paraclinoid segment aneurysms.

Materials and Methods

The various subtypes of these aneurysms, the nuances in the technique of clinoidectomy, and methods of proximal control are presented.

Results

Cavernous ICA is designated as C4, clinoidal segment (between the proximal and distal dural rings) as C5, and supraclinoid segment (between the distal dural ring up to the PComm artery as C6 segment. The techniques used for clipping various aneurysms are based upon their subtypes and location. In the first case, in a giant superior hypophyseal artery aneurysm directed toward the suprasellar region, an intradural clinoidectomy helped in accessing the neck of the aneurysm encroaching into the clinoidal segment of ICA. In the second case, concurrent bilateral "kissing" paraclinoid segment aneurysms were clipped using a unilateral approach. In the third case, clipping of a dissecting paraclinoid segment aneurysm is demonstrated.

Conclusions

Surgery still represents the most definitive form of treatment. It may also be used to evacuate an intracerebral hematoma, with an extremely tortuous proximal vessel or in an aneurysm with complex anatomy, with blister aneurysms, or following aneurysm regrowth following a failed endovascular procedure. Assessing the three-dimensional anatomy of various segments of ICA is an important step.

Endovascular Treatment for Lateral Wall Paraclinoid Aneurysms and the Influence of Internal Carotid Artery Angle

Lateral wall paraclinoid aneurysms (LPA) are a rare type of aneurysm located on the lesser curve side of the internal carotid artery (ICA) bend, at the level of the anterior clinoid process. The objective of this study was to assess the influence of flexion of the ICA on the morphology of aneurysms and outcome of endovascular treatment. Between 2003 and 2018, we treated 643 cases of unruptured paraclinoid aneurysms with endovascular therapy in our institution. Of those cases, aneurysms projecting laterally on preoperative angiography were defined as LPA. The degree of bending of the ICA (ICA angle) was measured and statistically analyzed in relation to the aneurysm characteristics and the occlusion status after treatment. In all, 43 aneurysms were identified. ICA angle was positively correlated with the maximum dome size of the aneurysm (P <0.01) and the aspect ratio (P <0.01), and negatively correlated with the volume coil embolization ratio (P <0.01). Complete occlusion (CO) was achieved in 23 cases (53.5%) immediately after treatment, and in 35 cases (81.4%) at follow-up. The mean ICA angle in the incomplete occlusion group was significantly larger than in the CO group (P = 0.01). Larger ICA angle resulted in recurrence, whereas smaller ICA angle was more likely to obtain progressive thrombosis (P = 0.02). Endovascular treatment for LPA was safe and effective. The degree of flexion of the ICA may contribute to the level of hemodynamic stress on the aneurysm, its morphology, and the embolization effect.

Simple and Reproducible Microcatheter Shaping Method for Coil Embolization of Medially-directed Paraclinoid Internal Carotid Artery Aneurysms

Objective

It is important to guarantee intra-aneurysmal stability of microcatheters during coil embolization. We developed a simple and reproducible microcatheter shaping method for medially-directed paraclinoid internal carotid artery aneurysms.

Methods

An injection needle cap was used to make a smooth curve on the mandrel, which was first wound around the back end of the cap to create a primary curve. Next, a secondary curve was created using near the tip of the cap. Thus, a two-dimensional (2D), pigtail-shaped mandrel with a two-stage curve was created. The pigtail-shaped mandrel was inserted from the tip of a straight microcatheter and heat-shaped using a heat gun. Lastly, a microcatheter having a curve whose tip was approximately 6 mm longer than that of the preshaped J was created. We evaluated the ease of navigating the microcatheter into the aneurysm and its stability during coil embolization.

Results

In all, 34 consecutive medially-directed paraclinoid internal carotid artery aneurysms were treated using the shaped catheters. It took 50-300 seconds (intermediate value: 90 seconds) from inserting the microcatheter with a microguide wire to navigate and place it into an aneurysm. There were no cases that required reshaping of the microcatheters during navigation into the aneurysm. There were no cases that resulted in kickback of the microcatheters from the aneurysm during coil placement, and microcatheter stability was good until the end of the procedure. In all, 12 cases required the balloon-assisted technique and three cases required stent-assisted coiling. The angiographic outcomes immediately after embolization were as follows: 25 cases (73.5%) with complete occlusion; 3 cases (8.8%) with dome filling; and 6 cases (17.6%) with a neck remnant. There were no perioperative complications.

Conclusion

The shaping method with a pigtail-shaped mandrel using an injection needle cap is simple and reproducible, and is useful for medially-directed paraclinoid internal carotid artery aneurysms.

Extent of anterior clinoidectomy for clipping of carotid-ophthalmic aneurysms predicted on three-dimensional computerised tomography angiography

AIM OF STUDY

We aimed to verify the value of computerised tomography angiography (CTA) on predicting the extent of anterior clinoidectomy that is optimal for particular carotid-ophthalmic aneurysms (COAs).

CLINICAL RATIONALE FOR STUDY

The anterior clinoid process (ACP) often impedes the complex microsurgery of COA. Complete removal of the ACP ensures safe clipping; however, it also may increase the risk of severe complications. The probability of performing a successful partial anterior clinoidectomy could be evaluated by preoperative CTA.

MATERIALS AND METHODS

28 patients with either a ruptured (n=4) or unruptured COA were included in this prospective, single-centre, observational study. One aneurysm was giant, two were large, and the rest were smaller. Successful aneurysm clipping was the aim in all cases. The anterior clinoidectomy was preoperatively planned on multiplanar three-dimensional reconstructions of CTA images (3D-CTA) which resembled the typical view of a frontotemporal craniotomy. Finally, the predicted clinoidectomy was compared to the extent of the actual clinoidectomy.

RESULTS

21 aneurysms (75%) projected superolateral or superior. The ACP was completely and selectively resected in 25% (7 of 28) and 67.9% of patients (19 of 28) respectively. Optic nerve (ON) unroofing was always performed in the case of total anterior clinoidectomy, but accompanied only 8 of 19 selective clinoidectomies (p = 0.03). The extent of the actual clinoidectomy was predicted by the 3D-CTA-based preoperative planning in 17 of 27 cases (63.0%). Particularly, prediction of the osteotomy was correct in 85.7% of complete, 62.5% of selective lateral, and 57.1% of medial clinoidectomy. None of the radiological and clinical factors determined the correlation between the planned and the actual extent of ACP removal. There was one incomplete occlusion among 23 obtained follow-up CTAs.

CONCLUSIONS

The predictive value of 3D-CTA on the extent of anterior clinoidectomy still remains unsatisfactory; it is limited by the individual variability of COA and its surrounding structures.

CLINICAL IMPLICATIONS

Currently, the role of 3D-CTA planning is restricted to educational purposes only.

Interdural course of the ophthalmic artery in the optic canal

OBJECTIVE

In the current neurosurgical and anatomical literature, the intracanalicular segment of the ophthalmic artery (OphA) is usually described to be within the optic nerve dural sheath (ONDS), implying direct contact between the nerve and the artery inside the optic canal. In the present study, the authors sought to clarify the exact relationship between the OphA and ONDS.

METHODS

Ten cadaveric heads were subjected to endoscopic endonasal and transcranial exposures of the OphA in the optic canal (5 for each approach). The relationship between the OphA and ONDS was assessed. Histological examination of one specimen of the optic nerve and the accompanying OphA was also performed to confirm the relationship with the ONDS.

RESULTS

In all specimens, the OphA coursed between the two layers of the dura (endosteal and meningeal) and was not in direct contact with the optic nerve, except for the first few millimeters of the proximal optic canal before it pierced the ONDS. Upon reaching the orbit, the two layers of the dura separated and allowed the OphA to literally float within the orbital fat. The meningeal dura continued as the ONDS, whereas the endosteal dura became the periorbita.

CONCLUSIONS

This study clarifies the interdural course of the OphA within the optic canal. This anatomical nuance has important neurosurgical implications regarding safe exposure and manipulation of the OphA.

Less Invasive Modified Extradural Temporopolar Approach for Paraclinoid Lesions: Operative Technique and Surgical Results in 80 Consecutive Patients

Background  Extradural temporopolar approach for paraclinoid lesions can provide extensive and early exposure of the anterior clinoid process, and complete mobilization and decompression of the optic nerve and internal carotid artery, which can prevent intraoperative neurovascular injury. The present study investigated the usefulness of our less invasive modified technique and discussed its operative nuances. Methods  We retrospectively reviewed medical charts of 80 consecutive patients with neoplastic (21 patients) and vascular lesions (59 patients) who underwent the modified extradural temporopolar approach between September 2009 and March 2014. Results  Preoperative visual acuity worsened in 4 patients (5.0%) and worsening of visual field function occurred in 10 patients (12.5%). Postoperative outcome was good recovery in 71 patients, moderate disability in 6, severe disability in 2, and death in 1 (due to reruptured aneurysm). No operation-related mortality occurred in the series. Conclusion  Less invasive modified extradural temporopolar approach is safe and can be recommended for the surgical treatment of deeply located aneurysms and skull base tumors to reduce the risk of intraoperative optic neurovascular injury.

Anterior clinoidectomy for paraclinoid aneurysms in Helsinki Neurosurgery

Background:

In this video abstract, we present an intradural anterior clinoidectomy for management of some paraclinoid aneurysms. Quick adenosine cardiac arrest performed instead of an anterior clinoidectomy and proximal temporary clipping usually allows us a proximal control of aneurysms in Helsinki Neurosurgery. However, when the neck of the aneurysm remains hidden under the anterior clinoid process, or when some complex aneurysms have reduced space for placing temporary clips obstructing the definitive clipping, anterior clinoidectomy is the most available option.

Technique:

The patient with multiple intracranial aneurysms had a ruptured anterior cerebral artery aneurysm associated with a right middle cerebral artery aneurysm and a right small paraclinoid aneurysm. The patient underwent surgical clipping of all aneurysms by a right lateral supraorbital approach at one-stage surgery. After the associated aneurysms were clipped, the hidden paraclinoid aneurysm required an anterior clinoidectomy for definitive clipping. A small durotomy over the anterior clinoid process was made with microscissors after bipolar coagulation. Subsequently, the anterior clinoidectomy was performed under visual control with the use of an electric high-speed diamond drill (3 mm diameter). The direction and size of the drilling were performed according to the anatomical configuration and exact location of the aneurysm determined by the preoperative radiological analysis of the case. A definitive clip was applied after complete visualization of aneurysm. Postoperative computed tomography angiography demonstrated absence of complications.

Conclusion:

Anterior clinoidectomy is a useful procedure aiming at a proper definitive clipping of paraclinoid aneurysms with challenging locations and configurations.

Videolink:

http://surgicalneurologyint.com/videogallery/right-clinoidectomy/

Suction Decompression during Anterior Clinoidectomy for Direct Clipping of Paraclinoid Aneurysm Involving the Anterior Clinoid Process

Surgical clipping of paraclinoid aneurysms involving the anterior clinoid process (ACP) can present great challenges because strong adhesion may hinder dissection of the surrounding anatomical structures from the aneurysm dome. On the other hand, retrograde suction decompression (RSD) through direct puncture of the common carotid artery is a useful adjunct technique for clipping of these aneurysms. The present case illustrates that direct clipping of paraclinoid aneurysms involving the ACP can be achieved safely and less invasively using RSD during anterior clinoidectomy. Postoperatively, her clinical course was uneventful. RSD is a useful technique during anterior clinoidectomy in direct clipping of paraclinoid aneurysms involving the ACP.

Modified extradural temporopolar approach with suction decompression for clipping of large paraclinoid aneurysm: Technical note

Background:

Surgical clipping of complicated large paraclinoid aneurysms are still challenging because strong adhesion of aneurysm itself may hinder the dissection of the perforators and the surrounding anatomical structures from the aneurysm dome.

Methods:

We describe 13 consecutive patients and the clipping of complicated, large-sized paraclinoid aneurysms using a modified extradural temporopolar approach combined with retrograde suction decompression and discuss its advantages and pitfalls.

Results:

Modified extradural temporopolar approach with suction decompression (SD) assistance was performed in all patients. There was no complication related to the surgical procedure. Postoperative outcome was good recovery in 7 patients, moderate disability in 4, and severe disability in 2 caused by severe subarachnoid hemorrhage. Favorable outcomes were achieved in 10 patients (84.6%).

Conclusion:

We recommend its less invasive, safe, and useful combined technique in the treatment of symptomatic paraclinoid aneurysms, which carry the risk of neurovascular injury caused by dissection from the aneurysm dome.

Carotico-clinoid foramina and a double optic canal: A case report with neurosurgical implications

Background:

The lesser wing of the sphenoid is a clinically important structure, particularly with regard to its anatomical relationship with neurovascular structures including the optic nerve, ophthalmic artery, and internal carotid artery. Anterior clinoidectomy, a neurosurgical procedure utilized to access paraclinoid aneurysms and neoplasms, is often complicated by the presence of anatomical variants including the carotico-clinoid foramen and the accessory optic canal.

Case Description:

A rare case report is presented documenting the simultaneous occurrence of bilateral carotico-clinoid foramina and a unilateral accessory optic canal.

Conclusion:

The presence of an accessory optic canal may be misconstrued as a carotico-clinoid foramen or pneumatization of the anterior clinoid process, lesser sphenoidal wing, or optic strut. The case report documents two clinically important variant structures occurring ipsilaterally, each with the potential to masquerade as the other radiographically and present complications to both neurosurgeons and radiologists. Knowledge of the unique combination of anatomical variants presented in this report may prevent adverse surgical events during anterior clinoidectomy procedures including hemorrhage of the ophthalmic artery or internal carotid artery and subsequent vision loss or death.

Impact of Endovascular Technique on Fluoroscopy Usage: Stent-Assisted Coiling versus Flow Diversion for Paraclinoid Internal Carotid Artery Aneurysms

Flow diversion is increasingly being utilized for the treatment of internal carotid artery (ICA) aneurysms. The purpose of this study was to evaluate the impact of endovascular technique--flow diversion versus stent-assisted coiling (SAC) on fluoroscopy time in patients treated for wide-neck paraclinoid ICA aneurysms. A retrospective review identified the 20 most recent consecutive patients treated for wide-neck paraclinoid ICA aneurysms by flow diversion and SAC respectively. Fluoroscopy time, cumulative dose area-product (DAP), contrast usage, intra-procedural complications, and total procedure time were collected and compared between the two treatment techniques. Treatment groups were comparable in terms of demographics, contrast usage, and clinical and angiographic outcomes. Flow diversion was associated with a significant reduction in fluoroscopy time (52.0 minutes versus 77.4 minutes), and demonstrated a strong trend towards shorter total procedure time (172 minutes versus 202 minutes). Average patient radiation exposure as measured by DAP was lower in the flow diversion group, 13225 mGy(x)cm(2) versus 15124 mGy(x)cm(2), although this finding was not statistically significant. There was no significant difference in contrast usage between the two groups, 152 ml and 159 (flow diversion and SAC respectively). The rate of complete aneurysm occlusion was higher in the flow diversion group (80% versus 60%). Endovascular treatment of paraclinoid ICA aneurysms with flow diversion is associated with shorter fluoroscopy times compared to stent-assisted coiling. There is also a likely reduction in overall procedure time. These results should be considered when recommending a treatment course for patients with such lesions.

Bilobulated paraclinoid aneurysm mimics double aneurysms: a comparison of endovascular coiling and surgical clipping treatments

This report presents two cases of subarachnoid hemorrhage caused by rupture of paraclinoid aneurysms. Both aneurysms presented a bilobulated appearance upon image study. Both cases were treated successfully, the first with surgical clipping and the second with endovascular coiling. The special bilobulated feature of paraclinoid aneurysm in this particular anatomic location suggests its close relationship with the carotid dural ring. This relationship caused varying degrees of difficulty in both coiling and clipping the aneurysm. We compared the limitations and advantages of both treatments, and suggest that surgical clipping may be the treatment of choice in this region.

Endoscopic endonasal transplanum approach to the paraclinoid internal carotid artery

Objective To investigate the relevance of an endoscopic transnasal approach to the surgical treatment of paraophthalmic aneurysms. Setting Binasal endoscopic transplanum surgery was performed. Participants Seven cadaver heads were studied. Main Outcome Measures (1) Dimensions of the endonasal corridor, including the operative field depth, lateral limits, and the transplanum craniotomy. (2) The degree of vascular exposure. (3) Surgical maneuverability and access for clip placements. Results The mean operative depth was 90 ± 4 mm. The lateral corridors were limited proximally by the alar rim openings (29 ± 4 mm) and distally by the distance between the opticocarotid recesses (19 ± 2 mm). The mean posteroanterior distance and width of the transplanum craniotomy were 19 ± 2 mm and 17 ± 3 mm, respectively. Vascular exposure was achieved in 100% of cases for the clinoidal internal carotid artery (ICA), ophthalmic artery, superior hypophyseal artery, and the proximal ophthalmic ICA. Surgical access and clip placement was achieved in 97.6% of cases for vessels located anterior to the pituitary stalk (odds ratio [OR] 73.8; 95% confidence interval [CI] 7.66 to 710.8; p = 0.00). Conclusion The endoscopic transnasal approach provides excellent visualization of the paraclinoid region vasculature and offers potential surgical alternative for paraclinoid aneurysms.