Clinoid and paraclinoid aneurysms: surgical anatomy, operative techniques, and outcome

doi:10.1016/S0090-3019(98)00137-2

Surgical Neurology

Volume 51, Issue 5, May 1999, Pages 477-488

https://doi.org/10.1016/S0090-3019(98)00137-2 Get rights and content

Abstract

Background

Paraclinoid or ophthalmic segment aneurysms arise from the internal carotid artery (ICA) between the roof of the cavernous sinus and the origin of the posterior communicating artery. Clinoid aneurysms arise between the proximal and distal carotid dural rings. The complex anatomy of clinoid and paraclinoid ICA aneurysms often makes them difficult to treat by microsurgery. The natural history of these aneurysms varies, based on their location and anatomic relationships. Accurate preoperative assessment of the origin of these aneurysms is therefore a critical aspect of their management.

Methods

The authors reviewed 35 clinoid and paraclinoid ICA aneurysms operated in 28 patients and classify them according to their anatomic location and angiographic pattern. The operative techniques, surgical outcomes, and indications for surgery are reviewed.

Results

Based on surgical anatomy and angiographic patterns, the aneurysms were classified into two categories: clinoid segment and paraclinoid (ophthalmic) segment. The clinoid segment aneurysms consisted of medial, lateral and anterior varieties. The paraclinoid aneurysms could be classified topographically into medial, posterior and anterior varieties, or based on the artery of origin into ophthalmic, superior, hypophyseal, and posterior paraclinoid aneurysms. Ophthalmic aneurysms were most common (40%), followed by posterior ICA wall aneurysms (29%), superior hypophyseal aneurysms (14%), and clinoid aneurysms (17%). Twenty patients (71%) had single aneurysms. Of the remaining eight, six had bilateral aneurysms and two had unilateral multiple aneurysms. Of the 35 aneurysms, 32 were clipped satisfactorily, as confirmed by intraoperative or postoperative angiography. One small broad-based aneurysm was wrapped, and two others were treated by trapping and bypass techniques. Three patients who had bilateral aneurysms underwent successful clipping of four contralateral, left-sided aneurysms via a right frontotemporal, transorbital approach. On follow-up (mean, 39 months), 25 patients were in excellent condition (returned to their prior occupation), two were in good condition (independent, but not working), and one died postoperatively of vasospasm.

Conclusion

Our increased knowledge of anatomy and refinements in operative techniques have greatly improved the surgical treatment of clinoid and paraclinoid aneurysms.

Section snippets

Materials and methods

We reviewed our operative experience with 35 clinoid and paraclinoid ICA aneurysms treated between 1988 and June 1996. The majority of the aneurysms were treated at The George Washington University Medical Center; some were treated at the University of Pittsburgh Medical Center by LNS. We obtained patients’ clinical information from their charts and reviewed their arteriograms and intraoperative photographs. Each patient underwent cerebral angiography to determine the size, shape, and exact

Demographics

Our series included 35 clinoid and paraclinoid aneurysms in 28 patients. There were 6 clinoid (5 medial, 1 lateral) aneurysms, 14 ophthalmic aneurysms, 5 superior hypophyseal aneurysms, and 10 posterior paraclinoid aneurysms. Twenty patients (71%) had single aneurysms. Of the remaining eight, six had bilateral aneurysms and two had unilateral multiple aneurysms (Table 1 ). One patient had a giant intracavernous aneurysm, a large paraclinoid aneurysm, and two middle cerebral artery bifurcation

Treatment

Of the 35 aneurysms, 31 were clipped satisfactorily as confirmed by intraoperative angiography. One ophthalmic aneurysm was not clipped but was wrapped because of its small size and the absence of a neck. One 3.0-cm superior hypophyseal aneurysm was clipped and a superficial temporal artery (STA)-to-MCA bypass was done prophylactically. On postoperative angiography the aneurysm and ICA were thrombosed. The patient developed a small capsular infarct and a mild hemiparesis, but recovered

Complications

The postoperative complications are detailed in Table 2. One patient who had suffered SAH from a posterior paraclinoid aneurysm developed a postoperative epidural hematoma that was removed successfully. She subsequently suffered severe vasospasm unresponsive to hypertensive, hypervolemic therapy and angioplasty, and died of massive brain infarction. Interestingly, she had not undergone an orbital osteomy for aneurysm exposure. Another patient developed recurrent epidural hematomas and

Outcome

Patients’ outcome was assessed at 3 months and 1 year postoperatively, with annual follow-up thereafter, and graded according to the Glasgow Outcomes Scale. Twenty-five patients were in excellent condition (GOS 5, returned to previous occupation), two were in good condition (GOS 4, independent with some disability), and one died postoperatively. When patients with unruptured and ruptured aneurysms are considered separately, of 20 patients with unruptured aneurysms, 18 had an excellent outcome,

Classification

Multiple systems of classification of these aneurysms have been used by various authors in the literature 5, 8, 12, 13, 14, 18, 31. We have used a system that is based on the ICA segment of origin of the aneurysm (clinoid or ophthalmic ICA segment), based on the branch-point of origin of the aneurysm from the ICA, and on the location of the neck in relation to the ICA. When the aneurysm reaches a large or giant proportion, one may be able to only identify the broad segment of origin from the

Acknowledgements

We thank Jennifer Pryll (Pogorzala) for the illustrations, and Joseph Reister for preparation of the manuscript.

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Cited by (109)

Endovascular Treatment and Microsurgical Clipping for the Management of Paraclinoid Intracranial Aneurysms: A Systematic Review and Meta-Analysis
2023, World Neurosurgery
We aimed to compare the efficacy and safety of microsurgical clipping versus endovascular treatment (EVT) for paraclinoid aneurysms.
A systematic search for studies including patients with paraclinoid aneurysms treated with a microsurgical or endovascular technique was conducted in 6 databases from inception to February 2022. Efficacy outcomes included complete angiographic occlusion at last follow-up, favorable functional outcome, and recurrence of the aneurysm. For safety, we assessed a composite of intraoperative and postoperative complications. Data were pooled using a random-effects model.
A total of 95 studies including 6711 patients, 3029 in the surgical group and 3682 in the EVT group were found. Pooled rates of complete occlusion were 94% (95% CI 91%–96%; I² = 0%) in the surgical group and 69% (95% CI 63%–74%; I² = 79%) in the EVT group, respectively. The favorable functional outcome rate was 86% (95% CI 76%–92%; I² = 72%) with surgical treatment and 95% (95% CI 92%–97%; I² = 61%) with EVT. The rate of aneurysm recurrence with surgical treatment was 1% (95% CI 0%–4%; I² = 0%) and 12% (95% CI 9%–16%; I² = 57%) with EVT. The composite safety outcome rate in the surgical group was 24% (95% CI 18%–30%; I² = 90%) and 10% (95% CI 8%–13%; I² = 71%) in the EVT group.
Our findings suggest that microsurgical clipping seems to have a higher efficacy than EVT in terms of angiographic occlusion and aneurysm recurrence; however, EVT seems to be safer in terms of intraoperative and postoperative complications. Considering the heterogeneity and low-level evidence of the data available, further prospective randomized studies are warranted to confirm our findings.
Efficacy of 3D evaluation of unruptured paraclinoid aneurysms within Leksell GammaPlan® for determination of their intradural localization
2023, Journal of Clinical Neuroscience
Determination of the intradural unruptured paraclinoid aneurysm localization is difficult, but critical for selection of the optimal treatment strategy.
To assess efficacy of the three-dimensional (3D) evaluation of unruptured paraclinoid aneurysms within Leksell GammaPlan® (LGP; Elekta AB; Stockholm, Sweden) for determination of their intradural localization.
Overall, 125 incidentally diagnosed unruptured paraclinoid aneurysms in 118 patients (mean age, 55 years) underwent 3D evaluation of their localization within LGP using post-contrast thin-slice constructive interference in steady state (CISS) images, which in 41 cases were additionally co-registered and fused with the axial computed tomography angiography (CTA) source images.
According to the evaluation within LGP, paraclinoid aneurysms were considered intradural, transitional, and extradural in 75, 25, and 25 cases respectively. Overall, 51 of 75 aneurysms deemed to be intradural, underwent microsurgical management, and intraoperative visual inspection confirmed their intradural localization in 45 cases, whereas it was transitional in 3, and extradural in 3. If during preoperative 3D evaluation within LGP only post-contrast CISS images were used, prediction of the pure intradural localization of aneurysm was correct in 88 % of cases (95 % CI: 79–97 %), and of the pure or partial (i.e., transitional) intradural localization in 94 % of cases (95 % CI: 88–100 %), whereas it was 100 % if co-registration and fusion of the contrast-enhanced CISS and CTA source images was done.
Intradural localization of the unruptured paraclinoid aneurysms may be effectively predicted based on their 3D evaluation within LGP using post-contrast thin-slice CISS and CTA source images, which may help with clinical decision-making.
Optic Foraminotomy versus Anterior Clinoidectomy for Small Superior-Projecting Paraclinoid Aneurysms: Visual and Angiographic Outcome Evaluation
2023, World Neurosurgery
Optic foraminotomy (OF) has been recently proposed as an alternative to anterior clinoidectomy (AC) for selected types of paraclinoid aneurysms. In this study, OF and AC were compared for small superior-projecting paraclinoid aneurysms assuming visual and angiographic results as outcome measures. Indications for OF are also discussed.
Data of patients who underwent surgery for a paraclinoid aneurysm in the last 10 years were collected across 3 tertiary hospitals. Small to regular-size and superior projecting aneurysms were sorted. Multiple and complex aneurysms were excluded. Records of patients who went through OF were compared with those of patients who underwent AC. Neurologic outcome was reported as a modified Rankin Scale. Aneurysm complete occlusion rate and rate of approach-related worsened vision were selected as outcome measures of efficacy and safety, respectively, of the OF versus AC. Unpaired t test and χ² test were used for numerical and categorical variables, respectively. A P value less than 0.05 was considered statistically significant.
OF and AC groups involved 18 and 25 patients, respectively. Complication rate, overall neurologic outcome, rate of approach-related worsened vision, and complete occlusion rate did not differ between the groups. The average follow-up was 51 ± 34 and 60 ± 41 months in the OF and AC groups, respectively.
Compared to AC, OF did not show either a higher rate of approach-related worsened vision or a lower aneurysm complete occlusion rate. OF can be considered a valid alternative to the AC for small superior-projecting dorsal ICA wall paraclinoid aneurysms.
The Intersection Between the Oculomotor Nerve and the Internal Carotid Artery to Distinguish Extracavernous and Intracavernous Paraclinoid Aneurysms Using Anatomic Dissections–A New 3T Magnetic Resonance Imaging Protocol Confirmed by Three-Dimensionally Printed Biomodels
2022, World Neurosurgery
To evaluate the relationship between the oculomotor nerve (CNIII) and the internal carotid artery (ICA) as a new anatomic-radiologic landmark for distinguishing the exact location of a paraclinoid intracranial aneurysm (IA).
Microanatomic dissections were performed in 20 cavernous sinuses to evaluate the ICA paraclinoid region. Based on anatomic observations, a new magnetic resonance (MRI) protocol to classify paraclinoid aneurysms was proposed. MRI of 42 IAs from 34 patients was independently analyzed and classified as intracavernous, extracavernous, or transitional by 2 neuroradiologists. To validate the proposed MRI protocol, each IA was classified by a three-dimensionally (3D) printed biomodel and agreement with the radiologic classifications was evaluated. Of 42 IAs, 23 undergoing microsurgeries were also classified by direct visualization.
We observed that the true cavernous sinus roof is defined by the carotid-oculomotor membrane, which has an intimate relationship with the intersection between the superior limit of the CNIII and the ICA. Based on this intersection, all 42 IAs were radiologically classified and agreement with the 3D printed biomodels was observed in 95% IAs. Concordance tests showed a statistically significant (P < 0.05) agreement between the classifications. All 23 IAs treated had the radiologic and 3D biomodel classification confirmed.
The intersection between the ICA and the CNIII, which crosses it transversely in its entire diameter, is a reliable anatomic-radiologic landmark to correctly classify paraclinoid aneurysms. Through a new MRI protocol, it is possible to radiologically identify this intersection and to easily distinguish the intracavernous and extracavernous ICA paraclinoid aneurysms.
Paraclinoid aneurysms: Outcome analysis and technical remarks of a microsurgical series
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Citation Excerpt :
Despite this trend, microneurosurgery has proved to hold a primary role in younger patients (<40 years of age), ruptured aneurysms, cases of severely tortuous or stenosed cervical and/or intracranial ICA, and also conditions requiring immediate aneurysms occlusion, as the warning syndromes [3,8–10,12,13,40–54]. In comparison with PED and specifically to the paraclinoid aneurysms, microneurosurgery has also shown a higher and more durable occlusion rate, with an acceptable morbidity [8–17,55]. All these aspects confirm how effective microsurgical clipping and bypass can be for paraclinoid aneurysms in carefully selected patients.
A critical appraisal of the surgical results of paraclinoid aneurysms is essential in the flow diverters era.
This study overviews the data of a three-decade surgical series of paraclinoid aneurysms while focusing on their technical remarks.
Overall data of a surgical consecutive series of paraclinoid aneurysms treated between 1993 and 2021 were retrospectively reviewed. Aneurysms were classified according to size and projection. Indications for surgery were different based on the availability of endovascular techniques, especially flow diverter, at the time of treatment. A statistical comparison between ruptured and unruptured aneurysms was accomplished.
58 patients were operated upon. Ophthalmic aneurysms were 68%, giant aneurysms 20%, and ruptured aneurysms 45%. Clipping and bypass were executed in 91% and 9% of cases, respectively. An mRS of 0–2 was achieved in 77% of patients, independently by the clinical onset. The mortality rate was 5%. Visual field was improved or unchanged in 71% of elective patients, whereas the incidence of de novo third and sixth cranial nerves deficit was 8% and 5%, respectively. On an average follow-up of 53.3 ± 38 months, a complete and durable aneurysm exclusion was achieved in 91.3% of patients with a single surgery.
Microneurosurgery is still a valuable treatment option for selected ruptured and unruptured paraclinoid aneurysms. In our experience, it has proven to be definitive and durable, with acceptable morbidity and mortality. Clipping is the treatment of choice in most surgical cases, achieving a good visual outcome in symptomatic patients.
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An aneurysm embedded in a pituitary adenoma is rare, and treatment for both the aneurysm and pituitary adenoma is complex and controversial.
A 53-year-old woman presented with a visual field defect. Magnetic resonance imaging showed a pituitary adenoma and coexistence of an aneurysm located at the orifice of the superior hypophyseal artery (SHA) from the internal carotid artery (ICA). The aneurysm was embedded in the pituitary adenoma; therefore, obliteration of the aneurysm was needed prior to tumor removal to prevent intraoperative rupture of the aneurysm. Although endovascular coil embolization was tried first, it was not successful. A combined endoscopic endonasal approach and transcranial approach was performed for simultaneous tumor removal and aneurysm clipping. A bilateral subfrontal approach was selected for aneurysm clipping because, using this approach, the parent artery was safely controlled from the ipsilateral trajectory, whereas exposure and clipping of the aneurysm were easily done from the contralateral trajectory. Additionally, the supine head position without rotation is comfortable for endoscopic endonasal surgery. The tumor was totally removed, and the aneurysm was safely and completely obliterated with a clip. The patient's postoperative course was uneventful, and her visual disturbance improved.
A combined endoscopic endonasal and bilateral subfrontal approach is effective for a pituitary adenoma associated with an ICA-SHA aneurysm.

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Vascular: AneurysmClinoid and paraclinoid aneurysms: surgical anatomy, operative techniques, and outcome

Abstract

Section snippets

Materials and methods

Demographics

Treatment

Complications

Outcome

Classification

Acknowledgements

Amer J Ophthal

Surg Neurol

Surgery for paraclinoid carotid artery aneurysms

J Neurosurg

Anatomical variations in the pituitary gland and adjacent structures in 225 human autopsy cases

J Neurosurg

Aneurysms of the ophthalmic segmenta clinical and anatomical analysis

J Neurosurg

Endovascular occlusion of intracranial aneurysms with electrically detachable coilscorrelation of aneurysm neck size and treatment results

AJNR

Contralateral and ipsilateral microsurgical approaches to carotid-ophthalmic aneurysms

Neurosurgery

Microsurgical anatomy of the supraclinoid portion of the internal carotid artery

J Neurosurg

Neurosurgical management of cerebral aneurysms following unsuccessful or incomplete endovascular embolization

J Neurosur

Pterional approach to the contralateral orbit

Neurosurg

Surgical treatment of internal carotid siphon aneurysms

Neurol Res

Carotid cave aneurysms of the internal carotid artery

J Neurosurg

“Subclinoid” carotid aneurysm with erosion of the anterior clinoid process and fatal intraoperative rupture

Neurosurgery

Carotid ophthalmic aneurysms. A study of 19 patients

J Neurosurg

Intracranial aneurysms treated with Guglielmi detachable coilmidterm clinical results of a consecutive series of 100 patients

J Neurosurg

Vascular: Aneurysm
Clinoid and paraclinoid aneurysms: surgical anatomy, operative techniques, and outcome