Usefulness of MR imaging for the assessment of nonophthalmic paraclinoid aneurysms

Efficacy of 3D evaluation of unruptured paraclinoid aneurysms within Leksell GammaPlan® for determination of their intradural localization

BACKGROUND

Determination of the intradural unruptured paraclinoid aneurysm localization is difficult, but critical for selection of the optimal treatment strategy.

OBJECTIVE

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

The diagnostic accuracy of MRI in determining the relations between paraclinoid aneurysms and the cavernous sinus

Purpose

The location of paraclinoid aneurysms is determinant for evaluation of its intradural compartment and risk of SAH after rupture. Advanced MRI techniques have provided clear visualization of the distal dural ring (DDR) to determine whether an aneurysm is intracavernous, transitional or intradural for decision-making. We analyzed the diagnostic accuracy of MRI in predicting whether a paraclinoid aneurysm is intracavernous, transitional or intradural.

Methods

We conducted a prospective cohort between January 2014 and December 2018. Patients with paraclinoid aneurysms underwent 3D fast spin-echo MRI sequence before surgical treatment. The DDR was the landmark for MRI characterization of the aneurysms as follow: (i) Intradural; (ii) Transitional; and (iii) Intracavernous. The MRI sensitivity, specificity, positive and negative likelihood ratios were determined compared to the intraoperative findings. We also evaluated the intertechnique agreement using the Cohen’s kappa coefficient (κ) for dichotomous classifications (cavernous vs non-cavernous).

Results

Twenty patients were included in the cohort. The accuracy of MRI showed a sensitivity of 86.7% (95%CI:59.5–98.3) and specificity of 90.0% (95%CI:55.5–99.8). Analyzing only patients without history of SAH, accuracy test improved with a sensitivity of 92.3% (95%CI:63.9–99.8) and specificity reached 100% (95%CI: 63–100). Values of Cohen’s kappa (κ), intertechnique agreement was considered substantial for dichotomous classifications (κ = 0.754; p < 0.001). For patients without previous SAH, intertechnique agreement was even more coincident for the dichotomous classification (κ = 0.901; p < 0.001).

Conclusion

3D fast spin-echo MRI sequence is a reliable and useful technique for determining the location of paraclinoid aneurysms in relation to the cavernous sinus, particularly for patients with no history of SAH.

Retrospective review of 290 small carotid cave aneurysms over 17 years

OBJECTIVE

The carotid cave is a unique intradural region located along the medial aspect of the internal carotid artery. Small carotid cave aneurysms confined within this space are bound by the carotid sulcus of the sphenoid bone and are thought to have a low risk of rupture or growth. However, there is a lack of data on the natural history of this subset of aneurysms.

METHODS

The authors present a retrospective case series of 290 small (≤ 4 mm) carotid cave aneurysms evaluated and managed at their institution between January 2000 and June 2017.

RESULTS

No patient presented with a subarachnoid hemorrhage attributable to a carotid cave aneurysm, and there were no instances of aneurysm rupture or growth during 911.0 aneurysm-years of clinical follow-up or 726.3 aneurysm-years of imaging follow-up, respectively.

CONCLUSIONS

This series demonstrates the benign nature of small carotid cave aneurysms.

Comprehensive review of imaging of intracranial aneurysms and angiographically negative subarachnoid hemorrhage

Intracranial aneurysms confer the risk of subarachnoid hemorrhage (SAH), a potentially devastating condition, though most aneurysms will remain asymptomatic for the lifetime of the patient. Imaging is critical to all stages of patient care for those who harbor an unruptured intracranial aneurysm (UIA), including to establish the diagnosis, to determine therapeutic options, to undertake surveillance in patients who elect not to undergo treatment or whose aneurysm(s) portends such a low risk that treatment is not indicated, and to perform follow-up after treatment. Neuroimaging is equally as important in patients who suffer an SAH. DSA remains the reference standard for imaging of intracranial aneurysms due to its high spatial and temporal resolution. As noninvasive imaging technology, such as CTA and MRA, improves, the diagnostic accuracy of such tests continues to increasingly approximate that of DSA. In cases of angiographically negative SAH, imaging protocols are necessary not only for diagnosis but also to search for an initially occult vascular lesion, such as a thrombosed, ruptured aneurysm that might be detected in a delayed fashion. Given the crucial role of neuroimaging in all aspects of care for patients with UIAs and SAH, it is incumbent on those who care for these patients, including cerebrovascular neurosurgeons, interventional neurologists and neuroradiologists, and diagnostic radiologists and neurointensivists, to understand the role of imaging in this disease and how individual members of the multispecialty team use imaging to ensure best practices to deliver cutting-edge care to these often complex cases. This review expounds on the role of imaging in the management of UIAs and ruptured intracranial aneurysms and in the workup of angiographically negative subarachnoid hemorrhage.

Identification of the Distal Dural Ring and Definition of Paraclinoid Aneurysms According to Bony Landmarks on 3-Dimensional Computed Tomography Angiography: A Cadaveric and Radiological Study

BACKGROUND

Determining if paraclinoid aneurysms are intradural or extradural is critical for surgical planning.

OBJECTIVE

To create an easily reproducible diagnostic method based on bony anatomy that precisely locates the distal dural ring (DDR) to determine the position of paraclinoid aneurysms as intradural, transitional, or extradural.

METHODS

Bilateral anatomic dissections of 10 cadaveric heads (20 sides) were performed to evaluate DDR anatomy. We observed a plane that reflects the position of the DDR passes through 4 bony landmarks: 1) The anterior clinoid-internal carotid artery intersection, 2) the optic strut, 3) the optico-carotid elevation, and 4) the base of the posterior clinoid process. This landmark-based plane can thus define the location of the DDR using 3-dimensional computed tomography angiography (CTA). This was confirmed in 27 surgical patients with intradural/transitional aneurysms and 7 patients with extradural aneurysms confirmed with magnetic resonance imaging (MRI). The DDR plane method easily classified aneurysm locations as intradural (above the DDR plane), extradural (below the DDR plane), or transitional (the DDR plane crosses the aneurysm). The aneurysm's location was subsequently confirmed intraoperatively or with MRI.

RESULTS

The DDR plane method determined if paraclinoid aneurysms were intradural, transitional, or extradural in all 34 cases examined. The visibility of the anatomic features that define the DDR plane was also verified in 82% to 89% of CTA images from 100 patients.

CONCLUSION

The DDR plane method provides a useful diagnostic tool to evaluate the position of the DDR and determine the anatomic location of paraclinoid aneurysms.

Distance Between the Falciform Ligament and Distal Dural Ring as a Surgical Landmark for the Treatment of Paraclinoid Aneurysms

OBJECTIVE

It is difficult to completely comprehend the anatomy of the structures surrounding the paraclinoid region before aneurysm and tumor treatment therein. When treating paraclinoid aneurysms, it is important to determine the location of the aneurysm as intradural or extradural. Thus, accurate prediction of the position of the distal dural ring (DDR) is necessary. To this end, we focused on the falciform ligament (FL), which is easily visualized on images based on its anatomic features. We measured the distance between the FL and the DDR in patients undergoing paraclinoid aneurysm operations.

METHODS

Between January 2017 and July 2018, 15 patients who underwent clipping for paraclinoid aneurysm treatment were retrospectively identified. The distance between the FL and the DDR was measured using a microscale at the time of the operation.

RESULTS

The patients comprised 14 women and 1 man. The mean aneurysm diameter was 7.29 ± 2.21 mm and the median size was 6.5 mm. Eleven of the aneurysms were on the left and 4 were on the right side. The mean distance between the FL and the DDR was 3.50 ± 0.17 mm and the median distance was 3.50 mm. The distance between the FL and the DDR was almost the same across cases (3.5 mm).

CONCLUSIONS

The position of the FL can be easily predicted using preoperative three-dimensional computed tomography angiography based on its anatomic features. In this study, the DDR was located 3.5 mm proximal to the FL along the internal carotid artery. This information is useful for predicting the position of the DDR.

Feasibility of High-Resolution 3-Dimensional Sampling Perfection with Application-Optimized Contrast Using Different Flip Angle Evolution Imaging for the Preoperative Detection of Parasinus Meningioma: A Pilot Study Compared with Contrast-Enhanced Magnetic Resonance Venography

OBJECTIVES

To prospectively evaluate the diagnostic value of 3.0 Tesla magnetic resonance 3-dimensional sampling perfection with application-optimized contrast using different flip angle evolution (3D-SPACE) in the detection of sinus wall invasion and sinus patency in parasinus meningiomas.

METHODS

In this study, 28 patients with suspected meningiomas adjacent to the venous sinus underwent conventional magnetic resonance imaging, contrast-enhanced magnetic resonance venography, and 3D-SPACE scans. We collected patient charts and surgical reports for demographic details, histologic analysis, and neurologic performance preoperatively and postoperatively. Images obtained by each technique were assessed independently by 2 neurosurgeons for characteristics of sinus infiltration, wall invasion, lumen patency, and collateral veins.

RESULTS

The blood flow signal inside the lumen and collateral veins were depressed and presented as black, contrasting well with the sinus wall on 3D-SPACE imaging. When the curved-planar reconstruction images were combined, it was intuitive and accurate to detect the extent of sinus wall invasion by meningioma and also to detect lumen patency. An intratumoral "false lumen" was shown to maintain the blood flow inside the sinus at a totally invaded lesion. Moreover, collateral veins enveloped in a meningioma with their confluence points of the venous sinus were easily observed on 3D-SPACE images.

CONCLUSION

With an integrative presentation of parasinus meningioma, wall invasion, lumen patency, and collateral veins, high-resolution 3D-SPACE imaging provides a reliable technique to accurately assess venous sinus invasion preoperatively.

Intraoperative cerebral angiography by intravenous contrast administration with 3-dimensional rotational fluoroscopy in patients with intracranial aneurysms: a feasibility study

BACKGROUND

Intraoperative imaging of cerebral aneurysms may be desirable in emergency situations with large space-occupying hematomas or to visualize vessels after clip placement. Mobile 3-dimensional fluoroscopes are available in a number of neurosurgical departments and may be useful in combination with simple image postprocessing to depict cerebral vessels.

OBJECTIVE

To assess whether intracranial aneurysms are detectable with appropriate image quality with intraoperative 3-dimensional fluoroscopy with intravenous contrast administration.

METHODS

Eight patients were included in the study. The patients' heads were fixed in a radiolucent Mayfield clamp. First, a rotational fluoroscopy scan was performed without contrast agent. Then, a second scan with 50 mL iodine contrast agent was performed. The DICOM (digital imaging and communications in medicine) data of both scans were transferred to an Apple PowerMac workstation, subtracted, and reconstructed with OsiriX imaging software. The images were compared with preoperative angiograms.

RESULTS

No adverse effects were observed during contrast administration. The entire procedure from fluoroscope positioning to the production of usable 3-dimensional images took 5 to 6 minutes with an image acquisition time of 2 × 24 seconds. The configuration of the aneurysm and the vessel anatomy were assessable. Previous coiling limited image quality in 1 patient.

CONCLUSION

This technique quickly provides images of adequate quality to assess the configuration of intracranial aneurysms, which may be helpful when immediate intraoperative information about intracranial vessel pathologies is required. The positioning of the fluoroscope, image acquisition, and processing can be completely integrated into the surgical workflow.

Junctional Internal Carotid Artery Aneurysms: The Schrödinger's Cat of Vascular Neurosurgery

Objectives Despite advances in neuroimaging, it is not always definitive whether a paraclinoid aneurysm is intradural or entirely extradural. We illustrate the potential use of surgical exploration in these aneurysms that we refer to as "junctional" aneurysms. Methods Retrospective review of eight patients with unruptured aneurysms who underwent a planned surgical exploration of a junctional aneurysm. Results Of the eight patients, three underwent exploration of the aneurysm during surgery for a different aneurysm. All three of these were found to be extradural. Five patients underwent a craniotomy for the exclusive purpose of clarifying the location of the aneurysm. Two of these cases were found to be intradural and were clipped. Two cases were found to be extradural. In one patient, the initially extradural aneurysm was converted into an intradural aneurysm during removal of the anterior clinoid process, necessitating surgical clipping. One transient third nerve palsy was observed. Discussion Until further progress in neuroimaging allows clinicians to determine unequivocally the exact anatomical location of a paraclinoid aneurysm, we advocate the use of the term junctional aneurysm to reflect the clinical uncertainty inherent in management decisions made regarding these aneurysms. We have illustrated a strategy of surgical exploration in select patients.

Intraoperative 3D rotational angiography: an emergency tool for the diagnosis of intracranial aneurysms

It was the objective of this report to present a case of recurrent aneurysmal subarachnoid hemorrhage (SAH) and intracerebral hemorrhage (ICH) in which an MCA aneurysm was detected by 3D rotational fluoroscopy in an emergency situation. A 44-year-old woman was admitted from an external department after repeated SAH and temporal ICH. Due to progressive anisocoria and cardiocirculatory instability, she was transferred to the operating room without angiography. After a 3D rotational fluoroscopy baseline scan, another scan with 50 ml of iodine contrast agent was performed. The Digital Imaging and Communications in Medicine (DICOM) data sets were subtracted and reconstructed using the OsiriX® free imaging software. No adverse effect was observed during and after the administration of the contrast agent. The entire procedure from positioning of the fluoroscope to the production of utilizable 3D images was completely integrated into the surgical workflow with an image acquisition time of 2 × 24 s. The configuration of the aneurysm, the aneurysm-carrying vessel, and the distal vessel anatomy were well assessable. This technique quickly supplies images at adequate quality to assess the configuration of an intracranial aneurysm and is a useful diagnostic tool if the patient's critical condition prohibits aneurysm diagnostics by angiography or CT angiography.

Utility of 320-detector row CT for diagnosis and therapeutic strategy for paraclinoid and intracavernous aneurysms

BACKGROUND

The aim of this study was (1) to assess the diagnostic accuracy of 320-detector row computed tomography (CT) for paraclinoid and intracavernous aneurysms, and (2) to investigate whether this method provides sufficient information for surgery.

METHODS

A total of 14 patients with 16 unruptured proximal ICA aneurysms underwent three-dimensional CT angiography (3D-CTA) fusion imaging, which was created by superimposing 3D-CT venography data and/or 3D-bone data onto 3D-CTA data using 320-detector row CT, magnetic resonance imaging (MRI), and 3D digital subtraction angiography (DSA). The images of each modality were assessed using intraoperative findings as the reference standard.

RESULTS

All aneurysms were clearly visualized on 320-detector row CT. Bone subtraction and arterio-venous discrimination were accurate. On 3D-CTA fusion images, 11 aneurysms were diagnosed as "extracavernous" and five as "intracavernous". No discordance in aneurysm location between the 3D-CTA fusion images and the intraoperative findings was found. In contrast, discordance between MRI and intraoperative findings were found in five of the 16 cases (31%), which was significantly more frequent than with 3D-CTA (p = 0.043). The findings DSA, which was performed in nine patients, were also in excellent agreement with the intraoperative findings. However, 3D-CTA fusion imaging provided more comprehensive information, including venous and osseous structures, than 3D-DSA. The 320-detector row CTA after surgery demonstrated a clear relationship between the clip and aneurysmal neck with notably few artifacts, which suggested the utility of this modality for postoperative assessment.

CONCLUSIONS

The 320-detector row CT provided high accuracy for the diagnosis of paraclinoid and intracavernous aneurysms. This technique also provided comprehensive depiction of the aneurysms and surrounding structures. Therefore, this modality might be useful for the diagnosis of the paraclinoid and intracavernous aneurysms and for developing a surgical treatment plan.

Toward an endovascular internal carotid artery classification system

SUMMARY

Does the world need another ICA classification scheme? We believe so. The purpose of proposed angiography-driven classification is to optimize description of the carotid artery from the endovascular perspective. A review of existing, predominantly surgically-driven classifications is performed, and a new scheme, based on the study of NYU aneurysm angiographic and cross-sectional databases is proposed. Seven segments - cervical, petrous, cavernous, paraophthlamic, posterior communicating, choroidal, and terminus - are named. This nomenclature recognizes intrinsic uncertainty in precise angiographic and cross-sectional localization of aneurysms adjacent to the dural rings, regarding all lesions distal to the cavernous segment as potentially intradural. Rather than subdividing various transitional, ophthalmic, and hypophyseal aneurysm subtypes, as necessitated by their varied surgical approaches and risks, the proposed classification emphasizes their common endovascular treatment features, while recognizing that many complex, trans-segmental, and fusiform aneurysms not readily classifiable into presently available, saccular aneurysm-driven schemes, are being increasingly addressed by endovascular means. We believe this classification may find utility in standardizing nomenclature for outcome tracking, treatment trials and physician communication.

[Paraclinoid region: descriptive anatomy and radiological correlations with MR imaging]

OBJECTIVE

The paraclinoid region has a complex anatomy. The purpose of this study was to depict in details its anatomical landmarks and their radiological translations with magnetic resonance imaging (MRI).

MATERIAL AND METHOD

Ten anatomical specimens (20 paraclinoid regions) were prepared, then dissected and further analyzed with MRI in order to describe their important radio-anatomical structures (dural folds, osseous surfaces, arteries and nerves) along with their course and measurements, and the reference points of the carotid distal dural ring. The paraclinoid MR protocol consisted in a T2 high-resolution sequence with thin and contiguous slices acquired in a coronal (diaphragmatic) and sagittal oblique (carotid) plane. Reproducibility in living subjects was evaluated on 15 patients (30 paraclinoid regions). Statistical comparison was made between laboratory and MR measurements obtained on cadavers.

RESULTS

A detailed description of paraclinoid anatomy and structures was provided. Its landmarks were satisfactorily identified with the dedicated MR protocol. Reproducibility in living subjects was obtained. No statistical difference was found between laboratory and MR measurements.

CONCLUSION

This study provides a precise description of paraclinoid anatomical structures and their radiological correlations. This paraclinoid MR protocol allows locating paraclinoid lesions in comparison with the cavernous sinus roof, which is of paramount importance for the management of paraclinoid carotid artery aneurysms.

Distinction between Intradural and Extradural Aneurysms Involving the Paraclinoid Internal Carotid Artery with T2-Weighted Three-Dimensional Fast Spin-Echo Magnetic Resonance Imaging

OBJECTIVE

The precise intra- vs. extradural localization of aneurysms involving the paraclinoid internal carotid artery is critical for the evaluation of patients being considered for aneurysm surgery. The purpose of this study was to investigate the clinical usefulness of T2-weighted three-dimensional (3-D) fast spin-echo (FSE) magnetic resonance (MR) imaging in the evaluation of unruptured paraclinoid aneurysms.

METHODS

Twenty-eight patients with unruptured cerebral aneurysms in their paraclinoid regions were prospectively evaluated using a T2-weighted 3-D FSE MR imaging technique with oblique coronal sections. The MR images were assessed for the location of the cerebral aneurysm in relation to the dural ring and other surrounding anatomic compartments, and were also compared with the surgical or angiographic findings.

RESULTS

All 28 aneurysms were identified by T2-weighted 3D FSE MR imaging, which showed the precise anatomic relationships in regards to the subarachnoid space and the surrounding anatomic structures. Consequently, 13 aneurysms were determined to be intradural and the other 15 were deemed extradural as they were confined to the cavernous sinus. Of the 13 aneurysms with intradural locations, three superior hypophyseal artery aneurysms were found to be situated intradurally upon operation.

CONCLUSION

High-resolution T2-weighted 3-D FSE MR imaging is capable of confirming whether a cerebral aneurysm at the paraclinoid region is intradural or extradural, because of the MR imaging's high spatial resolution. The images may help in identifying patients with intradural aneurysms who require treatment, and they also can provide valuable information in the treatment plan for paraclinoid aneurysms.

Identification of the distal dural ring with use of fusion images with 3D-MR cisternography and MR angiography: application to paraclinoid aneurysms

BACKGROUND AND PURPOSE

The distal dural ring (DDR) represents the anatomic border between the extradural and intradural internal carotid arteries (ICAs). The purpose of this study was to examine whether 3D-MR cisternography and MR angiography (MRA) fusion images can identify the boundary between the CSF and the cavernous sinus, which might represent the DDR.

MATERIALS AND METHODS

Thirty-six consecutive patients with 39 ICA aneurysms were examined with use of MR fusion images with 3D-cisternography and MRA on a 1.5T unit. Two neuroradiologists evaluated the configuration of the carotid cave and the location of the aneurysms on fusion images and classified them as intradural, transdural, and extradural aneurysms.

RESULTS

The borderline between the CSF and the cavernous sinus was visualized on fusion images in all patients. The carotid cave configuration in 72 ICAs was classified as having no dent (n = 31), a shallow dent (n = 27), and a deep dent (n = 14). The MR fusion images led to the classification of 39 ICA aneurysms as 21 intradural, 6 transdural, and 12 extradural. The interobserver agreement of MR fusion images was excellent (kappa = 0.80).

CONCLUSIONS

Fusion images with 3D-cisternography and MRA yielded clear visualization of the boundary between the suprasellar cistern and cavernous sinus indicating the DDR. This imaging technique may provide additional information in consideration of a treatment option for paraclinoid aneurysms.

Intrasellar rupture of a paraclinoid aneurysm with subarachnoid hemorrhage: usefulness of MR imaging in diagnosis

Characterization of paraclinoid aneurysms may be difficult because of the complexity of anatomic structures involved, and differentiation between intradural and extradural lesions is crucial. We report a case of a patient with a unique presentation of a paraclinoid aneurysm with intrasellar hemorrhage in which the presence of intrasellar blood and the relationship of the paraclinoid aneurysmal neck and sac to the dural rings were elegantly demonstrated on MR imaging and were critical in choosing the target lesion for treatment.