Superior cerebellar artery aneurysms: incidence, clinical presentation and midterm outcome of endovascular treatment

Exoscopic Clipping of a Superior Cerebellar Artery Aneurysm via a One-Piece Orbitozygomatic Approach: Educational Operative Video

Superior cerebellar artery (SCA) aneurysms are rare. They represent 1%-2% of all intracranial aneurysms and are usually treated endovascularly.1 However, when the aneurysm configuration is not optimal for endovascular treatment, microsurgical clipping remains a valid alternative treatment option.2,3 We present the case of a 66-year-old male patient, with an incidental 7-mm wide-neck SCA aneurysm, with the parent vessel coming directly out of the aneurysm neck (Video 1). The different possible endovascular treatment options were reviewed and deemed not optimal for this specific aneurysm, potentially resulting either in incomplete aneurysm occlusion or vessel occlusion. Microsurgical clipping was considered the most suitable treatment option for this specific aneurysm. Surgery was facilitated by the high-riding localization of the aneurysm, waiving the need for a posterior clinoidectomy to obtain proximal control at the basilar artery. An orbitozygomatic approach was chosen to obtain an optimal caudocranial working angle and reduce the need for brain retraction. This video highlights the thought process in choosing the optimal treatment for this rare type of cerebral aneurysm, and the important surgical steps to safely approach and clip an SCA aneurysm.

Current research status and future of endovascular treatment for basilar artery aneurysms

Aneurysms occurring along the basilar artery (BA) account for <1% of all intracranial aneurysms. Endovascular treatment (EVT) in particular is recommended for large unruptured BA aneurysms and ruptured BA aneurysms. Given that EVT techniques vary, a detailed review of EVT for BA aneurysms is necessary. In this review, the following issues were discussed: the anatomy and anomalies of the BA, the classification of BA aneurysms, the natural history of BA aneurysms, the status of open surgery, the use of EVT for various types of BA aneurysms and the deployment of new devices. According to the findings of this review and based on our experience in treating BA aneurysms, traditional coiling EVT is still the optimal therapy for most BA aneurysms. However, in some BA aneurysms, flow diverter (FD) deployment can be used. In addition, there are also some new devices, such as intrasaccular flow disruptors and stent-like devices that can be used to treat BA aneurysms. In general, EVT can yield good clinical and angiographic outcomes for patients with BA aneurysms. In addition, recent new devices and techniques, such as new-generation FDs generated via surface modification and virtual reality simulation techniques, show promise for EVT for BA aneurysms. These devices and techniques may further improve EVT outcomes for BA aneurysms.

Vertebral Artery Access Considerations in Coil Embolization of Small Superior Cerebellar Artery Aneurysm

BACKGROUND

Coiling of small superior cerebellar artery aneurysms (sSCAAs) is challenging. We aimed to describe anatomic considerations in the vertebral and basilar artery (VA and BA) morphology for decision making in the coiling of sSCAAs.

METHODS

Eleven patients with sSCAAs (<5 mm) treated at our institution between April 2015 and February 2022 were included to show our concept of deciding access routes in the coiling of sSCAAs. The access route was decided on the basis of VA characteristics, BA curvature, and aneurysm laterality. Adequate aneurysm occlusion on angiography (Raymond-Roy grading scale I and II), good outcome (modified Rankin Score 0-2) at the last follow-up, and adverse outcomes were evaluated.

RESULTS

Simple coiling (n = 2), a balloon-assisted technique (n = 3), and stent-assisted technique (n = 6) were selected. At the last follow-up (median 13.0 months), adequate aneurysm occlusion and good outcome were obtained in all 9 patients (n = 10). Adverse outcomes were not observed. When VA dominance was equal, in the straight BA, the microcatheter insertion into the ipsilateral VA to the aneurysm was favorable to form a "fulcrum" on the contralateral side and obtain microcatheter stability. When an aneurysm was on the concave aspect of the curved BA, microcatheter insertion into the ipsilateral VA was favorable. As for the convex aspect's aneurysm location, the microcatheter insertion into the contralateral VA can be favored. Further, we described the VA origin classification as it relates to ease of access from a transradial approach.

CONCLUSIONS

Vertebrobasilar morphology may be important in deciding access routes in the coiling of sSCAAs.

Flow diversion for basilar quadrifurcation aneurysms

BACKGROUND

Flow-diverting devices (FDDs), such as the Pipeline Embolization Device, have been gaining traction for treating challenging posterior circulation aneurysms. Few previous studies have focused on using FDDs to treat aneurysms of the basilar quadrifurcation.

METHODS

We retrospectively reviewed the use of FDDs to treat patients with basilar quadrifurcation aneurysms. Patients were assessed for aneurysm type, previous aneurysm treatment, technical success, periprocedural complications, and long-term aneurysm occlusion.

RESULTS

34 patients were assessed; aneurysms of the basilar apex (n=23) or superior cerebellar artery (SCA) (n=7), or both (n=1), and posterior cerebral artery (PCA) (n=3). The mean (SD) largest aneurysm dimension was 8.7 (6.1) mm (range 1.9-30.8 mm). 14 aneurysms were previously surgically clipped or endovascularly coiled. All aneurysms had a saccular morphology. Complete or near-complete occlusion was achieved in 30 of 34 patients (88%) at final angiographic follow-up, a mean (SD) of 6.6 (5.4) months (range 0-19 months) postoperatively. No patient experienced postoperative symptomatic occlusions of the SCA or PCA; 4 patients developed asymptomatic posterior communicating artery occlusions; 28 patients (82%) experienced no complications; whereas 3 (9%) experienced major complications and 3 (9%) experienced minor complications; and 1 patient died as a result of subarachnoid hemorrhage.

CONCLUSION

Flow diversion may be a safe and effective option to treat basilar quadrifurcation aneurysms. Previously treated basilar quadrifurcation aneurysms with recurrence or residual lesion may benefit from additional treatment with an FDD. Further prospective studies should be directed toward validating these findings.

Half-and-Half Approach for Multiple Aneurysms at the Superior Cerebellar and Middle Cerebral Arteries

Aneurysms at the superior cerebellar artery (SCA) are commonly treated endovascularly because of their location around the basilar artery,1,2 but they are not intimately related with thalamoperforators. Therefore in younger patients, those with wide-necked aneurysms, or those with multiple ipsilateral aneurysms, surgery remains a treatment option.3 We present a 52-year-old woman with dizziness in whom multiple, unruptured intracranial aneurysms were identified. Imaging demonstrated a 9-mm right-sided SCA aneurysm and 5-mm right and mirror 3-mm left M1 segment middle cerebral artery aneurysms. The patient gave consent to undergo surgery after counseling regarding her treatment options. A pterional and temporal craniotomy was performed to allow for half-and-half subtemporal and transsylvian approaches (Video 1). Here, we discuss the nuances of the approach related to the anatomy of SCA aneurysms. The challenges of the surgery can be mediated with techniques including division of the tentorium for enhanced exposure and early proximal control with temporary clinping or the use of adenosine (cardiac arrest). Our patient remained neurologically stable postoperatively and in 1-year follow-up. SCA aneurysms are easily visualized by the subtemporal and transsylvian approaches; they are frequently located adjacent to the posterior cerebral artery above and the SCA below. A modified transcavernous approach using the orbitozygomatic craniotomy has been described for access to basilar tip aneurysms.4 While comparable, this case demonstrates the efficient workflow to clip multiple aneurysms using a single, combined approach. In patients with multiple aneurysms presenting ipsilaterally or with comorbid conditions that complicate endovascular embolization, surgery should be considered as a definitive and safe treatment strategy. The patient consented to publication.

An Update on the Superior Cerebellar Artery Origin Type

Background and Objectives: The microanatomy of the superior cerebellar artery (SCA) is clinically significant. We, thus, aimed at patterning unilateral and bilateral possibilities of SCA origin. Materials and Methods: In total, 205 archived records of computed tomography and magnetic resonance angiograms were used. There were defined types of SCA origin from the basilar artery (BA): "0"-absent SCA, "1"-preterminal, "2"-collateral SCA, with SCA appearing as a terminal branch of BA, and "3"-SCA from the posterior cerebral artery (PCA) of the cerebral type. Fenestrations and duplications of SCA were recorded. Bilateral combinations of types were recorded as follows: A (1 + 0), B (1 + 1), C (1 + 2), D (1 + 3), E (1 + duplicated SCA), F (2 + 2), G (2 + 3), H (3 + 3), I (3 + duplicated SCA), J (1 + fenestrated SCA). Results: Type 0 SCAs were found in 0.25%, type 1 in 71.29%, type 2 in 19.06%, and type 3 in 9.41%. Absent and fenestrated SCAs were each found in a single case. The most frequent combinations were B (58.05%), C (13.17%) and F (13.17%). Bilateral symmetrical types occurred in 70.7% of cases. Fetal types of PCA and the artery of Percheron modified the BA ends. Combinations of C, F, and G changed the BA ends or tips; thus, different subtypes resulted in five BA bifurcation patterns, including five BA trifurcations and one BA quadrifurcation. BA trifurcation was also found in cases with duplicated SCAs. Conclusions: The SCA has various anatomical possibilities of origin and bilateral combinations that are not presented in anatomical lectures. Details on the specific end of the BA should be gathered on a case-by-case basis.

Endoscopic endonasal transclival clipping of a cerebellar arteriovenous malformation feeding vessel and associated aneurysm; a 2D operative video

Positioned along the ventral surface of the pons, proximal superior cerebellar artery (SCA) aneurysms account for only 1.7% of all intracranial aneurysms [1]. Unlike more commonly encountered basilar artery aneurysms, patients often experience good outcomes when treated via endovascular coiling or surgical clipping [1,2]. These lesions frequently have a lateral projection and paucity of perforator arteries [2]. With further development of endoscopic endonasal techniques, access to this region is possible via a direct frontal exposure to the ventral brainstem, basilar artery and branching vessels. To date, there are only a limited number of reports describing an endoscopic endonasal transclival (EETC) approach for surgical clipping [3-5]. In this operative video, we detail the surgical clipping of a cerebellar arteriovenous malformation feeding vessel and an associated aneurysm using the EETC approach in a 59-year-old woman who presented with sudden onset of a severe headache. The feeding vessel and aneurysm's midline location, just below the take-off of the SCA made it a good candidate for this surgery. Major steps included in this video include 1) transsphenoidal exposure of and subsequent drilling of the clivus, 2) dural opening into the pre-pontine cistern and dissection of the aneurysm, 3) clipping of the aneurysm, and 4) multi-layered closure of the skull base defect. Overall, the patient tolerated the procedure well and was found to have no residual filling of the aneurysm or the AVM feeding vessel at 2-year follow-up. EETC is a viable surgical option for the treatment of aneurysm located along the midline of the pre-pontine cistern.

The Superior Cerebellar Artery: Variability and Clinical Significance

The superior cerebellar artery (SCA) arises from the distal part of the basilar artery and passes by the oculomotor, trochlear, and trigeminal nerves. SCA is known to play a crucial role in the development of trigeminal neuralgia. However, due to its anatomical variability, it may also trigger other neurovascular compression (NVC), including hemifacial spasm, oculomotor nerve palsy, and ocular neuromyotonia. Additionally, it may be associated with ischemic syndromes and aneurysm development, highlighting its clinical significance. The most common anatomical variations of the SCA include duplication, a single vessel origin from the posterior cerebral artery (PCA), and a common trunk with PCA. Rarely observed variants include bifurcation and origin from the internal carotid artery. Certain anatomical variants such as early bifurcation and caudal course of duplicated SCA trunk may increase the risk of NVC. In this narrative review, we aimed to examine the impact of the anatomical variations of SCA on the NVCs based on papers published in Pubmed, Scopus, and Web of Science databases with a snowballing approach. Our review emphasizes the importance of a thorough understanding of the anatomical variability of SCA to optimize the management of patients with NVCs associated with this artery.

Management of saccular superior cerebellar artery aneurysms: The Buffalo experience case series and systematic review

BACKGROUND

Results of the management of superior cerebellar artery (SCA) aneurysms are typically reported in combination with those for all posterior circulation aneurysms. We report our experience with the management of SCA aneurysms and a systematic review of the endovascular management of these rare aneurysms.

METHODS

Patients with saccular SCA aneurysms that were not associated with arteriovenous malformations and who presented to our institute between 2000 and 2017 were identified. Patient demographics, aneurysm characteristics, interventions, and follow-up data were collected, compared, and analyzed. For the review, data including number of aneurysm treated, outcomes, follow-up, and occlusion rates were collected.

RESULTS

Mean age of the 31 identified patients was 57.4 ± 12.3 years; 19.4% were men. Mean aneurysm size was 5.1 ± 2.9 mm. Seven of 21 patients with unruptured aneurysms were managed conservatively. Ten patients (32.3%) presented with ruptured aneurysms (mean aneurysm size, 6.2 ± 3.2 mm). Treatment was successfully completed in 22 patients: 13-primary coiling, 7-stent-assisted coiling, and 2-microsurgical clipping. Complete angiographic aneurysm occlusion after primary treatments was achieved in 19 (86.4%) patients. The total complication rate among treated patients was 4.2% (1 of 24 treated aneurysms). No minor complications occurred. However, in 2 patients, coil embolization was attempted but aborted due to coil protrusion into the parent artery. Clinical and angiographic follow-up data were available for 26 observed or treated patients. Mean follow-up duration was 5.3 ± 4.5 years. Six articles met our review inclusion criteria and demonstrated similar mean treated aneurysm sizes ranging from 4.6-7.7 mm, and follow-up from these articles ranged from 15.3-50 months.

CONCLUSIONS

Endovascularly treated patients with ruptured and unruptured SCA aneurysms, of which most were <7 mm, had good clinical outcomes with minimal complications.

Stent-assisted Coil Embolization Using a Transcirculation Technique for Superior Cerebellar Artery Aneurysm: A Report of Two Cases

Stent-assisted coil embolization (SACE) is useful for treating wide-necked aneurysms. Most superior cerebellar artery (SCA) aneurysms have a wide neck, but there are few reports of SCA aneurysms treated with SACE.

One reason is that the anatomical characteristic of SCA aneurysm is not suitable for standard SACE. It is often challenging to deliver a stent to SCA via the basilar artery in an anterograde manner. In contrast, it is not difficult to deliver a stent to SCA from the anterior circulation via the posterior communicating artery. This method, in which a catheter is navigated from the anterior to the posterior circulation, is called a transcirculation technique.

We report two cases of SCA aneurysm successfully treated with SACE using transcirculation technique. This approach is helpful for wide-necked SCA aneurysms.

Anatomic Risk Factors for S1 Segment Superior Cerebellar Artery Aneurysm Rupture: A Radiologic Study on 81 Consecutive Patients

BACKGROUND

Due to treatment associated risks, it is still debatable which unruptured aneurysm should be treated. Anatomic and morphologic characteristics may aid to predict the rupture risk of superior cerebellar artery (SCA) aneurysm and possibly support in decision- making during treatment.

OBJECTIVES

To identify morphologic characteristics that could predict the rupture of SCA aneurysms.

METHODS

A retrospective analysis of computed tomography angiography images of 81 consecutive patients harboring SCA aneurysm who were treated between 1980 to 2014 at Helsinki University Hospital was performed.

RESULTS

Of the 81 analyzed SCA aneurysms, 30 (37%) were unruptured and remaining 51 (63%) presented with subarachnoid hemorrhage. The mean ± SD size of unruptured SCA aneurysms was 6.2 ± 6.3 mm; mean size of ruptured SCA aneurysms was 5.9 ± 5.4 mm. The mean ± SD aspect ratio was 0.9 ± 0.3 in unruptured and 1.14 ± 0.44 in ruptured SCA aneurysms. The mean ± SD degree angle between basilar artery and aneurysm was 74.7 ± 24.4 in unruptured and 65.9 ± 23 ruptured SCA aneurysms. Patients with ruptured SCA aneurysm showed significantly higher aspect ratio (Mann-Whitney U, P = 0.01) and smaller aneurysm to basilar artery angle (Mann-Whitney U, P = 0.039). Aspect ratio >1.1 had 2.3 times higher risk of rupture (odds ration [OR] 2.3, 95% confidence interval [CI] 0.84-6.34). An aneurysm to basilar angle <70 degrees had 2.8 times higher risk of rupture (OR 2.75, 95% CI 1.086-6.96).

CONCLUSIONS

Ruptured SCA aneurysms are usually small in size. Higher aspect ratio and smaller angle between SCA aneurysm and basilar artery had significantly higher risk of SCA (S1 segment) aneurysm rupture.

Fusiform superior cerebellar artery aneurysm treated with flow diversion: A case report

Background:

Fusiform aneurysms of the distal superior cerebellar artery are rare and challenging to treat. Due to the rarity of these lesions, there is little consensus regarding their management. Treatment options have traditionally included parent artery sacrifice with either an endovascular approach or microsurgical clipping. Given the small diameter of the superior cerebellar artery, flow diversion has not been typically considered as a viable treatment option for these aneurysms.

Case Description:

A 67-year-old female presented complaining of severe sudden onset headache. Noncontrast head CT demonstrated no intracranial hemorrhage. Head CT angiogram demonstrated a 4.2 mm fusiform aneurysm in the distal right superior cerebellar artery. The patient underwent treatment with the Pipeline embolization device which was deployed in the right superior cerebellar artery covering the aneurysm. Six-month posttreatment follow-up angiogram demonstrated resolution of the aneurysm with patency of the parent vessel.

Conclusion:

To the best of our knowledge, this is the first report of a distal superior cerebellar artery aneurysm treated with the Pipeline embolization device. The use of a Pipeline stent to create flow diversion should be considered in a case of a fusiform aneurysm of the right superior cerebellar artery. Treatment with flow diversion may allow for the treatment of the aneurysm while preserving patency of the parent vessel.

A Case of Ruptured Cerebral Aneurysm with Asymmetric Fusion of Basilar Apex

Objective

We report a case of a ruptured cerebral aneurysm in which a bifurcation pattern at the tip of the basilar artery was asymmetric fusion type and the superior cerebellar artery (SCA) branched from the posterior cerebral artery (PCA) on the caudal fusion type side.

Case Presentation

A 45-year-old woman presented with a subarachnoid hemorrhage with a headache. Cerebral angiography revealed that the right SCA diverged from the PCA and a small cerebral aneurysm had developed at this site. This cerebral aneurysm was successfully treated by coil embolization.

Conclusion

There have been no previous reports on cerebral aneurysms at the site of this normal variation.

Delayed extensive brain edema caused by the growth of a giant basilar apex aneurysm treated with basilar artery obliteration: a case report

Background

Partially thrombosed giant aneurysms at the basilar apex (BA) artery are challenging lesions with a poor prognosis if left untreated. Here we describe a rare case of extensive brain edema after growth of a surgically treated and thrombosed giant basilar apex aneurysm.

Case presentation

We performed a proximal surgical basilar artery occlusion on a 64-year-old female with a partially thrombosed giant BA aneurysm. MRI showed no ischemic lesions but showed marked edema adjacent to the aneurysm. She had a good recovery, but 3 months after surgical occlusion, her gait deteriorated together with urinary incontinence and worsening right hemiparesis. MRI showed that the aneurysm had grown and developed intramural hemorrhage, which caused extensive brain edema and obstructive hydrocephalus. She was treated by a ventriculoperitoneal shunt placement. Follow-up MRI showed progressive brain edema resolution, complete thrombosis of the lumen and shrinkage of the aneurysm. At 5 years follow-up the patient had an excellent functional outcome.

Conclusions

Delayed growth of a surgically treated and thrombosed giant aneurysm from wall dissection demonstrates that discontinuity with the initial parent artery does not always prevent progressive enlargement. The development of transmural vascular connections between the intraluminal thrombus and adventitial neovascularization by the vasa vasorum on the apex of the BA seems to be a key event in delayed aneurysm growth. Extensive brain edema might translate an inflammatory edematous reaction to an abrupt enlargement of the aneurysm.

Adenosine-Induced transient asystole during surgical treatment of basilar artery aneurysms

Aim

To evaluate the safety and efficacy of adenosine-induced transient asystole (AITA) during surgery for basilar artery aneurysms.

Materials and Methods

All the patients with basilar artery aneurysms operated using AITA at our institute during two years period (August 2013-July 2015) were included in this study.

Results

Adenosine was used in 11 patients with 13 basilar artery aneurysms. Seven of these aneurysms were basilar bifurcation aneurysms, four were basilar-superior cerebellar artery junction aneurysms, and two were distal basilar trunk aneurysms. The indications for AITA were narrow corridor for placement of temporary clip in 11 aneurysms, intraop rupture in 1 aneurysm, and circumferential dissection of a large aneurysm in 1. The mean dose of adenosine used for inducing asystole was 19.4 mg (range: 15-30 mg) and the mean total dose of adenosine used was 40.6 mg (range: 18-90 mg). A mean of 2 (range: 1-5) AITAs were required during surgical treatment of these aneurysms. The mean duration of a systole was 27 s (range: 9-76 s). There were no complications related to AITA in these patients except for transient rebound hypertension in one patient. Check angiogram revealed complete obliteration of 11 aneurysms and small residual neck in 2 aneurysms. Modified Rankin Scale at three months of follow-up was 0 in seven patients, 1 in two patients, 4 in one patient, and 6 in one patient.

Conclusion

AITA during surgical management of basilar artery aneurysms is a safe and effective technique and has an important role during surgery for these aneurysms.

Superior Cerebellar Artery Aneurysms Causing Facial Pain: A Comprehensive Review

BACKGROUND

Trigeminal neuralgia caused by superior cerebellar artery aneurysms (TGN-SCAAs) is a rare event without previous analysis.

OBJECTIVE

To describe the features of TGN-SCAA based on 8 cases (7 from literature +1 illustrative case).

METHODS

All cases were thoroughly studied with gathering of their epidemiological, radiological, clinical, therapeutic, and outcome data.

RESULTS

The mean age at diagnosis was 61 yr. Gender distribution showed a female predominance (M: F = 2:6). Side distribution had a left dominance (75%). The aneurysms mean size was 15.4 mm (range: 5-27). All 5 proximal SCAAs (SCA-Basilar junction) presented a lateral-posterior projection, while all 3 distal SCAAs (s2 segment) had variable projections but constant direct trigeminal nerve (TN) contact. No hemorrhage occurred. TGN was the clinical onset in all 8 cases. The most frequent pain distribution was V1-2-3 (n = 3), followed by V1-2 (n = 1) and V1 alone (n = 1). Proximal SCAAs caused TGN through direct TN compression (n = 1), third nerve compression (n = 1), cavernous sinus compression (n = 1), or a combination thereof (n = 2). However, all distal SCAAs caused TGN by direct TN compression (n = 3). Two different treatment options were used: clipping (n = 4) and coiling (n = 4). The post-treatment Barrow Neurological Institute score for pain control was I in all cases (100%). The mRS score was 0 in 75% of cases.

CONCLUSION

TGN-SCAAs are infrequent lesions, characterized by large size, variable TGN mechanisms depending on their anatomic location, and mostly affecting the first and second trigeminal divisions. Both SCAA clipping and coiling were used equally, providing good neurological and pain relief results.

Superficial temporal artery-superior cerebellar artery bypass and direct clipping of a large unruptured superior cerebellar artery aneurysm through subtemporal approach: Surgical video

Background:

Superior cerebellar artery (SCA) aneurysms are rare. Current treatments include: direct clipping, trapping ± bypass, and endovascular methods (coiling, stenting, or flow diversion). Due to specific characteristics (wide base, location, and shape), a major challenge while dealing with SCA aneurysms is to preserve the flow of the parent artery and perforators. This video demonstrates a revascularization procedure, and clip reconstruction of a large unruptured basilar artery (BA)/SCA aneurysm performed through the subtemporal approach.

Case Description:

A 60-year-old woman presented with dizziness and headaches. Computed tomography angiography (CTA) and digital subtraction angiography showed a right unruptured large BA/SCA aneurysm. After multidisciplinary discussion, and considering gender, age, risk factors of the patient. Endovascular treatment was considered with a high risk of ischemic complications. Therefore, the patient was consented for a superficial temporal artery (STA)-SCA bypass through subtemporal approach followed by direct clipping/ trapping of the aneurysm. Postoperative CTA showed occlusion of the aneurysm and patency of the parent vessels. Postoperatively, the patient experienced immediate transient left mild monoparesis and right IV nerve palsy, which recovered completely at 6-months follow-up.

Results:

Surgical treatment of SCA aneurysms is decreasing due to the existence of endovascular therapies such as stents and flow diverters. However, some cases may necessitate surgical treatment and revascularization procedures to maintain the blood flow of the parent artery and to treat the previous lesion.

Conclusion:

The STA-SCA bypass through the subtemporal approach is a feasible option to maintain the blood flow of the parent artery in cases of SCA requiring surgical treatment and trapping/direct clipping of the aneurysm.

Distal Parent Vessel Occlusion of 2 Superior Cerebellar Artery Fusiform Aneurysms: Report of 2 Cases and Literature Review

Background

Fusiform superior cerebellar artery (SCA) aneurysms are rare, and their management represents a technical challenge. In complex aneurysms, endovascular parent vessel occlusion of the SCA may be a treatment option. Here, we present 2 cases of fusiform SCA aneurysms, 1 ruptured and 1 unruptured, as well as our institution's management with parent vessel occlusion. We also provide a review of the literature.

Cases Description

Case 1: A 42-year-old male was transferred from an outside hospital with subarachnoid hemorrhage. On admission, the patient had a Glasgow Coma Scale score of 8, a Hunt and Hess grade 4, and a Fisher grade 4. A diagnostic angiogram demonstrated a right SCA fusiform lesion with proximal and distal dilatations of 1.45 mm and 5.35 mm long, respectively, likely representing a single dissecting pseudoaneurysm. The distal dilatation was coiled, resulting in parent vessel occlusion. The patient recovered clinically and was discharged in stable condition.

Case 2: A 27-year-old female was transferred from an outside hospital due to a brainstem stroke. A diagnostic angiogram revealed an S2/S3 segment left SCA fusiform lesion, likely representing a dissecting aneurysm. The patient was neurologically intact at admission and managed conservatively. At the 2-month follow-up angiogram, the dissection had extended along the length of the SCA. Consequently, the patient underwent coil embolization of the distal left SCA. At the 6-month follow-up, the vessel remained obliterated and the patient's neurologic status had improved.

Conclusions

Endovascular coil embolization of fusiform SCA aneurysms offers a reasonable and safe treatment approach.

Dissecting distal cerebellar artery aneurysms: options beyond a parent vessel sacrifice

Parent vessel occlusion (PVO) is the conventional endovascular treatment (EVT) for dissecting distal cerebellar artery aneurysms (DCAA). The associated ischemic sequelae are often well-tolerated. However, at the outset, the magnitude of this risk is uncertain. Meanwhile, non-PVO endovascular treatments (EVT) are deemed to provide incomplete protection from a rebleed. This study reviews our experience in the management of dissecting DCAA with emphasis on the effectiveness of parent vessel-preserving endovascular strategies as compared to PVO. Our institutional database was reviewed for all the dissecting DCAA aneurysms treated by endovascular means between Nov 2015 and Oct 2018. Their clinical presentations, imaging findings, EVT techniques, and clinical outcomes were retrospectively evaluated. Eighteen dissecting DCAA were identified: 13 in the posterior-inferior cerebellar artery (PICA), 3 in anterior-inferior cerebellar artery (AICA), and 2 in superior cerebellar artery (SCA). Median patient age was 61 years (range 40-86; average 60.7 years) with a 5:1 female predominance. Nine (6 in the PICA and 3 in the AICA) patients were managed by parent vessel-preserving strategies (6 with isolated endosaccular coiling and 3 with telescoping stents) while the remaining 9 (7 in the PICA and 2 in the SCA) were treated by PVO.The frequency of early rebleed was the same (11%) in both the treatment arms. One patient from the PVO arm suffered an extensive cerebellar infarct that mandated decompressive craniectomy and adversely affected her recovery. There were no such complications in patients treated with parent vessel-preserving strategies. No recurrence/rebleed was encountered in the 3 aneurysms secured using telescoping stents. Overall, excellent clinical outcomes (mRS of 0 and 1) were sparsely seen in the patients who had PVO (89 vs 23%). In dissecting DCAA, aforedescribed, parent vessel-preserving strategies are as effective as the more frequently used option of PVO in preventing an early rebleed. However, these are technically challenging, may be feasible in a smaller proportion of patients, and would need meticulous imaging follow-up in the acute period. When successfully implemented, these strategies can deliver excellent clinical outcomes and eliminate the uncertain risk of ischemic complications associated with PVO.

Ruptured Distal Superior Cerebellar Artery Dissecting Aneurysm Treated with a Flow-diverting Device: Case Report and Review of Literature

Distal fusiform aneurysms of the superior cerebellar artery (SCA) are rare and present several challenges to clinicians, especially when ruptured. While several treatment options are available, including surgical clipping and endovascular coiling, numerous challenges still remain due to the presence of vital neighboring neurovascular structures. In addition, the complications that arise due to the compromise of brainstem perforators make these aneurysms difficult to treat.

This case report demonstrates the successful treatment of a ruptured fusiform aneurysm of the SCA with a flow-diverting device. We also conducted a literature review of the use of flow-diverting devices for treating such aneurysms.

When choosing a treatment modality for a ruptured aneurysm, clinicians must consider both the patient-specific variables as well as aneurysm morphology. Treatment options including microsurgical clipping, endovascular coiling, and flow diversion carry risks. Therefore, the clinician must decide which option best fits each situation. 

The Superior Cerebellar Artery Aneurysm: A Posterior Circulation Aneurysm with Favorable Microsurgical Outcomes

BACKGROUND

Superior cerebellar artery (SCA) aneurysms are usually grouped with aneurysms that arise from the upper basilar artery or more broadly, the posterior circulation. However, the SCA aneurysm has distinctive anatomy that facilitates safe surgical management, notably few associated perforating arteries, and excellent exposure in the carotid-oculomotor triangle.

OBJECTIVE

To demonstrate the outcomes of patients treated with microsurgery in a continuous surgical series.

METHODS

Sixty-two patients harboring 63 SCA aneurysms were retrospectively reviewed from a prospectively maintained database, focusing on clinical characteristics, surgical techniques, and clinical outcomes.

RESULTS

Of 31 patients (49%) presenting with subarachnoid hemorrhage, the SCA aneurysm was the source in 16 (25%). Thirty-three aneurysms were complex (52%) and 43 patients (59%) had multiple aneurysms. Fifty-seven SCA aneurysms (90.5%) were clipped and 5 were bypassed/trapped or wrapped. Complete angiographic occlusion was achieved in 91.7%. Permanent neurological morbidity occurred in 3 patients and 3 patients that presented in coma after subarachnoid hemorrhage died. All patients with "simple" aneurysms and without subarachnoid hemorrhage had improved or unchanged modified Rankin scale scores. Overall, outcomes were stable or improved in 82.5% of patients.

CONCLUSION

SCA aneurysms are favorable for microsurgical clipping with low rates of permanent morbidity and mortality. Microsurgery should be considered alongside endovascular techniques as a treatment option in many patients.

Surgical treatment of unruptured distal basilar artery aneurysm: durability and risk factors for neurological worsening

BACKGROUND

Distal basilar artery aneurysms (DBAs) consist of basilar apex and basilar artery-superior cerebellar artery bifurcation (BA-SCA) aneurysms. The authors aimed to investigate clinical and radiological differences between two locations and to evaluate the 12-month surgical outcome in unruptured DBAs.

METHODS

Fifty-six consecutive patients who underwent surgical treatment (37 basilar apex and 19 BA-SCA aneurysms) between April 2012 and February 2016 were retrospectively evaluated. In patients with a preoperative modified Rankin Scale score (mRS) of more than 1, neurological worsening (NW) was defined as an increase in one or more mRS. In patients without symptoms, NW was defined as mRS ≥2.

RESULTS

The mean age of the patient population was 64 ± 9.6 years, and 48 (86%) were female. Mean follow-up period was 2.6 ± 0.94 years. An excellent (mRS 0 to 1) outcome was archived in 31 (55%), 45 (82%), and 48 (87%) patients at 30 days, 6 months, and 12 months, respectively. Clinical and radiological characteristics showed no differences between two locations. One early death (1.8%) and one severe morbidity (1.8%) due to rupture were observed. The postoperative annual rupture rate was 1.4% overall (145 patient-years). After adjustment for age and location, large or giant DBA was related to 30-day and 12-month NW [n = 22 (39%) and n = 6 (11%); p = 0.009 and 0.002, respectively], aneurysm localization in the interpeduncular cistern (LIC) and perforator territory infarction were related to 30-day NW (p = 0.002 and 0.002), and DBA that needed bypass surgery and previously treated recurrent DBA were related to NW at 12 months (p = 0.017 and 0.001). Multivariate analysis showed that LIC was significantly related to perforator territory infarction (p = 0.003).

CONCLUSIONS

Clinical and radiological characteristics were not different between basilar apex and BA-SCA aneurysms; therefore, they should not be discussed separately. To avoid neurological worsening, results of surgical treatment for unruptured DBAs should be improved.

The Interlenticulostriate Approach to Very High-Riding Distal Basilar Trunk Aneurysms

BACKGROUND

Most high-riding distal basilar trunk aneurysms can be surgically approached via the transsylvian route and its orbitozygomatic variant. However, on rare occasions, the basilar bifurcation may be unusually high and an approach above the carotid terminus may be required.

OBJECTIVE

In this cadaveric study, we sought to determine the feasibility and exposure limits of the interlenticulostriate approach (ILSA).

METHODS

A standard transsylvian approach was performed in 10 cerebral hemispheres of 5 formalin-fixed, silicone-injected cadaver heads. The interpeduncular cistern was exposed via the opticocarotid window, carotid-oculomotor window, and supracarotid ILSA window. The latter was measured and an aneurysm clip or ventriculostomy stylet was placed as high as possible through each corridor. Using noncontrast 3-D rotational angiography, clip/stylet positions were measured relative to the dorsum sellae.

RESULTS

ILSA provided a 9.4 × 4.6 mm mean surgical corridor, just enough room for a standard clip applier. This space was limited by the carotid bifurcation inferiorly, the lenticulostriate arteries medially and laterally, and the optic tract superiorly. There was no difference between opticocarotid and carotid-oculomotor windows, in terms of clip position (+8.9 vs +8.6 mm, respectively; P = .78). In contrast, ILSA provided significantly improved superior exposure, compared with either approaches (mean stylet position: +14.3 mm; P = .005). The exposure benefit afforded by ILSA was consistent across all 10 hemispheres, ranging from +2.5 to +8 mm.

CONCLUSION

For high-riding distal basilar trunk aneurysms that cannot be reached via the frontotemporal orbitozygomatic approach, ILSA can provide a viable route of access. Vascular neurosurgeons should be familiarized with this approach.

Superior Cerebellar Artery Aneurysms, the "Sui Generis" in Posterior Circulation: The Role of Microsurgery in the Endovascular Era

BACKGROUND

Endovascular treatment in the present form has almost taken over the management of posterior circulation aneurysms. However, superior cerebellar artery (SCA) aneurysms are among the few that are said to be surgeon friendly with comparable outcome with microsurgery. This study includes a comparative analysis of the SCA aneurysms treated with microsurgery and endovascular techniques at our institute along with a pooled analysis of available literature on overall outcomes in these 2 forms of treatment.

METHODS

This retrospective study included our patients with SCA aneurysms from 2000 to 2015. Clinical outcomes were assessed by the Glasgow Outcome Scale (GOS) at discharge and modified Rankin Scale (mRS) at follow-up. A literature review was performed for clinical series on SCA aneurysms from 1991 to 2015 describing more than 10 patients for pooled analysis.

RESULTS

Among the 20 patients (microsurgery, 12; endovascular, 8), 66% from microsurgery and 75% from the endovascular arm had good outcomes (GOS score >3 and mRS score <3) (P = 0.54). Microsurgery had an 88.8% complete occlusion rate compared with 75% in endovascular treatment (P = 0.45). Pooled analysis of 12 studies showed that endovascular coiling is significantly associated with good clinical outcome (88.1% vs. 76.9%; P = 0.003). Microsurgery provides better radiologic outcome in terms of complete occlusion rate (90.1% vs. 67.4%; P = 0.0001) and lower recurrence rate (0% vs. 11.8%; P = 0.005).

CONCLUSIONS

Individual series on SCA aneurysms have not proved any outcome benefit of either treatment modality over the other. However, pooled analysis suggests that microsurgery provides complete and sustainable aneurysm occlusion, although with an inferior clinical outcome.

Infantile intracranial aneurysm of the superior cerebellar artery

Intracranial aneurysms in the pediatric population are rare. We report a case of a 3-month-old infant who presented with inconsolable crying, vomiting, and sunset eye sign. CT revealed a subarachnoid hemorrhage, with CT angiogram revealing a superior cerebellar artery aneurysm. An external ventricular drain was placed for acute management of hydrocephalus, with definitive treatment by endovascular technique with a total of six microcoils to embolize the aneurysm. Serial transcranial Dopplers revealed no subsequent vasospasm. Although aneurysms in the pediatric population are rare, once the diagnosis is established, early treatment results in better outcomes.

Infantile intracranial aneurysm of the superior cerebellar artery

Intracranial aneurysms in the pediatric population are rare. We report a case of a 3-month-old infant who presented with inconsolable crying, vomiting, and sunset eye sign. CT revealed a subarachnoid hemorrhage, with CT angiogram revealing a superior cerebellar artery aneurysm. An external ventricular drain was placed for acute management of hydrocephalus, with definitive treatment by endovascular technique with a total of six microcoils to embolize the aneurysm. Serial transcranial Dopplers revealed no subsequent vasospasm. Although aneurysms in the pediatric population are rare, once the diagnosis is established, early treatment results in better outcomes.

Microsurgical management of aneurysms of the superior cerebellar artery - lessons learnt: An experience of 14 consecutive cases and review of the literature

Objective:

This is a retrospective study from January 2002 to December 2012 analyzing the results of microsurgical clipping for aneurysms arising from the superior cerebellar artery (SCA).

Materials and Methods:

All patients with SCA were evaluated with computerized tomography angiography and/or digital subtraction angiography (DSA) prior to surgery. All patients in our series underwent microsurgical clipping and postoperative DSA to assess the extent of aneurysm occlusion. The Glasgow outcome scale (GOS) and the modified Rankin's scale (mRS) were used to grade their postoperative neurological status at discharge and 6 months, respectively.

Results:

Fourteen patients had SCA aneurysms (ruptured-9, unruptured-5). There were 10 females and 4 males with the mean age of 47.2 years (median - 46 years, range = 24–66 years). Subarachnoid hemorrhage (SAH) was seen in 11 patients. The mean duration of symptoms was 2.5 days (range = 1–7 days). The WFNS score at presentation was as follows: Grade 1 in 10 cases, II in 2 cases, III in 1 case and IV in 1 case. In the 9 cases with ruptured SCA aneurysm, average size of the ruptured aneurysms was 7.3 mm (range = 2.5–27 mm, median = 4.9 mm). The subtemporal approach was used in the first 7 cases. The extradural temporopolar (EDTP) approach was used in the last 5 cases. Complications include vasospasm (n = 6), third nerve palsy (n = 5) and hydrocephalus (n = 3). Two patients died following surgery. At mean follow-up 33.8 months (median - 25 months, range = 19–96 months), no patient had a rebleed. At discharge 9 (64%), had a GOS of 4 or 5 and 3 (21%) had a GOS of 3. At 6 months follow-up, 10/14 (71%) patients had mRS of 0–2, and 2 (14%) had mRS of 5.

Conclusions:

Aneurysms of the SCA are uncommon and tend to rupture even when the aneurysm size is small (<7 mm). They commonly present with SAH. The EDTP approach avoids complication caused by temporal lobe retraction and injury to the vein of Labbe.

Intracranial Aneurysms Occur More Frequently at Bifurcation Sites That Typically Experience Higher Hemodynamic Stresses

BACKGROUND:

Intracranial aneurysms (IAs) occur more frequently at certain bifurcations than at others. Hemodynamic stress, which promotes aneurysm formation in animal models, also differs among bifurcations, depending on flow and vessel geometry.

OBJECTIVE:

To determine whether locations that are more likely to develop IAs experience different hemodynamic stresses that might contribute to higher IA susceptibility.

METHODS:

We characterized the hemodynamic microenvironment at 10 sites in or around the circle of Willis where IAs commonly occur and examined statistical relationships between hemodynamic factors and the tendency for a site to form IAs. The tendency for each site to develop IAs was quantified on the basis of the site distribution from systematic literature analysis of 19 reports including 26 418 aneurysms. Hemodynamic parameters for these sites were derived from image-based computational fluid dynamics of 114 cerebral bifurcations from 31 individuals. Wall shear stress and its spatial gradient were calculated in the impact zone surrounding the bifurcation apex. Linear and exponential regression analyses evaluated correlations between the tendency for IA formation and the typical hemodynamics of a site.

RESULTS:

IA susceptibility significantly correlated with the magnitudes of wall shear stress and positive wall shear stress gradient within the hemodynamic impact zone calculated for each site.

CONCLUSION:

IAs occur more frequently at cerebral bifurcations that typically experience higher hemodynamic shear stress and stronger flow acceleration, conditions previously shown to promote aneurysm initiation in animals.

Endovascular management of fusiform superior cerebellar artery aneurysms: a series of three cases with review of literature

Distal superior cerebellar artery (SCA) aneurysms are rare. Fusiform aneurysms of SCA are rarer and more challenging to treat. Parent artery occlusion by endovascular coiling is the treatment option for these cases. Presence of good collateral circulation and paucity of perforators from S1 and S2 segments makes this a feasible option. From 2007 to 2010, we treated three patients (two men and one woman between the ages of 42 to 64 years) with distal fusiform SCA aneurysms using endovascular coiling. All the patients presented with symptoms of rupture and were treated in the acute phase. Informed and written high-risk consent was given by all patients prior to the procedure. Successful angiographic and clinical outcome was achieved in all three patients. Endovascular treatment of fusiform SCA aneurysms with coils is a safe and feasible option in the management of this rare entity.

Endovascular and microsurgical treatment of superior cerebellar artery aneurysms

Objective

Superior cerebellar artery (SCA) aneurysms are regarded as being as difficult to treat surgically as posterior circulation aneurysms. We describe here a series of 33 of these aneurysms treated with microsurgery or embolization.

Methods

Between June 1997 and August 2007, 33 patients (9 men, 24 women; age, 29 to 76 years) with SCA aneurysms underwent microsurgical (n = 12) or endovascular (n = 21) treatment. Twenty two patients presented with subarachnoid hemorrhage. Thirty aneurysms were located in the junction between the SCA and the basilar artery (BA), two in the proximal SCA (S1) and one in the distal SCA (S2-3).

Results

Of the 29 SCA aneurysms, located in the junction between the SCA and BA, which were available on conventional angiography, 20 were lateral-superior, six lateral-horizontal, two lateral inferior, and one posterior type. Of the 12 patients treated microsurgically, eight had clinically excellent or good outcomes. Causes of poor outcomes included initial poor clinical status (n = 2), infarction due to parent artery compromise (n = 1), and artery of Heubner injury due to surgery for a coexisting anterior communicating artery aneurysm (n = 1). Of the 21 patients treated endovascularly, 17 had clinical good or excellent outcomes. Causes of clinically poor outcomes included initial poor clinical status (n = 2) and infarction due to thrombosis of exposed coil mesh (n = 1). One patient underwent embolization resulted in death due to vasospasm. Three patients required additional embolization for coil compaction.

Conclusion

There was no morbidity related to perforator injury, regardless of the treatment modality. Embolization or microsurgery is an effective modality, with relatively low procedural morbidity and mortality rates.