Posteroinferior cerebellar artery aneurysms: surgical results for 38 patients

Giant aneurysms of the distal posterior inferior cerebellar artery - systematic review

BACKGROUND

Posterior inferior cerebellar artery (PICA) aneurysms are uncommon and are typically found at the origin or proximal segments of the vessel. Giant aneurysms are uncommon and present unique treatment challenges. Giant distal PICA aneurysms are exceedingly rare and have traditionally been managed via open surgical approaches.

METHODS

A total of 207 studies were assessed, identifying 26 cases of giant distal PICA aneurysms from 26 separate publications. One additional case is described followed by a review of presentation, anatomical characteristics, treatment and outcome.

RESULTS

Presentation was due to local mass effect in 19 (70%), hydrocephalus in 4 (15%) and acute haemorrhage in 5 (19%). All reported cases were partially (86%) or completely (14%) thrombosed. The telovelotonsillar segment was involved in 18/24 (75%) cases. Two cases (7%) were associated with an arteriovenous malformation. Twenty-two (81%) were managed surgically and 5 (19%) managed endovascularly. Outcome was good in 22 (85%) and poor in one (4%).

CONCLUSIONS

Giant distal PICA aneurysms can be managed effectively through a variety of open surgical and endovascular techniques.

Silk Vista Baby for the Treatment of Complex Posterior Inferior Cerebellar Artery Aneurysms

BACKGROUND

Treatment of small-caliber vessel lesions using flow diverters remains challenging because of vasculature's narrow luminal diameter and tortuosity. This in turn makes navigation and delivery of conventional devices with standard microcatheters more difficult. The Silk Vista Baby (SVB, Balt) flow diversion device was designed for ease of use in vessels with a smaller diameter, distal lesions, and 0.017 ″ microcatheter delivery systems.

OBJECTIVE

To report the outcomes of the SVB device on the treatment of posterior inferior cerebellar artery (PICA) aneurysms.

METHODS

Databases from different centers were retrospectively reviewed for PICA aneurysms treated with SVB. Demographic information, clinical presentation, radiographic characteristics, procedural complications, and immediate postprocedure outcomes were obtained.

RESULTS

Fourteen patients harboring 15 true PICA aneurysms were treated between January 2019 and June 2021. Nine were female (n = 9/14; 64.2%), and the mean age was 51 ± 14.9 years. Most patients had previously ruptured aneurysms, treated by another endovascular technique. Six aneurysms were located distally (n = 6/15; 40%). The mean neck size was 3 mm (SD 1.35, range 2.5-5 mm), whereas the mean PICA diameter was 1.6 mm (SD 0.26, range 1.5-1.7 mm). The mean length of follow-up was 6 months (SD 8.28, range 4.5-16 months). Treatment-related adverse events included 1 case of transient hypoesthesia. Two additional events were reported, but adjudicated as unrelated to the procedure. Complete occlusion, measured as Raymond-Roy class I, was achieved in all cases.

CONCLUSION

The SVB device was safely and effectively used in the treatment of PICA aneurysms. The smaller delivery system profile reduces the risk of procedure complications and creates new treatment options for distal lesions.

Treatment of Proximal Posterior Inferior Cerebellar Artery Aneurysms by Intrasaccular Flow Disruption: A Multicenter Experience

BACKGROUND AND PURPOSE

Treatment of PICA aneurysms can be technically challenging by either surgical or endovascular means. Our aim was to report our preliminary experience with intrasaccular flow disruption using the Woven EndoBridge (WEB) for the treatment of proximal PICA aneurysms.

MATERIALS AND METHODS

Sixteen PICA aneurysms treated with the WEB at 3 institutions were retrospectively reviewed. Baseline patient and aneurysm characteristics, procedural specifics, clinical outcomes, and angiographic results were evaluated.

RESULTS

All aneurysms were located at the proximal, anteromedullary segment of the PICA. Seven aneurysms were ruptured. The median aneurysm size was 3.9 mm (range, 2-12 mm), and all aneurysms were wide-neck. WEB deployment failed in 1 case due to WEB protrusion in a small PICA aneurysm. Additional stent implantation was required for 2 aneurysms to improve intra-aneurysmal WEB positioning. One patient developed a partial posterior cerebral artery territory infarction with transient hemianopsia. Intraoperative rerupture of a ruptured aneurysm could be immediately stopped by WEB deployment due to intrasaccular stasis; however, it might have contributed to a slight disability of the patient. At last angiographic follow-up, 12/15 aneurysms (80%) were completely occluded and 3/15 (20%) had a neck remnant.

CONCLUSIONS

The preliminary results indicate that WEB treatment of proximal PICA aneurysms is feasible with a reasonable safety and efficacy profile. The advantages of intrasaccular flow disruption include preservation of the PICA, durable aneurysm occlusion, and omission of antiplatelet therapy. The low-profile WEB 17 delivery system might enable navigation to distal PICA aneurysms, which needs to be addressed further.

Surgical and Endovascular Treatment of Saccular Posterior Inferior Cerebellar Artery Aneurysms: Systematic Review and Meta-Analysis

OBJECTIVE

The optimal treatment modality for saccular aneurysms of the posterior inferior cerebellar artery (PICA) remains unclear. A previous meta-analysis on the topic included a heterogenous study population, limiting the conclusions that can be drawn from its results. The aim of this study was to perform a systematic review and meta-analysis to compare outcomes of microsurgical and endovascular treatment (EVT) of these aneurysms.

METHODS

A search of 4 online databases was performed for studies describing the management of saccular PICA aneurysms. The primary outcome was complete aneurysm occlusion. Data were also collected on neurologic outcomes, cranial nerve palsies, and requirement for re-treatment. A random effects model was used for calculation of pooled proportions. Our protocol was registered with PROSPERO (CRD42021232784).

RESULTS

A total of 17 studies were included in the final analysis, reporting the treatment outcomes of 455 aneurysms, with a mean follow-up of 20 months. The pooled occlusion rates were 94.8% (95% confidence interval [CI] 90.6%-97.8%) for surgical treatment and 69.1% (95% CI 55.0%-81.7%) for EVT. Pooled rates of good neurologic outcome (modified Rankin scale score ≤2, Glasgow Outcome Scale score ≥4) at last follow-up were 78.1% (95% CI 67.4%-87.1%) for surgery and 77.6% (95% CI 67.9%-86.0%) for EVT.

CONCLUSIONS

This meta-analysis demonstrates that in the treatment of saccular PICA aneurysms, microsurgical clipping results in superior angiographic outcomes, similar functional outcomes, but higher rates of lower cranial nerve palsy compared with EVT. Further studies are required to assess the duration and severity of cranial nerve palsies following surgical treatment, and long-term aneurysm occlusion and the requirement for re-intervention following EVT.

Midline suboccipital approach to a vertebral artery–posterior inferior cerebellar artery aneurysm from the rostral end of the patient using ORBEYE

Background:

The midline suboccipital approach with the patient in the prone position is safe and effective for clipping vertebral artery–posterior inferior cerebellar artery (VA–PICA) aneurysms. Using a conventional surgical microscope from the rostral end of the patient for this approach without an extreme head-down position requires the surgeon to overhang the visual axis of the microscope and perform surgical manipulations in an uncomfortable posture. We report performing the midline suboccipital approach from the rostral end with slight head-down position using ORBEYE, a new high-definition (4K) three-dimensional exoscope.

Case Description:

A 65-year-old woman was admitted for clipping of a right unruptured VA–PICA aneurysm (maximum diameter, 5mm) located medially and ventral to the hypoglossal canal. After induction of general anesthesia, the patient was placed in the prone position with the head titled slightly downward. A midline suboccipital approach was performed from the rostral end of the patient using ORBEYE. Clipping was safely accomplished in a comfortable posture. No operative complications occurred. Postoperative computed tomography angiography showed complete aneurysmal obstruction.

Conclusion:

Exoscopic surgery using ORBEYE is feasible for a midline suboccipital approach to VA–PICA aneurysms from the rostral end of the patient with the patient in the prone with slight head-down position.

Overlapping Pure LIVS Jr. Stents for Isolated Ruptured Dissecting Aneurysm of the Proximal Posterior Inferior Cerebellar Artery

We report our experience in treating a ruptured dissecting posterior inferior cerebellar artery (PICA) aneurysm. To our knowledge, this is the first reported case of overlapping stenting without coils for a ruptured dissecting aneurysm of the proximal PICA. A 66-year-old male patient presented with sudden altered mental state and a subarachnoid hemorrhage (SAH). The cerebral angiography revealed a long segmental dissecting aneurysm on proximal PICA. Overlapping stents were deployed to the dissecting site, and angiogram showed intact distal PICA flow and decreased contrast staining in the dissecting site. Successful flow diversion was achieved with stents. Procedure-associated complications did not occur. The patient’s postoperative course was uneventful. In follow-up cerebral angiography, dissecting aneurysm achieved complete remodeling. The decision that led to the choice of treatment is discussed.

Microsurgical Clipping of a Posterior Inferior Cerebellar Artery Aneurysm Following Failed Pipeline Stent

Aneurysms of the posterior inferior cerebellar artery (PICA) are rare, with limited consensus on appropriate management. These aneurysms have been noted to have a faster growth rate and are more prone to rupture. Accessing these aneurysms for microsurgical clipping is challenging, and has traditionally required significant removal of the occipital condyle, putting the patient at risk for future complications. Therefore, some have opted to utilize minimally invasive techniques such as a pipeline stent, though these methods can fail to cause complete occlusion of the aneurysm. The current case describes a patient who was found to have a PICA aneurysm that was initially managed with a pipeline stent. However, upon further follow up, the aneurysm showed continued filling, leading to the decision to clip the aneurysm. In this case, we describe the use of a far lateral approach for accessing and clipping a PICA aneurysm with minimal removal of the occipital condyle. The patient successfully tolerated the surgery and was discharged home. 

Case Report: Endovascular Treatment of a Giant Distal PICA Aneurysm in Association With a Cerebellar AVM: A Report on Treatment Considerations and a Literature Review

Background: Distal posterior inferior cerebellar artery (PICA) aneurysms are uncommon intracranial vascular lesions. The coincidence of these aneurysms and Arteriovenous malformation (AVM) is even more rare. Since 1956, a total of 57 cases of distal PICA aneurysms associated with AVM have been reported with clear and adequate description. None of these reports describe a giant prenidal aneurysm at this particular location. The paucity of natural history data as well as lack of consensus about treatment strategies in such cases present a significant challenge that requires an individualized management approach.

Case Description: A 68-year-old male presented with recurrent episodes of nausea and vomiting precipitated by physical exertion and change of head position. An MRI of the brain demonstrated a giant partially thrombosed right posterior inferior cerebellar artery (PICA) aneurysm with mass effect on the floor of the fourth ventricle. A conventional cerebral angiogram revealed a giant (3.1 x 3.1 x 2.8cm) distal right PICA pre-nidal aneurysm with two smaller distal PICA aneurysms. An AVM (Spetzler-Martin Grade 1) supplied by the right PICA as well as the right superior cerebellar artery (SCA) was also identified on cerebral angiography (not seen on an MRI). Endovascular coil embolization with parent vessel sacrifice was performed to occlude the giant aneurysm. Due to the asymptomatic nature, low risk of rupture, and the patient's age, AVM treatment was deferred.

Conclusion: This paper presents the first case of a giant PICA aneurysm associated with cerebellar AVM. For PICA aneurysm-AVM complexes, meticulous evaluation of the morphology, associated anatomy, and comparative risk analysis for both lesions are key for treatment planning. Distal PICA aneurysms can be treated safely with parent vessel occlusion, particularly in the case of prenidal aneurysms.

Functional Outcomes After Treatment of Posterior Inferior Cerebellar Artery Aneurysms

Objective Aneurysms of the posterior inferior cerebellar artery (PICA) are a rare cause of subarachnoid hemorrhage. Treatment for this type of aneurysm may be microsurgical clipping or endovascular. This decision is based on patient characteristics, aneurysm location and dimensions, along with surgeon and institutional experience. In this study we aim to assess the outcomes of surgical and endovascular treatment of PICA aneurysms. Methods We retrospectively reviewed the charts of 52 patients who were admitted to Vancouver General Hospital for ruptured or symptomatic PICA aneurysms between 2005 and 2015. Modified Rankin scores were assigned at the time of discharge and at two subsequent follow-up time points. The mean short-term follow-up period post-operatively was 11.1 months and the mean long-term follow-up period was 19.3 months. Clinical and radiological characteristics were collected for all patients. Results Of the 52 patients, two died prior to obtaining treatment. Of the 50 patients who were treated for their PICA aneurysm, 39 presented with subarachnoid hemorrhage while 11 had symptomatic unruptured PICA aneurysms. Overall, 11 patients had endovascular treatment (coil embolization) while 39 patients underwent microsurgical clipping/trapping of the aneurysm. At the time of hospital discharge, patients in the microsurgical group trended towards a better the modified Rankin Scale score (2.3) compared to the endovascular group, though this did not reach significance (3.0) (p=0.20). The long-term score in the endovascular group (1.6) was also comparable to the microsurgical group (1.9) (p=0.55). Conclusion While the early outcomes in patients treated endovascularly appear better, there is no statistically significant difference in outcomes between the microsurgical and endovascular treatment groups at short- and long-term follow-up.

Endovascular sacrifice of the proximal posterior inferior cerebellar artery for treatment of ruptured intracranial aneurysms

BACKGROUND

Ruptured aneurysms of the intracranial vertebral artery (VA) or posterior inferior cerebellar artery (PICA) are challenging to treat as they are often dissecting aneurysms necessitating direct sacrifice of the diseased segment, which is thought to carry high morbidity due to brainstem and cerebellar stroke. However, relatively few studies evaluating outcomes following VA or proximal PICA sacrifice exist. We sought to determine the efficacy and outcomes of endovascular VA/PICA sacrifice.

METHODS

A retrospective series of ruptured VA/PICA aneurysms treated by endovascular sacrifice of the VA (including the PICA origin) or proximal PICA is reviewed. Collected data included demographic, radiologic, clinical, and disability information.

RESULTS

Twenty-one patients were identified. Median age was 57 years (IQR 11); 15 were female. The Hunt and Hess grade was mostly 3 and 4 (18/21). Seven cases (33%) involved VA-V4 at the PICA take-off, and 14 cases (67%) involved the PICA exclusively. For VA pathology, V4 was sacrificed in all cases, while for PICA pathology, sacrificed segments included anterior medullary (4/14), lateral medullary (7/14), and tonsillomedullary (3/14) segments. Four patients went to hospice (19%). Twelve patients (57%) had evidence of stroke on follow-up imaging: cerebellar (8), medullary (1), and both (3). One patient required suboccipital decompression for brainstem compression. No aneurysm re-rupture occurred. Median discharge modified Rankin Scale score was 2.0 (IQR 2), which decreased to 1.0 (IQR 1) at median follow-up of 6.5 months (IQR 23).

CONCLUSIONS

Endovascular sacrifice of V4 or PICA aneurysms may carry less morbidity than previously thought, and is a viable alternative for poor surgical candidates or those with good collateral perfusion.

Treatment of a giant complicated distal posterior inferior cerebellar artery aneurysm: A case report and literature review

Giant intracranial aneurysms, especially giant aneurysms of the distal posterior inferior cerebellar artery (PICA), remain the most difficult and challenging cerebrovascular lesions for neurosurgeons to treat. The morbidity and mortality rates of microsurgical clipping are relatively high, and endovascular embolization is also associated with many complications. In the present report, the case of a 46-year-old female patient who presented with headache and dizziness for 3 years, which was aggravated and combined with limb weakness for 1 day, is presented. A CT scan showed a lesion occupying the fourth ventricle, with slight bleeding. A MR scan also revealed a lesion occupying the fourth ventricle and compressing the brainstem, and there was distortion of the cisterns around the brainstem. CT angiography examination showed a giant irregular aneurysm located in the PICA. After evaluation, the PICA aneurysm was removed, and the PICA was clipped via a microsurgical technique without ischemia or neurological sequelae. Long-term follow-up demonstrated that the symptoms of headache and dizziness disappeared without relapse. Based on a review of the literature, this method may represent an alternative strategy for the treatment of giant PICA aneurysms, especially for aneurysms not suitable for direct clipping or endovascular embolization.

Treatment of acute thrombosis during stent-assisted coil embolization of ruptured proximal posterior inferior cerebellar artery aneurysm

Aneurysms located in the posterior inferior cerebellar artery (PICA) are not a majority of the intracranial aneurysms cases. Many challenges were addressed in the endovascular procedure to treat the disease. The authors have successfully diagnosed and treated a ruptured proximal PICA aneurysm. However, digital subtraction angiography showed acute thrombosis in the vertebral artery in the procedure, which probably could be an acute in-stent thrombosis. The tirofiban hydrochloride injection was subjected through a microcatheter, and then, the second Neuroform EZ stent was planted. In the 6-month follow-up, no recurrence of the aneurysm and complete patency of the right PICA at the site of aneurysm formation were found. We believe that the treatment of PICA aneurysms with Neuroform EZ stents could get a favorable result. Combination of tirofiban hydrochloride and Neuroform EZ stent could be an effective approach in treating acute thrombotic complications.

Surgical Management and Outcomes of Aneurysms of Posterior Inferior Cerebellar Artery: Location-Based Approaches with Review of Literature

Background  Posterior inferior cerebellar artery (PICA) is a tortuous, variable, and uncommon site for aneurysms. Surgical management of PICA aneurysms involves careful selection of approach based on the location of the aneurysm and meticulous dissection of the neurovascular structures and perforators.

Materials and Methods  We did a retrospective review of all the PICA aneurysms operated at our institute in the past 10 years along with the site, presentation, and approach used for the same. Preoperative World Federation of Neurosurgical Society scores and follow-up modified Rankin scores (mRS) were also evaluated. During the same period, data for intervention cases of PICA aneurysm were also collected with follow-ups for a comparative analysis.

Results  A total of 20 patients with 21 PICA aneurysms were reviewed. All the reviewed cases presented with subarachnoid hemorrhage, and the most common location was the lateral medullary segment and vertebral artery (VA)–PICA junction. Midline approaches were used for distal PICA cases, with far-lateral approach reserved for anterior medullary/VA–PICA junction. No lower cranial nerve palsies were recorded at follow-up. Four cases needed cerebrospinal fluid diversion and two developed cerebellar infarcts. All cases were mRS 0 to 2 at follow-up.

Conclusion  Our series compares well with some of the larger surgical series of PICA aneurysms. This may be due to early referral patterns and early surgery (<24 hours) policy at our institution. Anatomical knowledge of PICA anatomy and sound perioperative management are keys to good outcomes in these cases.

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.

Coil Embolization Results of the Ruptured Proximal Posteriori Inferior Cerebellar Artery Aneurysm: A Single-Center 10 Years' Experience

OBJECTIVE

To report a single-center experience with endovascular treatment of ruptured proximal posterior inferior cerebellar artery (PICA) aneurysms.

METHODS

Between January 2007 and December 2016, among 1403 patients with aneurysmal subarachnoid hemorrhage, 15 with ruptured proximal PICA aneurysms underwent endovascular embolization at our institution. Aneurysmal obliteration with a single microcatheter was performed in 9 patients. Additional microcatheter or stent-assisted coil embolization was performed in 4 patients and parent artery occlusion in 2 patients.

RESULTS

Immediate angiographic results showed 10 complete occlusions (66.7%, 10/15). Five patients showed incomplete occlusion (remnant neck in 4 patients, remnant aneurysm in 1). Of those, 2 patients experienced recurrence and required conversion to microsurgical clipping. The remaining 2 patients remained in relatively stable condition. Procedure-related complications occurred in 3 patients (20%, with thromboembolic complications in 2 patients and intraprocedural rupture in 1). Clinical outcome was excellent: Glasgow Outcome Score 4 or 5 in 12 of 15 patients (80%). There was no rebleeding during follow-up.

CONCLUSIONS

Ruptured proximal PICA aneurysms may be effectively treated with endovascular coil embolization. A variety of coil embolization techniques are required to obliterate an aneurysm without parent artery occlusion. Given that recurrence is possible, follow-up is required. Surgical clipping can be performed for recurrence with a relatively low risk of complications, because the aneurysm is unruptured. Coil embolization of a proximal PICA aneurysm in the acute phase can be a good treatment modality with good patient outcomes.

Microsurgical Clipping of Ruptured Distal Posterior Inferior Cerebellar Artery Aneurysm: 3-Dimensional Operative Video

The distal posterior inferior cerebellar artery (PICA) is a rare site of aneurysm formation. Only small case series and case reports regarding surgical treatment are found in the literature.The PICA is divided into 5 segments (anterior medullary, lateral medullary, tonsilomedullary, telovelotonsillary, and cortical), and the distal ones represent the most complex, due to anatomic variations. We present a case of a 69-yr-old female patient who has suffered from a sudden and intense occipital headache, associated with nausea and vomiting. CT scan showed intraventricular hemorrhage, and further investigation with MRI and MR Angiography revealed a small distal PICA aneurysm, at the superior part of the medial aspect of the left cerebellar tonsil. Digital angiography has demonstrated the aneurysm at the tonsilomedullary segment of the PICA. In this 3-dimensional video, the authors show the microsurgical clipping of a saccular distal PICA aneurysm in the close relation to a choroidal branch, performed by median suboccipital craniotomy. Step-by-step of the dissection, relevant surrounding anatomy and aneurysm clipping is demonstrated. The patient signed the Institutional Consent Form, which allows the use of his/her images and videos for any type of medical publications in conferences and/or scientific articles.

Simple Lateral Suboccipital Approach and Modification for Vertebral Artery Aneurysms: A Study of 52 Cases Over 10 Years

INTRODUCTION

Complex skull base approaches are frequently used to treat intracranial vertebral artery (VA) and proximal posterior inferior cerebellar artery (PICA) aneurysms. These complex procedures are associated with higher risk of neurovascular injury. Hence, a less-invasive surgical approach is needed to improve the efficacy and safety of treatment.

METHODS

A retrospective analysis was conducted on clinical and radiologic data from surgeries in which simple lateral suboccipital and "lateral-enough" approaches were used to clip VA aneurysms in the Department of Neurosurgery at Helsinki University Central Hospital from 2000 to 2009.

RESULTS

Fifty-two VA or PICA aneurysms were treated using the simple lateral suboccipital approach. Sixteen patients (31%) presented with an unruptured aneurysm, 21 patients (40%) with World Federation of Neurosurgical Societies (WFNS) grade 1-3, and 15 patients (29%) with World Federation of Neurosurgical Societies grade 4-5. The aneurysms were saccular in 48 cases (92%), dissecting in 3 cases (6%), and fusiform in 1 case (2%). The most common aneurysm location was the VA-PICA junction (81%). The mean final modified Rankin Scale score was 2, and in unruptured cases, all patients had favorable clinical outcomes. The main causes of unfavorable outcome were poor preoperative clinical grade (P = 0.002), preoperative intraventricular hemorrhage (P = 0.008), postoperative hydrocephalus (P = 0.003), brain infarction (P = 0.005), and postoperative pneumonia (P < 0.001).

CONCLUSIONS

We describe a 10-year experience using a simple lateral suboccipital approach and its modification by the senior author (J.H.) to treat VA and proximal PICA aneurysms. Unfavorable outcome was related to the poor preoperative clinical grade, preoperative intraventricular hemorrhage, and postoperative pneumonia.

Variations of Occipital Artery-Posterior Inferior Cerebellar Artery Bypass: Anatomic Consideration

BACKGROUND

Advances in diagnosis of posterior inferior cerebellar artery (PICA) aneurysms have revealed the high frequency of distal and/or dissecting PICA aneurysms. Surgical treatment of such aneurysms often requires revascularization of the PICA including but not limited to its caudal loop.

OBJECTIVE

To examine the microsurgical anatomy involved in occipital artery (OA)-PICA anastomosis at various anatomic segments of the PICA.

METHODS

Twenty-eight PICAs in 15 cadaveric heads were examined with the operating microscope to take morphometric measurements and explore the specific anatomy of bypass procedures.

RESULTS

OA bypass to the p2, p3, p4, or p5 segment was feasible with a recipient vessel of sufficient diameter. The loop wandering near the jugular foramen in the p2 segment provided sufficient length without requiring cauterization of any perforating arteries to the brainstem. Wide dissection of the cerebellomedullary fissure provided sufficient exposure for the examination of some p3 segments and all p4 segments hidden by the tonsil. OA-p5 bypass was placed at the main trunk before the bifurcation in 5 hemispheres and at the larger hemispheric trunk in others.

CONCLUSION

Understanding the possible variations of OA-PICA bypass may enable revascularization of the appropriate portion of the PICA when the parent artery must be occluded. A detailed anatomic understanding of each segment clarifies important technical nuances for the bypass on each segment. Dissection of the cerebellomedullary fissure helps to achieve sufficient exposure for the bypass procedures on most of the segments.

Safety and efficacy of treatment strategies for posterior inferior cerebellar artery aneurysms: a systematic review and meta-analysis

INTRODUCTION

We conducted a systematic review of the literature to evaluate the safety and efficacy of treatment strategies for PICA aneurysms.

METHODS

A systematic search of Medline, EMBASE, Scopus, and Web of Science was done for studies published through November 2015. We included studies that described treatment of PICA aneurysms with ≥10 patients. Random-effects meta-analysis was used to pool the following outcomes: complete occlusion, technical success, periprocedural morbidity/mortality, stroke rates, aneurysm recurrence/rebleed, CN palsies rates, and long-term neurological morbidity/mortality.

RESULTS

We included 29 studies with 796 PICA aneurysms. When considering all ruptured PICA aneurysms, complete occlusion rates were 97.1 % (95 % CI = 94.5-99.0 %) in the surgical group and 84.3 % (95 % CI = 73.8-92.6 %) in the endovascular group. Aneurysm recurrence occurred in 1.4 % (95 % CI = 0.3-3.3 %) after surgery and in 6.9 % (95 % CI = 3.6-10.9 %) after endovascular treatment. Overall neurological morbidity and mortality were 14.4 % (95 % CI = 8.7-21.2 %) and 9.8 % (95 % CI = 5.8-14.8 %) after surgery and 15.1 % (95 % CI = 10.5-20.2 %) and 17.1 % (95 % CI = 11.5-23.7 %) after endovascular treatment, respectively. When considering all unruptured PICA aneurysms, complete occlusion rates were 92.9 % (95 % CI = 79.5-100 %) in the surgical group and 75.7 % (95 % CI = 45.4-97.1 %) in the endovascular group. Overall long-term good neurological outcome rates were 91.5 % (95 % CI = 74.4-100 %) in the surgical series and 93.3 % (95 % CI = 82.7-99.5 %) in the endovascular group.

CONCLUSIONS

Our meta-analysis demonstrated that both treatment modalities are technically feasible with high rates of technical success and effective with sufficient long-term aneurysm occlusion rates. Our data suggest that surgery is associated with superior angiographic outcomes. While endovascular therapy could be a reasonable first-line treatment option for proximal PICA aneurysms, surgery remains a highly effective first-line choice for distal PICA aneurysms. These findings should be considered when deciding the best therapeutic strategy.

Ruptured Distal Posterior Inferior Cerebellar Artery (PICA) Aneurysms Associated with Cerebellar Arterial Venous Malformations (AVMs): A Case Series and Review of the Literature Demonstrating the Need for Angiographic Evaluation and Feasibility of Endovascular Treatment

OBJECTIVE

The characteristics, diagnosis, and preferred management strategies for distal posterior inferior cerebellar artery (PICA) aneurysms associated with cerebellar arteriovenous malformation (AVMs) are poorly understood. We present a case series with attention to aneurysm angioarchitecture, diagnostic imaging, treatment approaches, and a thorough review of the literature. With this information, we demonstrate a specific anatomical pattern for these aneurysms, an underreported need for conventional digital subtraction angiography (DSA) during evaluation, along with the utility of endovascular treatment with liquid embolic agents.

METHODS

Neurosurgical patients from 2005 to 2016 were reviewed to identify PICA aneurysms along with distal PICA aneurysms. Details of their presentation, imaging studies, associated AVMs and treatment were recorded. A thorough literature search of previous case series and case reports of distal PICA aneurysms with and without associated small cerebellar AVMs was performed with PubMed and Google Scholar.

RESULTS

Thirty-four patients with PICA aneurysms were identified at our institution, 12 of which were in a distal segment. All 12 of these patients underwent DSA as a part of their evaluation. Of the 12 patients with distal PICA aneurysms, 9 presented with subarachnoid hemorrhage and intraventricular hemorrhage. Five of these patients had a small occult cerebellar AVM. All nine patients presenting with a ruptured distal PICA aneurysm had a Fischer grade 4 subarachnoid hemorrhage. Of the five patients with a small occult cerebellar AVM, the AVM nidus was missed on computed tomography angiogram (CTA) interpretation but easily visualized with DSA. CTA followed by DSA with concurrent endovascular treatment was performed in 9 of the 12 patients with distal PICA aneurysms. Two of the 12 patients were treated with microsurgical clip ligation, and one mycotic aneurysm was identified and treated with antibiotics. Parent vessel sacrifice was used distal to the aneurysm in all 5 associated AVM cases with liquid embolic agents as well as AVM embolization in 3 of the 5 cases. Fifty-one well-described case reports of distal PICA aneurysms associated with small cerebellar AVMs have been reported in the literature. A total of 12 well-described case series of distal PICA aneurysms that comment on associated AVMs describe an associated small cerebellar AVM incidence of 4%-50%. In our case series, the incidence of an associated small cerebellar AVM with a distal PICA aneurysm was 42%.

CONCLUSIONS

In cases of distal PICA aneurysms, there is a frequent association of a small cerebellar AVM. In our series, CTA was an inadequate diagnostic study to identify the associated AVM, and DSA was necessary to definitely visualize the AVM nidus. Endovascular treatment of the aneurysm and AVM with the use of liquid embolic agents was a feasible and useful management strategy.

Posterior inferior cerebellar artery reimplantation: buffer lengths, perforator anatomy, and technical limitations

OBJECTIVE

Reimplantation of the posterior inferior cerebellar artery (PICA) to the vertebral artery (VA) is a safe and effective bypass option after deliberate PICA sacrifice during the treatment of nonsaccular and dissecting aneurysms at this location. However, the anatomy and limitations of this technique have not been studied. The goal of this study was to define the surgical anatomy and buffer lengths specific to the proximal segment of the PICA related to 2 variations of PICA reimplantation: 1) reimplantation “along-VA” (simulating a dissecting VA aneurysm), and 2) reimplantation “across-VA” (simulating a nonclippable, proximal PICA aneurysm).

METHODS

Ten cadaver heads (20 sides) were prepared for surgical simulation. Twenty far-lateral approaches were performed. The PICA was mobilized and reimplanted onto the VA according to 2 different paradigms: 1) transposition along the axis of the VA (along-VA) to simulate a dissecting VA, and 2) transposition perpendicular to the axis of the VA (across-VA) to simulate a nonclippable, proximal PICA aneurysm. The buffer lengths provided by mobilization of the artery in each paradigm were measured and the anatomy of perforator branching on the proximal PICAs was analyzed.

RESULTS

The PICA was reimplanted in all surgical simulations. The most common perforating artery on the P1 and P2 segments was the short circumflex type. No direct perforator was found on the P1 segment. The mean buffer length with reimplantation along the VA axis was 13.43 ± 4.61 mm, and it was 6.97 ± 4.04 mm with reimplantation across the VA. The PICA was less maneuverable when it was reimplanted across the VA, due to perforator branches of the PICA (P3 segment).

CONCLUSIONS

The buffer lengths measured in this study describe the limitations of PICA reimplantation as a revascularization procedure for nonsaccular aneurysms in this location. PICA reimplantation is a revascularization option for dissecting VA aneurysms incorporating the PICA origin that are < 13 mm in length, and for nonsaccular proximal PICA aneurysms that are < 6 mm in diameter. The final decision to reimplant the PICA depends on careful inspection of perforator anatomy that is not visible preoperatively on angiography, as well as an assessment of technical difficulty intraoperatively.

Endovascular treatment of posterior inferior cerebellar artery aneurysms: a 7-year single-center experience

Aim

To report our experience with endovascular treatment of posterior inferior cerebellar artery (PICA) aneurysms.

Methods

Between January 2007 and December 2014, 40 patients with 42 PICA aneurysms were treated with endovascular embolization at our institution. Twenty-eight patients had 29 saccular aneurysms and 12 patients had 13 fusiform/dissecting aneurysms. The endovascular modalities were: (1) selective occlusion of the aneurysm with or without stent assistance (n=19); (2) occlusion of the aneurysm and the parent artery (n=22); and (3) occlusion of the aneurysm including the vertebral artery and PICA origin (n=1). Specifically, selective embolization was performed in 93.3% of aneurysms (14/15) proximal to the telovelotonsillary segment.

Results

Immediate angiographic results included 31 complete occlusions (74%), 3 nearly complete occlusions (7%), and 8 incomplete occlusions (19%). Mean follow-up of 20 months in 31 aneurysms showed 27 stable results, 3 further thromoboses, and 1 recurrence. Final results included 27 complete occlusions (87.1%) and 4 incomplete occlusions (12.9%). There were 5 overall procedural-related complications (12.5%), including 1 infarction (2.5%) and 4 intraprocedural ruptures (10.0%). Procedure-related morbidity and morbidity was 5.0% (2/40) and 2.5% (1/40), respectively. Clinical outcome was excellent (Glasgow Outcome Scale 5 in 31 of 33 patients at long-term follow-up).

Conclusions

PICA aneurysms may be effectively treated by different endovascular approaches with favorable clinical and radiologic outcomes. Further studies are required to compare the safety and efficacy of endovascular treatment with open surgery.

Ten years of experience in endovascular treatment of ruptured aneurysms of the posterior inferior cerebellar artery

BACKGROUND

The aim of this study is to present our 10 years of experience in endovascular treatment of ruptured posterior inferior cerebellar artery (PICA) saccular aneurysms and to compare clinical presentation and outcome after endovascular treatment between patients with PICA aneurysms and patients with aneurysms in different locations.

METHODS AND FINDINGS

Out of 932 patients with a ruptured intracranial aneurysm treated endovascularly in our institution, 38 aneurysms were located at the posterior inferior cerebellar artery. Clinical presentation, mean aneurysm diameter and outcome of the therapy in this group were compared with the same for ruptured aneurysms in other locations. Patients discharged with favourable outcomes were checked angiographically in the follow-up period. Thirty-four patients with ruptured PICA aneurysms were treated by selective endovascular coiling. Two patients with wide-necked aneurysms had endovascular stents implanted. In two cases, the parent vessel was occluded due to failure to catheterise the target aneurysm. The evaluated variables did not differ significantly between two groups, but significantly more ruptured aneurysms in the PICA group were under 6 mm in diameter. 29.4% of controlled aneurysms needed additional reembolisation in the follow-up period.

CONCLUSIONS

Clinical presentation, extension of subarachnoid haemorrhage and outcome after endovascular treatment did not differ significantly between patients with ruptured aneurysms located on the PICA and patients with aneurysms located elsewhere intracranially. Endovascular treatment is an effective method of therapy in patients with ruptured PICA aneurysms. In our experience, even when sacrificing of the PICA is required, the results of treatment are favourable.

Endovascular treatment of PICA aneurysms with a Low-profile Visualized Intraluminal Support (LVIS Jr) device

OBJECTIVE

To describe the treatment of posterior inferior cerebellar artery (PICA) aneurysms with the Low-profile Visualized Intraluminal Support Device (LVIS Jr) stent.

MATERIALS AND METHODS

The databases of three institutions were retrospectively reviewed. Patients who underwent endovascular treatment of PICA aneurysms using a reconstructive technique where the LVIS Jr stent was totally or partially deployed into the PICA were included in the analysis. Clinical presentation, aneurysm and PICA sizes, procedural complications, and clinical and angiographic follow-up information was recorded and analyzed.

RESULTS

Seven patients who underwent endovascular treatment of PICA aneurysms with an LVIS Jr stent were identified. Four aneurysms were treated in the acute phase of subarachnoid hemorrhage (SAH). There were no symptomatic complications. One patient had spasm distal to the stent as a result of mechanical straightening of the vessel. One patient was treated in the acute phase of SAH and required a gycoprotein IIb/IIIa inhibitor after the stent was implanted. This patient needed to be re-treated to complete embolization. All patients had good clinical outcomes (Glasgow Outcome Scale 5). No in-stent stenosis or occlusion was seen on short-term angiographic follow-up and the aneurysms were occluded.

CONCLUSIONS

This small series suggests that the use of a reconstructive technique with the LVIS Jr stent for the treatment of PICA aneurysms is feasible, safe and effective in the short term.

Using the Endoscopic Endonasal Transclival Approach to Access Aneurysms Arising from AICA, PICA, and Vertebral Artery: An Anatomical Study

Objective To explore the use of the endoscopic endonasal transclival approach (EEA) for clipping anterior inferior cerebellar artery (AICA), posterior inferior cerebellar artery (PICA), and vertebral artery (VA) aneurysms. Design Anatomical study. Participants Fifteen adult cadavers. Main Outcome Measures Length of artery exposed and distance from the nasal ala to the arteries. Results The length of the right and left VA exposed were 1.7 ± 0.6 cm and 1.6 ± 0.6 cm, respectively. The distance to the right VA was 11.1 ± 0.9 cm and to the left was 11.1 ± 0.8 cm. Right and left AICA were exposed for an average length of 1.1 ± 0.3 cm and 0.8 ± 0.3 cm, respectively. The distance to the right AICA was 10.3 ± 0.8 cm and to the left was 10.3 ± 0.8 cm. The right PICA was exposed for a length of 0.5 ± 0.2 cm at a distance of 10.9 ± 0.5 cm. The left PICA was exposed for a length of 0.5 ± 0.2 cm at a distance of 11.1 ± 0.9 cm. Conclusion The EEA can provide direct access to AICA, PICA, and VA, making it a potential alternative to the traditional approaches for the clipping of aneurysms arising from those arteries.

Clinical characteristics and long-term outcomes in patients with ruptured posterior inferior cerebellar artery aneurysms: a comparative analysis

OBJECT

Subarachnoid hemorrhage (SAH) from ruptured posterior inferior cerebellar artery (PICA) aneurysms is uncommon, and long-term outcome data for patients who have suffered such hemorrhages is lacking. This study investigated in-hospital and long-term clinical data from a prospective cohort of patients with SAH from ruptured PICA aneurysms enrolled in a randomized trial; their outcomes were compared with those of SAH patients who were treated for other types of ruptured intracranial aneurysms. The authors hypothesize that PICA patients fare worse than those with aneurysms in other locations and this difference is related to the high rate of lower cranial nerve dysfunction in PICA patients.

METHODS

The authors analyzed data for 472 patients enrolled in the Barrow Ruptured Aneurysm Trial (BRAT) and retrospectively reviewed vasospasm data not collected prospectively. In the initial cohort, 57 patients were considered angiographically negative for aneurysmal SAH source and did not receive treatment for aneurysms, leaving 415 patients with aneurysmal SAH.

RESULTS

Of 415 patients with aneurysmal SAH, 22 (5.3%) harbored a ruptured PICA aneurysm. Eight of them had dissecting/fusiform-type aneurysms while 14 had saccular-type aneurysms. Nineteen PICA patients were treated with clipping (1 crossover from coiling), 2 were treated with coiling, and 1 died before treatment. When comparing PICA patients to all other aneurysm patients in the study cohort, there were no statistically significant differences in age (mean 57.6 ± 11.8 vs 53.9 ± 11.8 years, p = 0.17), Hunt and Hess grade median III [IQR II–IV] vs III [IQR II–III], p = 0.15), Fisher grade median 3 [IQR 3–3] vs 3 [IQR 3–3], p = 0.53), aneurysm size (mean 6.2 ± 3.0 vs 6.7 ± 4.0 mm, p = 0.55), radiographic vasospasm (53% vs 50%, p = 0.88), or clinical vasospasm (12% vs 23%, p = 0.38). PICA patients were more likely to have a fusiform aneurysm (36% vs 12%, p = 0.004) and had a higher incidence of lower cranial nerve dysfunction and higher rate of tracheostomy/percutaneous endoscopic gastrostomy placement compared with non-PICA patients (50% vs 16%, p < 0.001). PICA patients had a significantly higher incidence of poor outcome at discharge (91% vs 67%, p = 0.017), 1-year follow-up (63% vs 29%, p = 0.002), and 3-year follow-up (63% vs 32%, p = 0.006).

CONCLUSIONS

Patients with ruptured PICA aneurysms had a similar rate of radiographic vasospasm, equivalent admission Fisher grade and Hunt and Hess scores, but poorer clinical outcomes at discharge and at 1- and 3-year follow-up when compared with the rest of the BRAT SAH patients with ruptured aneurysms. The PICA's location at the medulla and the resultant high rate of lower cranial nerve dysfunction may play a role in the poor outcome for these patients. Furthermore, PICA aneurysms were more likely to be fusiform than saccular, compared with non-PICA aneurysms; the complex nature of these aneurysms may also contribute to their poorer outcome.

Intracranial Vertebral Artery Aneurysms: Clinical Features and Outcome of 190 Patients

BACKGROUND

Vertebral artery (VA) aneurysms comprise approximately one-third of posterior circulation aneurysms. They are morphologically variable, and located critically close to the cranial nerves and the brainstem. We aim to represent the characteristics of these aneurysms and their treatment, and to analyze the outcome.

METHODS

We reviewed retrospectively 9709 patients with intracranial aneurysms. Of these, we included 190 with aneurysms at the VA or VA-posterior inferior cerebellar artery junction. These patients were treated in the Department of Neurosurgery, Helsinki, Finland, between 1934 and 2011.

RESULTS

The 190 patients had 193 VA aneurysms, among which 131 (68%) were ruptured. The VA aneurysm caused a mass effect in 7 and ischemia in 2 patients. Compared to 4387 patients with a ruptured aneurysm in other locations, those with a VA aneurysm were older, their aneurysms were more often fusiform, and more often caused intraventricular hemorrhages. Among surgically treated aneurysms, clipping was the treatment in 91 (88%) saccular and 11 (50%) fusiform aneurysms. Treatment was endovascular in 13 (9%), and multimodal in 6 (4%) aneurysms. Within a year after aneurysm diagnosis, 53 (28%) patients died. Among the survivors, 104 (93%) returned to an independent or to their previous state of life; only 2 (2%) were unable to return home.

CONCLUSIONS

Microsurgery is a feasible treatment for VA aneurysms, although cranial nerve deficits are more common than in endovascular surgery. Despite the challenge of an often severe hemorrhage, of challenging morphology, and risk for laryngeal palsy, most patients surviving the initial stage return to normalcy.

Successful treatment of a ruptured aneurysm at the vertebral artery-posterior inferior cerebellar artery junction and simultaneous treatment of the stenotic vertebral artery with a single flow-diverting stent: a case report

Introduction

This is the first report on the simultaneous successful treatment of a large ruptured saccular aneurysm and stenotic parent artery with a single flow-diverting stent.

Case presentation

We report the case of a 68-year-old Caucasian man with occlusion of the right vertebral artery and a ruptured aneurysm at the junction of the left posterior inferior cerebellar artery-left vertebral artery that was successfully treated by the deployment of a single flow-diverting stent in the stenotic left vertebral artery. Stent deployment was complicated by thrombotic occlusion of the basilar artery, which was successfully reopened. The patient recovered completely, and follow-up angiography at 4 months and 1 year showed patent vertebral artery with gradual shrinkage of the aneurysm.

Conclusions

This report contributes to the literature on treatment of large ruptured aneurysms localized in stenotic arteries and in areas of the endocranium where a mass of embolic material in the aneurysm (coils) might compromise the circulation in the parent blood vessel or compress vital brain structures.

Endovascular treatment of ruptured distal posterior inferior cerebellar artery aneurysms: report of 11 cases

OBJECTIVE

To investigate the clinical characteristics and endovascular treatment of ruptured distal posterior inferior cerebellar artery (PICA) aneurysms.

METHODS

11 consecutive patients (7 women, 4 men, mean age of 49.2 years) with ruptured distal PICA aneurysms were studied retrospectively. All had onset of acute intraventricular or cerebellar haemorrhage, and subarachnoid hemorrhage (SAH). Hunt-Hess (HH) grades were H-H I in 1 patient, H-H II in 5 patients, H-H 111 in 4 patients and H-H IV in 1 patient on admission.

RESULTS

All patients were treated by endovascular treatment, seven cases got endosaccular coiling and four cases got parent artery occlusion at the same time. All the patients were followed up one to four years. Recurrences occurred in 1 patient two years post-treatment, and were successfully retreated by endosaccular coiling and parent artery occlusion. The occluded PICA was recanalized one year post-treatment but without any growth of the aneurysm in one case. One year post-treatment, 2 patients had a modified Rankin Scale (mRS) score of 0, 8 patients had a mRS score of 1 and 1 patient had a mRS score of 2.

CONCLUSIONS

Coiling of ruptured distal PICA aneury, with or without parent vessel occlusion, was feasible, relatively safe and effective in preventing early/medium-term rebleeding. A strict angiographic follow-up, however, was necessary to detect recurrence.

Endovascular treatment of proximal and distal posterior inferior cerebellar artery aneurysms

Object

Surgical clipping of posterior inferior cerebellar artery (PICA) aneurysms can be challenging and carries a potentially significant risk of morbidity and mortality. Experience with endovascular therapy has been limited to a few studies. The authors assess the feasibility, safety, and efficacy of endovascular therapy in the largest series of proximal and distal PICA aneurysms to date.

Methods

A total of 76 patients, 54 with proximal and 22 with distal PICA aneurysms, underwent endovascular treatment at Jefferson Hospital for Neuroscience between 2001 and 2011.

Results

Endovascular treatment was successful in 52 patients (96.3%) with proximal aneurysms and 19 patients (86.4%) with distal aneurysms. Treatment consisted of selective aneurysm coiling in 60 patients (84.5%) (including 4 with stent assistance and 4 with balloon assistance) and parent vessel trapping in 11 patients (15.5%). Specifically, a deconstructive procedure was necessary in 9.6% of proximal aneurysms (5 of 52) and 31.6% of distal aneurysms (6 of 19). There were 9 overall procedural complications (12.7%), 6 infarcts (8.5%; 4 occurring after deliberate occlusion of the PICA), and 3 intraprocedural ruptures (4.2%). The rate of procedure-related permanent morbidity was 2.8%. Complete aneurysm occlusion was achieved in 63.4% of patients (45 of 71). One patient (1.4%) treated with selective aneurysm coiling suffered a rehemorrhage on postoperative Day 15. The mean angiographic follow-up time was 17.2 months. Recurrence and re-treatment rates were, respectively, 20% and 17.1% for proximal aneurysms compared with 30.8% and 23.1% for distal aneurysms. Favorable outcomes (moderate, mild, or no disability) at follow-up were seen in 93% of patients with unruptured aneurysms and in 78.7% of those with ruptured aneurysms.

Conclusions

Endovascular therapy is a feasible, safe, and effective treatment in patients with proximal and distal PICA aneurysms, providing excellent patient outcomes and adequate protection against rehemorrhage. The long-term incidence of aneurysm recanalization appears to be high, especially in distal aneurysms, and requires careful angiographic follow-up.

Comparative analysis of the transcranial "far lateral" and endoscopic endonasal "far medial" approaches: surgical anatomy and clinical illustration

OBJECTIVE

The main aim of our study was to analyze and compare the surgical anatomy pertinent to the dorsal transcranial transcondylar (far lateral approach) with that of the ventral endoscopic endonasal transcondylar (far medial approach) route.

METHODS

Eight cadaveric specimens were dissected and analyzed bilaterally. Brainstem exposure and surgical corridor areas were measured. In addition, we present three clinical scenarios to illustrate the clinical feasibility of the proposed surgical strategies.

RESULTS

The hypoglossal nerve, vertebral artery, and hypoglossal canal divide the lower third of the clivus into ventromedial and dorsolateral compartments. The far medial approach provides significantly larger exposure of the brainstem in the ventromedial compartment (464.6 ± 68.34 mm(2)) compared with the far lateral approach (126.35 ± 32.25 mm(2)), P < 0.01. The far lateral approach provides a wide exposure of the brainstem in the dorsolateral compartment (295.24 ± 58.03 mm(2), 74% of the dorsolateral compartment). The exposure of the brainstem in the dorsolateral compartment is not possible using the endonasal route. The surgical corridor from one compartment to the other, through the lower cranial nerves, was significantly larger on the far lateral approach (78.19 ± 14.54 mm(2)) than on the far medial (23.77 ± 15.17 mm(2)), P = 0.03.

CONCLUSIONS

The far medial approach offers a safe, wide exposure of the lower third of the clivus for lesions that expand ventromedial to the hypoglossal nerve. The far lateral approach is most suitable for lesions located dorsolateral to the lower cranial nerves. The vertebral artery and hypoglossal canal are the most important landmarks to guide surgical planning. A combined endonasal-transcranial approach should be considered for resection of extensive lesions involving both ventromedial and dorsolateral compartments. We strive to encourage skull base surgeons to integrate endoscopic and microscopic approaches to the posterior fossa.

Endovascular treatment of ruptured dissecting posterior inferior cerebellar artery aneurysms

Dissecting aneurysms of the posterior inferior cerebellar artery (PICA) distal to its origin from vertebral artery (VA) are very rare. Although rare, they associated with a high risk of rebleeding and they present a therapeutic challenge. This study reviewed the clinical presentations, angiographic characteristics of dissecting aneurysms of the PICA and to assess the clinical and angiographic outcomes of patients who underwent endovascular treatment. Ten patients with ten dissecting aneurysms who underwent endovascular treatment were identified in the clinical records of a single medical center from January 2000 to December 2010. The mean follow-up duration was 2.8 years. All patients presented with subarachnoid hemorrhage (SAH). They all underwent endovascular treatment, which included occlusion of the dissected segment and the parent artery after detailed angiographic evaluation of the vascular anatomy, and test occlusion of the PICA. In all patients the endovascular treatment was successfully completed without procedure related complications. Long-term follow-up studies in seven out of ten patients showed complete occlusion of the aneurysm with no new neurologic deficits. The clinical outcome was good in eight cases, whereas two patients with poor clinical condition at admission died during their initial hospital stay. Endovascular occlusion of the parent vessel and the dissected segment is relatively safe treatment option for dissecting aneurysms of the PICA distal to its origin.

Posterior inferior cerebellar artery aneurysms: Anatomical variations and surgical strategies

Context:

Posterior inferior cerebellar artery (PICA) aneurysms are associated with multiple anatomical variations of the parent vessel. Complexities in their surgical clipping relate to narrow corridors limited by brain-stem, petrous-occipital bones, and multiple neurovascular structures occupying the cerebellomedullary and cerebellopontine cisterns.

Aims:

The present study focuses on surgical considerations during clipping of saccular PICA aneurysms.

Setting and Design:

Tertiary care, retrospective study.

Materials and Methods:

In 20 patients with PICA aneurysms, CT angiogram/digital substraction angiogram was used to correlate the site and anatomical variations of aneurysms located on different segments of PICA with the approach selected, the difficulties encountered and the final outcome.

Statistical Analysis:

Comparison of means and percentages.

Results:

Aneurysms were located on PICA at: vertebral artery/basilar artery (VA/BA)-PICA (n=5); anterior medullary (n=4); lateral medullary (n=3); tonsillomedullary (n=4); and, telovelotonsillar (n=4) segments. The Hunt and Hess grade distribution was I in 15; II in 2; and, III in 3 patients (mean ictus-surgery interval: 23.5 days; range: 3-150 days). Eight patients had hydrocephalus. Anatomical variations included giant, thrombosed aneurysms; 2 PICA aneurysms proximal to an arteriovenous malformation; bilobed or multiple aneurysms; low PICA situated at the foramen magnum with a hypoplastic VA; and fenestrated PICA. The approaches included a retromastoid suboccipital craniectomy (n=9); midline suboccipital craniectomy (n=6); and far-lateral approach (n=5). At a follow-up (range 6 months-2.5 years), 13 patients had no deficits (modified Rankin score (mRS) 0); 2 were symptomatic with no significant disability (mRS1); 1 had mild disability (mRS2); 1 had moderately severe disability (mRS4); and 3 died (mRS6). Three mortalities were caused by vasospasm (2) and, rupture of unclipped second VA-BA junctional aneurysm (1).

Conclusions:

PICA aneurysms may present with only IV^th ventricular blood without subarachnoid hemorrhage. PICA may have multiple anomalies and its aneurysms may be missed on CT angiograms. Surgical approach is influenced by VA-BA tortuosity and variations in anatomy, location of the VA-BA junction and the PICA aneurysm relative to the brain-stem, and the pattern of collateral supply. The special category of VA-PICA junctional aneurysms and its management; and, the multiple anatomical variations of PICA aneurysms, merit special surgical considerations and have been highlighted in this study.

Clinical experiences of ruptured posteroinferior cerebellar artery aneurysms and anatomical analysis in the cadaver in a single center of China

OBJECTIVE

Posteroinferior cerebellar artery (PICA) aneurysms are uncommon and have not been well investigated previously. We report our series of 29 ruptured PICA aneurysms with surgical treatment along with the description of the surgical anatomy of the PICA to the lower cranial nerves in cadaveric specimen.

METHODS

All patients with ruptured PICA aneurysms who were surgically treated at the First Affiliated Hospital of Soochow University during the period from January 1995 to December 2008 were reviewed retrospectively. Data relating to clinical, radiological, and intraoperative findings were analyzed. Forty formalin-fixed cerebellar hemispheres provided the material for the study of describing the detailed surgical anatomic relationship of the PICA to the lower cranial nerves.

RESULTS

In our series, ruptured PICA aneurysms reached an incidence of 2.35% of all ruptured intracranial aneurysms. There were 13 aneurysms (44.8%) located in the proximal segment, and 16 (55.2%) located in the distal segment. Of these, 89.7% were saccular, 6.9% fusiform, and 3.4% dissecting aneurysms. Usually, the surgical outcome was influenced by Poor admission grade, the presence of obstructive hydrocephalus and associated distal AVM. In cadaveric specimen, 17.5% of PICAs passed between the glossopharyngeal and vagus nerves, 7.5% between the vagus and accessory nerves, and 62.5% through the rootlets of the accessory nerve.

CONCLUSION

This report summarizes the presentation and outcome of a large series of 29 patients with ruptured PICA aneurysms, and we conclude that ruptured PICA with surgical treatment usually gets well recovered. The study does, however, also demonstrate that the anatomic relationship of the PICA and lower cranial nerves is somehow variable and irregular. Recognition of the findings in cadaveric dissection is essential in treating lesions of this region.

Predicting factors affecting clinical outcomes for saccular aneurysms of posterior inferior cerebellar artery with subarachnoid hemorrhage

OBJECTIVE

The aim of this study is to investigate the clinical outcomes of surgery and coiling and analyze the predicting factors affecting the clinical outcomes of ruptured posterior inferior cerebellar artery (PICA) aneurysms.

METHODS

During the last 15 years, 20 consecutive patients with ruptured PICA aneurysms were treated and these patients were included in this study. The Fisher's exact test was used for the statistical significance of Glasgow Outcome Scale (GOS) according to initial Hunt-Hess (H-H) grade, treatment modalities, and the presence of acute hydrocephalus.

RESULTS

Eleven (55%) and nine (45%) patients were treated with surgical clipping and endovascular treatment, respectively. Among 20 patients, thirteen (65.0%) patients had good outcomes (GOS 4 or 5). There was the statistical significance between initial poor H-H grade, the presence of acute hydrocephalus and poor GOS.

CONCLUSION

In our study, we suggest that initial H-H grade and the presence of acute hydrocephalus may affect the clinical outcome rather than treatment modalities in the ruptured PICA aneurysms.

Transcondylar fossa (supracondylar transjugular tubercle) approach: anatomic basis for the approach, surgical procedures, and surgical experience

The authors clarify the anatomic basis and the usefulness of the transcondylar fossa approach (T-C-F A), in which the posterior portion of the jugular tubercle is removed extradurally through the condylar fossa with the atlanto-occipital joint intact. The authors first performed an anatomic study to identify the area to be removed using cadaveric specimens and then applied the T-C-F A to foramen magnum surgeries. The surgeries included clipping a vertebral artery-posterior inferior cerebellar artery aneurysm in 11 cases, microvascular decompression for glossopharyngeal neuralgia in 15 cases, and removing intradural foramen magnum tumors in 17 cases. Only the condylar fossa was removed, but the approach offered very good visualization of the lateral part of the foramen magnum and sufficient working space. These surgeries were performed safely without major complications. This skull base approach is minimally invasive and is not difficult. Therefore, it can be a standard approach for accessing intradural lesions of the foramen magnum. It can be combined with the transcerebellomedullary fissure approach from the lateral side and can also be easily changed to the transcondylar approach, if necessary.

Anatomical triangles defining surgical routes to posterior inferior cerebellar artery aneurysms

Object

Surgical routes to posterior inferior cerebellar artery (PICA) aneurysms are opened between the vagus (cranial nerve [CN] X), accessory (CN XI), and hypoglossal (CN XII) nerves for safe clipping, but these routes have not been systematically defined. The authors describe 3 anatomical triangles and their relationships with PICA aneurysms, routes for surgical clipping, outcomes, and angiographically demonstrated anatomy.

Methods

The vagoaccesory triangle is defined by CN X superiorly, CN XI laterally, and the medulla medially. It is divided by CN XII into the suprahypoglossal triangle (above CN XII) and the infrahypoglossal triangle (below CN XII). From a consecutive surgical series of 71 PICA aneurysms in 70 patients, 51 aneurysms were analyzed using intraoperative photographs.

Results

Forty-three PICA aneurysms were located inside the vagoaccessory triangle and 8 were outside. Of the aneurysms inside the vagoaccessory triangle, 22 (51%) were exposed through the suprahypoglossal triangle and 19 (44%) through the infrahypoglossal triangle; 2 were between triangles. The lesions were evenly distributed between the anterior medullary (16 aneurysms), lateral medullary (19 aneurysms), and tonsillomedullary zones (16 aneurysms). Neurological and CN morbidity linked to aneurysms in the suprahypoglossal triangle was similar to that associated with aneurysms in the infrahypoglossal triangle, but no morbidity was associated with PICA aneurysms outside the vagoaccessory triangle. A distal PICA origin on angiography localized the aneurysm to the suprahypoglossal triangle in 71% of patients, and distal PICA aneurysms were localized to the infrahypoglossal triangle or outside the vagoaccessory triangle in 78% of patients.

Conclusions

The anatomical triangles and zones clarify the borders of operative corridors to PICA aneurysms and define the depth of dissection through the CNs. Deep dissection to aneurysms in the anterior medullary zone traverses CNs X, XI, and XII, whereas shallow dissection to aneurysms in the lateral medullary zone traverses CNs X and XI. Posterior inferior cerebellar artery aneurysms outside the vagoaccessory triangle are frequently distal and superficial to the lower CNs, and associated surgical morbidity is minimal. Angiography may preoperatively localize a PICA aneurysm's triangular anatomy based on the distal PICA origin or distal aneurysm location.

Clinical outcomes of lower cranial nerve palsies caused by vertebral artery-posteroinferior cerebellar artery aneurysms after endovascular embolization

OBJECTIVE

To report clinical outcomes of lower cranial nerve palsy (LCNP) caused by vertebral artery (VA) aneurysms.

METHODS

Seventy-two patients with VA aneurysms, who were treated endovascularly between 2001 and 2008, were retrospectively studied to identify patients presenting LCNP without hemorrhage.

RESULTS

LCNP occurred in 12 patients (16·7%) initially caused by VA aneurysms: four located at vertebral artery-posteroinferior cerebellar artery (PICA) complex, seven at distal to PICA segment and one at proximal to PICA segment. Among these patients, ten patients were diagnosed as having dissecting aneurysms of the intracranial VA, and two were diagnosed having saccular aneurysms. Two patients were treated by sole stent placement, five patients were treated by stent coil embolization and five were treated by vertebral artery occlusion. Nosocomial pneumonia did not occur in our patients. Post-operative LCNP resolved completely within 6 months in nine patients (75%) and within 9 months in ten patients (83%). Two (1·9%) patients died of aneurismal bleeding and brainstem ischemia, respectively.

CONCLUSION

The results of this study can help to identify the effect and natural history of LCNP caused by VA aneurysms. These lesions can be effectively treated by endovascular embolization, even by VA occlusion.

Dissecting aneurysms of the distal segment of the posterior inferior cerebellar arteries: clinical presentation and management

BACKGROUND AND PURPOSE

Dissecting aneurysms of the distal segment of the PICA are rare. The purpose of this study was to evaluate the clinical presentations, imaging features, treatment options, and clinical outcomes of dissecting PICA aneurysms.

MATERIALS AND METHODS

Six patients with dissecting aneurysms in the distal segments of PICA were found in the database of a single medical center, from November 1996 to December 2008, and retrospectively evaluated. Treatment mode and follow-up clinical outcomes were analyzed.

RESULTS

Five patients with dissecting PICA aneurysms presented with acute intracranial hemorrhage and 1 patient presented with a large mass from an intramural hematoma. All 5 patients with intracranial hemorrhage were treated with endovascular occlusion of both the dissecting PICA aneurysm and the distal parent artery. The patient with the intramural hematoma underwent surgical trapping with end-to-end anastomosis. In 1 patient, the dissecting aneurysm recurred twice within a 5 year 3 month period, despite endovascular occlusion of both the aneurysm and the parent artery. The clinical outcome postprocedure was excellent in all patients, without permanent neurologic complication.

CONCLUSIONS

For the endovascular treatment of dissecting aneurysms in the distal PICA segments, we recommend occlusion of both the dissecting aneurysm and the parent artery to avoid leaving the point of initial intimal tear untreated. All of our patients had excellent clinical outcomes; however, our experience with recanalization illustrates the need for close follow-up of patients.