The clip-wrap technique in the treatment of intracranial unclippable aneurysms

Fusiform and dolichoectatic aneurysms are challenging lesions to treat with direct clipping. Treatment of these aneurysms often requires alternative surgical strategies, including extracranial-intracranial bypass, wrapping, or clip-wrap techniques. Nonetheless, these alternatives methods of treatment have been underused and frequently overlooked. OBJECTIVE: To report a series of nine cases of otherwise untreatable aneurysms managed using the clip-wrap technique and discuss its surgical nuances. METHOD: In the last four years, 9 cases of ruptured aneurysms treated by the clip-wrap techniques were identified in the Division of Neurological Surgery, University of São Paulo, School of Medicine. RESULTS: The aneurysms were located at middle cerebral artery (2), anterior choroidal artery (1), anterior communicating artery (1), carotid ophthalmic (3), posterior cerebral artery (1) and posterior-inferior cerebellar artery (1). Three were dolichoectatic, 4 were unsuitable to complete surgical clipping because parent or efferent vessels arises from the aneurysm sac (1 MCA, 1 AcomA, 1 CO, 1 PICA aneurysms) and two, although ruptured aneurysms, were too small (<2mm) to be directly clipped. No early or late rebleeding was observed after 2 years mean follow-up. One patient deceased due to pulmonary tromboembolism. CONCLUSION: Clip-wrap techniques for the treatment of fusiform and otherwise unclippable aneurysms seem to be safe and it can be associated with a low rate of acute or delayed postoperative complications. It can prevent rebleeding and represents an improvement when compared with the natural history.

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

Interventional Neuroradiology ◽

10.1177/1591019915622164 ◽

2016 ◽

Vol 22 (2) ◽

pp. 129-137 ◽

Cited By ~ 15

Author(s):

Robert Juszkat ◽

Paweł Kram ◽

Katarzyna Stanisławska ◽

Roman Jankowski ◽

Bogumiła Stachowska-Tomczak ◽

...

Keyword(s):

Endovascular Treatment ◽

Clinical Presentation ◽

Posterior Inferior Cerebellar Artery ◽

Years Of Experience ◽

Endovascular Stents ◽

Ruptured Aneurysms ◽

Ruptured Intracranial Aneurysm ◽

Cerebellar Artery ◽

Pica Aneurysms

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.

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Endovascular Surgery for Proximal Posterior Inferior Cerebellar Artery Aneurysms: An Analysis of Glasgow Outcome Score by Hunt-Hess Grades

Neurosurgery ◽

10.1227/01.neu.0000204127.81249.28 ◽

2006 ◽

Vol 58 (4) ◽

pp. 619-625 ◽

Cited By ~ 51

Author(s):

Robert A. Mericle ◽

Adam S. Reig ◽

Matthew V. Burry ◽

Eric Eskioglu ◽

Christopher S. Firment ◽

...

Keyword(s):

Posterior Inferior Cerebellar Artery ◽

Endovascular Surgery ◽

Glasgow Outcome Score ◽

Clinical Grade ◽

Outcome Score ◽

Fisher Grade ◽

Cerebellar Artery ◽

Pica Aneurysms ◽

Angiographic Result

Abstract OBJECTIVE: Proximal posterior inferior cerebellar artery (PICA) aneurysms represent a subset of posterior circulation aneurysms that can be routinely treated with either clipping or coiling. The literature contains limited numbers of patients with proximal PICA aneurysms treated with endovascular surgery. We report our experience with endovascular surgery of proximal PICA aneurysms with emphasis on patients with poor Hunt-Hess grades. METHODS: We reviewed 31 consecutive patients with proximal PICA aneurysms who were treated with endovascular surgery. The following data were analyzed: age, sex, size of aneurysm, Hunt-Hess grade at presentation, Fisher grade at presentation, angiographic result after embolization, complications, number of days hospitalized, duration of follow-up, angiographic follow-up results, and Glasgow Outcome Score at follow-up. RESULTS: Excellent angiographic occlusion was achieved in 30 of 31 (97%) patients. Clinical follow-up with Glasgow Outcome Score was performed on every patient an average of 10 months later. Twenty-one of 31 (68%) patients had good outcomes (Glasgow Outcome Score I or II) at follow-up. Of the patients who presented with a favorable clinical grade (Hunt-Hess 0–III), 13 of 15 (87%) had good outcomes at follow-up. Of the patients who presented with a poor clinical grade (Hunt-Hess Grade IV or higher), 8 of 16 (50%) had good outcomes at follow-up. CONCLUSION: This series demonstrates the safety and efficacy of endovascular surgery for proximal PICA aneurysms. Many patients with poor Hunt-Hess grades from ruptured PICA aneurysms ultimately had a good outcome. This could be secondary to early, aggressive treatment of hydrocephalus and the minimally invasive nature of the endovascular approach.

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LVIS Blue as a low porosity stent and coil adjuvant

Journal of NeuroInterventional Surgery ◽

10.1136/neurintsurg-2017-013608 ◽

2018 ◽

Vol 10 (7) ◽

pp. 682-686 ◽

Cited By ~ 7

Author(s):

Matthew J Koch ◽

Christopher J Stapleton ◽

Scott B Raymond ◽

Susan Williams ◽

Thabele M Leslie-Mazwi ◽

...

Keyword(s):

Coil Embolization ◽

Intracranial Aneurysms ◽

Posterior Inferior Cerebellar Artery ◽

Endovascular Embolization ◽

Superior Cerebellar Artery ◽

Anterior Communicating Artery ◽

Aneurysm Neck ◽

Proximal Internal Carotid Artery ◽

Cerebellar Artery

IntroductionThe LVIS Blue is an FDA-approved stent with 28% metallic coverage that is indicated for use in conjunction with coil embolization for the treatment of intracranial aneurysms. Given a porosity similar to approved flow diverters and higher than currently available intracranial stents, we sought to evaluate the effectiveness of this device for the treatment of intracranial aneurysms.MethodsWe performed an observational single-center study to evaluate initial occlusion and occlusion at 6-month follow-up for patients treated with the LVIS Blue in conjunction with coil embolization at our institution using the modified Raymond–Roy classification (mRRC), where mRRC 1 indicates complete embolization, mRRC 2 persistent opacification of the aneurysm neck, mRRC 3a filling of the aneurysm dome within coil interstices, and mRRC 3b filling of the aneurysm dome.ResultsSixteen aneurysms were treated with the LVIS Blue device in conjunction with coil embolization with 6-month angiographic follow-up. Aneurysms were treated throughout the intracranial circulation: five proximal internal carotid artery (ICA) (ophthalmic or communicating segments), two superior cerebellar artery, two ICA terminus, two anterior communicating artery, two distal middle cerebral artery, one posterior inferior cerebellar artery, and two basilar tip aneurysms. Post-procedurally, there was one mRRC 1 closure, five mRRC 2 closures, and 10 mRRC 3a or 3b occlusion. At follow-up, all the mRRC 1 and mRRC 3a closures, 85% of the mRRC 3b closures and 75% of the mRRC 2 closures were stable or improved to an mRRC 1 or 2 at follow-up.ConclusionsThe LVIS Blue represents a safe option as a coil adjunct for endovascular embolization within both the proximal and distal anterior and posterior circulation.

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Revascularization and Aneurysm Surgery

Neurosurgery ◽

10.1227/neu.0000000000000312 ◽

2014 ◽

Vol 74 (5) ◽

pp. 482-498 ◽

Cited By ~ 66

Author(s):

M. Yashar S. Kalani ◽

Wyatt Ramey ◽

Felipe C. Albuquerque ◽

Cameron G. McDougall ◽

Peter Nakaji ◽

...

Keyword(s):

Carotid Artery ◽

Cerebral Artery ◽

Superficial Temporal Artery ◽

Posterior Inferior Cerebellar Artery ◽

Superior Cerebellar Artery ◽

External Carotid ◽

Occipital Artery ◽

Aneurysm Surgery ◽

Cerebellar Artery

Abstract BACKGROUND: Given advances in endovascular technique, the indications for revascularization in aneurysm surgery have declined. OBJECTIVE: We sought to define indications, outline technical strategies, and evaluate the outcomes of patients treated with bypass in the endovascular era. METHODS: We retrospectively reviewed all aneurysms treated between September 2006 and February 2013. RESULTS: We identified 54 consecutive patients (16 males and 39 females) with 56 aneurysms. Aneurysms were located along the cervical internal carotid artery (ICA) (n = 1), petrous/cavernous ICA (n = 1), cavernous ICA (n = 16), supraclinoid ICA (n = 7), posterior communicating artery (n = 2), anterior cerebral artery (n = 4), middle cerebral artery (MCA) (n = 13), posterior cerebral artery (PCA) (n = 3), posterior inferior cerebellar artery (n = 4), and vertebrobasilar arteries (n = 5). Revascularization was performed with superficial temporal artery (STA) to MCA bypass (n = 25), STA to superior cerebellar artery (SCA) (n = 3), STA to PCA (n = 1), STA-SCA/STA-PCA (n = 1), occipital artery (OA) to PCA (n = 2), external carotid artery/ICA to MCA (n = 15), OA to MCA (n = 1), OA to posterior inferior cerebellar artery (n = 1), and in situ bypasses (n = 8). At a mean clinical follow-up of 18.5 months, 45 patients (81.8%) had a good outcome (Glasgow Outcome Scale 4 or 5). There were 7 cases of mortality (12.7%) and an additional 9 cases of morbidity (15.8%). At a mean angiographic follow-up of 17.8 months, 14 bypasses were occluded. Excluding the 7 cases of mortality, the majority of aneurysms (n = 42) were obliterated. We identified 7 cases of residual aneurysm and recurrence in 6 patients at follow-up. CONCLUSION: Given current limitations with existing treatments, cerebral revascularization remains an essential technique for aneurysm surgery.

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

Journal of NeuroInterventional Surgery ◽

10.1136/neurintsurg-2020-016261 ◽

2020 ◽

Vol 12 (8) ◽

pp. 777-782

Author(s):

James G Malcolm ◽

Jonathan A Grossberg ◽

Nealen G Laxpati ◽

Ali Alawieh ◽

Frank C Tong ◽

...

Keyword(s):

Posterior Inferior Cerebellar Artery ◽

High Morbidity ◽

Brainstem Compression ◽

Cerebellar Artery ◽

Diseased Segment ◽

Suboccipital Decompression ◽

Pica Aneurysms ◽

Ruptured Intracranial Aneurysms ◽

Dissecting Aneurysms

BackgroundRuptured 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.MethodsA 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.ResultsTwenty-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).ConclusionsEndovascular 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.

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

Journal of NeuroInterventional Surgery ◽

10.1136/neurintsurg-2016-012489 ◽

2016 ◽

Vol 9 (1) ◽

pp. 45-51 ◽

Cited By ~ 17

Author(s):

Feng Xu ◽

Yong Hong ◽

Yongtao Zheng ◽

Qiang Xu ◽

Bing Leng

Keyword(s):

Endovascular Treatment ◽

Posterior Inferior Cerebellar Artery ◽

Endovascular Embolization ◽

Parent Artery ◽

Selective Embolization ◽

Single Center Experience ◽

Cerebellar Artery ◽

Long Term Follow Up ◽

Pica Aneurysms

AimTo report our experience with endovascular treatment of posterior inferior cerebellar artery (PICA) aneurysms.MethodsBetween 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.ResultsImmediate 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).ConclusionsPICA 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.

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Isolated abducens nerve palsy associated with subarachnoid hemorrhage: a localizing sign of ruptured posterior inferior cerebellar artery aneurysms

Journal of Neurosurgery ◽

10.3171/2017.2.jns162951 ◽

2018 ◽

Vol 128 (6) ◽

pp. 1830-1838 ◽

Cited By ~ 2

Author(s):

Jan-Karl Burkhardt ◽

Ethan A. Winkler ◽

George F. Lasker ◽

John K. Yue ◽

Michael T. Lawton

Keyword(s):

Subarachnoid Hemorrhage ◽

Cranial Nerve ◽

Posterior Inferior Cerebellar Artery ◽

Artery Aneurysm ◽

Abducens Nerve ◽

Dorello’S Canal ◽

Ruptured Aneurysms ◽

Fisher Grade ◽

Cerebellar Artery ◽

Pica Aneurysms

OBJECTIVECompressive cranial nerve syndromes can be useful bedside clues to the diagnosis of an enlarging intracranial aneurysm and can also guide subsequent evaluation, as with an acute oculomotor nerve (cranial nerve [CN] III) palsy that is presumed to be a posterior communicating artery aneurysm and a surgical emergency until proven otherwise. The CN VI has a short cisternal segment from the pontomedullary sulcus to Dorello’s canal, remote from most PICA aneurysms but in the hemodynamic pathway of a rupturing PICA aneurysm that projects toward Dorello’s canal. The authors describe a cranial nerve syndrome for posterior inferior cerebellar artery (PICA) aneurysms that associates subarachnoid hemorrhage (SAH) and an isolated abducens nerve (CN VI) palsy.METHODSClinical and radiological data from 106 surgical patients with PICA aneurysms (66 ruptured and 40 unruptured) were retrospectively reviewed. Data from a group of 174 patients with other aneurysmal SAH (aSAH) were analyzed in a similar manner to control for nonspecific effects of SAH. Univariate statistical analysis compared incidence and risk factors associated with CN VI palsy in subarachnoid hemorrhage.RESULTSOverall, 13 (4.6%) of 280 patients had CN VI palsy at presentation, and all of them had ruptured aneurysms (representing 13 [5.4%] of the 240 cases of ruptured aneurysms). CN VI palsies were observed in 12 patients with ruptured PICA aneurysms (12/66 [18.1%]) and 1 patient with other aSAH (1/174 [0.1%], p < 0.0001). PICA aneurysm location in ruptured aneurysms was an independent predictor for CN VI palsy on multivariate analysis (p = 0.001). PICA aneurysm size was not significantly different in patients with or without CN VI palsy (average size 4.4 mm and 5.2 mm, respectively). Within the PICA aneurysm cohort, modified Fisher grade (p = 0.011) and presence of a thick cisternal SAH (modified Fisher Grades 3 and 4) (p = 0.003) were predictors of CN VI palsy. In all patients with ruptured PICA aneurysms and CN VI palsy, dome projection and presumed direction of rupture were directed toward the ipsilateral and/or contralateral Dorello’s canal, in agreement with laterality of the CN palsy. In patients with bilateral CN VI palsies, a medial projection with extensive subarachnoid blood was observed near bilateral canals.CONCLUSIONSThis study establishes a localizing connection between an isolated CN VI palsy, SAH, and an underlying ruptured PICA aneurysm. CN VI palsy is an important clinical sign in aSAH and when present on initial clinical presentation may be assumed to be due to ruptured PICA aneurysms until proven otherwise. The deficit may be ipsilateral, contralateral, or bilateral and is determined by the direction of the aneurysm dome projection and extent of subarachnoid bleeding toward Dorello’s canal, rather than by direct compression.

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The Woven EndoBridge for unruptured intracranial aneurysms: Results in 95 aneurysms from a single center

Interventional Neuroradiology ◽

10.1177/15910199211003428 ◽

2021 ◽

pp. 159101992110034

Author(s):

Tom De Beule ◽

Thierry Boulanger ◽

Sam Heye ◽

Williem J van Rooij ◽

Wim van Zwam ◽

...

Keyword(s):

Posterior Inferior Cerebellar Artery ◽

Superior Cerebellar Artery ◽

Morbidity Rate ◽

Anterior Communicating Artery ◽

Unruptured Aneurysms ◽

Unruptured Intracranial Aneurysms ◽

Cerebellar Artery ◽

Woven Endobridge ◽

The Web

Background and purpose The Woven EndoBridge (WEB) is an intrasaccular flowdisruptor that is increasingly used for the treatment of (wide-necked) aneurysms. We present our experience with the WEB for unruptured aneurysms. Materials and methods Between April 2014 and August 2019, 93 patients with 95 unruptured aneurysms were primarily treated with the WEB. There were 69 women and 24 men, mean age 61 years (median 58, range 37–80). Results Of 95 aneurysms, 86 had been discovered incidentally, 3 were symptomatic and 6 were additional to another ruptured aneurysm. Location was anterior communicating artery 33, middle cerebral artery 29, basilar tip 19, carotid tip 8, posterior communicating artery 4, posterior inferior cerebellar artery 1, superior cerebellar artery 1. Mean aneurysm size was 6 mm (median 6, range 3–13 mm). In one aneurysm additional coils were used and in another, a stent was placed. There was one procedural rupture without clinical sequelae. There were two thrombo-embolic complications leading to permanent deficit in one patient (mRS 2). Morbidity rate was 1.0% (1 of 93, 95%CI 0.01–6.5%) and mortality was 0% (0 of 93, 95%CI 0.0–4.8%). Angiographic follow-up at six months was available in 85 patients with 87 aneurysms (91%). Of 87 aneurysms, 68 (78%) were completely occluded, 14 (16%) had a neck remnant and 5 were incompletely occluded. Four aneurysms were retreated. Retreatment rate was 4.5% (4 of 87, 95%CI 1.7–13.6%). Conclusion WEB treatment of unruptured aneurysms is safe and effective. Additional devices are needed only rarely and retreatment at follow-up is infrequent.

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Microneurosurgical Management of Posterior Inferior Cerebellar Artery Aneurysms: Results of a Consecutive Series

Acta Neurochirurgica Supplement - Trends in Cerebrovascular Surgery and Interventions ◽

10.1007/978-3-030-63453-7_5 ◽

2021 ◽

pp. 33-38

Author(s):

Mattia Del Maestro ◽

Sabino Luzzi ◽

Renato Galzio

Keyword(s):

Posterior Inferior Cerebellar Artery ◽

Cranial Nerves ◽

Lateral Approach ◽

Senior Author ◽

Preoperative Imaging ◽

Imaging Evaluation ◽

Complex Anatomy ◽

Cerebellar Artery ◽

Pica Aneurysms

AbstractAneurysms of the posterior inferior cerebellar artery (PICA) are uncommon. The complex anatomy of PICA and its intimate relationships with medulla, lower cranial nerves, and jugular tubercle makes the surgical treatment of these aneurysms fascinating. The reported is study aimed at a critical review of the overall results of a personal series of PICA aneurysms, treated by the senior author, R. Galzio. Demographics, charts, videos, outcome, and follow-up of a cohort of PICA aneurysms managed in the last 10 years were retrospectively analyzed, focusing only upon those treated with microneurosurgery. Twenty-five patients, harboring a single aneurysm, were operated on. Fifteen aneurysms were ruptured. Nineteen were proximal, all of these being been treated through a far-lateral approach. Trans-condylar or trans-tubercular variants were rarely necessary and however reserved to peculiar cases. Twenty-three aneurysms underwent direct treatment consisting of clip ligation. At 6-month follow-up, 60% of patients had a modified Rankin Score (mRS) of 0–2. Given the high anatomical variability of both PICA and patients’ bony anatomy, a case-by-case meticulous preoperative imaging evaluation is mandatory for the choice of the most suitable and tailored surgical corridor which, in turn, is pivotal to achieve the best outcome.

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Trapping and P2-P3 Posterior Inferior Cerebellar Artery Reanastomosis for Treatment of a Ruptured Fusiform Aneurysm: Application of Fourth-Generation Technique: 2-Dimensional Operative Video

Operative Neurosurgery ◽

10.1093/ons/opab338 ◽

2021 ◽

Author(s):

Tyler T Lazaro ◽

Visish M Srinivasan ◽

Patrick C Cotton ◽

Jacob Cherian ◽

Jeremiah N Johnson

Keyword(s):

Posterior Inferior Cerebellar Artery ◽

Lateral Approach ◽

Fourth Generation ◽

Cerebellar Artery ◽

Far Lateral Approach ◽

Close Proximity ◽

Far Lateral ◽

Pica Aneurysms ◽

Distal Artery

Abstract Aneurysms of the posterior inferior cerebellar artery (PICA) represent the second most common posterior circulation aneurysm and commonly have complex morphology. Various bypass options exist for PICA aneurysms,1-6 depending on their location relative to brainstem perforators and the vertebral artery, and the presence of nearby donor arteries. We present a case of a man in his late 40s who presented with 3 d of severe headache. He was found to have a fusiform right P2-segment PICA aneurysm. Preoperative angiogram demonstrated the aneurysm and a redundant P3 caudal loop that came in close proximity to the healthy P2 segment proximal to the aneurysm. The risks and benefits of the procedure were discussed with the patient, and they consented for a right far lateral approach craniotomy with partial condylectomy for trapping of the aneurysm with bypass. The aneurysm was trapped proximally and distally. The P3 was transected just distal to the aneurysm and brought toward the proximal P2 segment, facilitated by a lack of perforators on this redundant distal artery. An end-to-side anastomosis was performed. Postoperative angiogram demonstrated exclusion of the aneurysm and patent bypass. The patient recovered well and remained without any neurological deficit at 6-mo follow-up. This case demonstrates the use of a “fourth-generation”5,7,8 bypass technique. These techniques represent the next innovation beyond third-generation intracranial-intracranial bypass. In this type 4B reanastomosis bypass, an unconventional orientation of the arteries was used. Whereas reanastomosis is typically performed end-to-end, the natural course of these arteries and the relatively less-mobile proximal P2 segment made end-to-side the preferred option in this case. Fourth-generation bypass techniques open up more configurations for reanastomosis, using the local anatomy to the surgeon's advantage. The patient consented to the described procedure and consented to the publication of their image.

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