Impact of subcallosal artery origin and A1 asymmetry on surgical outcomes of anterior communicating artery aneurysms.

BACKGROUND: Surgical clipping of anterior communicating artery (ACoA) aneurysms remains challenging due to their complex anatomy. Anatomical risk factors for ACoA aneurysm surgery require further elucidation. The aim of this study is to investigate whether proximity of the midline perforating artery, subcallosal artery (SubCA), and associated anomaly of the ACoA complex affect functional outcomes of ACoA aneurysm surgery. METHODS: A total of 92 patients with both unruptured and ruptured ACoA aneurysms, who underwent surgical clipping, were retrospectively analyzed from a multicenter, observational cohort database. Association of ACoA anatomy with SubCA origin at the aneurysmal neck under microsurgical observation was analyzed in the interhemispheric approach subgroup (n = 56). Then, we evaluated whether anatomical factors associated with SubCA neck origin affected surgical outcomes in the entire cohort (both interhemispheric and pterional approaches, n = 92). RESULTS: In the interhemispheric approach cohort, combination of A1 asymmetry and aneurysmal size ≥ 5.0 mm was stratified to have the highest probability of the SubCA neck origin by a decision tree analysis. Then, among the entire cohort using either interhemispheric or pterional approach, combination of A1 asymmetry and aneurysmal size ≥ 5.0 mm was significantly associated with poor functional outcomes by multivariable logistic regression analysis (OR 6.76; 95% CI 1.19-38.5; p = 0.03) as compared with A1 symmetry group in the acute subarachnoid hemorrhage settings. CONCLUSION: Combination of A1 asymmetry and larger aneurysmal size was significantly associated with SubCA aneurysmal neck origin and poor functional outcomes in ACoA aneurysm surgery. Interhemispheric approach may be proposed to provide a wider and unobstructed view of SubCA for ACoA aneurysms with this high-risk anatomical variant.

Long-Term Volume Reduction Effects of Endovascular Embolization for Intracranial Meningioma: Preliminary Experience of 5 Cases.

BACKGROUND: Preoperative endovascular embolization of intracranial meningiomas denatures the tumor tissue, reduces intraoperative blood loss, and facilitates surgical removal. However, as most meningiomas are surgically removed within a few days after embolization, the effect of long-term volume reduction of the tumor due to the endovascular embolization remains unknown. METHODS: Five patients with intracranial meningioma underwent endovascular embolization between January 2006 and December 2014 and were followed without surgical resection for >14 days. The reduction in tumor and peritumoral edema volumes on sequential head magnetic resonance imaging, along with the clinical symptoms, were retrospectively reviewed. RESULTS: All the tumors indicated a 10%-30% volume reduction 30 days after embolization, which continued thereafter; no meningioma regrowth was observed for >90 days in 2 of 5 cases. Moreover, the peritumoral edema volume was reduced by 30%-70% at 30 days after embolization, and no subsequent increase was observed for >60 days in 4 of 5 cases. The neurologic symptoms related to the tumor mass effect improved after embolization. CONCLUSIONS: Endovascular embolization of intracranial meningiomas with n-butyl cyanoacrylate reduced the tumor and peritumoral edema volumes by 10%-30% and 30%-70%, respectively, within 30 days. Volume and edema reduction effect of embolization may last longer than expected, beyond the timing when most meningiomas are resected after embolization. In this study, we described our preliminary results of the volume reduction of intracranial meningiomas that were embolized using n-butyl cyanoacrylate and monitored without any surgical resection for >14 days. We believe that our study makes a significant contribution to the literature because we showed that volume and edema reduction effect of embolization may last longer than expected, beyond the timing when most meningiomas are resected after embolization.

Infiltrated Embolization of Meningioma with Dilute Cyanoacrylate Glue.

We describe the efficacy and technical aspects of infiltrated preoperative embolization of meningioma by penetration of very dilute glue. In this method, a 13% n-butyl-cyanoacrylate (NBCA)-lipiodol mixture is injected extremely slowly from the middle meningeal artery (MMA) in a similar manner to plug and push injection of ethylene vinyl alcohol copolymer mixed with tantalum and dimethyl sulfoxide (Onyx®) after the tortuous side feeders are proximally embolized. The glue is infiltrated into small tumor arteries and extends to inaccessible feeders from deep meningeal arteries. Since 2011, we have used this technique in the embolization of 32 cases preoperatively diagnosed with meningioma. Intratumoral embolization was possible in 30 cases (94%), and a greater than 50% reduction in contrast area of contrast-enhanced T1-weighted MR imaging (T1-WI) was achieved in 18 cases (56%). Two cases achieved complete devascularization, showing a remarkable shrinkage in tumor size after embolization. If excessive reflux of embolization and the resulting migration of glue into normal arteries is achieved, this method provides extremely effective devascularization on surgical extirpation. It might also be applicable to surgically untreatable meningiomas as a semi-radical treatment option.

Significance of Anomalous Anterior Inferior Cerebellar Artery-Posterior Inferior Cerebellar Artery Common Trunk Compression in Microvascular Decompression for Hemifacial Spasm.

BACKGROUND: The anterior inferior cerebellar artery-posterior inferior cerebellar artery (AICA-PICA) common trunk anomaly is reportedly one of the most common vessel variants in the posterior circulation, but reports of hemifacial spasm (HFS) associated with AICA-PICA common trunk are very rare. In the present study, we describe methods of microvascular decompression (MVD) for HFS caused by AICA-PICA common trunk compression. METHODS: Among 159 patients who underwent MVD for HFS, 16 patients had compression of the root exit zone by the AICA-PICA common trunk anomaly. The types of compression were classified into 2 groups: common trunk artery compression group and branching vessel compression group. RESULTS: The common trunk artery compression group consisted of 11 patients (69%), and the branching vessel compression group consisted of 5 patients (31%). The rostral branch (feeding the original AICA territory) coursed between the seventh and eighth cranial nerves in 5 patients, and in 13 patients (81%), the offending vessel harbored perforators around the root exit zone. Among 16 patients, 14 (87.5%) required interposition of the common trunk or the branching vessel, and in 2 patients, decompression was completed by the transposition method. Fifteen patients experienced sufficient results, and 1 had severe residual spasm. Transient facial palsy developed in 2 patients. No patients encountered recurrence. CONCLUSIONS: Reports concerning decompression methods of AICA-PICA common trunk anomaly are very rare. The tortuosity of the common trunk and perforators from the offending vessel make the usual repositioning of the offending artery much more difficult, and adequate decompression techniques are required for successful MVD.

Reappearance of Cranial Nerve Dysfunction Symptoms Caused by New Artery Compression More than 20 Years after Initially Successful Microvascular Decompression: Report of Two Cases.

Reappearance of symptoms of cranial nerve dysfunction is not uncommon after successful microvascular decompression (MVD). The purpose of this study was to report two quite unusual cases of recurrent and newly developed hemifacial spasm (HFS) caused by a new conflicting artery more than 20 years after the first successful surgery. In Case 1, the first MVD was performed for HFS caused by the posterior inferior cerebellar artery (PICA) when the patient was 38 years old. After 26 symptom-free years, HFS recurred on the same side of the face due to compression by the newly developed offending AICA. In Case 2, the patient was first operated on for trigeminal neuralgia by transposition of the AICA at 49 years old, but 20 symptom-free years after the first MVD, a new offending PICA compressed the facial nerve on the same side, causing HFS. These two patients underwent reoperation and gained satisfactory results postoperatively. Reappearance of symptoms related to compression of the root exit zone (REZ) by a new offending artery after such a long symptom-free interval since the first effective MVD is rare. Here, we describe two such unusual cases and discuss how to manage and prevent such reappearance of symptoms after a long time interval.

Microvascular Decompression for Hemifacial Spasm Associated with Bilateral Vertebral Artery Compression.

BACKGROUND: Microvascular decompression (MVD) has been established as an effective treatment for hemifacial spasm (HFS). However, replacement of bilateral vertebral arteries (VAs) from the root exit zone (REZ) is difficult and requires special techniques. Reports of HFS cases associated with bilateral VA compression are quite rare. This study investigated the characteristics of these arteries and methods for safe and definite decompression. METHODS: Among 131 patients who underwent MVD for HFS, 33 patients (25.2%) had associated VA compression; 4 patients (3.1%) had bilateral VA compression. Sufficient dissection of the arachnoid membrane allowed good visualization around the REZ, and the dolichoectatic VAs were successfully transposed and fixed to the nearby dura mater in 3 cases. RESULTS: The offending arteries were bilateral VAs plus the posterior inferior cerebellar artery in 2 cases, bilateral VAs plus the anterior inferior cerebellar artery-posterior inferior cerebellar artery in 1 case, and bilateral VAs in 1 case. The contralateral VA of the symptomatic side was more ectatic, dolichoectatic, and tougher than the ipsilateral VA in 3 patients and was difficult to remove. In 3 patients treated with the transposition method, complete resolution of spasm was experienced immediately after surgery. Minimal residual spasm occurred in 1 patient treated with the interposition method. Transient facial palsy developed in 1 case, and moderate hearing loss developed in another case. CONCLUSIONS: HFS caused by bilateral VA compression is rare; however, replacement of VAs from the REZ is not easy because such VAs are invariably dolichoectatic and tough. Treatment of such cases requires special techniques.

Risk factors and consequences of unexpected trapping for ruptured anterior communicating artery aneurysms.

BACKGROUND: While clipping cerebral aneurysms at the neck is optimal, in some cases this is not possible and other strategies are necessary. The purpose of this study was to describe the incidence, risk factors, and outcomes for inability to clip reconstruct ruptured anterior communicating artery (ACoA) aneurysms. METHODS: Of the 70 cases of ruptured ACoA aneurysms between January 2006 and December 2013, our institutional experience revealed four cases of small ACoA aneurysms that had been considered clippable prior to operation but required trapping. When a unilateral A2 segment of anterior cerebral artery (ACA) was compromised by trapping, revascularization was performed by bypass surgery. Clinical presentation, angiographic characteristics, operative approach, intraoperative findings, and treatment outcomes were assessed. RESULTS: Very small aneurysm under 3 mm was a risk factor for unexpected trapping. The reason for unexpected trapping was laceration of the aneurysmal neck in two cases, and lack of clippaple component due to disintegration of entire aneurysmal wall at the time of rupture in the others. Aneurysms with bilateral A1 were treated with sole trapping through pterional approach in two cases. The other two cases had hypoplastic unilateral A1 segment of ACA and were treated with combination of aneurysm trapping and revascularization of A2 segment of ACA through interhemispheric approach. No patients had new cerebral infarctions of cortical ACA territory from surgery. Cognitive dysfunction was observed in three cases, but all patients became independent at 12-month follow up. CONCLUSIONS: Unexpected trapping was performed when ruptured ACoA aneurysms were unclippable. Trapping with or without bypass can result in reasonable outcomes, with acceptable risk of cognitive dysfunction.

Endovascular treatment of sphenoid wing dural arteriovenous fistula with pure cortical venous drainage.

Curative endovascular treatment of sphenoid wing dural arteriovenous fistula (dAVF) with pure cortical venous drainage is challenging because of its rarity, lack of accessible dural sinus for transvenous embolization (TVE), and proximity of skull base vital regions. Direct surgery to disconnect venous reflux has been favored. We report the curative endovascular treatment of two sphenoid wing dAVFs with pure cortical venous drainage. One patient revealed complete obliteration of dAVF by a single session of transarterial embolization (TAE). As part of strategic TAE for this complex dAVF, we used a novel approach to create a complete flow-arrest condition in which coils and an occlusion balloon were combined. A liquid agent was then injected across the pathological fistula and into the parent venous apparatus, thereby occluding the lesion. The other patient was treated with percutaneous TVE after TAE was unsuccessful. With a specific strategy and appropriate devices, the microcatheter was successfully introduced through sigmoid sinus, transverse sinus, superior sagittal sinus, and refluxing cortical vein by puncture of the jugular vein. Coils were deployed at the venous side of the fistula, resulting in successful obliteration of the dAVF. Sphenoid wing dAVF with pure cortical venous drainage could be curable by endovascular treatment with proper strategy and instruments when anatomical condition permits.

[Research of postoperative complications after coil protrusions in embolization of unruptured cerebral aneurysms].

OBJECTIVES: Postoperative courses in "coil-protruded" cases in embolization of unruptured cerebral aneurysms remain unknown. The purpose of this study is to investigate postoperative complications after coil protrusions. METHODS: From May 2003 to December 2007, 90 consecutive cases with unruptured cerebral aneurysm treated by coil embolization were examined at National Cerebral and Cardiovascular Center. All patients received antiplatelet therapy prior to the procedure. The patterns of protrusions were classified into three; tail (T), loop (L), unraveled (U). RESULTS: Coil protrusions were observed in 17 cases (18.9%). Symptomatic ischemic complications occurred in 7 cases (7.8%). One case occurred in coil protrusions (group P) and 6 cases occurred in no coil protrusions (group N). Infarctions on MR diffusion-weighted image within 7 days after embolization were found in 10 cases (58.8%) in group P and in 28 cases (38.4%) in group N. Infarction on MR fluid attenuated inversion recovery 7 days or later were found in 0 in group P, and in 4 (5.5%) in group N. There were no significant differences. The number of each protrusion pattern was as follows: T was 12 cases, L was 3 cases and U was 2 cases. Symptomatic ischemia was observed in one case (8.3%) in T. Infarctions on MR diffusion-weighted image within 7 days after embolization were found in 7 (58.3%), 1 (33.3%) and 2 (100%), respectively. There were no significant differences between the three morphological patterns. CONCLUSION: In this retrospective study, coil protrusion after embolization of unruptured cerebral aneurysms on antiplatelet therapy, did not increase the incidence of ischemic complications.

[Carotid artery stenting for radiation-induced carotid stenosis].

PURPOSE AND METHODS: To evaluate the outcome and lesion characteristics in patients with radiation induced carotid stenoses (RI-CS) treated by carotid artery stenting (CAS), a total of five patients with RI-CS (six lesions) were retrospectively analyzed. RESULTS: Four lesions had their most stenotic site at the common carotid artery (CCA). All cases had contralateral carotid or vertebral artery stenosis (>50%). All patients had risk factors of atherosclerosis and all lesions contained unstable plaques at the stenotic site. A total of seven procedures were carried out and procedural success was obtained in all cases. Asymptomatic embolic infarctions associated with procedure were observed in four cases by diffusion-weighted MR imaging. In-stent thrombi were observed in two cases, one of which developed a neurological symptom three days after the procedure. CONCLUSION: CAS is a technically successful intervention for RI-CS. Care should be taken according to the characteristics of the plaque, which usually is vulnerable and long. Appropriate choice of a protection method could help in the reduction of unfavorable embolic complications and close postoperative follow up is mandatory.

Multiple cerebral aneurysms in a patient with CREST syndrome.

Systemic sclerosis (SSc) associated with cerebral aneurysm is rare. We describe a patient with multiple cerebral aneurysms with the calcinosis, Raynaud's phenomenon, esophageal dysmotility, sclerodactyly, telangiectasia (CREST) variant of SSc. A 61-year-old woman with a 20-year history of CREST syndrome was incidentally found to have four cerebral aneurysms located at the C2, C3 and C5 segments of the right internal carotid artery (ICA) and the C2 segment of the left ICA. The bilateral C2 segment aneurysms were successfully clipped using 2-stage surgery. To date, intracranial aneurysms have been reported in only two other patients with CREST syndrome. We hypothesize that the pathogenesis of the aneurysm is related to CREST syndrome. Elucidating the true incidence of cerebral aneurysms associated with CREST syndrome would help to clarify the relationship between SSc-related autoantibodies and aneurysm formation.

Growth potential and response to multimodality treatment of partially thrombosed large or giant aneurysms in the posterior circulation.

OBJECTIVE: This study examined the growth potential and response to multimodality treatment of partially thrombosed large or giant aneurysms in the posterior circulation. METHODS: The 17 aneurysms arose from nonbranching sites of the vertebral artery (VA) in 6 patients and from branching sites in 11 patients (the VA-posteroinferior cerebellar artery [PICA], 3 cases; basilar artery [BA] fenestration, 1 case; BA-superior cerebellar artery [SCA], 5 cases; and BA tip, 2 cases). RESULTS: Endovascular trapping was performed in 5 VA aneurysms at nonbranching sites, 2 VA-PICA cases with or without revascularization of the PICA, and 1 BA fenestration case. Endosaccular embolization was performed in 2 BA-SCA aneurysms as the sole treatment or after superficial temporal artery-SCA bypass for a broad-necked lesion. Surgical proximal occlusion (PO) with or without revascularization of the PICA was performed in 2 VA cases. Endovascular treatment failed to prevent growth in 1 VA-PICA case and the broad-necked BA-SCA case. Simple flow alteration by PO of 3 BA aneurysms, with gadolinium enhancement on T1-weighted images, did not prevent growth. Maximum flow reduction by various combinations of bypass (superficial temporal artery-posterior cerebral artery or superficial temporal artery-SCA) and BA PO, aimed at reducing hemodynamic stress on the neck, was tailored to 5 cases, including those refractory to PO; it achieved marked shrinkage in 2 cases and stabilization of the aneurysms in 3 cases. The aneurysms harboring neither gadolinium enhancement nor hyperintensity on fluid-attenuated inversion recovery images showed significantly lower growth potential before treatment and a lesser degree of shrinkage after tailored treatment than the remaining cases (P = 0.03 and P = 0.01, respectively). Overall, marked shrinkage was achieved in 27%, moderate shrinkage in 20%, stabilization in 47%, enlargement in 7%, and favorable outcome in 71%. Maximum flow reduction strategy for BA aneurysms tended to show higher shrinking efficacy than endovascular trapping for VA and BA aneurysms (P = 0.08). CONCLUSION: For aneurysms at nonbranching sites, endovascular trapping may be effective, although its shrinking efficacy may be moderate. For the most formidable BA aneurysms at branching sites, maximum flow reduction may cause marked shrinkage, even of aggressive lesions.

Successful "blind-alley" formation with bypass surgery for a partially thrombosed giant basilar artery tip aneurysm refractory to upper basilar artery obliteration. Case report.

Partially thrombosed giant aneurysms that are located at the basilar artery (BA) bifurcation and are not amenable to clip application are among the most challenging lesions for neurosurgeons. They compress vital structures such as the brainstem and the thalamus, and the prognosis is extremely poor when they are left untreated. Although obliteration of the upper BA is a promising approach for these aneurysms, some lesions are refractory to this treatment, and effective additional strategies have not been clearly established. The authors report a case treated by placement of clips in the unilateral posterior cerebral artery (PCA) and posterior communicating artery as well as by superficial temporal artery-PCA bypass after unsuccessful upper BA obliteration. Complete thrombosis and dramatic shrinkage of the aneurysm were obtained.

[Therapeutic strategy for isolated dissecting aneurysms of the posterior inferior cerebellar artery: report of three cases and review of literature].

Dissecting aneurysm of the posterior inferior cerebellar artery (PICA) is a relatively rare disease and its treatment has not been well established. The authors analyzed the clinical and anatomical features of 38 reported lesions and three of our cases to clarify the "best therapeutic modality". The average age was 45.0 years old and 27 patients were male. Left-sided predominance (26 cases) was noted. As to the mode of onset, 23 cases were subarachnoid hemorrhage, 16 were ischemia, and 6 were Wallenberg's syndrome. Anatomically, the sites of dissection were located in the proximal segment of PICA in 31 lesions (75.6%). Review of the cases show that 30 (75%) patients underwent surgical therapy, and 7 (17.5%) patients underwent endovascular treatment. Twenty six patients who took surgical therapy and 5 patients who took endovascular treatment had excellent or good outcome. The critical point in therapeutic procedure is the preservation of perforating branches arising from PICA, therefore surgical trapping with the revascularization of PICA (usually extracranial-PICA anastomosis), in which these tiny branches are secured under microscopic manipulation, has the advantage in principle.

Unruptured paraclinoid aneurysms: a management strategy.

OBJECT: To elucidate an optimal managenent strategy for unruptured paraclinoid aneurysms, the authors retrospectively reviewed their experience in the treatment of 100 patients who underwent 112 procedures for111 paraclinoid aneurysms performed using direct surgery and/or endovascular treatment. METHODS: Between 1997 and 2002, 111 unruptured paraclinoid aneurysms categorized according to a modified al-Rodhan classification (Group la, 30 anterior wall lesions; Group lb, 25 ventral paraclinoid lesions; Group IL 18 true ophthalmic artery lesions; Group III, 37 carotid cave lesions; and Group IV, one transitional lesion) were treated by direct surgery (35 lesions) and/or endovascular treatment (77 lesions) (one aneurysm was treated by both procedures). In lesions in Groups Ia, Ib, II, and III that were treated by endovascular treatment, complete aneurysm obliteration was achieved in 50, 65, 50, and 78%, respectively, and the combined transient and permanent morbidity rates due to cerebral embolic events were 20, 25, 20, and 13.9%, respectively. Overall, the transient morbidity rate after endovascular treatment was 14.3% and the permanent morbidity rate was 6.5%. Notably, permanent visual deficits caused by retinal embolism occurred after endovascular treatment in two patients with Group II aneurysms. Direct surgery was mainly performed in Groups Ia (20 lesions), Ib (five lesions), and II (eight lesions), with complete neck clip occlusion achieved in 80, 80, and 71.4%, respectively; the transient and permanent morbidity rates associated with aneurysms treated by surgery were 8.6 and 2.9%, respectively. CONCLUSIONS: Endovascular therapy for superiorly projecting paraclinoid aneurysms (Groups Ia and II) is associated with lower rates of complete obliteration than direct surgery, and with rates of cerebral embolic events comparable to those of endovascular treatment in the other groups. Furthermore, endovascular treatment for Group II aneurysms entails additional risks of retinal embolism. Therefore, direct surgery is recommended for the treatment of paraclinoid aneurysms projecting superiorly. For other groups, especially for Group III, endovascular treatment is the acceptable first line of therapy.

[Management strategy for infectious cerebral aneurysms: report of four cases].

The surgical and/or endovascular treatment of four patients with infectious cerebral aneurysm associated with infective endocarditis was reported. Two patients presented with intracerebral hemorrhage. One of them, with large hematoma, was treated surgically and the other, with small hematoma, was treated by endovascular surgery. The third patient, with unruptured aneurysm of the distal anterior cerebral artery, was treated by endovascular parent-artery occlusion without neurological deterioration. The fourth patient, with unruptured aneurysm of the distal middle cerebral artery, was initially treated with antibiotics, resulting in stabilization of the aneurysm. However, three weeks after open heart surgery, the aneurysm ruptured, causing a large cerebral hematoma. Despite prompt evacuation of the hematoma and surgical resection of the aneurysm, this patient remained in a vegetative state. Management strategy of intracranial infective aneurysms is discussed.

[Restenosis after CEA: pathogenesis and treatment].

This study examined the incidence and mechanism of restenosis after carotid endarterectomy (CEA) in Japanese patients. To determine the optimal management for carotid restenosis, we retrospectively compared re-CEA with stent placement. One hundred and twenty-six patients who had received 135 CEA with primary suture were studied with angiography or duplex ultra-sonography as a follow-up study to detect restenosis (> 50% diameter reduction). Data was collected regarding demographics of the patients suffering restenosis, including age, sex, other risk factors. Recurrent carotid stenosis (more than 50% stenosis) developed in 9 CEA sites (6.7%) during a mean follow-up interval of 11.0 months (4.7-46.7 months). Recurrent carotid stenosis occurred to a significantly higher degree in women (p = 0.015). There was no significant difference in other risk factors. All patients who developed carotid restenosis were asymptomatic. Re-do CEA and carotid stenting were used to treat restenosis in 3 and 5 patients, respectively. No operative procedure was performed in the remaining one patient with milder restenosis (55%). The 30-day stroke morbidity-mortality rate was 33.3% in CEA and 0% in stent placement. In only one of 4 early restenosis patients, there was a bright lesion in diffusion weighted MR images after stent placement. To treat restenosis after CEA, stent placement is indicated because of a lower risk of distal emboli and there being no need to dissect the previous wound. To prevent restenosis, through plaque removal is necessary and patch closure may be needed especially in females.

Dissecting aneurysms of the vertebral artery: a management strategy.

OBJECT: The authors present a retrospective analysis of their experience in the treatment of vertebral artery (VA) dissecting aneurysms and propose a management strategy for such aneurysms, with special emphasis on the most formidable VA dissecting aneurysms, which involve the origin of the posterior inferior cerebellar artery (PICA). METHODS: Since 1998, 18 patients with VA dissecting aneurysms, 11 of whom presented with subarachnoid hemorrhage (SAH), have been treated by endovascular surgery at the authors' institution. Obliteration of the entire segment of the dissected site with coils (internal trapping) was performed for aneurysms without involvement of the origin of the PICA (12 cases; among these the treatment-related morbidity rate was 16.7%). The treatment strategy applied to PICA-involved VA dissecting aneurysms presenting with SAH (three cases) included proximal occlusion of the parent artery followed by internal trapping of the aneurysm (one case), proximal occlusion of the parent artery followed by occipital artery (OA)-PICA bypass (one case), and two-staged internal trapping of the aneurysm involving double PICAs (one case). For PICA-involved VA dissecting aneurysms that were not associated with SAH at presentation (three cases), OA-PICA bypass was performed and followed by internal trapping of the aneurysm (two cases). In the remaining case in which a fetal-type posterior communicating artery was present, internal trapping was performed following successful balloon test occlusion (BTO). Overall, there was no sign of infarction in the PICA territory, despite complete occlusion of aneurysms involving the PICA. There was no recurrent bleeding or ischemic symptoms during the follow-up periods. The overall treatment-related morbidity rate for the VA dissecting aneurysms involving the PICA was 16.7%. CONCLUSIONS: Dissecting VA aneurysms that do not involve the PICA can be safely treated by internal trapping. For those lesions that do involve the PICA, a decision-making algorithm is advocated to maximize the efficacy of the treatment as well as to minimize the risks of treatment-related morbidity based on BTO.