Background and Purpose: Significantly more flow diverter (FD) stents, such as the Pipeline^TM Flex Embolization Device (PFED; Medtronic, Irvine, CA, USA), are being deployed to treat large internal aneurysms. However, the safety and effects of these devices for treating recurrent intracranial aneurysms after endovascular therapy have not been evaluated in detail. The present study aimed to determine the safety of FDs in treating recurrent intracranial aneurysms.

Methods: Clinical and radiological data from five patients (mean age, 69 years; female, 4; male, 1), with five aneurysms (average size, 18.4 mm), who underwent endovascular treatment with PFED for recurrent internal carotid artery aneurysms at the Osaka National Hospital from October 2015 to July 2018 were retrospectively analyzed.

Results: During a mean follow-up of 21 months, 3 (60%) and 2 (40%) aneurysms became completely and partially occluded, respectively. One female patient with distal embolism completely recovered three months after treatment.

Conclusion: The PFED is minimally invasive, alleviates the mass effects of aneurysms, and would thus be important for treating recurrent intracranial aneurysms after endovascular treatment.

Most unruptured cerebral aneurysms are asymptomatic and associated with extremely low rates of surgical complications. Therefore, the control of ruptures before clipping the aneurysmal neck should be of considerable prognostic significance. We retrospectively assessed data from 255 consecutive surgical patients with a total of 312 aneurysms treated between September 2006 and June 2019, and selected eight aneurysms that ruptured before clipping. Of the eight intraoperative aneurysm ruptures, four (50%) were anterior communicating artery aneurysms (Acom Ans). The incidence of intraoperative aneurysm rupture was 3.1% of patients and 2.6% of aneurysms. The main contributor to aneurysm rupture was dissection around the aneurysms. The outcomes were favorable in all patients. We considered that the following factors might be involved in the likelihood of an Acom An rupture: the Acom is developmentally fragile, involves several blood vessels, is located deep in the brain, and adheres to the optic chiasma, in addition to the frontal lobe. These considerations indicate that direct surgical manipulation, especially for Acom Ans, can result in intraoperative ruptures and is thus very important for surgeons to bear in mind.

Objective: Intraoperative monitoring of motor evoked potentials (MEPs) is useful for preventing postoperative motor dysfunction during microsurgical clipping of cerebral aneurysms. However, it is uncertain whether MEP is useful for surgery in patients with preoperative hemiparesis. Furthermore, when the MEP disappears, we are not able to anticipate the degree of motor dysfunction. We examined the correlation between MEP findings and functional prognosis in patients with rup- tured cerebral aneurysms with preoperative hemiparesis.

Methods: Among the 127 cases of ruptured cerebral aneurysms, 12 patients with preoperative hemiparesis were included. Five of the 12 patients had subarachnoid hemorrhage (SAH) alone, 2 had temporal hematoma, 2 had Sylvian hematoma, and 3 had putaminal hematoma. Transcranial stimulation MEPs (Tc-MEPs) were recorded on the affected and healthy sides with stimulation intensity up to 200 mA. Cortical stimulation MEP (C-MEP) was recorded only on the affected side, and the stimulation intensity was up to 25 mA. We examined the correlation between the stimulation thresholds of TcMEP and C-MEP, and the degree of postoperative hemiparesis (manual muscle test [MMT] ). In TcMEP, the affected side threshold/healthy side threshold (A/H) ratio was also evaluated. MMT was defined as 5/5 without paralysis, 5-/5 and 4/5 as mild paralysis, and 3/5 to 1/5 as severe paralysis.

Results: There were five cases without paralysis, none of which were accompanied by an intracranial hematoma. There were 3 cases of mild paralysis and 4 of severe paralysis, all of which were accompanied by intracranial hematoma. C-MEP could be recorded in cases with or without mild paralysis; however, it could not be recorded in cases of severe paralysis. A/H ratios were 1.0-1.3 (mean 1.1), 1.0-1.4 (mean 1.2), and 1.5-3.2 (mean 2.5) in the groups without paralysis, with mild hemiparesis, and with severe paralysis, respectively. The thresholds on the affected side of Tc-MEP were significantly higher than those on the healthy side in patients with severe paresis (p＜0.05).

Conclusions: Even though the patients presented with severe preoperative paralysis, there was a possibility that the functional prognosis might be good in cases where C-MEP could be recorded and where there were small A/H ratios in Tc-MEP. It was suggested that the severity of paralysis could be predicted by examining the A/H ratio of Tc-MEP, if MEP disappears during surgery. The number of cases is still small, and further studies are necessary.

We report the clinical features of six patients who underwent direct surgery at our hospital for large or giant cervical internal carotid artery aneurysms (CICAAs). Three patients underwent aneurysm resection with end-to-end anastomosis of the internal carotid artery (ICA), and three patients underwent proximal occlusion of the ICA. Five patients had good outcomes, including one case with transient dysphagia. In one case, a middle cerebral artery embolization occurred due to ICA occlusion, and the patient died due to extensive cerebral infarction. To avoid ischemic complications in direct surgery for CICAA, preoperative cerebral blood flow assessment and perioperative antithrombotic therapy are indispensable. In addition, to avoid lower cranial nerve palsy during dissection of the aneurysm from surrounding structures, a bloodless surgical field; safe, reliable internal shunt insertion and vascular suture techniques; and an accurate understanding of the anatomy of the neck are also necessary.

Peripheral cerebellar artery aneurysms are very rare lesions. The reported incidences of the superior cerebellar artery (SCA), anterior inferior cerebellar artery (AICA), and posterior inferior cerebellar artery (PICA) peripheral aneurysms are 0.07%, 0.3%, and 1.0%, respectively. We performed neck clipping of one SCA aneurysm, one AICA aneurysm, and five PICA aneurysms between 2009 and 2018. The three aneurysms were ruptured ones. The outcome was good, with minimal surgical complications in all seven patients. Three illustrative cases are presented in detail.

Case 1 was of a 77-year-old woman who presented with a subarachnoid hemorrhage due to rupture of a peripheral SCA aneurysm. Neck clipping of the aneurysm was successfully performed using the occipital interhemispheric transtentorial approach. Case 2 involved a 68-year-old woman with a partially thrombosed, unruptured aneurysm of the PICA. The aneurysm was found embedded in the floor of the fourth ventricle and was associated with perianeurysmal edema of the medulla oblongata. The aneurysm was exposed using trans-cerebello-medullary fissure approach, and neck clipping was successfully performed. Case 3 involved a 56-year-old man with a peripheral AICA aneurysm. The aneurysm was exposed between the abducens and the auditory nerves through the lateral suboccipital route. The aneurysm was occluded without damage to the cranial nerves or brainstem.

Case selection is important in performing microsurgery or intravascular surgery for peripheral cerebellar aneurysms. Neck clipping should be applied as far as possible to achieve complete aneurysm obstruction without sacrificing the parent artery.

Blood blister-like aneurysm (BBA) is associated with high rebleeding and mortality rates. Treating a ruptured BBA arising from the anterior wall of the internal carotid artery is particularly challenging. Several reports on numerous treatment modalities suggest the following techniques: direct clipping and wrap-clipping, trapping using the extracranial to intracranial bypass (EC-IC bypass), coil embolization, stent-assisted coil embolization, and flow diverting stent. However, there is currently no definite and standard treatment strategy to manage BBA. It is our understanding that certain cases of BBA that permit a clear visualization of the neck of the aneurysm can be treated via direct clipping. Direct clipping is considered the best treatment strategy as it is possible to maintain anterograde blood flow. Furthermore, we can be prepared to regulate unexpected bleeding from the aneurysm and subsequently reduce its internal pressure by positioning an assist balloon directly under the aneurysm. Thereafter, we can successfully dissect and observe the neck of the aneurysm and safely attach a clip to the same. Therefore, a combination of direct clipping and an assist balloon can be considered as a new treatment strategy for BBA.

The lateral spinal arteries (LSA) serve as an important collateral pathway when there is occlusion of the vertebral artery (VA) or posterior inferior cerebellar artery (PICA). We report a case of subarachnoid hemorrhage (SAH) due to a ruptured LSA. A 69-year-old female was admitted to our department due to sudden posterior cervical pain. Computed tomography (CT) of the head showed SAH in the craniocervical junction with intraventricular hemorrhaging. The digital subtraction angiography (DSA) showed the LSA, with an aneurysm, which serves as collateral circulation into the PICA. Endovascular treatment was performed and the proximal parent artery was occluded because it was not possible to navigate a microcatheter close enough to the aneurysm. However, after 18 days, the DSA showed new collateral circulation and the aneurysm was present again. We decided to perform direct surgery to remove the aneurysm after which the patient made a good recovery. Ruptured aneurysms of the LSA are rare, and occlusion of the proximal parent artery without obliteration of the aneurysm can result in early revascularization into the aneurysm via a newly-formed collateral network. Direct surgery can be an effective cure.

We encountered four female patients aged 45-66 years (mean age, 56.3 years) who were treated with stent-assisted embolization of the posterior inferior cerebellar artery (PICA) aneurysm to preserve the artery. One and three patients had a right and left PICA aneurysm, respectively, and two aneurysms were ruptured. In all patients, the PICA ipsilateral to the aneurysm was inserted with a microcatheter from the contralateral vertebral artery (VA), and subsequently embolized by stent placement distal to the VA. A postoperative asymptomatic cerebellar infarction was observed in one patient, but no complications occurred and all patients exhibited a modified Rankin score of 0 before discharge. No stent obstruction occurred throughout the postoperative follow-up period (6-12 months). The stent could be expanded in a thin blood vessel, such as the PICA, to embolize the aneurysm. However, cases of obstruction have been reported. Thus, stent application in each patient should be investigated.

Aneurysms involving an accessory anterior cerebral artery (ACA), a vascular anomaly arising from the anterior communicating artery, are extremely rare. We report here a case of multiple ruptured aneurysms involving the accessory ACA, which was treated with a two-stage surgery, resulting in a satisfactory postoperative course. A 54-year-old woman presented at our hospital complaining of a severe headache. Computed tomography (CT) of the head revealed a subarachnoid hemorrhage and intracerebral hematoma at the right medial frontal lobe. CT angiography revealed aneurysms in the anterior communicating artery complex and the distal portion of the accessory ACA. The rupture of the distal aneurysm caused the hemorrhage, and thus the aneurysm was clipped. One month later, stent-assisted coil embolization of the anterior communicating artery aneurysm was performed. After a satisfactory postoperative course, the patient was discharged with a modified Rankin score of 2. Accessory ACA aneurysms involve an extremely complex morphological structure. In the case of multiple aneurysms, an adequate surgical strategy for treating each aneurysm should be adopted.

Oculomotor nerve palsy (ONP) may be caused by compression of the oculomotor nerve by the internal carotid artery-posterior communicating artery aneurysm (IC-PC AN) and/or basilar artery-superior cerebellar artery aneurysm (BA-SCA AN). During clipping, the oculomotor nerve can be observed directly and decompressed. However, the positional relationship between the aneurysm and oculomotor nerve is difficult to evaluate during intra-aneurysmal embolization. Constructive interference in steady state (CISS) allows detailed study of blood vessels and nerves in subarachnoid cisterns with high resolution. We herein report two cases of cerebral aneurysms presenting with ONP that were anatomically evaluated using CISS. Case 1 involved an 81-year-old woman who presented with a severe headache. She had no other neurological deficits. Computed tomography (CT) showed subarachnoid hemorrhage, while cerebral angiography revealed a left BA-SCA AN. Intra-aneurysmal embolization was performed; the framing coil spread throughout the aneurysm, and the other coils were placed using the Russian doll technique. The volume embolization rate was 43.4%. The following day, she developed left ONP. CISS on the 10th postoperative day revealed that the aneurysm was in contact with the left oculomotor nerve. The patient’s ONP gradually improved although the recovery was partial. Case 2 involved a 62-year-old woman who presented with a headache and subsequent right ONP. CT showed no subarachnoid hemorrhage, and cerebral angiography revealed the right IC-PC AN with a posterolateral projection. The aneurysm was constricted in the middle portion. CISS visualized that the right oculomotor nerve spanned along with the constriction. Intra-aneurysmal embolization was performed; the aneurysm was compartmentalized with the segment around the apex and the neck and embolized in each segment intentionally by the double-catheter technique while preventing damage to the oculomotor nerve. The volume embolization rate was 44.0%. The patient’s ONP steadily improved, and she fully recovered 1 year later. In endovascular treatment, anatomical information regarding structures around blood vessels is challenging to comprehend. CISS may be helpful for the evaluation of the surrounding structures. Utilizing information from CISS for endovascular treatment remains a challenge for the future.

Intracranial aneurysms are sometimes associated with oculomotor nerve palsy. We report five surgical cases of unruptured internal carotid-posterior communicating artery aneurysms presenting with oculomotor nerve palsy. In such cases, the internal carotid artery runs closely to the skull base, reducing the operative field around the aneurysm. Therefore, anterior clinoid process drilling or a cerebellar tent incision should be performed, if necessary, to ensure safe operative maneuvers. The distance between the internal carotid artery and anterior-posterior clinoid process may be a useful preoperative indicator for tent incisions.