We report a retrospective analysis of 11 cases of non-ruptured cerebellar arteriovenous malformations (AVMs) among 294 cases of intracranial AVMs between 1981 and 2004. Eight of 11 cases were surgically treated. Seven patients had good outcomes (modified Rankin scale 0-2) and 1 patient was dead because of brainstem dysfunction after the removal of a giant cerebellar AVM. Surgical treatment is indicated for symptomatic cases, particularly for pediatric cases and cases associated with intracranial aneurysms because of the high bleeding rate and poor outcome after the hemorrhage. However, surgical treatment is contraindicated for arteriovenous malformations that extend to the cerebellar peduncle or brainstem, particularly for giant cerebellar AVM because of the high morbidity and mortality rates.

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We present an optimal treatment for unruptured small (3 cm or less) cerebral arteriovenous malformations (AVM) among conservative treatment, gamma knife surgery (GKS) and microsurgery using clinical decision analysis according to patients' age. All cases for this study were small AVMs. We analyzed 973 cases with conservative treatment, 176 with GKS and 110 with microsurgery. The expected utility indexes were calculated from the results of each group. We hypothesized the standardized expected utility indexes as 100 in healthy, 75 in disabled and 0 in dead. Microsurgery was the first choice for patients younger than 55 years with AVM located in a surgically accessible region. GKS is recommended for patients aged between 55 and 70, and the best treatment is observation for patients older than 70 years. The proposed clinical decision analysis is very useful in obtaining informed consent for choosing the treatment modality for unruptured small AVM.

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The treatment of unruptured cerebral arteriovenous malformation (AVM) is still controversial. We have been treating these patients according to the Spetzler & Martin (S&M) grading system. We retrospectively evaluated the outcomes of 46 unruptured AVM patients and also evaluated the bleeding rate during follow-up period. Recently we also started performing functional MRI, tractography, and 3-dimensional (3D) angiography for these patients before treatment.
In 18 of 22 patients in S&M Grade I and II, AVMs were surgically removed and the outcome was good. Six of 9 patients in S&M Grade IV and V, were conservatively treated. In patients in S&M Grade III, various treatments were performed according to the location of the AVM, but all their outcomes were favorable. The rate of permanent surgical complications was 15.3% in 26 unruptured AVM patients. Based on our treatment results, aggressive treatment should be performed in patients with S&M Grade I and II. However, treatment decisions must be carefully considered based on functional MRI, tractography of AVM, and 3D angiography.

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We discuss several issues in considering indication of radiosurgery for unruptured cerebral arteriovenous malformations. The risk of hemorrhage until obliteration was reduced by 54% compared to that before radiosurgery. Hemorrhage risk was further reduced after obliteration, but a small risk of hemorrhage (12% of that before radiosurgery) remained, although the outcome of these patients was favorable. The risk of radiation-induced complications could be reduced with addition of MRI or CT in treatment planning. Further safety can be achieved by integrating tractography into treatment planning. The surgical resection of the nidus becomes easier after radiosurgery. The frequency of radiosurgery-induced malignancy may be comparable to that of surgical mortality. Patients generally tend to select less-invasive treatment.
Nevertheless, long-term complications must be considered in treating patients with unruptured cerebral arteriovenous malformations.

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The use of the minimally invasive procedures in neurosurgery significantly reduces perioperative morbidity. We present some experiences of minimally invasive surgeries for intracranial aneurysms. Interfascial skin flap separation avoided injury of the facial nerve at the pterional approach. The perpendicular from the burr hole behind the frontozygomatic suture points to the anterior clinoid process when the patient's head is rotated to the opposite side by 30 degrees. This burr hole can be defined as the smallest pterional craniotomy. The small craniotomy at the forehead wrinkle allowed the shortest surgical route to Acom aneurysms. The following surgical techniques provided a wide operative view without brain retractor. Insertion of Bemsheets into the sylvian fissure served as a retractor, and head position with vertex down allowed the frontal lobe to fall away. Resection of the meningo-orbital band made it easy to remove the anterior clinoid process, which provided a wide working space to avoid optic nerve injury and excessive brain retraction. Combined surgery of bypass and endovascular surgery or of bypass and clipping surgery avoided peripheral artery occlusion. Posteriorly projecting IC-PC aneurysms were clipped easily via the anterior temporal approach, and the Pcom artery was successfully spared by intraoperative endoscopic observation.
The key point of minimally invasive aneurysm surgery is minimizing complications by carefully selecting surgical procedures.

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Patients who have symptomatic, medically refractory, vertebrobasilar artery stenosis have a high risk of stroke. The benefits of vascular reconstruction surgery and balloon angioplasty for these lesions are limited, and these treatments are associated with considerable complications. Recently stent placement in the intracranial arteries became available and is expected to improve the results of endovascular treatments.
We review our experience with endovascular treatment for symptomatic intracranial vertebrobasilar artery stenosis. Forty patients with intracranial vertebrobasilar artery stenosis were treated with endovascular surgery. Indication of the endovascular surgery was medically refractory symptomatic patients with over 60% angiographical stenosis. Balloon angioplasty was firstly performed in all patients. Stenting was performed only in cases with insufficient dilatation, dissection or restenosis after balloon angioplasty. Successful dilatation was obtained in all cases. Twelve patients underwent stenting in initial treatments. The stenosis rate reduced to 25.2% after balloon angioplasty and 16.1% after stenting. No neurological complications occurred after procedure. The restenosis rates after treatments were 25.9% after balloon angioplasty and 23.5% after stenting. During the follow-up period, only 1 patient developed stroke of posterior circulation.
Endovascular surgery for symptomatic vertebrobasilar artery stenosis has become more feasible and safer after the introduction of stenting. Prevention of restenosis is the next problem to be solved.

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We evaluate the influence of surgery for unruptured aneurysms on cerebral blood flow and neuropsychological estimate. We evaluated the cases of 28 consecutive patients with unruptured cerebral aneurysm treated with direct surgery accompanied by craniotomy. Before and after surgery, MRI, ¹²³I-IMP-SPECT with 3D-SSP analysis and MMSE were performed. There was not a significant decrease in MMSE. In ¹²³I-IMP-SPECT, it was recognized that the cerebral blood flow was decreased at the frontal operculum of operative site.
These results indicate that careful neuropsychological evaluation is essential to make a favorable treatment plan for unruptured aneurysms.

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In our previous standard CAS procedure, we selected the intended predilatation balloon, stent, and postdilatation balloon in advance, before treatment got under way. The sizes were chosen according to images captured from 3D-DSA. From April 2003 to March 2004, we treated 17 patients using this method, with which predilatation, stent deployment and postdilatation were done successively under one-time occlusion of the ICA using the PercuSurge GuardWire device (Medtronic Vascular, Santa Rosa, CA). In the 4 patients of this series, the postdilatation balloon was too small to obtain adequate vessel diameter, requiring re-postdilatation.
In our modified procedure, however, only the intended predilatation balloon and stent are prepared in advance. After predilation and deployment of the stent in the lesion, an aspiration catheter is used to aspirate possibly dislodged emboli. The occlusion balloon is then deflated and antegrade flow is restored, while the aspiration catheter is removed followed by the intravascular ultrasound sonography. This study aids us to determine the appropriate postdilatation balloon size by measurements done after stent deployment. From April 2004 to March 2005, 18 patients were treated with this method. Not 1 patient needed re-postdilatation, and we henceforth made this our new standard procedure.
Although the exact mechanism is unknown, the periprocedural rate of cerebral ischemic events has become lower with this new procedure.

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Patients with aneurysmal subarachnoid hemorrhage (SAH) may experience re-rupture, vasospasm, or systemic complications, which were the major cause of poor outcome. Thus, critical management in the stroke care unit (SCU) with meticulous monitoring and close neurologic observation is vital. We started neurosurgical services in April 2000, and an SCU was established in June 2003. We clinically evaluated 74 consecutive patients with SAH between April 2000 and June 2005, which were divided into 2 groups, non-SCU and SCU groups, before and after the establishment of the SCU. The non-SCU group had 37 patients and the SCU group had 37 patients. Clinical outcomes were assessed with modified Rankin scale and Glasgow outcome scale at 3-month follow-up. Statistical analysis demonstrated that the frequency rates of re-rupture before clipping and neurological worsening caused by vasospasm were remarkably reduced. The re-rupture rates before clipping were 27.0% for non-SCU patients vs. 2.7% for SCU patients (p=0.0033). The rates of neurological worsening caused by vasospasm were 39.1% for non-SCU patients vs. 6.1% for SCU patients (p=0.0022). The rates of good recovery were 16.2% for non-SCU patients vs. 70.3% for SCU patients (p<0.0001). The death rate for non-SCU patients was 40.5% vs. 18.9% for SCU patients (p=0.042).
Thorough management in SCU with expert nursing enabled a markedly reduced rate of re-rupture and vasospasm, significantly improving the outcome of patients with SAH.

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We evaluate the morphology of the carotid plaque using echogram, CT scan and MRI and compare those neuroradiological findings with histological findings of the plaque.
We evaluated 14 cases operated with carotid endoarterectomy for carotid stenosis. We estimated the findings of the echogram, enhanced CT scan and black blood MRI (BB MRI), in comparison with the histological findings of the carotid plaque.
Echogram, enhanced CT scan and MRI clearly demonstrated the plaque in cervical carotid stenosis. In most cases, echograms could show the plaque, but in some cases could not due to the back shadow caused by plaque calcification. Enhanced CT scan clearly demonstrated the calcification and the neovasculization in plaque. BB MRI clearly showed the carotid plaque. Low-intensity lesions in T1 and T2 weighted images showed hard and fibrous plaque. High-intensity lesions in T1 and T2 weighted images showed soft plaque with lipoprotein and/or hemorrhage.
This study demonstrates the potential of a systemic approach to atherosclerotic plaque with enhanced CT scan and BB MRI compared with histological findings of the carotid plaque. These estimations elucidate the growth mechanism of carotid plaque.

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