The current quality of the endoscopic image displayed on the TV monitor permits beneficial and safe employment of endoscopy for access to the blind corner during aneurysm surgery under the microscope. To achieve this concept in daily surgery, the author has principally used a high-resolution rigid endoscope with an angle of vision most frequently at 70°. To facilitate this useful but hazardous endoscopy-assisted aneurysm surgery, we developed 2 surgical systems. In one, the endoscopic image is observed through the eye lenses of the microscope. This frees the neurosurgeon from the major inconvenience of having to discontinue watching the microscopic view in order to look at the endoscopic image on the video monitor. This made it possible to look at the endoscope image while observing the microscope image at the same time. In the other system, an endoscopic system was equipped with a rigid endoscope and a holder mounted on a mobile post. This facilitated rapid and easy employment of endoscopy during open surgery. The holder with flexible supporting arms had sufficient holding strength to firmly sustain the weight of an endoscope without interrupting the view under the microscope. A touch of its hand switch easily terminated the motion of the supporting arm, and the endoscope remained stable in the required position. If the switch was pressed again, the supporting arm regained free movement.
We have routinely employed microsurgical techniques assisted by the endoscopy in aneurysm surgery for more than 10 years. The maneuvers are steadily performed under simultaneous observation of the microscopic and endoscopic images. There are many advantages in combined use of an endoscope with the microscope. The obvious benefits of the endoscopy-assisted aneurysm surgery are correct clip placement on the aneurysm neck and avoidance of accidental arterial occlusion during clipping. Our increasing experience has convinced us that endoscopy-assisted microneurosurgery is essential for aneurysm surgery.

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We performed perfusion computed tomography (PCT) in patients with hyper-acute stroke to evaluate its usefulness for the indication of percutaneous transluminal revascularization.
The subjects were 21 patients with stroke in the carotid system admitted within a few hours of onset when no ischemic change could be detected by the initial CT but was already present as confirmed by PCT parameters of either mean transit time (MTT), cerebral blood flow (CBF) or cerebral blood volume (CBV). Percutaneous transluminal revascularization was performed in all patients at the earliest possible opportunity. The CBF and CBV values were calculated in regions of interest (ROIs) selected in the ischemic lesion, and compared with the same location on the opposite side (ROI ratio).
Patients with visual decreases in CBF and CBV as well as delay of MTT suffered severe infarction. Patients with only delay of MTT were saved from extensive infarction by the reperfusion treatment. Some patients with ischemia visually identified by both MTT and CBF suffered severe infarction, but others only had localized infarction. The ROI ratio of the CBV was increased in these patients with localized infarction but decreased in the patients with severe infarction. The mean ROI ratios associated with subsequent infarction were 0.438±0.276 (mean±SD) for CBF and 0.873±0.290 for CBV, and those associated with no subsequent infarction were 0.862±0.429 for CBF and 1.289±0.486 for CBV.
Delay of MTT indicates reconstruction whereas decreased CBV carries no indication. The decision-making is difficult in patients in whom visual evaluation cannot confirm decreased CBF. In such cases, the ROI ratio of CBV must be measured if any decrease in CBF is suspected.

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We have operated on 21 patients with an unruptured anterior communicating aneurysm by the pterional approach. Partial resection of the gyrus rectus was performed in 10 patients (44%). Of these patients, 1 patient had postoperative memory disturbances. We present this patient and discuss the responsibility of the gyrus rectus for memory deficit.
A 61-year-old right-handed woman underwent MRI for the evaluation of chronic headache and was found to have an anterior communicating aneurysm. The aneurysm was 8 mm in size and arose from the junction of the anterior communicating artery and the left A2 segment. The fundus of the aneurysm was buried in the right gyrus rectus. A right pterional approach with partial resection of the gyrus rectus was employed. The aneurysm was successfully clipped and the postoperative course was uneventful. Postoperative CT showed only postoperative changes and postoperative MRI demonstrated only a small discrete right gyrus rectus lesion. However, the patient complained of memory disturbances on the third postoperative day. Neuropsychological tests performed 1 month after surgery revealed typical anterograde amnesia.
Our case suggests that the gyrus rectus resection may be responsible for postoperative memory deficits. We propose a possible mechanism of our patient's amnesia: the gyrus rectus resection may result in disconnection of the pathway between the basal forebrain and the hippocampal region or the cortex, depriving these areas of cholinergic innervation.

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Embolectomy has been sporadically carried out for acute middle cerebral artery (MCA) occlusion since the late 1950s. But since the introduction of local intra-arterial fibrinolysis, emergency embolectomy has not been widely carried out. Fibrinolysis, however, is not effective in all patients, and for those patients, we have applied acute embolectomy. Between October 1997 and March 2002, 9 patients with acute MCA occlusion were treated by embolectomy. The 9 patients had a mean time from onset to recanalization of 6 hours 32 minutes. Five of the 9 patients showed good recovery in Glasgow outcome scale, 2 were severely disabled, 1 was in a vegetative state, and 1 died of cardiac complication. None of the 9 patients had symptomatic hemorrhagic infarction requiring surgical removal.
In conclusion, emergency embolectomy can achieve good recovery even in patients with insufficient fibrinolysis after acute MCA occlusion.

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Thrombosed giant aneurysm (TGA) possesses a high growth potential. In patients with TGAs, clinical symptoms evolve most commonly from its mass effect. Surgical interventions are therefore required to prevent TGA growth. We analyze the clinical characteristics and histopathological findings of TGAs, and discuss possible mechanisms underlying their growth. We have treated 30 cases of TGA during the last 10 years. Of these, 10 underwent direct surgery and 20 were treated by endovascular surgery. Endovascular obliteration of TGAs frequently fails to terminate their growth when contrast-enhancement of the aneurysmal wall is demonstrated on CT or MRI. Incomplete endovascular obliteration of TGAs does not appear to reduce their growth potential. Complete thrombosis of TGAs, induced either spontaneously or by surgical modification of the blood flow, does not necessarily indicate termination of their growth.
The growth of TGAs can be terminated when both the aneurysmal lumen and vascular channels of the aneurysmal wall are physically isolated from the blood flow through direct surgery: neck clipping or trapping. Together with the histopathological findings of TGAs, the above-mentioned characteristics suggest that 2 mechanisms may underlie their growth: intraluminal thrombus accumulation, and proliferation of vascular channels of the aneurysmal wall. Radical surgery to isolate TGAs from the blood flow, before they become too large to be operated on safely, may be advisable.

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It is well known that the conditions of the superficial sylvian veins vary from patient to patient. But despite this considerable variation, a dissecting method of the sylvian veins in the transsylvian approach has not yet been systematically described. We introduce a simple, systematic 3-step approach, which is similar to the anterior interhemispheric approach by Ito Zentaro.
Step 1: Open the Insular Cistern
The incision of the arachnoid membrane is performed along the temporal side of the sylvian vein, beginning about 5cm distal from the temporal tip. The insular cistern should be exposed, during which time the M2 portion can be identified.
Step 2: Dissect the fissure like opening an envelope with a knife
The vertex of the head is slightly elevated at the beginning of this step. The arachnoid trabecula is incised toward the base of the sylvian fissure from the deep layer to the superficial layer, as if opening an envelope with a knife.
Step 3: Open the Sylvian Vallecula
The vertex of the head is slightly down at the beginning of this step. In this step, the sylvian vallecula should be exposed. Next, the carotid cistern is opened. As a result the M2-M1-ICA is exposed completely.
By using these 3 steps, we dissect the sylvian fissure safely and easily and preserve all sylvian veins to prevent venous infarction.

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To examine flowdynamic change after superficial temporal artery (STA)-middle cerebral artery (MCA) bypass surgery, we measured the pulsatility index (PI) and end-diastolic blood flow velocity (Vd) of the donor STA by percutaneous direct microvascular Doppler sonography. In 63 patients (5-76 y/o) who had received STA-MCA bypass surgery for either ischemic stroke (11 cases), supportive therapy before parent artery occlusion in the treatment of internal carotid giant aneurysm (3 cases), or moyamoya disease (49 cases) (total 96 sides of STA), PI was 1.01±0.41 and Vd was 18.9±8.4 cm/sec. When compared to normal volunteers (6-76 y/o, 70 sides of STA) (PI: 1.96±0.63 and Vd: 5.6±2.5 cm/sec), PI decreased and Vd increased after STA-MCA bypass with high statistical significance (p<0.0001 and p<0.0001, respectively). Low PI and high Vd indicate that STA flow has changed from extracranial flow to intracranial flow.
STA flowdynamics can be quantitatively assessed by measuring PI and Vd of the donor STA. This new bedside method is easy, noninvasive and useful to identify functional patency of the STA-MCA bypass.

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We report a difficult case of endoscopic hematoma evacuation due to micro-arteriovenous malformation (AVM).
A 60-year-old male presented with left hemiparesis and confusion. Computed tomography demonstrated right putaminal hemorrhage, but cerebral angiography revealed no definite vascular abnormalities. Endoscopic hematoma evacuation was immediately undertaken using a transparent sheath. Massive arterial hemorrhaging occurred following hematoma decompression, so endoscopic evacuation was aborted and open craniotomy initiated. Arterial bleeding from around the hematoma cavity indicated occult arteriovenous fistula. After evacuation of the hematoma, abnormal vessels were identified and completely resected. Pathological diagnosis was an arteriovenous malformation and clinical diagnosis was micro-AVM, as described by Yasargil in 1987.
The point of endoscopic hematoma evacuation using a transparent sheath was to position the burr hole for keyhole surgery rather than stereotaxic aspiration. If micro-AVM is suspected during the endoscopic procedure, the procedure must be changed to open craniotomy. The best burr hole position also provides the optimal approach for open craniotomy. Operative instruments and procedures must be developed to improve safety for this endoscopic surgery.

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We report a case of unruptured “true posterior communicating artery” (Pcom) aneurysm associated with ruptured internal carotid-posterior communicating artery (IC-PC) aneurysm in a 72-year-old woman, treated successfully by direct surgery. Left internal carotid angiography and three-dimensional CT angiography revealed an IC-PC aneurysm 8 mm in maximum diameter protruding inferolaterally, with a small bulge on the Pcom side which was regarded as part of the IC-PC aneurysm. Intraoperative inspection revealed that the prominence initially thought to be part of the IC-PC aneurysm was a true Pcom aneurysm forming a kissing aneurysm pair with the IC-PC aneurysm. The 2 aneurysms were completely dissected and both were clipped.
This is the first reported case of kissing aneurysms of the IC-PC aneurysm and true Pcom aneurysm. A true Pcom aneurysm forming kissing aneurysms with IC-PC aneurysm, as in the present case, may be difficult to diagnose preoperatively. Careful intraoperative observation and complete dissection are therefore important for a good outcome.

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Based on our clinical experience of 240 cases, we present the noticeable anatomical structures and our principles of procedures during carotid endarterectomy (CEA). We also present a newly developed self-retaining retractor and spring hook for CEA. The noticeable anatomical structures are as follows: the internal jugular and facial veins, the hypogrossal nerve and ansa cervicals, vagus nerve, superoir laryngeal nerve, and branches of the external carotid artery. Our principles of exposure of the carotid arteries during CEA are the meticulous anatomical dissection and identification of the cervical structures and the intentional circumferential dissection of the carotid complex. Our perioperative cerebral complication rate (mortality and morbidity) is 2.4%, and the incidence of the basic technical complications such as cranial nerve palsy and wound hematoma are 0.4% and 1.3%, respectively. The meticulous anatomical dissection and the intentional circumferential dissection of the carotid complex are essential to minimize postoperative complications.

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We describe a technique of clipping on wrapping method using Bemsheet to treat short aneurysms such as broad-based aneurysms, so-called blister aneurysms and dissecting aneurysms. After the aneurysm and its parent artery have been circumferentially wrapped with a strip of Bemsheet, an aneurysm clip is applied on the sheet to clip the aneurysm between the 2 leaves of the sheet utilizing the counter-pressure effect between the clip and the sheet pulled by forceps. This technique avoids several risks, including slipping out of the clip or neck avulsion during clip application to blister aneurysms because the sheet cushions the hard blade of the clip. Furthermore, recurrence of aneurysm following incomplete neck obliteration is also avoided due to tethering effect of the sheet to the clip.
Twenty-three of 25 patients for whom this method was employed were successfully treated by complete occlusion of aneurysm. One patient with a blister aneurysm originating from the anterior wall of the internal carotid artery died of rerupture of aneurysm due to possible incomplete neck obliteration. One patient developed postoperative narrowing of the parent artery.
The most important key point of this technique for blister aneurysm arising from internal carotid artery is to tighten the sling of 2 strips of the sheet which were placed proximally and distally to posterior communicating. And those strips were pulled strongly by forceps perpendicularly to the internal carotid artery in order to obtain the most effective counter-pressure. To avoid the possibility of postoperative narrowing of parent artery due to granuloma formation, plastic adhesive should not be used.

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