Operation of the aneurysm at the anterior part of Willis ring is one of the most common surgeries in the neurosurgical field and a large number of excellent textbooks or articles about this surgery have been published. From my personal experience of 485 cases, I have noticed several ways to rapidly complete clipping-surgery. Rapid surgery never means hasty surgery, but precise step-by-step surgery will lead to rapid surgery. Thus, no procedure should ever be done hastily. I offer the following four tips: 1) The surgeon should ensure complete hemostasis at each surgical step, which will make the following microscopic dissection smoother. 2) The surgeon should be aware of the appropriate steps of arachnoid dissection. The different steps should be considered based on the aneurysm's location. In the case of internal carotid (IC) aneurysm, the chiasmatic cistern should first be dissected to preserve the proximal IC for possible premature rupture. The proximal Sylvian fissure is then be opened, and finally the neck of the aneurysm should be carefully dissected. In the pterional approach for the anterior communicating aneurysm, the Sylvian fissure should first be opened widely, which will make the frontal lobe relaxed against the following surgical retraction. The proximal IC, chiasmatic cistern, and interhemisphric fissure should then be dissected in order. As for the middle cerebral (MC) aneurysm, I prefer to approach from the distal side, since the initial dissection of the proximal MC may sometimes be difficult behind the aneurysmal dome. 3) The appropriate method of arachnoid dissection should be practiced. The most important point is for the left hand to make the arachnoid membrane tensional for the correct observation of the dissecting plane. 4) The operative field should be properly expanded. For this purpose, the microscope and self-retractor should frequently be replaced. With the use of these techniques, the overall outcome of my department has improved a great deal. Although approximately 40 percent of the patients with subarachnoid hemorrhage belong to WFNS Grade IV or V in my clinic, the ratio of independent patients (Glasgow Outcome Scale; GR+MD) has significantly increased from 61.7%to 69.7%in the past four years. Since the number of neurosurgeons in Japan is increasing greatly, neurosurgeons are experiencing less surgery. Thus, these surgical tips should be helpful for inexperienced neurosurgeons.

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Spontaneous dissection of the anterior cerebral artery (ACA) is an unusual condition, and the natural history of the intracranial arterial dissection is not well known. We report our surgical strategy for the dissection of ACA. In our series of ACA dissections, 5 cases presented an ischemia and 1 showed an SAH. Case 1 showed the dissection of the A2 portion of the ACA presenting weakness of the right lower extremity. According to Yonas et al., the dissection between the internal elastica and the media causes a cerebral ischemia and the dissection between the media and the adventitia causes an SAH. In Case 1, the pathological study revealed a dissection between the media and the adventitia in spite of a cerebral ischemia. Case 3 after initial headache showed a mild paresis of the right leg and the dissection of A2, A3 portion of ACA in the repeated angiography. The pericallosal-pericallosal side-to-side anastomosis and callosomarginal artery-callosomarginal artery side-to-side anastomosis with the ligation of the proximal A2 portion was performed. The pseudo lumen was detected in the anterior internal frontal artery after the arteriostomy. Preoperative left CAG did not reveal a double lumen sign but mild stenosis of the anterior internal frontal artery. This is the first report of intraoperative detection of intracranial arterial dissecting pseudo lumen. Obliteration of the dissecting entry in the surgical treatment of arterial dissection is essential. Therefore, it is considered that the trapping of the dissection and the revascularization of the ACA is necessary to prevent postoperative infarction and future rupture of the dissection. The pressure in the true lumen of the dissecting vessels is elevated by producing A3-A3 anastomosis, and the increasing pressure of the true lumen will compress the pseudo lumen after the blocking of the entry. We conclude that the occlusion of the entry and revascularization for the dissecting arteries might be the first choice in the surgical treatment for the patients of ACA dissection.

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We conducted flow visualization studies and measurements of intraaneurysmal flow volume using a flat three-dimensional acrylic aneurysm model. Flow visualization was done by the tracer particle technique and the particle streamlines were pursued through a charge-coupled device (CCD) camera. Analysis of intraaneurysmal flow volume was carried out by means of dye injection. Monitoring of time-related concentration of the aneurysms allowed calculation of the mean transit time (MTT) using the height-over area method. Fundamental intraaneurysmal flow was composed of inflow, circulation flow, and outflow. These fundamental flow patterns were strongly influenced by the flow ratio into the distal branches. A nearly symmetric flow ratio failed to achieve full intraaneurysmal flow. The critical flow ratio to raise inflow into an aneurysm was considered to be 3:1, and the best flow ratio to develop intraaneurysmal flow in our three-dimensional model was 4:1. An increase of the aneurysmal size and changes in geometrical features such as the daughter formation, the dumbbell shape narrowing and narrowing of the neck led to a stagnant area or very sluggish flow area at the dome side. Geometries favoring aneurysmal rupture are considered to be closely associated with low-flow condition.

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Gamma knife radiosurgery has become one of the major treatments for cerebral arteriovenous malformations (AVMs), especially, for deep-seated AVMs such as brain stem, basal ganglia and thalamus. However, a brain edema and/or bleeding following gamma knife radiosurgery are often observed in the follow-up period. We focused on AVMs in the basal ganglia and thalamus, and investigated the outcome of gamma knife radiosurgery. Among 85 AVMs treated by gamma knife radiosurgery and followed by MRI and/or angiography for more than 2 years, 22 AVMs were located in the basal ganglia and thalamus. The complete obliteration rate of these 22 AVMs was 54.5%, and radiation-induced edema was observed on MRI in 31.8%of these AVMs. In comparison with AVMs in the cerebral hemisphere, radiation-induced edema in the basal ganglia and thalamus frequently became symptomatic. Therefore, in the treatment of large AVMs in the basal ganglia and thalamus, other therapeutic modalities such as intravascular surgery before gamma knife treatment, fractionated irradiation, and low-dose irradiation should be considered.

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In this study we present recent clinical results of coil embolization for ruptured cerebral aneurysm.
From May 1996 to March 1997, 99 patients presented with ruptured cerebral aneurysms, of which 82 cases (83%) were treated with endosaccular coil embolization using GDC. There were 32 males and 50 females, and the ages were 26 to 78 (average 50.1) years old. The locations were 28 A-com, 4 ACA, 21 ICA, 14 MCA, 6 VA, 6 BA and 3 of other locations. The sizes of the aneurysms were 63 small (2-7mm), 15 medium (8-14mm) and 4 large (15-20mm). Hunt & Hess grades were 23 Grade I, 25 Grade II, 23 Grade III, 7 Grade IV and 4 Grade V. Seventeen cases were treated with open skull surgery because of anatomical problems for embolization (11 cases) or massive intracerebral hematoma (6 cases). Glasgow outcome scale (GOS) was assessed 2 to 5 months after the embolization.
Overall clinical results were 44 (54%) good recovery, 17 (21%) moderate disability, 12 (14%) severe disability, 1 (1.2%) vegetative and 8 (9.8%) death. The GOS was correlated with the clinical grade of SAH at admission and 44 (91.7%) of 48 Hunt & Hess Grade I or II patients had favorable outcomes. The location of the aneurysm was not associated with the GOS. Vasospasm was seen in 13.9% and influenced the GOS.
The results of embolization as the initial treatment of ruptured cerebral aneurysms are comparable to direct open skull surgery.

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Treatment strategy for vertebral artery dissecting aneurysm (VADA) remains controversial even though satisfactory results have been reported with proximal clipping (PrC) and trapping. We report 9 cases of VADA and reviewed the literatures with special reference to time and rate of rebleeding, timing of surgery, result and risk of acute staged surgery and the natural history. Rebleeding occurred in 50.0% of our cases and in 21.4-79.4% of the reported ones. Twenty-five of 78 cases, which included reported cases and ours, rebled on day zero. Acute staged surgeries were performed in 21 cases, with satisfactory results. We also discuss the risk of PrC. Natural healing has been reported in only 3 cases presented with subarachnoid hemorrhage. We therefore recommend the following strategy for treating VADA: 1) Acute staged surgery should be done primarily. 2) Proximal clipping should be the first procedure. 3) According to the intraoperative findings of the Doppler sonography and change in the aneurysm size after proximal clipping, the operating method should be changed to trapping. 4) Postoperative angiography should be done within a few days after the proximal clipping.

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We investigated follow-up angiography and outcome in 28 patients undergoing local fibrinolytic therapy (LFT) for intracranial or cervical artery occlusion to determine the incidence of distal shift of the embolus or no apparent angiographic change. The location of the occlusion was the cervical internal carotid artery (ICA) in 6 cases, the intracranial ICA in 8 cases, the horizontal portion of the middle cerebral artery (Ml) in 8 cases, the distal middle cerebral artery (MCA) in 5 cases, and the posterior cerebral artery (PCA) in 1 case. Angiography the day after LFT demonstrated recanalization in 2 cases of cervical ICA occlusion, 4 cases of intracranial ICA occlusion, 7 cases of M1 occlusion, and 6 cases of MCA and PCA occlusion. No apparent angiographic change was found in 2 cases of cervical ICA occlusion. Various distal shifts were found in the other 3 cases. Five patients died, 3 of severe brain edema, 1 of hemorrhagic infarction due to recanalization, and 1 of gastrointestinal bleeding. In many cases spontaneous recanalization after LFT was achieved by the next day. Although recanalization may not occur immediately after LFT, spontaneous recanalization often occurs in the early stage, so the zone of penumbra can be rescued with a low incidence of hemorrhagic infarction.

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We customized and used stimulation probes (SP) for the intraoperative stimulation of the fourth ventricle floor (IoS). The facial nerve was intraoperatively monitored 7 times prior to resection of 6 cavernous angiomas in the pons and puncture of 1 cystic metastatic tumor in the pons during 3 years. We made 5 types of SP, which were composed of handpiece and electrode. From No.1 to No.5, they were improved for IoS. Both adequate manipulation of handpiece, electrode and proper flexibility of electrode were required to provide precise and safe stimulation of the intended site. The latest SP, No.5 made from the steel handpiece and silver-ball electrode coated with silicon is improved in several ways and is best suited for IoS.

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Due to recent developments in MRI and microsurgical techniques and improvement in diagnostic techniques, more aged patients are undergoing craniotomy for surgical operations such as non-ruptured aneurysmal clipping and STA-MCA bypass surgery, during which the brain may collapse due to aspiration of the cerebrospinal fluid. Collapse of the brain could lead to postoperative subdural fluid effusion, which sometimes requires surgical management. Aged patients take a particularly long time to recover postoperatively from complications such as subdural effusion or hematoma due to brain atrophy. This slow recovery often leads to new complications, resulting in a long hospitalization. To resolve this problem, we have designed a new simple technique using a fibrin glue and gelform. We have obtained good results from the use of this method, in which gelform, sliced off to the one third with fibrinogen, was added to thrombin. In addition to the above method, we have also designed a“floating bypass”technique in which the recipient MCA artery is sealed with gelform soaked in fibrin glue and saline is injected into the subarachnoid space using a 5Fr tube. In this paper, we report new simple and effective techniques to prevent postoperative subdural fluid effusion.

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We report 2 cases of symptomatic delayed vasospasm after neck clipping of unruptured juxta-dural ring aneurysms of the left internal carotid artery. Case 1 is a 53-year-old woman with multiple unruptured juxta-dural ring aneurysms. Case 2 is a 21-year-old woman with a carotid ophthalmic aneurysm. Aphasia and/or Gerstmann syndrome appeared 8 days and 12 days after clipping surgery, respectively. Angiograms revealed severe vasospasm of the left middle cerebral artery in Case 1 and the left M2 portion in Case 2. These symptoms were fully resolved by intra-arterial papaverine treatment and hyperbaric oxygen therapy. We emphasize that vasospasm is a possible complication after clipping of unruptured juxta-dural ring aneurysms.

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A 61-year-old man presented wtih right-sided hemiparesis due to stenosis of the cervical internal carotid artery. He was conservatively treated by antiplatelet therapy and dietary management because of high-positioned stenosis, which is surgically hard to access, and because of rapid improvement of the symptoms. Reevaluation 9 months after the first angiography demonstrated complete disappearance of the carotid stenosis and resolution of the symptoms. The observation, though rare, in this case emphasizes the efficacy of antiplatelet therapy combined with dietary management for atherosclerotic disease. We discuss the mechanism of resolution of carotid stenosis.

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