Sacrifice of the bridging veins and/or inappropriate brain retraction may result in postoperative brain damage associated with the pterional approach to an unruptured aneurysm. We report a less invasive pterional approach preserving the bridging veins without the use of brain retractors in 104 patients with unruptured aneurysms (112 pterional approaches).
The bridging veins from the frontal lobe to the superficial sylvian vein (SSV) were successfully preserved by 3 types of dissection of the sylvian fissure based on the preoperative stereoscopic carotid venogram (lateral and right oblique view): Type I, dissection on the frontal side of SSV (conventional method) in 47 approaches, including 17 approaches that were not related to SSV; Type II, dissection between SSVs in 31 approaches; Type III, dissection on the temporal side of SSV in 34 approaches.
A wide operative view preserving the bridging veins without brain retractors contributes to the safe dissection and clipping of an unruptured aneurysm, preserving the parent arteries and perforators.

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Techniques of less invasive neurosurgery have recently been reported. We eliminated some peri-operative procedures such as wound drainage, conventional angiography and shaving of hair to reduce patients' physical and psychological invasion and evaluated the merits of our less invasive method.
From April 2001 through December 2004, 66 patients underwent surgery for asymptomatic unruptured intracranial aneurysms. Patients were assigned to 3 groups: Group A with elimination of postoperative wound drainage comprised 13 cases, Group B with elimination of conventional angiography in addition to elimination of drainage comprised 30 cases, and Group C with elimination of scalp shaving comprised 23 cases. As we minimized invasive procedures, patients experienced less stress, had shorter hospital stays and had lower hospitalization costs. Elimination of conventional angiography reduced complication rates and elimination of wound drainage and scalp shaving reduced psychological invasions related to changes in appearance.
The objective of less invasive techniques is primarily to protect brain functions, but techniques to reduce peri-operative physical and psychological invasion of patients are also important. Our less invasive procedures help patients return to their normal life more rapidly and improve patient's satisfaction and quality of life.

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We investigated surgical indication and factors relating to risks of rupture in 274 consecutive patients with unruptured cerebral aneurysms. Of the total, 114 (41.6%) patients were surgically treated: 96 were treated with craniotomy, and 18 were treated with coil embolization. The incidence of cases undergoing surgical intervention tended to expand with the increase of their aneurysm size except for cases with large or giant aneurysms. In cases with small aneurysms less than 4 mm, the presence of a familial history of subarachnoid hemorrhage, additional ruptured aneurysms, additional large aneurysms, posterior circulation aneurysms and intractable anxiety of patients were the reasons for surgical intervention.
Nine of 17 (52.9%) cases with additional aneurysms suffering subarachnoid hemorrhage, 32 of 46 (69.6%) patients with a familial history of subarachnoid hemorrhage and 28 of 36 (77.8%) cases whose aneurysm had bleb formation underwent surgical intervention. Complete clipping was achieved in 94 of 96 (97.9%) cases treated with craniotomy, and a sufficient initial embolization rate of over 90% was obtained in all cases treated with coil embolization. Surgical complication affecting patients ADL was observed in only 1 of 119 (0.9%) treated cases, and consequent rupture of aneurysms occurred in 2 older patients during follow-up in 155 conservative cases.
To decide surgical indication for unruptured cerebral aneurysms, it is important to consider factors related to risks of rupture.

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Complication of the surgical treatment for unruptured cerebral aneurysms is not ignorable especially for high-risk patients whose preoperative score is more than 2. The preoperative score consisted of aneurysm size (0: below 14 mm, 1: 15-24 mm, 2: over 25 mm), location (0: other location than posterior fossa and paraclinoid, 1: paraclinoid, 2: posterior fossa), multiplicity (0: treatable with single approach, 1: different approach necessary), and systemic diseases (0: no disease other than cerebral aneurysm, 1: one disease, 2: more than 2 diseases). Since 1997, we have conducted preoperative scoring and managed the unruptured cerebral aneurysms with scores of over 2 by observation, intravascular surgery or clipping surgery. Surgical results were evaluated using a modified Rankin scale (mRS). Before scoring, surgical complications exceeding mRS III occurred in 7.5% of cases, whereas this figure declined to 2.5% in the surgical results since 1997. When results of clipping surgery and intravascular surgery were compared, the former showed 3.8% and the latter showed 0% of complications exceeding mRS III.
The results indicate that clipping surgery combined with intravascular surgery improves surgical outcome for unruptured cerebral aneurysms with high risk.

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There have been 2 major treatment approaches for patients with severe subarachnoid hemorrhage (SAH): aggressive treatment for all patients irrespective of grade, and treatment of patients selected based on certain indices.
We treated 34 patients with poor-grade SAH classified by the Hunt and Kosnik criteria according to an aggressive protocol we had devised (A). To evaluate its efficacy, we compared the results with those obtained in 103 patients treated by the previous protocol (B) involving a selective strategy, and focused on the problems of treating patients with poor-grade SAH. Protocol A: Patients showing no flow in the initial angiogram received supportive care alone; the remaining patients underwent clipping surgery with or without external decompression, or coil embolization; hypothermia or normothermia (for elderly patients or those with complications) was introduced when intracranial pressure (ICP) exceeded 25 mmHg. Protocol B: Patients with SAH+hematoma causing a mass effect underwent emergency surgery; the remaining patients were pretreated for 12 h with control of blood pressure and intracranial pressure, and then radical surgery was performed on all patients who were Grade III or better and on patients at Grade IV below 75 years of age and without systemic complications.
Mean arrival time of patients treated by protocol A was 4 h, compared with 1 h in the protocol B group, and the difference was significant. The proportion of patients who underwent radical treatment was 87.5% in A and 53.4% in B, and the difference was also significant. However, a favorable outcome classified as GR or MD by the GOS was seen in 43.8% of patients in group A and 42.7% of those in group B; the death rate was 28.1% and 36.9%, respectively, indicating no significant difference of outcome between the 2 protocols. Hypothermia was effective for management of ICP, but this carries a risk of vasospasm. SjO₂ monitoring was useful for control of rewarming and also for predicting outcome during the ultra-early phase.
The significantly delayed arrival of patients treated by protocol A suggests that a proportion of patients whose neurological grade may improve within several hours might be initially excluded. If so, the figure of 43.8% for patients achieving GR+MD in protocol A might be improved further.

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We retrospectively analyzed 130 consecutive patients in Hunt and Kosnik Grade IV to V with ruptured intracranial aneurysm to investigate factors relating to unfavorable outcome.
The outcome at 2 months after on-set was evaluated according to the Glasgow Outcome Scale. GR and MD were defined as favorable outcome, but SD, VS, and D were considered unfavorable. Aneurysms in the anterior circulation of Willis circle were clipped surgically, and GDC embolization was performed in posterior circulation. Patients having normal brain stem reactions and spontaneous respiration were considered suitable for treatment of aneurysms.
Favorable outcomes were seen in 50.8% of Grade IV, and 8.5% of grade V patients. Treating methods—clipping or GDC—were not significant for favorable outcome. Cerebral infarction due to vasospasm, age of over 70 years old and hydrocephalus were significant for unfavorable outcome in Grade IV. GCS scores of 3, 4, and 5 were significant for unfavorable outcome in Grade V.
More sensitive monitoring and aggressive treatment of vasospasm, and active rehabilitation with safely managed cisternal drainage are necessary for more favorable outcomes.

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Direct surgery of paraclinoid aneurysms that could require anterior clinoidectomy for exposure, or of some basilar head aneurysms that could require going deep through the opticocarotid triangle for access, may injure the optic nerve. And also in surgery of large or giant aneurysms of the internal carotid artery that could compress the optic nerve, recovery and preservation of visual function, or sometimes even prevention from the worse, could become important issues.
We describe less invasive surgical techniques in surgery of aneurysms that may injure the optic nerve, based on our experience in 36 cases selected from among 528 aneurysm surgeries of the past 11 years.
The safe and easy method of anterior clinoidectomy that includes the following components may be useful: 1) drilling of the orbital roof, the lateral part of the anterior clinoid process and the optic canal should be performed though the extradural route, and 2) removal of the residual apex of the anterior clinoid process should be completed after moving to subdural space when the dura covering the process has been cut and pealed off.
A longer cut of the falciform ligament could be useful to make the optic nerve movable and to widen the opticotriangle space. A suction decompression technique for large and giant aneurysms should effectively ensure safe clipping near the optic nerve.

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In wide-neck intracranial aneurysms located at arterial bifurcation and small parent arteries, the standard remodeling technique of balloon-assisted coil embolization remains challenging. A new, more compliant remodeling balloon microcatheter has been developed for the treatment of these difficult aneurysms. We report coil embolization by the use of the remodeling technique with HyperForm balloon in 19 consecutive patients (with 21 aneurysms) with these difficult aneurysms. Twenty-one aneurysms consisted of 18 unruptured aneurysms, 2 ruptured aneurysms and 1 symptomatic aneurysm. Coil embolization was successfully performed in 18 of 19 patients (in 20 of 21 aneurysms). Angiographic results in 20 aneurysms showed 16 complete occlusions, 2 neck remnants and 2 residual flows. Sixteen patients presented excellent clinical outcomes.
The HyperForm balloon microcatheter allows the treatment of difficult wide-neck aneurysms located at arterial bifurcation and small parent arteries.

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We evaluated neuropsychological function, magnetic resonance (MR) images and cerebral blood flow (CBF) in patients with unruptured asymptomatic cerebral aneurysms.
Among consecutive operations (n=73) on 70 patients since 2000, direct surgery was performed in 53 operations on 50 patients, and intravascular surgery was performed in 20 operations on 20 patients. Surgical results of direct surgery were studied. Direct surgery was selected mainly for patients with small and anterior circulation aneurysms. MR imaging was conducted 1 week after surgery, and Wechsler Adult Intelligence Scale-Revised (WAIS-R) examination and CBF measurement using ¹³³Xe-SPECT were done before and 1 month after surgery.
Abnormal neurological findings were recognized postoperatively in 26% of surgeries. Among them, visual disturbance was permanent in 4% of surgeries, all of which were surgeries for paraclinoid internal carotid artery aneurysms. WAIS-R results deteriorated in 26% of surgeries at 1 month and at least in 5% of surgeries at 1 year after surgery. MR images at 1 week after surgery revealed brain damage in 30% of surgeries and subdural fluid collection in 19% of surgeries. Patients with large brain damage or thick subdural fluid collection frequently showed neurological deficits and/or WAIS-R deterioration. These complications were recognized frequently in patients with ACoA aneurysms. Resting CBF decreased significantly in the area supplied by the anterior cerebral artery and anterior border zone on the operated side postoperatively. The brain damage and subdural fluid collection were observed frequently and caused neurological deficits and neuropsychological dysfunction, although these were usually transient.
It may be necessary to evaluate neuropsychological function, MRI and CBF in patients with unruptured asymptomatic cerebral aneurysms to improve surgical results.

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The P2 bypass is one of the most difficult procedures in cerebrovascular surgery. Creating an anastomosis between the arterial graft and the P2 segment of the posterior cerebral artery is challenging because the P2 segment is located deep and high within the ambient cistern.
We describe the application of a skull base technique, mastoidectomy and partial rhomboid drilling of the middle fossa, in order to achieve the anastomosis deep in the ambient cistern without temporal lobe injury. Mastoidectomy with hearing preservation creates a presigmoid space, which enables a presigmoid transtentorial approach to the ambient cistern. After complete skeletonization of the semicircular canals, rhomboid drilling of the middle fossa can be performed, confirming the landmarks of the rhomboid, arcuate eminence, greater superficial petrosal nerve, posterior margin of the third branch of the trigeminal nerve, and petrous margin.
Partial rhomboid drilling, in which the posterior half of the rhomboid is drilled away, helps to reduce the requirement for temporal retraction during P2 bypass.

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Our previous study indicated that He⁺-irradiated collagen grafts with a fluence of 1×10¹⁴ ions/cm² have excellent blood compatible properties. Also, the collagen grafts demonstrated a high antithrombogenicity and graft patency. 150 keV-He⁺ irradiated collagen with a fluence of 1×10¹⁴ ions/cm² simultaneously has the 2 properties of antithrombogenicity and cell attachment. In vitro platelet adhesion and plasma protein adsorption were evaluated to investigate the mechanisms of antithrombogenicity of these surfaces. Antithrombogenicity of the He⁺-irradiated collagen was caused by the reduction of the plasma protein adsorption such as the von Willebrand factor by ion beam irradiation.
He⁺-irradiated collagen surfaces will be useful for the substrates of small-diameter vascular grafts.

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