In the recent large randomized trials performed in North America and Europe, the beneficial effects of and guidelines for carotid endarterectomy (CEA) were reconfirmed for both symptomatic and asymptomatic patients with high-grade carotid artery stenosis. These benefits can be realized only if perioperative mortality and morbidity are minimized. Clinical risk factors associated with an increased incidence of perioperative complications from CEA have been categorized into several groups, and Sundt et al. identified general medical, neurologic, and angiographically defined risk factors. Here we review the previous reports and our experiences, and present some clinical risk factors to identify patients with increased risk of perioperative events. Indication and surgical techniques in these patients with high risk factors are also discussed.

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Giant aneurysms are occasionally associated with thrombosis and present themselves as mass lesions due to continuous aneurysmal growth in spite of the presence of the intra-aneurysmal thrombosis. No consensus has been reached on the underlying growth mechanism or the best method for surgical management of partially thrombosed giant aneurysms. In this review article, we describe the growth mechanism and the optimal treatment for these aneurysms, especially concerning 7 patients with the aneurysm arising from the vertebral artery (VA) and the posterior inferior cerebellar artery (PICA). Pathological examination revealed that the aneurysms had staged clots, an open lumen, and intrathrombotic channels with or without an endothelial lining. New thrombus formation and hemorrhaging were seen around the channels. On the other hand, development of channels in the aneurysmal wall were rare. The authors suggest that the development of the intrathrombotic capillary channels may be an important factor in the growth of thrombosed giant aneurysms. The optimal treatment for aneurysms of this type, especially when located in the posterior fossa, is thought to be aneurysmectomy to decompress the brainstem or the cerebellum. If there is a risk of ischemic complications after occlusion of the VA or the PICA, reconstruction of these arteries is recommended.

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Objective : The aim of this study is to assess whether or not aneurysm (AN) surgery can be performed in patients with ruptured cerebral aneurysms using three-dimensional computed tomographic angiography (3D-CTA) alone, withut conventional angiography (CA). Also, we present our techniques to improve the diagnostic ability of 3D-CTA for AN surgery. Methods and Results : In our first study, 60 cases of aneurysmal subarachnoid hemorrhage (SAH) were prospectively evaluated, both by 3D-CTA and CA. Both 3D-CTA and CA had 100% accuracy in diagnosing ruptured ANs. Whereas in diagnosing unruptured ANs, the diagnostic accuracy of 3D-CTA was 96% and that of CA was 92%. Based on these results, 83 consecutive patients with SAH who underwent surgery in the acute stage since December 1996 were studied. All of the 83 ruptured ANs were effectively diagnosed by 3D-CTA. In order to get additional information, CA was carried out in seven of the cases (4 dissecting vertebral artery ANs, 2 basilar tip ANs and 1 small basilar-superior cerebellar artery AN). It was important to set an adequate scan range and to avoid the motion artifact. In order to prevent missing the AN, we have been using our own 12 routine images. Conclusions : The diagnostic accuracy of 3D-CTA is equal or superior to that of CA for ANs. Except in special cases, such as dissecting ANs, we consider that the patient with an AN can be operated on using only the information provided by 3D-CTA.

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Recent advances in neuroimaging of the spine and spinal cord are described based upon our clinical experiences with spinal disorders. Preoperative neuroradiological examinations, including magnetic resonance (MR) imaging and computerized tomography (CT) with three-dimensional reconstruction (3D-CT), were retrospectively analyzed in patients with cervical spondylosis or ossification of the posterior longitudinal ligament (130 cases), spinal trauma (43 cases) and intramedullary spinal cord tumors (92 cases). CT scan and 3D-CT were useful in elucidating the spine pathology associated with degenerative and traumatic spine diseases. Visualization of the deformity of the spine or fracture-dislocation of the spinal column with 3D-CT helped to determine the correct surgical treatment. MR imaging was most important in the diagnosis of both spine and spinal cord abnormalities. The axial MR images of the spinal cord were essential in understanding the laterality of the spinal cord compression in spinal column disorders and in determining surgical approaches to the intramedullary lesions. Although non-invasive diagnostic modalities such as MR imaging and CT scans are adequate for deciding which surgical treatment to use in the majority of spine and spinal cord disorders, conventional myelography is still needed in the diagnosis of nerve root compression in some cases of cervical spondylosis.

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To evaluate which MR imaging sequence is the best and most useful neuroimaging the surgical anatomy of the posterior fossa, various MR imaging sequences, combined with the oblique sagittal or coronal imaging direction suitable for the lateral or midline suboccipital approach to the posterior fossa, were estimated. MR examinations were performed with a T1-weighted, a T2-weighted, a FLAIR, a heavily T2-weighted, and a reversed heavily T2-weighted sequence. As a result, it was detemined that the best MR imaging sequence was a reversed heavily T2-weighted image, because of its clear visualization of the cranial nerves, vertebro-basilar system, the IVth ventricle, cerebellum and brain stem, including the bony structure. A reversed heavily T2-weighted MR cisternography of oblique sagittal or coronal view is a useful planning aid.

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Cerebral arterial trunk aneurysms unrelated to the branching zones can be classified into several pathological types based on the condition of the internal elastic lamina (IEL) and the state of the intima. Dissecting aneurysms should be recognized as one of those subtypes. In the pressent study, we analyzed the precise structure of 9 aneurysm specimens of cerebral dissecting aneurysms. We found that the primary mechanism of cerebral dissecting aneurysms is acute disruption of the IEL. In all of the 9 aneurysms studied, the pseudolumen was communicated with true lumen through the disrupted portion IEL. Most cerebral dissecting aneurysms presumably have one entry point into the pseudolumen and have no reentry.

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In this paper discuss the surgical treatment of dural arteriovenous fistulas around the superior sagittal and transverse sigmoid sinuses. Although transarterial or transvenous embolization are primarily used in the treatment of dural arteriovenous fistulas, it is very difficult to completely obliterate the fistulas. The final goal of treatment of this lesion should be complete occlusion of the lesion. Otherwise, the possibility of recurrence and the risk of bleeding from the lesion will continue. We are considering that surgical resection of the lesion with the affected sinus is the best way to accomplish the final goal of treatment, that is the complete obliteration of the lesion. To decrease the risk of intraoperative bleeding, the arterial supply into the lesion was embolized before the surgery. In the practical surgery, the bone flap was constructed piecemeal and meticulous hemostasis was carried out, because bleeding from the epidural space was usually remarkable. Using B-mode echo imaging, the affected sinus was distinguished from the unaffected sinus. The direction of the draining cortical venous blood flow was detected with a micro-Doppler flow meter, and then the area of the dura mater and dural sinus involved with the arteriovenous fistula were confirmed and removed totally. Postoperatively, late intracerebral hemorrhage or edema may be induced by venous infarction or hyperperfusion pressure breakthrough secondary to the shut down of the draining cortical venous blood flow.

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Improvement of the prognosis for patients with gliomas near the motor strip requires maximum tumor resection with preservetion of the motor function. Preoperative functional and anatomical imaging was used to correlate the anatomical relationship between the tumor, the motor strip, and the descending motor pathways. A magnetic resonance (MR) imaging-linked whole head magnetoencephalography system was used to localize the somatosensory evoked magnetic fields caused by stimuli of the lip, the thumb, the median nereve, and the ulnar nerve. Functional MR imaging was performed with a 1.5 Tesla scanner during repetitive opening and closing of each hand and lip protrusion. The hand-digit motor cortices were located in the so-called "precentral knob" inside the characteristic inverted-omega shape on axial MR images of the brain on the basis of the pattern of the sulcus. The hand-digit somatosensory cortices were localized at the lateral shoulder of the inverted-omega shape. The operative field was simulated by superimposing the superficial venous image obtained by MR imaging using a three-dimensional phase contrast technique on the surface anatomy scan (SAS) of the brain obtained by the multiple-slice SAS method. The hand-digit motor cortices were located in the so-called" middle knee" or "Broca's middle bend". The SAS superimposed on the superficial venous image revealed the surface anatomical relationship between the tumor and the hand-digit motor cortices. Fiber mapping images using diffusion-weighted MR imaging are useful for evaluating the white matter neuronal tracts incuding the descending motor pathways. Combination of these preoperative anatomical and functional imaging methods allowed projection of the best surgical approach and extent of resection of tumors around the motor strip without causing additional motor deficit. Maximum tumor resection with minimal morbidity is possible using intraoperative neurophysiological mapping methods such as direct cortical and subcortical simulation techniques to localize the motor pathways with a neuronavigation system.

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