Introduction: A prospective study was conducted to determine the surgical standard for small unruptured intracranial aneurysms (SUAVe Study, Japan). The aims of this study were to clarify the natural history of incidentally found small unruptured aneurysms (less than 5 mm in diameter) without treatment and to identify risk factors associated with rupture. Materials and Methods: From September 2000 to January, 2004, 540 aneurysms (446 patients) were registered. Of these, 448 unruptured aneurysms<5 mm in size (374 patients) have been followed up for a mean of 42.5 months (1,553.5 aneurysm-years and 1,306.5 person-years). We calculated the average annual rupture rate of small unruptured aneurysms and also investigated risk factors that contribute to rupture and enlargement of these aneurysms. Results: Seven aneurysms ruptured (three of 250 single type aneurysms and 4 of 198 multiple type aneurysms). The average annual risks of rupture associated with small unruptured aneurysms were 0.54% overall, 0.34% for single aneurysms, and 0.95% for multiple aneurysms. Patient<50 years of age (p = 0.046 ', hazard ratio (HR), 5.23; 95% CI, 1.03-26.52), aneurysm diameter of≧4.0 mm (p=0.023; HR, 5.86; 95% CI, 1.27-26.95), hypertension (p=0.023 ; HR, 7.93 ; 95% CI, 1.33-47.42), and multiplicity of aneurysm (p=0.0048 ; HR, 4.87 ; 95% CI, 1.62-14.65) were found to be significant predictive factors for rupture of small aneurysms. On the other hand, 30 aneurysms (25 cases) enlarged during follow-up. Women (p=0.042 ; HR, 2.95; 95% CI, 1.04-8.35), aneurysm diameter of≧4.0 mm (p=0.0025 ; HR, 3.34; 95% CI, 1.53-7.31), multiplicity of aneurysm (p=0.036; HR, 1.72; 95% CI, 1.24-3.75), and current smoking (p=0.027; HR, 3.59; 95% CI, 1.19-10.86) were revealed to be significant predictive factors for aneurysm enlargement. Conclusion: The annual rupture rate of small unruptured aneurysms is quite low. In particular, careful attention should be paid to the treatment indications for single-type unruptured aneurysms<5 mm. If the patient is<50 years of age, has hypertension, and multiple aneurysms with diameters of≧4 mm, surgical or endovascular treatment should be considered to prevent future aneurysmal rupture. Most importantly, treatment decisions for unruptured aneurysm should not be based solely on the morphological factors of aneurysms, also on the patientrelated risk factors.

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In recent years, Computational Fluid Dynamics (CFD) techniques have been used in various fields. At present, mechanisms for cerebral aneurysm appearance, enlargement, and rupture are not yet fully understood. Many papers have addressed the use of CFD analysis in the medical field. Some of these papers investigate various flow parameters (Wall Shear Stress: WSS, Shear Strain Rate: SSR, Oscillatory Shear Index: OSI, Energy Loss: EL, Pressure Loss Coefficient: PLC) which might be related to aneurysm growth and rupture, using CFD. Amongst these measurable factors, wall shear stress (WSS) attracts much attention. However, there are still many controversial opinions on the role of WSS is cerebral aneurysm dynamics. In this paper, we report the results of CFD analysis on cerebral aneurysms and we compare our results to other recent papers in the field.

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Endovascular treatment for cerebral aneurysms originally started with simple helical bare platinum coils. Since then, balloon neck remodeling technique, complex shape coils, surface modification coils and stent assisted embolization have been developed to treat difficult aneurysms with stable long-term results. ISAT revealed the superiority of endovascular treatment for acutely ruptured aneurysms. However, the efficacy of endovascular treatment for unruptured aneurysms has not been established yet, even though there are many retrospective reports with good outcomes. As a new treatment modality, a flow diverter has started to be used to treat giant, partially thrombosed or fusiform aneurysms, which were difficult to cure by conventional methods, with promising initial results. Endovascular treatment employing this new method enables us to treat more aneurysms than ever.

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The purpose of treating asymptomatic unruptured cerebral aneurysm (aUCA) is not only to prevent subarachnoid hemorrhage but also to improve a patient's quality of life (QOL) by removing the fear of eventual rupture. We surveyed actual QOL of patients with aUCAs to see whether the surgical intervention could be justified based on improvement of QOL. Patients' QOL were examined using the MOS Short Form 36-Item Health Survey (SF-36), one of the most prevalent health-related QOL measures worldwide. The following trends were discovered in the prospective and retrospective studies of population actually underwent surgery : A statistically significant decrease of QOL was found prior to the surgery, which may have been caused by the mere knowledge of the aneurysm. A further but temporal decline of QOL was also found after the clipping surgery, which nonetheless returned to the standard of that found in the Japanese reference population within 3 years. We also came to realize how acknowledgment of one's own risk associated with aneurysm interfered with the activity of daily life and resulted in a decline of QOL among the population that underwent brain check-up examinations. There was also an interesting trend worth mentioning that the QOL in elderly patients did not fluctuate like it did in the younger cohorts regardless of the knowledge of aUCAs or before/after surgery, so that we assume that QOL issues may not interfere with the decision-making process for surgery in elderly patients. The stressful open skull surgery procedure still remains the major treatment for aUCAs so that decision-making is quite a difficult task that every neurosurgeon has to face. Our study suggests that improved QOL may well validate surgical treatment for aUCA and may serve as an additional guide for the difficult decision-making process for patients with aUCAs.

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Subarachnoid hemorrhage (SAH) resulting from rupture of an intracranial aneurysm (IA) is one of the most devastating forms of stroke. Given the catastrophic sequelae after subarachnoid hemorrhage, developing a novel therapeutic modality which prevents IA progression and rupture is imperative. Results from studies using an experimentally induced intracranial aneurysm model have provided us a wide variety of evidence supporting the notion that IA is closely associated with inflammation. Expression of monocyte chemotactic protein-1 (MCP-1) is up-regulated in rat IA walls at the early stage of IA formation, which is transactivated through nuclear factorkappa B (NF-κB), a family of transcriptional factors regulating various proinflammatory genes. MCP-1 recruits macrophages into aneurysmal walls, which secretes matrix metalloproteinases (MMPs) -2 and -9 causing degradation of the extracellular matrix in IA walls. Three-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins), widely used cholesterol-lowering drugs, have vascular protective effects known as "pleiotropic" effects. Treatment with statins suppresses the development of rat IAs by inhibiting inflammatory reactions in aneurysmal walls. Statin also has a preventive effect on the progression of preexisting rat IAs. Therefore, statin is a promising candidate of a novel medical treatment for the prevention of IA progression and rupture. A multi-center prospective randomized trial examining the inhibitory effect of statins on progression and rupture of human IAs, Small Unruptured Aneurysm Verification-Prevention Effect against Growth of cerebral Aneurysm Study Using Statin (SUAVe-PEGASUS) study is now ongoing.

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Percutaneous subdural tapping for chronic subdural hematoma (CSDH) can measure initial hematoma pressure, which cannot be measured using burr-hole craniotomy. Initial hematoma pressure has not been discussed as a risk factor for recurrence. We evaluated the clinical features for recurrence, which included initial hematoma pressure. The study involved 71 unilateral CSDH cases whose initial hematoma pressure was measured using percutaneous subdural tapping. Clinical recurrence was identified in 19 cases (23%). Age, sex, neurological grading, alcohol consumption, presence of head injury, hypertension, diabetes mellitus, antiplatelet, anticoagulant medication, hematoma volume on computed tomography (CT) images, and initial hematoma pressure were compared between non-recurrence and recurrence groups. The initial hematoma pressure was 12.6+4.5cmH_2O in the non-recurrence group, and 15.5±6.2cmH_2O in the recurrence group (p<0.05). The other factors did not differ significantly, except hematoma volume on CT images (92±45 ml in the non-recurrence group and 123±43 ml in the recurrence group, p<0.05). Cases with high initial hematoma pressure should be closely observed.

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Object: Spinal intradural extramedullary cavernous angiomas are a rare clinical entity. Only 23 surgically treated cases have been reported. The authors report on a unique case with a thoracic intradural extramedullary cavernous angioma in a patient who presented only sudden onset of abdominal pain at first. Cases: The 52-year-old woman presented with sudden onset of abdominal pain. Although her abdominal pain improved the next day, she complained of low back pain and was admitted to our hospital. MRI showed an intradural and extramedullary mass lesion situated between the Th10 and Th12 vertebral bodies. The patient underwent right hemilaminectomy at T10-12 with total removal of the lesion. Histopathological examination revealed that the lesion was a cavernous angioma. She was free of any neurological defect postoperatively. Conclusion: Complete surgical excision may be possible without causing morbidity in the treatment of intradural extramedullary cavernous angiomas. Since the outcome depends on the severity of preoperative neurological dysfunction, precise diagnosis and timely treatment are mandatory. The image of a spotty high intensity lesion in T2-weighted MRI is able to confirm the presence of the cavernous angioma.

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We report a case of recurrent cerebral infarctions caused by intravascular lymphoma (IVL) diagnosed solely by brain biopsy. A 58-year-old man presented with transient aphasia and epileptic seizures. Magnetic resonance imaging revealed multiple cerebral infarctions. He had repeatedly presented with multifocal cerebral infarction and seizure. Blood examinations showed LDH and sIL-2R serum levels, suggesting malignant lymphoma. Skin, bone marrow, and muscle biopsies failed to produce a diagnosis histologically. However, an open brain biopsy of the right insular cortex and temporal lobe disclosed large atypical intravascular cells in the small cortical vessels. The histological diagnosis was intravascular large B-cell lymphoma. Although he underwent R-CHOP therapy, he died 1 month after the definitive diagnosis. It is difficult to diagnose IVL because it has no specific symptoms or radiological findings. IVL should be considered as a differential diagnosis for incomprehensible multiple recurrent ischemic lesions. Brain biopsy can be useful for early diagnosis of IVL.

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