The current status and new development of intravenous rt-PA therapy and management of transient ischemic attack (TIA) were systematically reviewed. Recently, many clinical and registered studies have been reported from Japan, which indicated that the efficacy and safety of intravenous rt-PA therapy using a 0.6 mg/kg dose of alteplase were almost comparable with those reported in the USA and Europe where 0.9 mg/kg dosage of alteplase is standard. The problems which now confront us are expanding the therapeutic time window from 3 hours to 4.5 hours, and a comprehensive comparison of outcomes between the two dosing regimens, 0.6 vs. 0.9 mg/kg. We discussed expanding the therapeutic time window using sophisticated imaging protocols and the clinical implications of new rt-PA agents, sonothrombolysis and intravascular devices for thrombectomy. The concept of TIA has dramatically changed in this decade. TIA patients often have acute ischemic lesions which can be visualized only with diffusion-weighted imaging (DWI), and more frequently have ischemic events soon after the initial TIA episode, within 24 hours or a couple of days, much sooner than previously believed. High risk profiles are more easily indentified and timely and appropriate therapeutic interventions with risk controls, antiplatelet or anticoagulant agents, carotid endarterectomy or carotid stenting can avoid future catastrophic ischemic events in patients with acute TIA or more appropriately 'acute cerebrovascular syndrome (ACVS)' .With support from the MHLW our TIA research team is now carrying out clinical studies to establish management strategies for Japanese TIA patients.

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The present review focuses on the results of recent randomized controlled studies comparing the safety and efficacy of carotid stenting (CAS) and endarterectomy (CEA) for treating symptomatic and asymptomatic carotid stenosis, and we also discuss the impact of these studies on our clinical practice. Proper indications and systematic operator training systems are critical components for improving the periprocedural results for CAS and CEA. The routine use of a distal embolic protection device is also essential to prevent cerebral ischemic complications associated with CAS. Proper patient selection for either CAS or CEA is becoming more and more important to achieve excellent results in treating carotid stenosis with various risk profiles.

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Magnetic resonance (MR) imaging is widely used to assess atherosclerotic plaques in patients with carotid stenosis. However, the imaging techniques used in this field vary remarkably among institutions and vendors, and this may impair the accuracy of predicting intraplaque components. The image contrast of intraplaque components may deteriorate in cardinal techniques such as ECG-gated black-blood method. However, this issue may be resolved by using conventional spin-echo or MR angiography images, with appropriate scanning parameters. Further studies using standardized protocols are required in order to establish the clinical significance of MR stroke imaging and MR plaque imaging in the management of patients with cervical carotid stenosis.

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Mechanical thrombectomy for acute stroke has been used since the MERCI retriever was approved in Japan in 2010. The advantage of mechanical thrombectomy is to shorten time to recanalization compared with intravenous administration of rt-PA and local fibrinolytic therapy. The Penumbra system was also approved in 2011, and stent-like new generation thrombectomy devices have already been introduced for endovascular recanalization therapy for acute stroke in the United State and Europe. According to a retrospective study on the initial experience of MERCI retriever treatment at the top fifteen Japanese stroke centers, the successful recanalization rate is about 75% for TICI 2 A to 3, and 48% for TICI 2B to 3. Symptomatic intracranial hemorrhage occurred in 6%, and favorable outcomes were obtained in 28% of all cases and over 40% in successfully recanalized cases. Post market surveillance of the MERCI retriever and Penumbra system are on going in Japan. Mechanical thrombectomy is a promising treatment for acute stroke, as it has a wider time window compared with intravenous rt-PA administration, and which is indicated for only about 5% of acute stroke patients. New Mechanical thrombectomy technologies for acute stroke should be introduced after confirming their safety and efficacy.

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Purpose : Indication and usefulness of endovascular treatment for intracranial large vessel stenosis are considered based on our clinical experience and literature review. Material and Methods : A total of 56 patients who received endovascular treatment were analyzed. Endovascular treatment was performed for the patients with symptomatic intradural stenosis and symptomatic/asymptomatic extradural stenosis when the stenotic degree was greater than 70%. Results : The technical success rate was high (98.2%) and a favorable outcome was obtained in 93 % of the patients. On the other hand, morbidity and mortality were observed in 4 of 56 patients (7.0%), and these were caused by perforator occlusion and thrombotic/hemorrhagic complication. Discussion and conclusions : It has been reported that ischemic events occur in more than 10% of patients despite medical treatment, and the effect of intracranial stenting has been expected. However, it was reported that the clinical results of the aggressive medical treatment group were superior to those of the stenting group in randomized controlled trial (SAMMPRIS trial). Therefore, aggressive medical treatment would be standard for symptomatic intracranial large vessel stenosis and endovascular treatment will be indicated for medically refractory patients. Also, it seemed important to avoid treating lesions close to perforators and to perform appropriate antithrombotic treatment to decrease complications.

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Background and purposes : In clipping surgery for aneurysmal subarachnoid hemorrhage, the aneurysmal bleb is often conformed as the rupture point. Moreover, aneurysmal blebs have been identified as a factor for increased risk of rupture. We investigate possible associations between the hemodynamics and the formation of blebs in cerebral aneurysms. Methods : A patient with a growing aneurysmal bleb was selected for this study. Computational fluid dynamics simulations were performed under pulsatile flow conditions for the bleb model and the bleb cut model which was constructed by virtually removing the bleb. Results : Normalized wall shear stress (NWSS), gradient oscillatory number (GON), oscillatory shear index (OSI) and static pressure (SP) in the bleb formation area were higher than those in the aneurysmal dome. The aneurysm formation indicator (AFI) in the bleb formation area was similar to AFI in the aneurysmal dome. Wall shear stress gradient (WSSG) in the bleb formation area was smaller than WSSG in the aneurysmal dome. The specific parameter for bleb formation area was SP. Bleb growing states lead to reduction of OSI, NWSS, OSI and GON. In visualizations of flow structures, a high-flow jet impacted the bleb formation area. Conclusions : These results suggest that aneurysmal blebs are formed by damage caused by static pressure and the aneurysmal wall inflow jet based on the endothelial dysfunction.

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We report the case of a patient with posterior reversible encephalopathy syndrome (PRES) who underwent continuous ventricular drainage (CVD) for associated obstructive hydrocephalus. A 46-year-old man was transported to hospital with deteriorating headache, nausea, drowsiness and truncal ataxia. Magnetic resonance imaging revealed acute obstructive hydrocephalus secondary to edema of the cerebellar white matter, brainstem and thalamus. Continuous ventricular drainage was initiated for the management of obstructive hydrocephalus. Blood pressure and brain edema were managed using osmotic diuretics. One and a half months later, the patient was discharged without any symptoms. Although reports of PRES have been increasingly common in recent years, descriptions of such severe cases treated using CVD have been uncommon. Appropriate treatments should be selected based on an understanding of the etiology and clinical features of PRES.

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Background : Tumefactive multiple sclerosis (tMS) is a demyelinating disease which presents imaging features mimicking a malignant brain tumor, thereby requiring brain biopsy in most cases for definitive diagnosis. Case presentation: A 37-year-old man visited our clinic complaining of mild motor weakness in his left leg (5-/5). Brain MRI demonstrated a ring-enhancing lesion involving the bilateral posterior corpus callosum. Tumefactive MS was suspected as a possible diagnosis, but a cerebral spinal fluid (CSF) examination did not detect oligoclonal banding, and the patient was scheduled for further imaging studies including PET to confirm the diagnosis. A few days later, however, the patient returned to our hospital because of a rapid deterioration of the left hemiparesis accompanied with consciousness disturbance, and a 3-day consecutive steroid pulse therapy was performed which led to neurological improvement. However, a follow-up MRI showed further enlargement of the lesion, and open biopsy of the periventricular enhancing lesion was performed. Histological examination confirmed the diagnosis of demyelination, consistent with the diagnosis of tMS. After a one-month steroid treatment, the lesion on MRI shrunk in size, but the mild left hemiparesis (4+/5) remained as a sequela. Conclusion : When a definite diagnosis of tMS is not obtained by CSF examination or imaging studies, neurosurgeons should not hesitate to perform a histological examination for prompt definite diagnosis of the disease, because fulminant deterioration of clinical symptoms and permanent neurological deficit can occur in tMS.

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