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Extracranial--intracranial (EC-IC) arterial bypass surgery was developed to prevent subsequent stroke by improving hemodynamics distal to the occluded intracranial artery, but its utilization has been decreasing due to the development in medical treatment. However, EC-IC bypass surgery may be effective for arresting or reversing cognitive decline in patients with cerebral ischemia. A 69-year-old man with the left internal carotid artery occlusion that manifested as scattered cerebral infarction of the left hemisphere presented with dysarthria and transient right hemiparesis. Hemodynamic condition was impaired in the left side, and therefore, EC-IC bypass surgery was performed to prevent recurrence of cerebral infarction. Neuropsychological examination at 6 months after the surgery showed marked improvement as compared to the preoperative examination and there was no recurrence of stroke in the patient. EC-IC bypass may contribute to the improvement of cognitive function as well as the prevention of recurrence of cerebral infarction in patients with hemodynamic insufficiency, but there might be a threshold of hemodynamic impairment with respect to the reversibility of cognitive performance. Investigation of the target and timing can identify cases in which the cognitive function is improved by surgery. [ABSTRACT FROM AUTHOR]

Background: Intracranial embolism related to cerebral angiography is rare but one of the complications of the procedure. However, the standard management of acute intracranial embolism for this etiology has not been established, and there have been very few reports in the past. Case Description: A 68-year-old male was incidentally found to have an unruptured aneurysm of anterior communicating artery (ACoA). Immediately after the cerebral angiography for the purpose of detailed examination of the aneurysm, the right partial hemiparalysis and mild aphasia developed. Magnetic resonance imaging/angiography (MRI/A) revealed an occlusion in the peripheral part of the left middle cerebral artery (MCA). Due to the existence of magnetic resonance angiography-diffusion mismatch, emergent craniotomy was immediately performed to remove intra-arterial thrombus. We also performed clipping for an unruptured ACoA aneurysm with this approach. Postoperative MRI/A showed that the occluded artery was recanalized and a slight infarction was observed in the left cerebral hemisphere. The patient was discharged on foot and followed at outpatient clinic over 4 years without no neurological deficit. Conclusion: Emergent surgical embolectomy for distal MCA occlusion related to cerebral angiography followed by neck clipping for an unruptured aneurysm of the ACoA was successful in treating acute occlusion of the peripheral part of the MCA in a patient with an unruptured aneurysm. As there are few similar cases, there is controversy about the best management, but this surgical method can be a safe and effective treatment. [ABSTRACT FROM AUTHOR]

Background: Subarachnoid hemorrhage (SAH) due to rupture of basilar artery dissection (BAD) is extremely rare and often has a poor prognosis. Since ruptured BAD has high rate of rebleeding and mortality, treatment to prevent rerupture is mandatory in the acute phase. However, to date, no optimal treatment has been established which satisfies secure prevention of rerupture and ischemia simultaneously. Herein, we report a case of SAH due to BAD treated with proximal occlusion of basilar artery with superficial temporal artery (STA)-superior cerebellar artery (SCA) bypass, preventing rebleeding securely and ensuring adequate blood flow in the upper basilar region. Case Description: A 48-year-old male presenting with headache and altered mental status was found to have SAH and BAD. To prevent rerupture, proximal occlusion of basilar artery with STA-SCA bypass using anterior transpetrosal approach was performed. The postoperative course was relatively good and there is no evidence of recurrent arterial dissection. Conclusion: Proximal occlusion of the basilar artery combined with STA-SCA bypass was successful in preventing rerupture of BAD and ensuring blood flow in the upper basilar region. Although there is controversy regarding acute treatment for ruptured BAD, direct proximal occlusion with sufficient revascularization using bypass skull base technique may be one of the optimal treatments even in this era of endovascular treatment. [ABSTRACT FROM AUTHOR]

Background: Some complications associated with cisternal drainage have been reported; however, there are few reports on direct vascular injury caused by cisternal drain. We experienced two rare cases of thalamic infarction caused by cisternal drain placement during open clipping for a ruptured anterior communicating artery (AcomA) aneurysm through an anterior interhemispheric approach. Case Description: Two cases of ruptured AcomA aneurysm were treated by surgical clipping through an anterior interhemispheric approach, and then a cisternal drain was inserted from opticocarotid space toward prepontine cistern. Postoperatively, the magnetic resonance imaging showed unilateral anterior-medial thalamic infarction in both two cases. By reviewing the postoperative computed tomography and digital subtraction angiography, it was suspected that the cisternal drain, which was inserted slightly deep, obstructed the P1 perforator because of an anatomical variation involving a lowered basilar bifurcation and caused postoperative unilateral paramedian thalamic infarction. Conclusion: To avoid these complications, neurosurgeons should consider the potential for P1 perforator injury related to cisternal drain placement. [ABSTRACT FROM AUTHOR]

Background: Very large and giant aneurysms (=20 mm) of the internal carotid artery (ICA) bifurcation (ICAbif) are definitely rare, and optimal treatment is not established. Endovascular treatments are reported as suboptimal due to difficulties of complete occlusion and tendencies to recanalization. Therefore, direct surgery remains an effective strategy if the clipping can be performed safely and reliably, although very difficult. Case Description: Two cases of ICAbif aneurysms (>20 mm) were treated. Prior assistant superficial temporal artery (STA)-middle cerebral artery (MCA) bypass was performed to avoid ischemic complications during prolonged temporary occlusion of the arteries in both cases. In Case 1 (22-mm aneurysm), the dome was inadvertently torn in applying the clip because trapping had resulted in insufficient decompression. Therefore, in Case 2 (28-mm aneurysm), almost complete trapping of the aneurysm and subsequent dome puncture was performed, and the aneurysm was totally deflated by suction from the incision. This complete aneurysm decompression allowed safe dissection and successful clipping. Conclusion: Trapping, deliberate aneurysm dome puncture, and suction decompression from the incision in conjunction with assistant STA-MCA bypass can achieve complete aneurysm deflation, and these techniques enable safe dissection of the aneurysm and direct clipping of the aneurysm neck. Direct clipping with this technique for very large and giant ICAbif aneurysms may be the optimal treatment choice with the acceptable outcome if endovascular treatment remains suboptimal. [ABSTRACT FROM AUTHOR]

Background: Thoracic ossification of the yellow ligament (OYL) may contribute to myelopathy. In the case presented, the patient additionally had a chronic posterior fossa arachnoid cyst with an acquired Chiari I malformation and cervicothoracic syrinx. Case Description: A 40-year-old female with a posterior fossa arachnoid cyst found 17 years ago, and newly acquired Chiari I malformation (tonsils down 5 mm) with a C7-T5 syrnix, presented with the new onset of lower extremity myelopathy. The MR documented marked dorsolateral cord compression due to T11/T12 OYL. Six months following a laminectomy for resection of OYL, the patient was asymptomatic. Conclusion: In patients presenting with the new onset of lower extremity myelopathy, evaluation of the complete neuraxis may be warranted. Here, the patient has an unchanged posterior fossa arachnoid cyst with an acquired Chiari I malformation/C7-T5 syrinx. However, the patient's symptoms were fully attributed to the MRdocumented T11/T12 OYL that was successfully resected. [ABSTRACT FROM AUTHOR]

Aiming to suppress chatter vibration during machining of huge mechanical parts, dies, and molds, a design method for a damped arbor imbedded with a mass damper was devised. First, an analysis method coupled with Rayleigh's method was developed and used to calculate the stiffness of an arbor with a tapered hollow space for installing the mass damper inside. In the formulation of the vibrating system with two degrees of freedom, the displacement ratio is introduced for accurate calculation of the counter force of the damper mass. Then, the shape and size of the hollow space was optimized in order to maximize the negative real part of the compliance of the arbor. The proposed design method can increase the dynamic stiffness of the damped arbor with a hollow with the minimum reduction in its static stiffness. Furthermore, it is found that once the damper is optimized for the maximum length of an arbor in a certain design range, it can be applied to a shorter arbor without deterioration of dynamic stiffness. Finally, chatter noise and machined surface roughness measured experimentally proved that a damped arbor prototyped by the proposed design method has much higher cutting performance than a conventional one.

To improve cutting performance and suppress chatter vibration during machining of large mechanical parts with a long slender cutting tool, a design method was investigated for a tuned mass damper imbedded tool arbor. To clarify the effects of the dynamic stiffness and damping ratio of the weight which is supported at both ends inside the hollow space of the arbor on the dynamic compliance at the end of the arbor, finite element analysis was conducted. First, since the weight has twisting vibration in its 2nd order natural mode, it is necessary to consider 2 degrees of freedom of the motion to optimize the damper. Then, the relationship between the motion of the damper and damping performance is clarified in accordance with the change in spring constant of the weight. From the results, an area exists where there is little change in the maximum negative real part of the compliance due to the change in spring constant. Designing the spring constant in this area stabilizes the damping performance. Furthermore, comparison of the results of finite element analysis and the conventional particle model analysis revealed that the results of finite element analysis show a smaller real part of the compliance than those of particle model analysis. This is because the inertial forces of the weight are applied not to the end of the arbor but to the tool holder side of the arbor and the damping effect is smaller than that in the particle model.

We present a 37-year-old male case of cystic suprasellar huge craniopharyngioma, who presented with significant memory disturbance due to obstructive hydrocephalus. Combined interhemispheric and pterional approach was chosen to resect huge suprasellar tumor. Interhemispheric trans-lamina terminalis approach was quite effective to resect third ventricular tumor, while pterional approach was useful to dissect tumor out of basilar perforators and stalk. [ABSTRACT FROM AUTHOR]