• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.30 no.3
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• pp.209-219
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• 1994

The practical application of riblet to three dimensional double model, for viscous drag reduction, was studied analytically by intergal solution to three dimensional turbulent boundary layers. The case of a V-groove riblet technique on the shear stress and boundary layer velocities were incooperated in the computation of the flow over a smooth slender ship hull. As the results the possible mechanism of turbulent drag reduction by riblets are then suggested based on detailed studies of near-wall turbulence characteristics. And a turbulent boundary layer calculation scheme based on a momentum integral method was modified for the computer program. An example of the calculation results is presented.

• Journal of the Society of Naval Architects of Korea
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• v.41 no.5
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• pp.8-13
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• 2004

In order to better understand the characteristics of the flow field around the submerged hydrofoil of finite span with high speed and shallow submergence. a numerical code which can solve the flow around a fast lifting body under the free surface was developed and used to obtain various interesting features of the flow. The code was based on the panel method of Hess( 1972), and the free surface condition was linearized to conform with the assumption of the high Froude number. It is shown that the effect of the change of submerged depth. angle of attack and aspect ratio upon the sectional lift coefficient is rather significant for the case of the chosen example wing, which has the rectangular planform. Since Lee(2002)'s theoretical results were for the wing of elliptical planform, the direct comparison of the two results was not possible. It seems that more computational results are in need to compare the theoretical and the numerical prediction in detail.

• Journal of Korean Neurosurgical Society
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• v.46 no.1
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• pp.31-37
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• 2009

Objective : This study was performed to elucidate the technical and patient-specific risk factors for postoperative ischemia in patients undergoing temporary arterial occlusion (TAO) during the surgical repair of their aneurysms. Methods : Eighty-nine consecutive patients in whom TAO was performed during surgical repair of an aneurysm were retrospectively analyzed. The demographics of the patients were analyzed with respect to age. Hunt and Hess grade on admission, Fisher grade of hemorrhage, aneurysm characteristics, timing of surgery, duration of temporary occlusion, and number of temporary occlusive episodes. Outcome was analyzed at the 3-month follow-up, along with the occurrence of symptomatic and radiological stroke. Results : In overall, twenty-seven patients (29.3%) had radiologic ischemia attributable to TAO and fifteen patients (16.3%) had symptomatic ischemia attributable to TAO. Older age and poor clinical grade were associated with poor clinical outcome. There was a significantly higher rate of symptomatic ischemia in patients who underwent early surgery (p=0.007). The incidence of ischemia was significantly higher in patients with TAO longer than 10 minutes (p=0.01). In addition, patients who underwent repeated TAO, which allowed reperfusion, had a lower incidence of ischemia than those who underwent single TAO lasting for more than 10 minutes (p=0.011). Conclusion : Duration of occlusion is the only variable that needs to be considered when assessing the risk of postoperative ischemic complication in patients who undergo temporary vascular occlusion. Attention must be paid to the patient's age, grade of hemorrhage, and the timing of surgery. In addition, patients undergoing dissection when brief periods of temporary occlusion are performed may benefit more from intermittent reperfusion than continuous clip application. With careful planning, the use of TAO is a safe technique when used for periods of less than 10 minutes.

• Journal of Korean Neurosurgical Society
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• v.51 no.5
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• pp.268-271
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• 2012

Objective : To propose grading of intracerebral hemorrhage (ICH) in ruptured middle cerebral artery (MCA) aneurysms, which helps to predict the prognosis more accurately. Methods : From August 2005 to December 2010, 27 cases of emergent hematoma evacuation and aneurysm clipping for MCA aneurysms were done in the author's clinic. Three variables were considered in grading the ICH, which were 1) hematoma volume, 2) diffuse subarachnoid hemorrhage (SAH) that extends to the contralateral sylvian cistern, and 3) the presence of midline shifting from computed tomography findings. For hematoma volume of greater than 25 mL, we assigned 2 points whereas 1 point for less than 25 cc. We also assigned 1 point for the presence of diffuse SAH whereas 0 point for the absence of it. Then, 1 point was assigned for midline shifting of greater than 5 mm whereas 0 point for less than 5 mm. Results : According to the grading system, the numbers of patients from grade 1 to 4 were 4, 6, 8 and 9 respectively and 5, 7, 8, 4 and 3 patients belonged to Glasgow Outcome Scale (GOS) 5 to 1 respectively. It was found that the patients with higher GOS had lower ICH grade which were confirmed to be statistically significant (p<0.01). Preoperative Hunt and Hess grade and absence of midline shifting were the factors to predict favorable outcome. Conclusion : The ICH grading system composed of above three variables was helpful in predicting the patient's outcome more accurately.

• Journal of Korean Neurosurgical Society
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• v.30 no.6
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• pp.729-733
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• 2001

Objective : Antifibrinolytic treatment after aneurysmal subarachnoid hemorrhage has been shown to have no significant effect on outcome since a reduction in the rate of rebleeding was offset by an increase in the incidence of hydrocephalus and ischemic events. As the results of early aneurysm surgery and a change of strategy in the intensive medical treatment, outcome in patients with cerebral ischemia has been improved. On the other hand, rebleeding still remains as a major cause of death. A short course of tranexamic acid(TA) was tried to study its efficacy and safety in reducing the incidence of rebleeding before aneurysm surgery. Methods : A total of 507 patients with ruptured cerebral aneurysm operated within 3 days after the attack from 1990 to 1999 were included in this study. Group A consisted of 302 consecutive patients treated from 1990 through 1995 served as control. Two hundred-five patients in group B were treated with TA from 1996 through 1999. Both groups were evaluated for comparability of demographic and clinical variables including age, Hunt-Hess grade, Fisher grade, aneurysm location, hypertension, day of surgery, and initial hydrocephalus. The relationships of TA with rebleeding, ischemia, and chronic hydrocephalus were also studied. Results : There was no significant difference in patient demographics and clinical characteristics between group A and group B. Sixteen patients(5.3%) suffered a recurrent hemorrhage in group A and three(1.5%) in group B(p<0.05). Chronic hydrocephalus requiring a shunt was found in a significantly greater proportion in group B than in group A(p<0.05). The incidence of cerebral ischemia was not elevated in group B compared with group A. Conclusion : Considering the fact that the reduction of fatal rebleeding outweighed the increased incidence of hydrocephalus, the authors believe that a short course of TA is beneficial in diminishing the risk of rebleeding prior to early surgical intervention.

• Journal of Korean Neurosurgical Society
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• v.41 no.2
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• pp.100-104
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• 2007

Objective : Despite the widespread use of preoperative ventriculostomy in aneurysmal subarachnoid hemorrhage [SAH], there is no general consensus regarding the risk of bleeding associated with its use before aneurysm repair. This study was conducted to define the efficacy and rebleeding risk of ventriculostomy in aneurysmal SAH. Methods : The authors reviewed 339 consecutive patients with aneurysmal SAH who were treated at our hospital between January 1998 and December 2004. Results : Preoperative ventriculostomy was performed on 73 patients for acute hydrocephalus after aneurysmal SAH. The Hunt-Hess[H-H] grades of patients who underwent ventriculostomy were higher. Out of the 73 patients who underwent preoperative ventriculostomy, 58 [79%] demonstrated immediate clinical improvement after ventriculostomy. Of those same 73 patients 22 [30%] suffered aneurysmal rebleeding, whereas only 11 [4%] of the 266 patients who did not undergo ventriculostomy showed preoperative aneurysm rebleeding. The causes of rebleeding in the 22 patients who underwent ventriculostomy before surgery were related to the ventriculostomy procedure itself, subsequent cerebrospinal fluid [CSF] drainage, angiography and patient care procedures, such as endotracheal suction and nursing care. The mean time interval between SAH and surgery in the patients who underwent ventriculostomy was not statistically different from those who did not receive preoperative ventriculostomies [44.66 compared with 42.13 hours; p=0.73]. Conclusion : The preoperative ventriculostomy improved patients' clinical condition but increased the risk of rebleeding after aneurysmal SAH. When necessary, however, rapid change in transmural pressure during ventriculostomy must be avoided, careful management during ventricular drainage is needed, and surgery should be performed as soon as possible to prevent or reduce the incidence of rebleeding.

• Journal of Korean Neurosurgical Society
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• v.30 no.4
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• pp.425-429
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• 2001

Objective : Patients with poor grade aneurysm usually present with increased intracranial pressure(ICP), even those without an intracranial clot. Based on this fact, the present study investigated a significance of intracranial pressure monitoring in those patients. Patients and Methods : A total of 60 patients with Hunt and Hess Grade IV(50 patients) or V(10 patients) were treated for aneurysmal subarachnoid hemorrhage(SAH) during a 3-year-period, and intraparenchymal ICP was measured in the majority, immediately after arrival to the emergency room. Early surgery including intraoperative ventriculostomy was undertaken within 3 days after SAH. An ultraearly surgery was performed without preceding angiogram or ICP monitoring in patients with large sylvian hematomas, highly suggestive of middle cerebral artery aneurysm. Outcomes were assessed by the Glasgow Outcome Scale(GOS) at 6 months. Results : In overall, favorable outcome(GOS scores 1-2) was seen in 27(54.0%) of admission Grade IV and 1(10.0%) of admission Grade V patients. Of the 38 surgical patients with preoperative ICP monitorings, 25 patients (80.6%) exhibiting ICP values of less than 40mmHg showed favorable outcome, however, no patients with ICP values above 40mmHg recovered(Fisher's exact test, p=0.0001). Conclusion : It is concluded that a preoperative ICP above 40mmHg before ventriculostomy indicate significant vital brain destruction as intractable intracranial hypertension, and Grade IV patients at admission with an ICP below 40mmHg can be of benefit from early surgical intervention while Grade V patients still remains unfavorable.

• Journal of Korean Neurosurgical Society
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• v.29 no.7
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• pp.918-922
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• 2000

Objective : The authors analyzed the results of management outcomes for basilar bifurcation aneurysms treated with transcranial surgery and endovascular surgery. Methods : At the authors' institution between May 1989 and December 1998, 47 aneurysms with 45 patients were treated with transcranial surgery including surgical clipping/wrapping and endovascular surgery for basilar bifurcation aneurysms. The medical records and neuroimaging studies of the patients were reviewed retrospectively. Results : Of the 45 patients, 87 percent of the aneurysms were ruptured and 13% unruptured. Forty six percent of the patients had multiple aneurysms including basilar bifurcation aneurysm. Of the 39 patients with subarachnoid hemorrahge, 77% were in good neurological status(Hunt Hess grade I-III), 23% were in poor grade(H-H grade IV-V). Thirty two patients were treated with transcranial surgery and 15 patients were treated with endovascular surgery. Two patients who had treated with wrapping surgery later bled during follow-up period and treated with endovascular surgery. The management outcome of the transcranial surgery was : Glasgow outcome scale(GOS) I 66%, GOS II 12.5%, GOS III 6.3%, GOS IV 6.3% and GOS V(death) 9.4%. The major causes of morbidity related to transcranial surgery were perforator occlusion, vasospasm and retraction injury. The management outcome of the endovascular surgery was : GOS I 66.7%, GOS II 6.7%, and GOS V 26.7%. The major causes of mortality related to endovascular surgery were related to intraoperative aneurysmal bleeding. Conclusion : This report documents that more than 75% of patients undergoing treatment either transcranial or endovascular surgery can expect good clinical outcomes. Treatment modality in management of basilar bifurcation aneurysm must be carefully selected based on various considering factors.

• Journal of Korean Neurosurgical Society
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• v.58 no.4
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• pp.328-333
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• 2015

Objective : The goal of this study was to assess the effect of high-dose simvastatin on cerebral vasospasm and its clinical outcome after aneurysmal subarachnoid hemorrhage (SAH) in Korean patients. Methods : This study was designed as a prospective observational cohort study. Its subjects were aneurysmal SAH patients who had undergone aneurysm clipping or coiling. They were assigned to 1 of 3 groups : the 20 mg, 40 mg, and 80 mg simvastatin groups. The primary end-point was the occurrence of symptomatic vasospasm. The clinical outcome was assessed with the modified Rankin Scale (mRS) score after 1 month and 3 months. The risk factors of the development of vasospasm were assessed by logistic regression analysis. Results : Ninety nine patients with aneurysmal SAH were treated and screened. They were sequentially assigned to the 20 mg (n=22), 40 mg (n=34), and 80 mg (n=31) simvastatin groups. Symptomatic vasospasm occurred in 36.4% of the 20 mg group, 8.8% of the 40 mg group, and 3.2% of the 80 mg group (p=0.003). The multiple logistic regression analysis showed that poor Hunt-Hess grades (OR=5.4 and 95% CI=1.09-26.62) and high-dose (80 mg) simvastatin (OR=0.09 and 95% CI=0.1-0.85) were independent factors of symptomatic vasospasm. The clinical outcomes did not show a significant difference among the three groups. Conclusion : This study demonstrated that 80 mg simvastatin treatment was effective in preventing cerebral vasospasm after aneurysmal SAH, but did not improve the clinical outcome in Korean patients.

• Journal of Korean Neurosurgical Society
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• v.50 no.2
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• pp.81-88
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• 2011

Objective : The purpose of this study was to analyze the clinical and anatomic features involved in determining treatment modalities for anterior communicating artery (AcoA) aneurysms. Methods : The authors retrospectively evaluated 112 AcoA aneurysms with pretreatment clinical features including age, Hunt and Hess grade, medical or neurological comorbidity, and anatomical features including aneurysm size, neck size, dome-to-neck ratio, vessel incorporation, multiple lobulation, and morphologic scoring system. Post-treatment clinical results were classified according to the Glasgow Outcome Scale, and anatomic results in coiled patients were classified according to the modified Raymond scale. Using multivariate logistic regression, the probabilities for decision making between surgical clipping and coil embolization were calculated. Results : Sixty-seven patients (60%) were treated with surgical clipping and 45 patients (40%) with endovascular coil embolization. The clinical factor significantly associated with treatment decision was age (${\geq}$65 vs. <65 years) and anatomical factors including aneurysm size (small or large vs. medium), dome-to-neck ratio (<2 vs. ${\geq}$2), presence of vessel incorporation, multiple lobulation, and morphologic score (${\geq}$2 vs. <2). In multivariate analysis, older patients (age, 65 years) had significantly higher odds of being treated with coil embolization relative to clipping (adjusted OR=3.78; 95% CI, 1.39-10.3; p=0.0093) and higher morphological score patients (${\geq}$2) had a higher tendency toward surgical clipping than endovascular coil embolization (OR=0.23; 95% CI, 0.16-0.93; p=0.0039). Conclusion : The optimal decision for treating AcoA aneurysms cannot be determined by any single clinical or anatomic characteristics. All clinical and morphological features need to be considered, and a collaborative neurovascular team approach to AcoA aneurysms is essential.