Metal Artifact Reduction for Orthopedic Implants: Brain CT Angiography in Patients with Intracranial Metallic Implants

BACKGROUND: The purpose of this study was to qualitatively and quantitatively evaluate the effects of a metal artifact reduction for orthopedic implants (O-MAR) for brain computed tomographic angiography (CTA) in patients with aneurysm clips and coils. METHODS: The study included 36 consecutive patients with 47 intracranial metallic implants (42 aneurysm clips, 5 coils) who underwent brain CTA. The computed tomographic images with and without the O-MAR were independently reviewed both quantitatively and qualitatively by two reviewers. For quantitative analysis, image noises near the metallic implants of non-O-MAR and O-MAR images were compared. For qualitative analysis, image quality improvement and the presence of new streak artifacts were assessed. RESULTS: Image noise was significantly reduced near metallic implants (P < 0.01). Improvement of implant-induced streak artifacts was observed in eight objects (17.0%). However, streak artifacts were aggravated in 11 objects (23.4%), and adjacent vessel depiction was worsened in eight objects (17.0%). In addition, new O-MAR-related streak artifacts were observed in 32 objects (68.1%). New streak artifacts were more prevalent in cases with overlapping metallic implants on the same axial plane than in those without (P = 0.018). Qualitative assessment revealed that the overall image quality was not significantly improved in O-MAR images. CONCLUSION: In conclusion, the use of the O-MAR in patients with metallic implants significantly reduces image noise. However, the degree of the streak artifacts and surrounding vessel depiction were not significantly improved on O-MAR images.

What Should Be Considered to Cause the Early Post-Craniotomy Seizure: Antibiotics (Cefazolin) Irrigation

OBJECTIVE: Post-craniotomy seizure (PCS) is reported only rarely. However, our department noted a 433% increase in PCS for a year beginning September 2010, especially after cerebrovascular surgery. Our goal was to identify the cause of our unusual outbreak of PCS. METHODS: For almost one year after September 2010, cases of PCS increased significantly in our department. We analyzed 973 patients who had received a major craniotomy between January 2009 and November 2011. We included seizures that occurred only in the first 24 postoperative hours, which we defined as early PCS. After verifying the presence of PCS, we analyzed multiple seizure-provoking factors and their relation to the duration and character of seizure activity. RESULTS: Overall PCS incidence was 7.2% (70/973). Cefazolin (2 g/L saline) was the antibiotic drug used for intraoperative irrigation in 88.4% of the operations, and no PCS occurred without intraoperative cefazolin irrigation. When analyzed by operation type, clipping surgery for unruptured aneurysms was the most frequently associated with PCS (80%). Using logistic regression, only 2 g cefazolin intraoperative irrigation (p=0.024) and unruptured aneurysm clipping surgery (p<0.001) were associated with early PCS. The seizure rate of unruptured aneurysm clipping surgery using 2 g cefazolin intraoperative irrigation was 32.9%. CONCLUSION: Intraoperative cefazolin irrigation must be avoided in patients undergoing craniotomy, especially for clipping of unruptured aneurysms, because of the increased risk of early PCS.

Isolated Cortical Vein Thrombosis with Long Cord Sign

Isolated cortical vein thrombosis (ICVT) is a rare disease, accounting for less than 1% of strokes. A 46-year-old woman presented with progressive left side weakness. Magnetic resonance (MR) imaging with T2*-gradient echo (T2*-GE) sequence showed long cord sign at the right frontal cortex. The patient was treated with low molecular weight heparin, followed by oral warfarin for 6 months. The 3-month follow-up MR imaging showed recanalization of the previously thrombosed cortical vein. She was completely recovered without neurological deficits after 6 months. This provides that MR imaging with T2*-GE sequence can help to diagnosis the ICVT and outcomes of the ICVT are generally favorable.

Overexpressions of Vimentin and Integrins in Human Metastatic Spine Tumors

OBJECTIVE: To comparatively investigate the expression of several integrins in specimens of human bone metastases and degenerative bone tissue. METHODS: Degenerative cancellous tissue was obtained from a sample of human degenerative spine. Thirteen human specimens were obtained from metastatic spine tumors, whose primary cancer was colon cancer (n=3), hepatocellular cancer (n=3), lung cancer (n=4), and breast cancer (n=3). The expression of vimentin and integrins alphav, beta1, and beta3 was assessed in metastatic and degenerative specimens by immunohistochemistry and real-time reverse transcription-polymerase chain reaction (qRT-PCR). RESULTS: Immunohistochemical staining showed that vimentin and integrin alphav was broadly expressed in all tissues examined. By contrast, integrin beta1 was weakly expressed only in 38.4% (5/13) of tissues. Integrin beta3 was consistently negative in all cases examined. qRT-PCR analysis showed that vimentin gene expression was higher in all metastatic specimens, as compared to degenerative bone. The gene expression of integrin alphav in breast specimen was significantly higher than others (p=0.045). The gene expression of integrin beta1 was also higher in all metastatic specimens than in degenerative bone tissue. The gene expression of integrin beta3 was variable. CONCLUSION: Spinal metastatic tumors have mesenchymal characteristics such as increased expression of vimentin. The increased expression of integrin alphav and beta1 in spine metastatic tumors suggests that adhesive molecules such as integrin may have implications for the prevention of spine metastasis.

Usefulness of Fracture Risk Assessment Tool Using Lumbar Bone Mineral Density in Prediction of Osteoporotic Vertebral Fracture

OBJECTIVE: To investigate the value of lumbar bone mineral density (BMD) in fracture risk assessment (FRAX) tool. METHODS: One hundred and ten patients aged over 60 years were enrolled and divided into 2 groups as non-osteoporotic vertebral fracture (OVF) and OVF groups. The 10-year-risk of major osteoporotic vertebral fracture of each group was calculated by FRAX tool with femoral and lumbar spine BMDs to compare the usefulness of lumbar spine BMD in prediction of OVF. The blood level of osteocalcin and C-terminal telopeptide (CTX) as markers of activities of osteoblast and osteoclast, respectively were analyzed using the institutional database. RESULTS: In the OVF group, the ratio of patients with previous fracture history or use of glucocorticoid was higher than those in non-OVF group (p=0.000 and 0.030, respectively). The levels of T-score of femur neck and lumbar spine in OVF group were significantly lower than those in non-OVF group (p=0.001 and 0.000, respectively). The risk of OVF in FRAX using femur BMD in non-OVF and OVF groups was 6.7+/-6.13 and 11.4+/-10.06, respectively (p=0.007). The risk of using lumbar BMD in the 2 groups was 6.9+/-8.91 and 15.1+/-15.08, respectively (p=0.002). The areas under the receiver operator characteristic curve in the FRAX risk with lumbar and femur neck BMD were 0.726 and 0.684, respectively. The comparison of osteocalcin and CTX was not significant (p=0.162 and 0.369, respectively). CONCLUSION: In our study, the 10-year risk of major osteoporotic fracture in the OVF group of our study was lower than the recommended threshold of intervention for osteoporosis. Hence, a lower threshold for the treatment of osteoporosis may be set for the Korean population to prevent OVF. In the prediction of symptomatic OVF, FRAX tool using lumbar spine BMD may be more useful than that using femur neck BMD.

Slowly Recovering Isolated Bilateral Abducens Nerve Palsy after Embolization of Ruptured Anterior Communicating Artery Aneurysm

Bilateral abducens nerve palsy related to ruptured aneurysm of the anterior communicating artery (ACoA) has only been reported in four patients. Three cases were treated by surgical clipping. No report has described the clinical course of the isolated bilateral abducens nerve palsy following ruptured ACoA aneurysm obliterated with coil. A 32-year-old man was transferred to our institution after three days of diplopia, dizziness and headache after the onset of a 5-minute generalized tonic-clonic seizure. Computed tomographic angiography revealed an aneurysm of the ACoA. Magnetic resonance imaging showed focal intraventricular hemorrhage without brain stem abnormalities including infarction or space-occupying lesion. Endovascular coil embolization was conducted to obliterate an aneurysmal sac followed by lumbar cerebrospinal fluid (CSF) drainage. Bilateral paresis of abducens nerve completely recovered 9 weeks after ictus. In conclusion, isolated bilateral abducens nerve palsy associated with ruptured ACoA aneurysm may be resolved successfully by coil embolization and lumbar CSF drainage without directly relieving cerebrospinal fluid pressure by opening Lillequist's membrane and prepontine cistern.

Mobile Computed Tomography : Three Year Clinical Experience in Korea

OBJECTIVE: Obtaining real-time image is essential for neurosurgeons to minimize invasion of normal brain tissue and to prompt diagnosis of intracranial event. The aim of this study was to report our three-year experience with a mobile computed tomography (mCT) for intraoperative and bedside scanning. METHODS: A total of 357 mCT (297 patients) scans from January 2009 to December 2011 in single institution were reviewed. After excluding post-operative routine follow-up, 202 mCT were included for analysis. Their medical records such as diagnosis, clinical application, impact on decision making, times, image quality and radiologic findings were assessed. RESULTS: Two-hundred-two mCT scans were performed in the operation room (n=192, 95%) or intensive care unit (ICU) (n=10, 5%). Regarding intraoperative images, extent of resection of tumor (n=55, 27.2%), degree of hematoma removal (n=42, 20.8%), confirmation of catheter placement (n=91, 45.0%) and monitoring unexpected complications (n=4, 2.0%) were evaluated. A total of 14 additional procedures were introduced after confirmation of residual tumor (n=7, 50%), hematoma (n=2, 14.3%), malpositioned catheter (n=3, 21.4%) and newly developed intracranial events (n=2, 14.3%). Every image was obtained within 15 minutes and image quality was sufficient for interpretation. CONCLUSION: mCT is feasible for prompt intraoperative and ICU monitoring with enhanced diagnostic certainty, safety and efficiency.

Large Spinal Meningioma with Hemorrhage after Selective Root Block in the Thoraco-Lumbar Spine

Spinal meningioma accounts for 25% of all spinal cord tumors and occurs mostly in the thoracic region. Spontaneous intraspinal bleeding associated with spinal meningioma has rarely been reported. Most cases of hemorrhage associated with meningiomas are extratumoral and subarachnoid, whereas subdural and intratumoral hemorrhage cases have been reported to occur rarely. We experienced a case of a 58-year-old woman with thoracolumbar spinal meningioma accompanied by intraspinal subdural hematoma. She presented with progressively worsened back pain and newly developed weakness in the right lower extremity after a selective nerve root block in the lumbar spine. She underwent the operation and progressively showed neurological recovery during the postoperative course. We report a thoracolumbarspinal meningioma with subdural and intratumoral hemorrhage after a spinal procedure that caused a sudden neurological deterioration.

Dissecting Aneurysm of Vertebral Artery Manifestating as Contralateral Abducens Nerve Palsy

Isolated abducens nerve paresis related to ruptured vertebral artery (VA) aneurysm is rare. It usually occurs bilaterally or ipsilaterally to the pathologic lesions. We report the case of a contralateral sixth nerve palsy following ruptured dissecting VA aneurysm. A 38-year-old man was admitted for the evaluation of a 6-day history of headache. Abnormalities were not seen on initial computed tomography (CT). On admission, the patient was alert and no signs reflecting neurologic deficits were noted. Time of flight magnetic resonance angiography revealed a fusiform dilatation of the right VA involving origin of the posterior inferior cerebellar artery. The patient suddenly suffered from severe headache with diplopia the day before the scheduled cerebral angiography. Neurologic examination disclosed nuchal rigidity and isolated left abducens nerve palsy. Emergent CT scan showed high density in the basal and prepontine cistern compatible with ruptured aneurismal hemorrhage. Right vertebral angiography illustrated a right VA dissecting aneurysm with prominent displaced vertebrobasilar artery to inferiorly on left side. Double-stent placement was conducted for the treatment of ruptured dissecting VA aneurysm. No diffusion restriction signals were observed in follow-up magnetic resonance imaging of the brain stem. Eleven weeks later, full recovery of left sixth nerve palsy was documented photographically. In conclusion, isolated contralateral abducens nerve palsy associated with ruptured VA aneurysm may develop due to direct nerve compression by displaced verterobasilar artery triggered by primary thick clot in the prepontine cistern.

The Impact of Menopause on Bone Fusion after the Single-Level Anterior Cervical Discectomy and Fusion

OBJECTIVE: To evaluate the successful fusion rate in postmenopausal women with single-level anterior cervical discectomy and successful fusion (ACDF) and identify the significant factors related to bone successful fusion in pre- and postmenopausal women. METHODS: From July 2004 to December 2010, 108 consecutive patients who underwent single-level ACDF were prospectively selected as candidates. Among these, the charts and radiological data of 39 women were reviewed retrospectively. These 39 women were divided into two groups : a premenopausal group (n=11) and a postmenopausal group (n=28). To evaluate the significant factors affecting the successful fusion rate, the following were analyzed : the presence of successful fusion, successful fusion type, age, operated level, bone mineral density, graft materials, stand-alone cage or plating with autologous iliac bone, subsidence, adjacent segment degeneration, smoking, diabetes mellitus, and renal disease. RESULTS: The successful fusion rates of the pre- and postmenopausal groups were 90.9% and 89.2%, respectively. There was no significant difference in the successful fusion rate or successful fusion type between the two groups. In the postmenopausal group, three patients (10.8%) had successful fusion failure. In the postmenopausal group, age and subsidence significantly affected the successful fusion rate (p=0.016 and 0.011, respectively), and the incidence of subsidence in patients with a cage was higher than that in patients with a plate (p=0.030). CONCLUSION: Menopausal status did not significantly affect bone successful fusion in patients with single-level ACDF. However, in older women with single-level ACDF, the combination of use of a cage and subsidence may unfavorably affect successful fusion.

Feasibility of Endoscopic Endonasal Approach for Recurrent Pituitary Adenomas after Microscopic Trans-Sphenoidal Approach

OBJECTIVE: The surgical approach for recurrent pituitary adenoma after trans-sphenoidal approach (TSA) is challenging. We report the outcomes of the endoscopic TSA for recurrent pituitary adenoma after microscopic TSA. METHODS: From February 2010 to February 2013, endoscopic TSA was performed for removal of 30 recurrent pituitary adenomas after microscopic TSA. Twenty-seven (90%) patients had a clinically non-functioning pituitary adenoma. Twenty-four (80%) patients suffered from a visual disturbance related to tumor growth. The clinical features and surgical outcomes were retrospectively analyzed for the ophthalmological, endocrinological, and oncological aspects. RESULTS: The mean tumor volume was 11.7 cm3, and gross total resection was achieved in 50% of patients. The volumetric analysis based on the postoperative MR showed that the mean extent of resection rates were 90%. Vision was improved in 19 (79%) of 24 patients with visual symptoms, and endocrinological cure was achieved in all of three functioning pituitary adenomas; however, the post-operative follow-up endocrinological examination revealed a new endocrinological deficit in one patient. Two patients required antibiotics management for post-operative meningitis. CONCLUSION: The endoscopic TSA can be an effective treatment option for recurrent pituitary adenoma after microscopic TSA with acceptable outcome.

Early Experience of Pre- and Post-Contrast 7.0T MRI in Brain Tumors

We investigated the safety and clinical applicability of 7.0 Tesla (T) brain magnetic resonance imaging (MRI) in patients with brain tumors. Twenty-four patients with intraaxial or extraaxial brain tumors were enrolled in this study. 7.0T MRIs of T2*-weighted axial and T1-weighted coronal or sagittal images were obtained and compared with 1.5T brain MRIs. The T2*-weighted images from 7.0T brain MRI revealed detailed microvasculature and the internal contents of supratentorial brain tumors better than that of 1.5T brain MRI. For brain tumors located in parasellar areas or areas adjacent to major cerebral vessels, flow-related artifacts were exaggerated in the 7.0T brain MRIs. For brain tumors adjacent to the skull base, susceptibility artifacts in the interfacing areas of the paranasal sinus and skull base hampered the aquisition of detailed images and information on brain tumors in the 7.0T brain MRIs. This study shows that 7.0T brain MRI can provide detailed information on the intratumoral components and margins in supratentorial brain tumors. Further studies are needed to develop refined MRI protocols for better images of brain tumors located in the skull base, parasellar, and adjacent major cerebrovascular structures.

Quantitative Analysis of Intraoperative Indocyanine Green Video Angiography in Aneurysm Surgery

OBJECTIVE: Indocyanine green (ICG) videoangiography (VA) is being used in assessment of blood flow during cerebrovascular surgery. However, data collected during ICG angiography are usually interpreted qualitatively. In this study, quantitative analysis of ICG angiogram was attempted. MATERIALS AND METHODS: ICG VA, performed during aneurysm surgery was analyzed retrospectively. The angiogram was captured serially in regular time interval. The stacked images were then fed into an image analysis program, ImageJ. The selected areas of interest were as follows: parent and branch vessels, and dome of aneurysm. Changes of signals of measurement points were plotted. The time to peak, washout time, and the peak intensity between areas were compared. RESULTS: Among the 16 cases enrolled in this study, five cases were anterior communicating artery aneurysms, and 11 cases were middle cerebral artery bifurcation aneurysms. There was no signal intensity of aneurysm dome in our series. No difference in time to peak or maximum signal intensity was observed between vessels in each case. The average time to peak was 9.0 and washout time was 31.3 seconds. No significant difference in time profile was observed between anterior communicating artery aneurysms and middle cerebral artery bifurcation aneurysms. CONCLUSION: Findings of this study demonstrate that quantitative analysis is possible using a personal computer and common video capture and analysis software. It can be a good adjunctive to evaluation of vascular status during aneurysm surgery. It displays time profiles of multiple points of interest over time, and is helpful in objective evaluation of changes of blood flow over time. It might be helpful in various fields of cerebrovascular surgery.

Little Response of Cerebral Metastasis from Hepatocellular Carcinoma to Any Treatments

OBJECTIVE: We retrospectively evaluated the survival outcome of patients with brain metastasis from hepatocellular carcinoma (HCC). METHODS: Between 1991 and 2007, a total of 20 patients were diagnosed as having brain metastasis from HCC. The mean age of the patients was 55 +/- 13 years, and 17 (85.0%) were men. Seventeen (85.0%) patients had already extracranial metastases. The median time from diagnosis of HCC to brain metastasis was 18.5 months. Fourteen (70.0%) patients had stroke-like presentation due to intracerebral hemorrhage (ICH). Ten (50.0%) patients had single or solitary brain metastasis. Among a total of 34 brain lesions, 31 (91.2%) lesions had the hemorrhagic components. RESULTS: The median survival time was 8 weeks (95% CI, 5.08-10.92), and the actuarial survival rates were 85.0%, 45.0%, 22.5%, and 8.4% at 4, 12, 24, and 54 weeks. Age < 60 years, treatment of the primary and/or extracranial lesions, and recurrent ICH were the possible prognostic factors (p = 0.044, p < 0.001, and p = 0.111, respectively). The median progression-free survival (PFS) time was 3 months (95% CI, 0.95-5.05). CONCLUSION: The overall survival of the patients with brain metastasis from HCC was very poor with median survival time being only 8 weeks. However, the younger patients less than 60 years and/or no extracranial metastases seem to be a positive prognostic factor.

Mobile Computed Tomography : Early Experience in Korea

OBJECTIVE: With improved technology, the values of intraoperative computed tomography (iCT) have been reevaluated. We describe our early clinical experience with a mobile CT (mCT) system for iCT and discuss its clinical applications, advantages and limitations. METHODS: Compared with intraoperative magnetic resonance imaging, this mCT system has no need for major reconstruction of a preexisting operating room for shielding, or for specialized instruments or equipment. Patients are placed on a radiolucent head clamp that fits within the gantry. Because it consists simply of a scanner and a workstation, it can be moved between locations such as an operating room, an intensive care unit (ICU) or an emergency room without difficulty. Furthermore, it can achieve nearly all types of CT scanning procedures such as enhancement, temporal bone imaging, angiography and three-dimensional reconstruction. RESULTS: For intracranial surgery, mCT can be used for intraoperative real-time neuronavigation by interacting with preoperative images. It can also be used for intraoperative confirmation of the extent of resection of intracranial lesions and for immediate checks for preventing intraoperative unexpected accidents. Therefore, the goals of maximal resection or optimal treatment can be achieved without any guesswork. Furthermore, mCT can achieve improved patient care with safety and faster diagnosis for patients in an ICU who might be subjected to a ventilator and/or various monitoring devices. CONCLUSION: Our initial experience demonstrates that mCT with high-quality imaging offers very useful information in various clinical situations.

Retraction: Risk Factors of Recurrence after Gross Total Excision in Pediatric Craniopharyngioma

No abstract available.

Development of a Stereotactic Device for Gamma Knife Irradiation of Small Animals

OBJECTIVE: The authors developed a stereotactic device for irradiation of small animals with Leksell Gamma Knife(R) Model C. Development and verification procedures were described in this article. METHODS: The device was designed to satisfy three requirements. The mechanical accuracy in positioning was to be managed within 0.5 mm. The strength of the device and structure were to be compromised to provide enough strength to hold a small animal during irradiation and to interfere the gamma ray beam as little as possible. The device was to be used in combination with the Leksell G-frame(R) and KOPF(R) rat adaptor. The irradiation point was determined by separate imaging sequences such as plain X-ray images. RESULTS: The absolute dose rate with the device in a Leksell Gamma Knife was 3.7% less than the value calculated from Leksell Gamma Plan(R). The dose distributions measured with GAFCHROMIC(R) MD-55 film corresponded to those of Leksell Gamma Plan(R) within acceptable range. The device was used in a series of rat experiments with a 4 mm helmet of Leksell Gamma Knife. CONCLUSION: A stereotactic device for irradiation of small animals with Leksell Gamma Knife Model C has been developed so that it fulfilled above requirements. Absorbed dose and dose distribution at the center of a Gamma Knife helmet are in acceptable ranges. The device provides enough accuracy for stereotactic irradiation with acceptable practicality.

The Cubital Tunnel Syndrome with Medial Ganglion Cyst

The association of medial elbow ganglion cyst with cubital tunnel syndrome has been rarely reported. A 61-year-old man presented with progressive right hypothenar atrophy and paresthesia for 7 months. Ultrasonography and magnetic resonance imaging revealed ulnar nerve entrapment with a cystic ganglion in cubital tunnel. Decompression of ulnar nerve and excision of the ganglion were performed. Motor function of the ulnar nerve showed an improvement four months later after surgery. Because most ganglia are occult, imaging study is warranted especially in case with osteoarthritis. Excision of the ganglion performed concurrently with decompression of the ulnar nerve provide satisfactory results.

Postoperative Brain Swelling after Resection of Olfactory Groove Meningiomas

OBJECTIVE: Postoperative brain swelling after resection of olfactory groove meningiomas by bifrontal interhemispheric transbasal approach is a knotty subject. Pathogenesis and predictive factors were investigated to prevent the problem. METHODS: Eighteen patients of olfactory groove meningiomas who had undergone surgery were enrolled and retrospectively analyzed using their clinical and radiological data. Bifrontal interhemispheric transbasal approach was used in all patients. Magnetic resonance imaging and transfemoral cerebral angiography were available for investigation in 18 and 14 patients respectively. Postoperative clinical course, tumor volume, peritumoral edema, tumor supplying vessels, and venous drainage patterns were carefully investigated in relation to postoperative brain swelling. RESULTS: Seven patients (39%) developed clinically overt brain swelling after surgery. Among them, 4 patients had to undergo decompression surgery. In three patients, attempted bone flap removal was done by way of prevention of increased intracranial pressure resulted from intractable brain swelling and two of them eventually developed brain swelling which could be recovered without sequellae. Abnormal frontal base venous channel observed in preoperative angiography was significant predictive factor for postoperative brain swelling (p=0.031). However, tumor volume, peritumoral edema, and existence of pial tumor supplying vessels from anterior cerebral arteries were failed to show statistical significances. CONCLUSION: To prevent postoperative brain swelling in olfactory groove meningioma surgery, unilateral approach to preserve frontal base venous channels or temporary bone flap removal is recommended when it is indicated.

Aggressive Vestibular Schwannomas Showing Rapid Growth after Surgical Resection; Clinicopathological Analysis of 15 Cases

OBJECTIVE: Vestibular schwannomas(VS) are known to be relatively slow growing tumors. Some VS, however, rapidly regrow or recur after surgical resection. Our objective is to investigate clinicopathological characteristics of these tumors and to elucidate factors, which can predict a rapid regrowth or recurrence after surgical resection. METHODS: Twenty-nine patients with VS underwent reoperation for regrowth or recurrence at the Department of Neurosurgery in Seoul National University Hospital between 1978 and 2000. Among these, 15 VS regrew or recurred rapidly(annual growth rate larger than 15mm/year). To compare morphology and proliferative activity, 15 cases of VS were randomly selected among consecutive operative cases between 1991 and 1999 with tumor size more than 4cm. As pathological parameters, cellularity, pleomorphism, mitosis, necrosis, invasion to adjacent tissue, and microvascular proliferation were examined. Proliferative indices(Ki-67 index) were also evaluated. Statistical analysis was performed using Fischers exact test and ANOVA test. RESULTS: The mean ages at a diagnosis were respectively 40.6(range 21-63), and 49.7(range 35-67) [p=0.438]. Male to female ratio was respectively 7:7, and 5:10[p=0.462]. In radiological findings, aggressive group at initial presentation had more lobulating contour than CG(7/13 cases vs 3/15 cases, p=0.001). In pathologic findings, cellularity and pleomorphism were significantly higher than those of control group(p=0.001). Proliferative index(Ki-67 index) was higher in aggressive group than control group [2.28(range 0.1-8.6) vs 0.59(range 0-1.5), p=0.034]. CONCLUSION: Vestibular schwannoma presented with lobulating contour, high proliferative index(Ki-67 index), and high cellularity or pleomorphism should be frequently investigated radiologically during follow-up for early detection of regrowth or recurrence.