Kintomo Takakura

Clinical analysis of incidentally discovered unruptured aneurysms.

Background and Purpose We analyzed the risk factors for rupture of an intracranial aneurysm based on a retrospective angiographic study of ruptured and unruptured aneurysms. Methods The 44 cases of asymptomatic aneurysms were selected from 1612 patients whose lesions had been discovered fortuitously by angiography (2.7%) during the period from 1980 to 1989. All these patients were free from any sign of intracranial aneurysm. The variations in age, sex, and location of the aneurysms were analyzed compared with 638 ruptured aneurysms that had been treated in our institute during the same period. The size, shape, and arterial geometry of the unruptured aneurysms were examined angiographically. Results Unruptured aneurysm was discovered fortuitously in 44 (2.7%) of 1612 patients, with greater incidence in women aged older than 60 years. Unruptured aneurysms were less likely to occur in the anterior communicating artery (12.8%) and the middle cerebral artery (6.4%). However, they were frequently found in the internal carotid artery, with an incidence of 10.6% in the cavernous portion of the internal carotid artery, 19.1% in the internal cartoid-ophthalmic artery, 19.1% in the internal carotid-posterior communicating artery, and 12.8% in the internal carotid-anterior choroidal artery. Seven of the nine internal carotid-posterior communicating artery aneurysms showed a hypoplastic or aplastic posterior communicating artery. The mean diameter of the unruptured aneurysms was 4.8 mm, and 80% were smaller than 6 mm. Conclusions Intracranial aneurysms are formed not only at the bifurcation of an artery but also at its branching and bending points. However, an aneurysm located at the bifurcation, such as the anterior communicating artery and the middle cerebral artery, bleeds easily in contrast with lateral aneurysms such as those found at the branching and bending points on the internal carotid artery.

Usefulness of intraoperative magnetic resonance imaging for glioma surgery

BACKGROUND Radical resection of gliomas can increase patients survival. There is known concern, however, that aggressive tumour removal can result in neurological morbidity. The objective of the present study was to evaluate the usefulness of low magnetic field strength (0.3 Tesla) open intraoperative magnetic resonance imaging (iMRI) for complete resection of glioma with emphasis on functional outcome. METHODS From 2000 to 2004, 96 patients with intracranial gliomas underwent tumour resection with the use of iMRI in Tokyo Womens Medical University. There were 50 men and 46 women; mean age was 39 years. Tumour volume varied from 1.2 ml to 198 ml (median: 36.5 mL). Resection rate and postoperative neurological status were compared between control group (46 cases, operated on during the initial period after installation of iMRI), and study group (50 most recent cases, in whom surgery was done using established treatment algorithm and improved image quality). FINDINGS Overall, mean resection rate was 93%, and medial residual tumour volume was 0.17 ml. Total tumour removal was achieved in 44 cases (46%). Compared to control group, resection rate in the study group was significantly higher (91%, vs. 95%; P < 0.05), whereas residual tumour volume was significantly smaller (1.7 mL vs. 0.025 mL; P < 0.001). Nine patients in the control group (20%) and 24 in the study group (48%) experienced temporary postoperative neurological deterioration (P < 0.01), however, the rate of permanent morbidity evaluated 3 months after surgery did not differ significantly between the groups investigated (13% vs. 14%). CONCLUSIONS Use of iMRI during surgery for intracranial gliomas permits to attain aggressive tumour resection with good functional outcome. Nevertheless, surgical experience with the iMRI system, establishment of treatment algorithm, and improvement of image quality are of paramount importance for optimal results.

Low-grade glioma on stereotactic biopsy: How often is the diagnosis accurate?

The objective of the present study was an evaluation of the incidence and risk factors for erroneous histopathological diagnosis of low-grade glioma after stereotactic biopsy. Twenty-eight tumors diagnosed as low-grade glioma after stereotactic biopsy and surgically resected thereafter were analyzed. There were 13 astrocytomas, 7 oligodendrogliomas, and 8 mixed gliomas. All neoplasms had a lobar location. Seven tumors had contrast enhancement on MRI. The number of tissue samples obtained during stereotactic biopsy was one in 19 cases, two in 4, and three or more in 5. Complete diagnostic agreement in tumor typing and grading after stereotactic biopsy and surgical resection was attained in 10 cases (36%). Agreement in tumor typing was marked in 16 cases (57%). Erroneous typing was more frequent in tumors with an MIB-1 index of less than 3% (P = 0.0629) and mixed gliomas (P = 0.0801). Overgrading of WHO grade I tumors was marked in 3 cases (11%) and undergrading of WHO grade III gliomas in 8 cases (28%). Tumor undergrading was more frequent in cases with an MIB-1 index of more than 3% (P = 0.0045). The MIB-1 index detected after stereotactic biopsy was nearly always lower compared with those established after surgical resection (P < 0.0001). In conclusion, the histopathological diagnosis of low-grade glioma established after stereotactic biopsy is associated with a substantial risk of inaccuracy. Tumors with low proliferative activity and mixed gliomas are especially susceptible for erroneous tumor typing. Undergrading of high-grade gliomas may be suspected if the MIB-1 index in the tumor specimen constitutes more, than 3%.

Hemodynamic Study of the Anterior Communicating Artery

BACKGROUND AND PURPOSE The anterior communicating artery (ACoA) is a site of predilection for intracranial saccular aneurysms causing subarachnoid hemorrhage. ACoA aneurysms are frequently associated with an asymmetrical circle of Willis. In such cases, the ACoA is probably exposed to high hemodynamic stress caused by a considerable shunt flow across the ACoA to the distal segment of the contralateral anterior cerebral artery (ACA). In the present study, the flow pattern and flow-induced shear stress in the ACoA complex that may initiate aneurysmal lesions were studied under steady and pulsatile flow conditions. METHODS Flow visualization was studied with dye injection and birefringent flow visualization in symmetrical and asymmetrical models of various sizes of ACoA. The distribution of wall shear stress was measured using an electrochemical method based on a diffusion-controlled reaction of ferricyanide ion to ferrocyanide ion at a platinum electrode embedded in the wall of the ACoA model. RESULTS With equal flow rate (Reynolds number 150 to 600), vortical flow was formed in the mouth of the ACoA, and no cross flow through the ACoA was observed. The wall shear stress on the mid-wall of the ACoA was almost zero. However, as soon as the flow rate became unequal, a cross flow through the ACoA was observed. The stagnation point also appeared at the medial junction of the ACoA and ACA. The wall shear stress increased to a very high level at the wall of the ACoA and around the stagnation point. CONCLUSIONS Geometric changes from the symmetrical to the asymmetrical ACoA develop higher shear stress on the ACoA than critical values and the stagnation point at the ACoA junction. A combination of these hemodynamic factors is considered to play an important role in initiation of aneurysm.

Combined management of intracranial arteriovenous malformations with embolization and Gamma Knife radiosurgery: comparative evaluation of the long-term results

BACKGROUND Volume reduction of large AVMs attained with endovascular embolization can be potentially helpful for their subsequent radiosurgical management. The objective of the present retrospective analysis was comparative evaluation of the long-term outcome after GKR for intracranial AVM performed with and without initial embolization of the nidus. METHODS The long-term outcome in 15 patients with intracranial AVM treated with initial embolization and subsequent GKR was evaluated and compared with the series of 237 patients treated during the same period solely with GKR. All patients were followed at least 2 years after radiosurgery. RESULTS Mean reductions of the nidus volume and score of the radiosurgery-based grading system for AVMs after embolization constituted 6.9 +/- 2.4 mL and 0.7 +/- 0.2, respectively (P < .001). Complete obliteration of the nidus after GKR was marked in 10 cases (67%). It was attained in 9 (90%) of 10 AVMs with postembolization nidus volume less than 12 mL, and in 1 (20%) of 5 with postembolization nidus volume more than 12 mL (P < .05). Delayed cyst formation was met once (7%). Obliteration and long-term morbidity rates did not differ significantly in patients treated with and without preradiosurgical nidus embolization, whereas nidus volume was seemingly larger in the former cohort. CONCLUSIONS Combined management with embolization and GKR may be effective for selected cases of large intracranial AVM. Radiosurgery preceded by partial nidus embolization does not associate with increased rate of long-term complications.

Advanced computer-aided intraoperative technologies for information-guided surgical management of gliomas: Tokyo Women's Medical University experience.

The availability of the intraoperative MRI and real-time neuronavigation has dramatically changed the principles of surgery for gliomas. Current intraoperative computer-aided technologies permit perfect localization of the neoplasm, precise estimation of its volume, and clear definition of its interrelationships with the eloquent brain structures. This allows maximal tumor resection with minimal risk of postoperative disabilities. Under such conditions the medical treatment has become significantly dependent on the quality of the provided information and can be designated as information-guided management. Therefore, appropriate management of the wide spectrum of the intraoperative medical data and its adequate distribution between members of the surgical team for facilitation of the clinical decision-making is very important for attainment of the best possible outcome. Further progress in advanced neurovisualization, robotics, and comprehensive medical information technology has a great potential to increase the safety of the neurosurgical procedures for parenchymal brain tumors in the eloquent brain areas.

Low-dose gamma knife radiosurgery for cavernous sinus hemangioma: report of 3 cases and literature review.

Optimal management of cavernous sinus hemangiomas remains unclear. Total microsurgical removal of these neoplasms may be extremely difficult due to their rich vascularization. Three cases of cavernous sinus hemangioma treated with low-dose Gamma Knife radiosurgery are presented. Marginal dose varied from 10 to 13 Gy. Treatment planning and radiation dosimetry were done with a goal of conformal and selective coverage of the lesion with 50% prescription isodose line using multiisocenter technique. In all cases significant shrinkage of the neoplasm was marked at 3 months after treatment. Mean volume reduction at 12 months after radiosurgery was 60% (range: 45-75%). In all patients the shrinkage of the neoplasm was accompanied by notable improvement of the preexistent oculomotor nerve palsy. No radiosurgery-related complications were met during follow-up. In conclusion, low-dose Gamma Knife radiosurgery seems to be very effective for management of cavernous sinus hemangiomas, and can be considered as a treatment modality of choice for these lesions.

1H-MRS of intracranial meningiomas: What it can add to known clinical and MRI predictors of the histopathological and biological characteristics of the tumor?

OBJECTIVE The main goal of the present study was evaluation of proton magnetic resonance spectroscopy (¹H-MRS) in diagnosis of histopathologically aggressive intracranial meningiomas. METHODS Single-voxel ¹H-MRS of 100 intracranial meningiomas was performed before their surgical resection. Investigated metabolites included mobile lipids, lactate, alanine, N-acetylaspartate (NAA), and choline-containing compounds (Cho). According to criteria of World Health Organization (WHO) 82 meningiomas were assigned histopathological grade I, 11 grade II, and 7 grade III. The MIB-1 index varied from 0% to 27.3% (median, 1.6%). In 43 cases tight adhesion of the tumor to the pia mater or brain tissue was macroscopically identified at surgery. The consistency of 49 meningiomas was characterized as soft, 26 as hard, and 25 as mixed. RESULTS No one metabolic parameter had statistically significant association with histopathological grade and subtype, invasive growth, and consistency of meningioma. Univariate statistical analysis revealed greater ¹H-MRS-detected Cho content (P=0.0444) and lower normalized NAA/Cho ratio (P=0.0203) in tumors with MIB-1 index 5% and more. However, both parameters lost their statistical significance during evaluation in the multivariate model along with other clinical and radiological variables. It was revealed that non-benign histopathology of meningioma (WHO grade II/III) is mainly predicted by irregular shape (P=0.0076) and large size (P=0.0316), increased proliferative activity by irregular shape (P=0.0056), and macroscopically invasive growth by prominent peritumoral edema (P=0.0021). CONCLUSION While ¹H-MRS may be potentially used for the identification of meningiomas with high proliferative activity, it, seemingly, could not add substantial diagnostic information to other radiological predictors of malignancy in these tumors.

Spectroscopy-supported frame-based image-guided stereotactic biopsy of parenchymal brain lesions: comparative evaluation of diagnostic yield and diagnostic accuracy.

OBJECTIVE Comparative evaluation of diagnostic efficacy of stereotactic brain biopsy performed with and without additional use of spectroscopic imaging ((1)H-MRS) for target selection was done. METHODS From 2002 to 2006, 30 patients with parenchymal brain lesions underwent (1)H-MRS-supported frame-based stereotactic biopsy, whereas in 39 others MRI-guided technique was used. Comparison of diagnostic yield of the procedure in these two groups was performed. Additionally, the diagnostic accuracy was evaluated in 37 lesions, which were surgically resected within 1 month thereafter. RESULTS Stereotactic biopsy permitted establishment of a definitive histopathological diagnosis in 57 cases and diagnosis of low-grade glioma without specific tumor typing in 8 cases. In 4 cases tissue sampling was non-diagnostic. In 5 out of 8 cases with incomplete diagnosis and in all non-diagnostic cases target selection was performed without the use of (1)H-MRS (P=0.2073). The diagnostic yields of (1)H-MRS-supported and MRI-guided procedures were 100% and 90%, respectively (P=0.1268). Comparison of the histopathological diagnoses after stereotactic biopsy and surgical resection revealed complete diagnostic agreement in 13 cases, minor disagreement in 14 cases, and major disagreement in 10 cases. Among these last 10 cases, initial undergrading of non-enhancing WHO grade III gliomas was the most common (7 cases). The diagnostic accuracy of (1)H-MRS-supported and MRI-guided procedures was 67% and 79%, respectively (P=0.4756). CONCLUSION While in the present study the diagnostic yield of (1)H-MRS-supported frame-based stereotactic brain biopsy was 100%, its statistically significant diagnostic advantages over MRI-guided technique were not proved. Optimal selection of the spectroscopic target for tissue sampling remains unclear.

Risk factors for regrowth of intracranial meningiomas after gamma knife radiosurgery: importance of the histopathological grade and MIB-1 index.

INTRODUCTION The influence of histopathological grade and MIB-1 index of intracranial meningioma on the results of its radiosurgical management is not clear. The objective of the present retrospective study was to make an evaluation of these factors along with an analysis of other variables associated with progression-free survival after gamma knife radiosurgery (GKR). PATIENTS AND METHODS Thirty-four intracranial meningiomas with known detailed histopathological diagnosis were analyzed. Tumors of WHO histopathological grades I, II, and III were diagnosed in 24, 3, and 7 cases, respectively. The median MIB-1 index was 1.3% (range: 0-31.9%). In 14 cases the MIB-1 index was 3.0% and more. In 26 cases the treatment was done at the time of tumor recurrence. Median volume of the neoplasm at the time of GKR was 4.1 mL (range: 0.4-43.1 mL). Median marginal dose was 12 Gy (range: 8-19 Gy). Median length of follow-up constituted 63 months (range: 19-132 months). RESULTS Actuarial progression-free survival at 1, 3, 5, and 10 years constituted 100, 94, 83, and 58%, respectively. Histopathological grade II or III (p<0.0001), MIB-1 index 3% and more (p=0.0004), and non-skull base location (p=0.0026) of the tumor showed negative associations with progression-free survival in multivariate analyses. Actuarial progression-free survival at 5 years after GKR for benign and non-benign meningiomas constituted 100 and 45%, respectively (p<0.0001). CONCLUSION Radiosurgery is a highly effective management option for benign intracranial meningiomas, but growth control of non-benign ones is significantly worse. It requires close neuroradiological follow-up and necessitates the search for modified treatment strategies.