Kotaro Nakaya

Angles between A1 and A2 segments of the anterior cerebral artery visualized by three-dimensional computed tomographic angiography and association of anterior communicating artery aneurysms.

OBJECTIVE The angle of arteries at bifurcations, as well as the blood flow, are factors of hemodynamic stress on the apical region, where aneurysms often develop. Using images obtained with three-dimensional computed tomographic angiography, we sought to determine the angles between the A1 and A2 segments of the anterior cerebral artery of the anterior communicating artery (ACoA) complex associated with aneurysms. These angles cannot be detected by conventional cerebral angiography. METHODS The course of the anterior cerebral artery was studied using three-dimensional computed tomographic angiography in 42 consecutive patients with ACoA aneurysms. Twenty-one other subjects, randomly chosen from patients without aneurysms, served as controls. Bilateral A1-A2 angles of the contrast-opacified anterior cerebral artery were measured by three-dimensional computed tomographic angiography in patients with normoplastic A1 segments, and the relationship between the angle and the association of aneurysms was analyzed using cerebral angiography. RESULTS Of the 42 patients with ACoA aneurysms, 19 patients showed hypo- or aplastic A1 segments, as did only 2 of the 21 patients without ACoA aneurysms. The average A1-A2 angle was determined to be 116+/-24 degrees (mean+/-standard deviation) in 18 patients having ACoA complexes with normoplastic A1 segments with aneurysms; 17 patients without aneurysms had A1-A2 angles measuring 143+/-14 degrees (P < 0.0001). The A1-A2 angle associated with ACoA aneurysms was 103+/-20 degrees, which was much smaller than that of the non-aneurysm side in the former group (128+/-20 degrees) (P = 0.0036). CONCLUSION ACoA aneurysms are associated with the smaller A1-A2 angle junction of the ACoA complex, where higher hemodynamic stress may occur in patients with normoplastic A1 segments.

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.

Gamma Knife Radiosurgery for Benign Tumors With Symptoms From Brainstem Compression

PURPOSE This study evaluated the role of radiosurgery in the management of symptomatic patients with brainstem compression from benign basal tumors. METHODS AND MATERIALS Over a 17-year, period 246 patients (202 vestibular schwannomas and 44 meningiomas) with brainstem compression from benign skull-base tumors were managed with Gamma Knife radiosurgery. Median tumor volumes were 3.9 cm(3) (range, 0.8-39.0 mL) and 6.6 mL (range, 1.6-25.1 mL) for vestibular schwannomas and meningiomas, respectively. For both tumors, a median marginal dose of 13 Gy was prescribed. Median follow-up of patients was 65 months for vestibular schwannomas and 60 months for meningiomas. Patients were categorized into four groups on the basis of the tumor-brainstem relationship on neuroimaging. RESULTS Preservation of function was stratified according to grade of brainstem compression. We analyzed the effect of radiosurgery on symptoms of brainstem compression. The tumor control rate was 100 % for meningioma and 97% for vestibular schwannomas (although 5% required an additional procedure such as a ventriculoperitoneal shunt). In patients with vestibular schwannoma, serviceable hearing was preserved in 72.0%. Balance improved in 31.9%, remained unchanged in 56.5%, and deteriorated in 11.6% of patients who had imbalance at presentation. Balance improved significantly in patients who had less tumor compression (p = 0.0357) after radiosurgery. Symptoms improved in 43.2% of patients with meningioma. CONCLUSION Radiosurgery is a minimally invasive option for patients with benign basal tumors that indent or distort the brainstem. A high tumor growth control rate and satisfactory rate of neurological preservation and symptom control can be obtained with radiosurgery.

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.

Metabolic alterations in the peritumoral brain in cases of meningiomas: 1H-MRS study.

The objective of the present study was metabolic characterization of the peritumoral brain in the vicinity of meningiomas using proton magnetic resonance spectroscopy ((1)H-MRS). Data of long-echo (TR: 2000 ms, TE: 136 ms) single-voxel spectroscopic investigations were obtained during preoperative examination of 81 patients (19 men and 62 women; mean age, 56.5 years). Twenty-seven neoplasms were disclosed incidentally. Moderate-to-severe peritumoral edema was presented in 20 cases. Invasive growth of the tumor was macroscopically identified during surgery in 35 cases. Analyzed metabolites included N-acetylaspartate (NAA), choline-containing compounds (Cho), mobile lipids (Lip) and lactate (Lac). Compared to distant normal-appearing white matter (1)H-MRS of the brain in the vicinity of meningiomas disclosed statistically significant decrease of NAA content (P=0.0019). Investigated metabolic parameters depended on the presence of invasive tumor growth and prominent peritumoral edema, as well as on the size of the neoplasm, its location, and the patients age. More severe (1)H-MRS-detected peritumoral metabolic abnormalities associated with invasive growth of meningioma might be used for its prediction. The presence of meningioma-related neurological symptoms was mainly determined by the size of the tumor, while might be also associated with lower normalized NAA/Cho ratio and more frequent presence of a Lip peak in the peritumoral brain. In conclusion, decrease of NAA content constitutes the most prominent (1)H-MRS-detected brain abnormality in the vicinity of intracranial meningiomas. Peritumoral spectroscopic alterations are determined by a variety of factors, can be predictive for invasive tumor growth and may correspond to presented neurological symptoms.

Current Treatment Strategy of Gamma Knife® Surgery for Vestibular Schwannoma: Image-Guided and Robotized Microradiosurgery

Objective: Gamma Knife® surgery (GKS) is becoming a standard treatment ranked with surgical operation for acoustic schwannoma from the perspective of tumor control a

Image-Guided Micro Gamma Knife® Surgery for Skull-Base Tumors to Avoid Underlying Dysfunction of the Surrounding Vital Structures Using CISS with Gadolinium Enhancement

Rationale: Gamma Knife® surgery is one of the image-guided surgeries for brain tumors. Precise tumor visualization is required to complete dose planning to control tumor progression. In particular, surrounding vital structures should also be defined more clearly for the tumors to maintain their underlining function. Recently, we selected the special sequence, referred to as constructive interference in steady state (CISS), for MRI dedicated to skull-base tumors. We report the usefulness of this technique and evaluate its clinical utility. Methods: For skull-base and suprasellar tumors, we prefer to use CISS 0.5-mm slices with gadolinium enhancement. Each structure adjacent to the tumor can be visualized more clearly than scans without gadolinium, because the tumor is more clearly seen on the MRI without changing the findings of surrounding structures after gadolinium injection. Results: For skull-base tumors, we could visualize cranial nerves not only in the cisternal portion but also intracavernous portion, which helped distinguish nerves from the tumor. Finally, we performed optimal dose planning in every tumor to keep high conformity and selectivity to reduce toxicity and maintain underlying function. Conclusions: We demonstrate the use of the CISS imaging sequence for optimal dose planning for brain tumors with this dedicated sequence of MRI. This technique will decrease the risk of producing new neurological deficits in patients treated with Gamma Knife® radiosurgery.