Masahiro Izawa

Gamma knife radiosurgery for pituitary adenomas.

The purpose of this paper was to note a potential source of error in magnetic resonance (MR) imaging. Magnetic resonance images were acquired for stereotactic planning for GKS of a vestibular schwannoma in a female patient. The images were acquired using three-dimensional sequence, which has been shown to produce minimal distortion effects. The images were transferred to the planning workstation, but the coronal images were rejected. By examination of the raw data and reconstruction of sagittal images through the localizer side plate, it was clearly seen that the image of the square localizer system was grossly distorted. The patient was returned to the MR imager for further studies and a metal clasp on her brassiere was identified as the cause of the distortion.A-60-year-old man with medically intractable left-sided maxillary division trigeminal neuralgia had severe cardiac disease, was dependent on an internal defibrillator and could not undergo magnetic resonance imaging. The patient was successfully treated using computerized tomography (CT) cisternography and gamma knife radiosurgery. The patient was pain free 2 months after GKS. Contrast cisternography with CT scanning is an excellent alternative imaging modality for the treatment of patients with intractable trigeminal neuralgia who are unable to undergo MR imaging.The authors describe acute deterioration in facial and acoustic neuropathies following radiosurgery for acoustic neuromas. In May 1995, a 26-year-old man, who had no evidence of neurofibromatosis Type 2, was treated with gamma knife radiosurgery (GKS; maximum dose 20 Gy and margin dose 14 Gy) for a right-sided intracanalicular acoustic tumor. Two days after the treatment, he developed headache, vomiting, right-sided facial weakness, tinnitus, and right hearing loss. There was a deterioration of facial nerve function and hearing function from pretreatment values. The facial function worsened from House-Brackmann Grade 1 to 3. Hearing deteriorated from Grade 1 to 5. Magnetic resonance (MR) images, obtained at the same time revealed an obvious decrease in contrast enhancement of the tumor without any change in tumor size or peritumoral edema. Facial nerve function improved gradually and increased to House-Brackmann Grade 2 by 8 months post-GKS. The tumor has been unchanged in size for 5 years, and facial nerve function has also been maintained at Grade 2 with unchanged deafness. This is the first detailed report of immediate facial neuropathy after GKS for acoustic neuroma and MR imaging revealing early possibly toxic changes. Potential explanations for this phenomenon are presented.In clinical follow-up studies after radiosurgery, imaging modalities such as computerized tomography (CT) and magnetic resonance (MR) imaging are used. Accurate determination of the residual lesion volume is necessary for realistic assessment of the effects of treatment. Usually, the diameters rather than the volume of the lesion are measured. To determine the lesion volume without using stereotactically defined images, the software program VOLUMESERIES has been developed. VOLUMESERIES is a personal computer-based image analysis tool. Acquired DICOM CT scans and MR image series can be visualized. The region of interest is contoured with the help of the mouse, and then the system calculates the volume of the contoured region and the total volume is given in cubic centimeters. The defined volume is also displayed in reconstructed sagittal and coronal slices. In addition, distance measurements can be performed to measure tumor extent. The accuracy of VOLUMESERIES was checked against stereotactically defined images in the Leksell GammaPlan treatment planning program. A discrepancy in target volumes of approximately 8% was observed between the two methods. This discrepancy is of lesser interest because the method is used to determine the course of the target volume over time, rather than the absolute volume. Moreover, it could be shown that the method was more sensitive than the tumor diameter measurements currently in use. VOLUMESERIES appears to be a valuable tool for assessing residual lesion volume on follow-up images after gamma knife radiosurgery while avoiding the need for stereotactic definition.This study was conducted to evaluate the geometric distortion of angiographic images created from a commonly used digital x-ray imaging system and the performance of a commercially available distortion-correction computer program. A 12 x 12 x 12-cm wood phantom was constructed. Lead shots, 2 mm in diameter, were attached to the surfaces of the phantom. The phantom was then placed inside the angiographic localizer. Cut films (frontal and lateral analog films) of the phantom were obtained. The films were analyzed using GammaPlan target series 4.12. The same procedure was repeated with a digital x-ray imaging system equipped with a computer program to correct the geometric distortion. The distortion of the two sets of digital images was evaluated using the coordinates of the lead shots from the cut films as references. The coordinates of all lead shots obtained from digital images and corrected by the computer program coincided within 0.5 mm of those obtained from cut films. The average difference is 0.28 mm with a standard deviation of 0.01 mm. On the other hand, the coordinates obtained from digital images with and without correction can differ by as much as 3.4 mm. The average difference is 1.53 mm, with a standard deviation of 0.67 mm. The investigated computer program can reduce the geometric distortion of digital images from a commonly used x-ray imaging system to less than 0.5 mm. Therefore, they are suitable for the localization of arteriovenous malformations and other vascular targets in gamma knife radiosurgery.

Long-term complications after gamma knife surgery for arteriovenous malformations

OBJECT The authors analyzed of the long-term complications that occur 2 or more years after gamma knife surgery (GKS) for intracranial arteriovenous malformations (AVMs). METHODS Patients with previously untreated intracranial AVMs that were managed by GKS and followed for at least 2 years after treatment were selected for analysis (237 cases). Complete AVM obliteration was attained in 130 cases (54.9%), and incomplete obliteration in 107 cases (45.1%). Long-term complications were observed in 22 patients (9.3%). These complications included hemorrhage (eight cases), delayed cyst formation (eight cases), increase of seizure frequency (four cases), and middle cerebral artery stenosis and increased white matter signal intensity on T2-weighted magnetic resonance imaging (one case of each). The long-term complications were associated with larger nidus volume (p < 0.001) and a lobar location of the AVM (p < 0.01). Delayed hemorrhage was associated only with incomplete obliteration of the nidus (p < 0.05). Partial obliteration conveyed no benefit. Delayed cyst formation was associated with a higher maximal GKS dose (p < 0.001), larger nidus volume (p < 0.001), complete nidus obliteration (p < 0.01), and a lobar location of the AVM (p < 0.05). CONCLUSIONS Incomplete obliteration of the nidus is the most important factor associated with delayed hemorrhagic complications. Partial obliteration does not seem to reduce the risk of hemorrhage. Complete obliteration can be complicated by delayed cyst formation, especially if high maximal treatment doses have been administered.

Management of intracranial hemorrhage associated with anticoagulant therapy

BACKGROUND Intracranial hemorrhage may be a particularly devastating complication of anticoagulant therapy. Very few accounts have reported data on the duration of anticoagulant discontinuation following intracranial hemorrhage or the intensity of anticoagulation during treatment for it, although we must adequately manage such a complication. METHODS We analyzed the management of warfarin-related intracranial hemorrhages in 27 patients with cardiac diseases. We evaluated the degree of anticoagulation using the thrombotest. Anticoagulants were stopped as soon as the diagnosis of intracranial hemorrhage was established by computed tomographic scan. RESULTS Mechanical valve prosthesis patients, who required intensive long-term anticoagulant therapy, constituted the majority of our series (74.1%). Intraoperative hemostasis was brought under control despite low thrombotest values (13%-68%) at the time of surgery except for the acute subdural hematoma (SDH) patients with cerebral contusion. Early resumption of anticoagulant therapy (within 3 days) did not cause intracranial rebleeding in any operative patient. All the chronic SDH patients and some of the subcortical hematoma patients had a good outcome. All three patients with acute SDH and contusion, however, had a fatal outcome because of intracranial rebleeding within a short period of time or ineffective intraoperative hemostasis. CONCLUSIONS The patients with anticoagulant-related intracranial hemorrhage may undergo surgery with thrombotest values approximately between 20% and 60%, and anticoagulants can be resumed after an interval of 3 days. Aggressive surgery should particularly be performed in patients with anticoagulation-related chronic SDH or subcortical hemorrhage, as in the cases of anticoagulant-unrelated intracranial hemorrhage.

Gamma Knife radiosurgery for pituitary adenomas.

Ninety-two patients with pituitary adenomas have been treated during the last 5 years. Sixty-three of these patients had more than 6 months follow-up, and they form the basis of this report. Eighteen had non-functioning adenomas (NFA), and 36 had functioning adenomas (FA). The mean marginal dose was 22.5 Gy (NFA 19.5 Gy, FA 23.9 Gy). Control of tumor growth was achieved in 92%. A significant decrease of excessive hormone production was seen in 75.6%, and the endocrinopathy normalization rate was 26.7%. Post-radiosurgical complications were seen in 4.7%.

Current treatment of brain abscess in patients with congenital cyanotic heart disease.

OBJECTIVE The goal of this study was to define clearly the role of management in patients with cyanotic heart disease and brain abscesses by evaluating retrospectively the factors influencing poor outcome in these patients. METHODS This study included 62 patients with cyanotic heart disease and brain abscesses diagnosed in the computed tomography era. Basic characteristic parameters (number, size, location, computed tomographic classification and organism type of abscess, convulsion, type of cyanotic heart disease, age distribution, immunocompromised status, pretreatment neurological state, and intraventricular rupture of brain abscess [IVROBA]) and therapeutic parameters (type of antibiotics and duration of administration, steroid medication and therapeutic modalities, aspiration with or without cerebrospinal fluid drainage, total extirpation after aspiration, or primary extirpation and medical treatment) were evaluated as independent predictors of poor outcome (totally disabled state or death) by using univariate and multivariate logistic regression analysis. We also statistically estimated the possible causes of IVROBA and the multiplicity of brain abscess. RESULTS Although there were no statistically significant correlations between patients with good and poor outcomes in regard to other basic characteristic and therapeutic parameters, patients with poor outcomes were older (P < 0.02), more frequently had IVROBA (P < 0.005), and had a higher frequency of neurological deterioration (P < 0.01) than those with good outcomes. Multiple logistic regression analysis predicted that poor outcome increased the relative risk of IVROBA by a factor of 18.9 (odds rate, 18.9; 95% confidence interval, 1.7-211.6; P < 0.02). More patients with multiple abscesses had positive immunocompromised states than those with single abscesses (P < 0.01). Deep-located abscesses also more frequently had IVROBA (P < 0.005) and abscesses located in the parieto-occipital region ruptured into the occipital horn of the lateral ventricle in a short period (P < 0.02). CONCLUSIONS Our findings suggest that IVROBA strongly influences poor outcome in patients with cyanotic heart disease. The key to decreasing poor outcomes may be the prevention and management of IVROBA. To reduce operative and anesthetic risk in these patients, abscesses should be managed by less invasive aspiration methods guided by computed tomography. Abscesses larger than 2 cm in diameter, in deep-located or parieto-occipital regions, should be aspirated immediately and repeatedly, mainly using computed tomography-guided methods to decrease intracranial pressure and avoid IVROBA. IVROBA should be aggressively treated by aspiration methods for the abscess coupled with the appropriate intravenous and intrathecal administration of antibiotics while evaluating intracranial pressure pathophysiology.

Multivoxel proton MRS for differentiation of radiation-induced necrosis and tumor recurrence after gamma knife radiosurgery for brain metastases

Multivoxel proton magnetic resonance spectroscopy (MRS) was used for differentiation of radiation-induced necrosis and tumor recurrence after gamma knife radiosurgery for intracranial metastases in 33 consecutive cases. All patients presented with enlargement of the treated lesion, increase of perilesional brain edema, and aggravation or appearance of neurological signs and symptoms on average 9.3 ± 4.9 months after primary treatment. Metabolic imaging defined four types of lesions: pure tumor recurrence (11 cases), partial tumor recurrence (11 cases), radiation-induced tumor necrosis (10 cases), and radiation-induced necrosis of the peritumoral brain (1 case). In 1 patient, radiation-induced tumor necrosis was diagnosed 9 months after radiosurgery; however, partial tumor recurrence was identified 6 months later. With the exception of midline shift, which was found to be more typical for radiation-induced necrosis (P < 0.01), no one clinical, radiologic, or radiosurgical parameter either at the time of primary treatment or at the time of deterioration showed a statistically significant association with the type of the lesion. Proton MRS-based diagnosis was confirmed histologically in all surgically treated patients (7 cases) and corresponded well to the clinical course in others. In conclusion, multivoxel proton MRS is an effective diagnostic modality for identification of radiation-induced necrosis and tumor recurrence that can be used for monitoring of metabolic changes in intracranial neoplasms after radiosurgical treatment. It can be also helpful for differentiation of radiation-induced necrosis of the tumor and that of the peritumoral brain, which may have important clinical and medicolegal implications.

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.

Proton MRS of the peritumoral brain.

Long-echo (TR: 2000 ms, TE: 136 ms) proton MRS of the cerebral tissue in the vicinity to intracranial lesion was done in 15 patients, mainly with parenchymal brain tumors. Significant decrease of N-acetylaspartate (NAA) (P<0.001) and more frequent presence of lactate (P<0.01) comparing with distant normal white matter were found in the perilesional brain tissue. The level of NAA in the perilesional brain tissue had negative associations with presence of lactate in the lesion (P<0.05), excess of lactate in the lesion compared to perilesional brain (P<0.01), grade of the perilesional edema (P<0.01) and patients age (P<0.05). Multivariate analysis disclosed that identification of lactate in the lesion is associated with lower relative NAA content in the perilesional brain tissue, independently on the presence or absence of any other factor, including brain edema (P<0.001). In patients with lobar lesions who had at least one epileptic seizure during course of their disease the relative NAA content in the perilesional brain was significantly lower, comparing with those who were seizure-free (P<0.05). Therefore, lactate diffused from the tumor, or other metabolites secreted by lactate-producing neoplasm, should be considered as important contributors to the neuronal dysfunction in the surrounding brain. Decrease of NAA in the vicinity to intracranial lesions may reflect neuronal alteration responsible for associated epilepsy.

Prophylactic effect of papaverine prolonged-release pellets on cerebral vasospasm in dogs.

OBJECTIVE A drug delivery system using copoly(lactic/glycolic acid) was developed for the intracranial administration of papaverine. A rod-shaped implant prepared by a heat compression method was tested to determine its efficacy in preventing cerebral vasospasm in dogs. METHODS Sixteen dogs were randomly assigned to one of two groups, i.e., placebo or papaverine. Control angiography was performed, followed by right craniectomy and the induction of subarachnoid hemorrhage by the placement of a clot in the Sylvian fissure. Two pellets, containing either 25 mg of papaverine or no papaverine, were placed in the cistern. In in vitro studies, 56% of the actual papaverine loading was released in the first 4 days and 78% within 8 days. On Day 7, angiography was repeated and the animals were killed. A similar experiment using low-dose pellets containing 5 mg of papaverine, half of which was released within 7 days, was performed with 16 mongrel dogs. RESULTS There were significant differences between the papaverine- and placebo-treated groups in the reductions of vessel diameters of the internal carotid, middle cerebral, and anterior cerebral arteries on the clot side. The mean concentration of papaverine in the clot was 4.5 x 10(-4) mol/L. The low-dose pellet failed to prevent cerebral vasospasm, although the mean concentration of papaverine in the clot was 2.3 x 10(-5) mol/L. CONCLUSION A prolonged-release preparation of papaverine that could be implanted intracranially at the time of surgery prevented vasospasm significantly while maintaining an appropriate concentration of papaverine in the cistern.

Gamma Knife Radiosurgery for Meningiomas: Four Cases of Radiation-Induced Edema

We review 48 cases of meningioma treated with Gamma Knife radiosurgery. The mean marginal dose was 15 Gy and the mean follow-up was 12 months. Follow-up computed tomography and magnetic resonance imaging showed tumor shrinkage in 19 cases, central necrosis in 1 case, loss of contrast enhancement in 1 case, and no change in 27 cases. We noted 4 cases of radiation-induced edema in supratentorial meningiomas.