Radiosurgical pathology of brain tumors: metastases, schwannomas, meningiomas, astrocytomas, hemangioblastomas.

Systematic human pathological background to brain tumor radiosurgery explaining biological and pathophysiological effects of focused irradiation barely exists. The goal of this study was to explore histopathological changes evoked by single high-dose irradiation in a set of different brain tumors following Gamma Knife radiosurgery (GKRS). Light microscopy revealed that GKRS evokes degenerative and proliferative pathological changes in the parenchyma, stroma and vessels of the irradiated tumors.

The role of computer technology in radiosurgery.

Stereotactic radiosurgery treatment principles and irradiation techniques have shown little evolution since its introduction in 1968. Conversely, technology progress linked to computers has produced a major impact on the methods used for treatment planning and dose delivery. In order to fully comprehend modern radiosurgery approaches, one has to acquire good insight of the underlying technology, specifically computer software.

Integration of functional imaging in radiosurgery: the example of PET scan.

Radiosurgery relies critically on the imaging modalities that are used for targeting. Leksell Gamma Knife (LGK) radiosurgery presents the highest requirements in terms of imaging accuracy as the treatment is applied in a single high-dose session with no other spatial control than medical imaging. The advent of functional imaging modalities opens new challenges for LGK planning strategies.

Medical physics principles of radiosurgery.

Beside basic physical notions such as ionizing radiation, beam production and beam characteristics, this chapter will focus on two major principles that should always be considered in a radiosurgery procedure: conformity and selectivity. Those parameters are influenced by different physical beam properties, by the type of beam delivery device and by the way the dose is delivered. Conformity and selectivity should be evaluated for each treatment with the help of some specific indices, i.

Introduction: the contribution of pathology to radiosurgery.

The term radiosurgery signifies any kind of application of ionizing radiation energy, in experimental biology or clinical medicine, aiming at the precise and complete destruction of chosen target structures containing healthy and/or pathological cells, without significant concomitant or late radiation damage to adjacent tissues. The goal of this study is to explore the short- and long-term pathophysiological effects of high-dose focused irradiation on neural tissue and its pathologies with histological, electron-microscopical tissue culture and biological-biochemical methods. Radiosurgical pathology focuses its scope and microscope on tissue, cellular, genetic and molecular changes in the human organism and experimental animals, or in cell lines and other in vitro experiments, generated by the ionizing radiation delivered from radiosurgical devices.

Controlled delivery of glial cell line-derived neurotrophic factor by a single tetracycline-inducible AAV vector.

An autoregulated tetracycline-inducible recombinant adeno-associated viral vector (rAAV-pTet(bidi)ON) utilizing the rtTAM2 reverse tetracycline transactivator (rAAV-rtTAM2) was used to conditionally express the human GDNF cDNA. Doxycycline, a tetracycline analog, induced a time- and dose-dependent release of GDNF in vitro in human glioma cells infected with rAAV-rtTAM2 serotype 2 virus. Introducing the Woodchuck hepatitis virus posttranscriptional regulatory element (WPRE) downstream to the rtTAM2 coding sequence, resulted in a more rapid induction and a higher basal expression level.

Lack of minocycline efficiency in genetic models of Huntington's disease.

According to the recent controversy regarding the effects of minocycline in the R6/2 transgenic model of Huntington's disease (HD), this tetracycline has been re-evaluated in another model, the N171-82Q strain. Ten miligrams per kilogram minocycline was given daily from the age of 2 mo, corresponding to an early symptomatic stage. We did not observe improvement in survival, weight loss, or motor function in treated transgenic mice.

Endovascular treatment of middle cerebral artery aneurysms.

Introduction: Until recently, middle cerebral artery (MCA) aneurysms were mostly treated by surgery, and endovascular treatment (EVT) was only performed in selected cases. We prospectively evaluated the feasibility and the results of EVT when it is considered as the first therapeutic option for the treatment of MCA aneurysms.

Methods: From April 2004 to April 2005, 32 patients with 32 MCA aneurysms were treated in our institution.

Citicoline is not protective in experimental models of Huntington's disease.

We have evaluated the neuroprotective effects of citicoline in relevant phenotypic models of Huntington's disease induced by either the mitochondrial inhibitor 3-nitropropionic acid or the N-methyl-D-aspartate agonist quinolinic acid, which, respectively, reproduce the metabolic defect or the excitotoxicity seen in the disease. We found that citicoline failed to reverse behavioural and histological alterations induced by both neurotoxins. In addition, citicoline did not reduce PC12 cell death induced by the expression of an N-terminal fragment of mutated Huntingtin.

Correlation between dynamic susceptibility contrast perfusion MRI and methionine metabolism in brain gliomas: preliminary results.

Purpose: To evaluate in brain gliomas the relationship between tumor vascularity measured by MR-based maximum regional cerebral blood volume (rCBV) and tumor amino-acid metabolism based on maximum carbon-11 methionine (MET) uptake on positron emission tomography (PET).

Materials And Methods: Eighteen patients with histologically proven primary brain gliomas were included in the study. In addition to conventional MR sequences, dynamic MR images, including a first-pass gadopentetate dimeglumine T2*-weighted echo-planar perfusion sequence and a PET study using MET, were acquired.

Cerebral metastases pathology after radiosurgery: a multicenter study.

Background: To the authors' knowledge, comprehensive human pathologic investigations that explore fundamental radiosurgical effects on metastatic brain tumors are sparse in the literature. The objective of this study was to analyze histopathologic findings in a set of clinically recurrent cerebral metastases after patients underwent stereotactic radiosurgery (SRS).

Methods: In a series of 7500 patients who underwent radiosurgery, 2020 patients (27%) harbored cerebral metastases.

Effect of beam channel plugging on the outcome of gamma knife radiosurgery for trigeminal neuralgia.

Purpose: We studied the influence of using plugs for brainstem protection during gamma knife radiosurgery (GKR) of trigeminal neuralgia (TN), with special emphasis on irradiation doses delivered to the trigeminal nerve, pain outcomes, and incidence of trigeminal dysfunction.

Methods And Materials: A GKR procedure for TN using an anterior cisternal target and a maximum dose of 90 Gy was performed in 109 patients. For 49 patients, customized beam channel blocking (plugs) were used to reduce the dose delivered to the brainstem.

[Transsphenoidal approach with low field MRI for pituitary adenoma].

Introduction: Appropriate evaluation of resection remains one of the major difficulties of surgical treatment of pituitary adenoma. The transsphenoidal approach does not allow direct visual control. Endoscopy provides useful information but may no distinguish well residual adenoma from the pituitary gland.

Retractable self-expandable stent for endovascular treatment of wide-necked intracranial aneurysms: preliminary experience.

Objective: Intracranial stenting combined with endosaccular coiling is a therapeutic alternative for the endovascular treatment (EVT) of wide-necked intracranial aneurysms. The current limitation of available stents is the impossibility to reposition them once they are partially deployed. Recently, the first retractable self-expandable stent has been developed and we sought to evaluate the use of this stent for EVT of wide-necked intracranial aneurysms.

The Zeiss-MKM system for frameless image-guided approach in epidural motor cortex stimulation for central neuropathic pain.

Object: Twelve patients (seven female, and five male, mean age 55.6 years) suffering from refractory central (ischemic/traumatic [eight cases]) and neuropathic pain (trigeminal neuropathy [four cases]) underwent surgery for the implantation of an epidural motor cortex stimulation (MCS) device in which the authors used a frameless neuronavigation system, the Zeiss-MKM microscope.

Methods: The authors assessed the spatial accuracy of the neuronavigation system and its potential contribution to improve the quality of targeting pain.

Integrated positron emission tomography and magnetic resonance imaging-guided resection of brain tumors: a report of 103 consecutive procedures.

Object: The aim of this study was to evaluate the integration of positron emission tomography (PET) scanning data into the image-guided resection of brain tumors.

Methods: Positron emission tomography scans obtained using fluorine-18 fluorodeoxyglucose (FDG) and L-[methyl-11C]methionine (MET) were combined with magnetic resonance (MR) images in the navigational planning of 103 resections of brain tumors (63 low-grade gliomas [LGGs] and 40 high-grade gliomas [HGGs]). These procedures were performed in 91 patients (57 males and 34 females) in whom tumor boundaries could not be accurately identified on MR images for navigation-based resection.

Role of intracanalicular volumetric and dosimetric parameters on hearing preservation after vestibular schwannoma radiosurgery.

Purpose: To analyze the relationship between hearing preservation after gamma knife radiosurgery (GKR) for vestibular schwannoma (VS) and some volumetric and dosimetric parameters of the intracanalicular components of VS.

Methods And Materials: This study included 82 patients with a VS treated by GKR; all patients had no NF2 disease, a Gardner-Robertson hearing class 1-4 before treatment, a marginal dose of 12 Gy, and a radiologic and audiologic follow-up > or =1 year post-GKR. The volume of both the entire tumor and the intracanalicular part of the tumor and the mean and integrated dose of these two volumes were correlated to the auditory outcomes of patients.

Endovascular treatment of intracranial aneurysms with a branch arising from the sac.

Background And Purpose: The endovascular treatment (EVT) of intracranial aneurysms is no more limited by the presence of a branch at the neck or by the neck width. Saccular aneurysms with a branch arising from the sac, however, are mostly candidates for surgery rather than embolization. We prospectively evaluated the feasibility and safety of the EVT in such cases.

11C-methionine PET for the diagnosis and management of recurrent pituitary adenomas.

Purpose: The detection of recurrent pituitary adenoma by magnetic resonance imaging (MRI) is rendered uncertain by the tissue remodelling that follows surgery or radiotherapy. We aimed to evaluate the contribution of PET with 11C-methionine (MET-PET) in the detection and management of recurrent pituitary adenoma.

Methods: Thirty-three patients with pituitary adenoma were evaluated postoperatively by MET-PET, either because of biological evidence of active residual tumour or because of MRI demonstration of non-functional adenoma growth.

Comparison of functional MR imaging guidance to electrical cortical mapping for targeting selective motor cortex areas in neuropathic pain: a study based on intraoperative stereotactic navigation.

Purpose: To assess the concordance between data from functional MR imaging (fMRI) guidance and the intraoperative electrical cortical mapping (iCM) in targeting selective motor cortex areas in refractory neuropathic pain.

Methods: Twenty-one patients (11 women and 10 men; mean age, 55.6 years) with refractory central (ischemic, 8 cases) and neuropathic pain (trigeminal neuropathy, 6 cases; syrinx/amputation/plexus trauma, 7 cases) underwent surgery for the implantation of an epidural electrode for chronic motor cortex stimulation (MCS) with general anesthesia and a frameless neuronavigation system used for the image-guided targeting procedure.

Integration of [11C]methionine-positron emission tomographic and magnetic resonance imaging for image-guided surgical resection of infiltrative low-grade brain tumors in children.

Objective: To evaluate the interest of integrating positron emission tomography (PET) images with the radiolabeled tracer [(11)C]methionine (Met) into the image-guided navigation planning of infiltrative low-grade brain tumors (LGBTs) in children.

Methods: Twenty-two children underwent combined Met-PET with magnetic resonance imaging (MRI) scans in the planning of a navigation procedure. These children presented an LGBT (astrocytomas, 10; oligodendrogliomas, 4; ependymomas, 4; gangliogliomas, 4) located close to functional areas.

Positron emission tomography for the early postsurgical evaluation of pediatric brain tumors.

Object: The object was to study the value of postoperative positron emission tomography (PET) to assess the extension of brain tumor resection.

Methods: Twenty children operated on for total resection of a glial tumor (18 low-grade, 2 anaplastic) presented a signal on postoperative magnetic resonance (MR) images raising the question of a possible tumor residue. PET was performed early ((18)F-Fluoro-deoxyglucose in 1, (11)C-methionine in 16, both in 3) to further characterize the nature of the abnormal MR signal in order to consider second-look surgery.

Combination of functional magnetic resonance imaging-guided neuronavigation and intraoperative cortical brain mapping improves targeting of motor cortex stimulation in neuropathic pain.

Objective: To evaluate, regardless of the clinical results, the contribution of combining functional magnetic resonance imaging (fMRI) with intraoperative cortical brain mapping (iCM) as functional targeting methods for epidural chronic motor cortex stimulation (MCS) in refractory neuropathic pain.

Methods: Eighteen neuropathic pain patients (central stroke in six; trigeminal neuropathy in six; syrinx or amputation in six) who underwent operations for epidural MCS were studied with preoperative fMRI and iCM. fMRI investigated motor tasks of hands (as well as foot and tongue, when painful).

Modern multimodal neuroimaging for radiosurgery: the example of PET scan integration.

Radiosurgery relies critically on medical imaging modalities. Leksell Gamma Knife (LGK) radiosurgery presents the highest requirements in terms of imaging accuracy as the treatment is applied in a single high-dose session with no other spatial control than medical imaging. The advent of new imaging modalities opens challenges for LGK planning strategies.

Use of the Leksell gamma knife C with automatic positioning system for the treatment of meningioma and vestibular schwannoma.

Object: The authors report their experience using the Leksell gamma knife C (GK-C) for the treatment of meningioma and vestibular schwannoma (VS).

Methods: In December 1999, the first commercially available clinical GK-C was installed at the Université Libre de Bruxelles (Erasme Hospital, Brussels, Belgium). In January 2000, the system was upgraded and equipped with the automatic positioning system (APS).