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Benoit Pirotte, Philippe Voordecker, Freddy Joffroy, Nicolas Massager, David Wikler, Danielle Baleriaux, Marc Levivier and Jacques Brotchi

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. In these patients, the positions of the central sulcus, defined by stereotactic magnetic resonance MR imaging, intraoperative somatosensory evoked potentials (SSEPs) and subdural visual verification, were correlated into the stereotactic neuronavigation planning procedure. The mean spatial accuracy of distance between (MR) imaging–defined and actual central sulcus was 2.4 mm (range 5–10 mm). The intraoperative SSEP-defined central sulcus was close to that defined by MR imaging (mean distance 6.4 mm). Although very precise, intra-operative SSEP recordings were impaired by artifacts and wave attenuation in six of the 12 patients. Stereotactic correlations between anatomical and functional data in the navigation system corrected final targeting in 10 of 12 cases. Pain relief was obtained in eight patients. Indeed, inappropriate targeting probably explains the reported variable success rate of MCS and certainly underestimates the actual efficacy.

Conclusions

Since intraoperative SSEP monitoring has, for many years, been considered the standard procedure to approach motor target, the development of an accurate stereotactic image guidance system could help to increase the efficacy of MCS on the alleviation of pain. The excellent spatial accuracy provided by the Zeiss-MKM navigation system allows precise data correlations that represent a remarkable means to validate functional MR imaging as an alternative to SSEP. The authors believe that developing stereotactic image guidance with such a navigation system could improve the success rate of MCS.

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Benoit J. M. Pirotte, Alphonse Lubansu, Nicolas Massager, David Wikler, Serge Goldman and Marc Levivier

Object

Most intrinsic infiltrative brainstem lesions diagnosed in children are gliomas, and these carry a very bad prognosis. Although the utility and risk of stereotactically guided biopsy procedures in intrinsic infiltrative brainstem lesions have been widely questioned, the neuroimaging diagnosis may be inaccurate in approximately 25% of cases, and the consequences of empirical therapy should not be underestimated. Stereotactic biopsy sampling is still performed in many centers, but the reported diagnostic yield ranges from 83 to 96%. The authors integrated positron emission tomography (PET) images into the planning for stereotactic biopsy procedures to direct the biopsy needle's trajectory to hypermetabolic foci of intrinsic infiltrative brainstem lesions. Their aim was to assess the benefit of the technique in terms of target selection and diagnostic yield.

Methods

Twenty children with newly diagnosed intrinsic infiltrative brainstem lesions underwent a PET-guided stereotactic biopsy procedure. The PET tracer was18F-2-fluoro-2-deoxy-D-glucose (FDG) in six cases, 11C-methionine in eight, and both agents were used in six. A single biopsy target was selected in the area of highest PET tracer uptake in all cases. The PET data were compared with diagnoses and outcome.

Results

Use of PET guidance improved target selection and provided tumor diagnosis in all trajectories and in all children (high-grade glioma was diagnosed in 10, low-grade glioma in five, and nonglial tumor in five). The PET-guided trajectories provided a higher diagnostic yield than those guided by magnetic resonance imaging alone, which allowed the sampling to be reduced to a single trajectory. The PET data might also carry a prognostic value that could be useful for oncological management.

Conclusions

These data support the suggestion that PET guidance improves the diagnostic yield of stereotactic biopsy sampling, allows the practitioner to reduce the number of sampling procedures, and might lead to a reassessment of the utility of and indications for stereotactic biopsy in children with intrinsic infiltrative brainstem lesions.

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Olivier De Witte, Ilan Goldberg, David Wikler, Sandrine Rorive, Philippe Damhaut, Michel Monclus, Isabelle Salmon, Jacques Brotchi and Serge Goldman

Object. Positron emission tomography with l-[methyl-11C]methionine (MET-PET) provides information on the metabolism of gliomas. The aim of this study was to determine the predictive value of MET-PET in the treatment of patients with gliomas.

Methods. Since 1992, 85 patients with a World Health Organization (WHO) classification—verified glioma underwent PET studies in which MET was injected before (74 cases) or after treatment (11 cases). Analysis of PET data was conducted by the same investigator using two scales: a qualitative visual grading scale and a quantitative scale (ratio between tumor uptake and normal brain uptake, classified on a seven-level scale).

Uptake of MET was present in 98% of gliomas. The investigator judged this uptake to be moderate to very high based on visual inspection (qualitative scale). For all grades of gliomas, a visual grade of 3 was statistically associated with a shorter patient survival period (p < 0.005). The tumor/normal brain uptake ratio was significantly influenced by the histological grade of the tumor. A statistically poor outcome was demonstrated when this ratio was higher than a threshold of 2.2 for a WHO Grade II tumor and 2.8 for WHO Grade III tumor. For Grade II and III tumors, oligodendrogliomas had a higher uptake of MET than astrocytomas.

Conclusions. Uptake of MET was present in 98% of the gliomas studied. A high uptake is statistically associated with a poor survival time. The intensity of MET uptake represents a prognostic factor for WHO Grade II and III tumors considered separately.

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Marc Levivier, David Wikler Jr., Nicolas Massager, Philippe David, Daniel Devriendt, Jose Lorenzoni, Benoit Pirotte, Françoise Desmedt, Stephane Simon Jr., Serge Goldman, Paul Van Houtte and Jacques Brotchi

Object. The authors review their experience with the clinical development and routine use of positron emission tomography (PET) during stereotactic procedures, including the use of PET-guided gamma knife radiosurgery (GKS).

Methods. Techniques have been developed for the routine use of stereotactic PET, and accumulated experience using PET-guided stereotactic procedures over the past 10 years includes more than 150 stereotactic biopsies, 43 neuronavigation procedures, and 34 cases treated with GKS. Positron emission tomography—guided GKS was performed in 24 patients with primary brain tumors (four pilocytic astrocytomas, five low-grade astrocytomas or oligodendrogliomas, seven anaplastic astrocytomas or ependymomas, five glioblastomas, and three neurocytomas), five patients with metastases (single or multiple lesions), and five patients with pituitary adenomas.

Conclusions. Data obtained with PET scanning can be integrated with GKS treatment planning, enabling access to metabolic information with high spatial accuracy. Positron emission tomography data can be successfully combined with magnetic resonance imaging data to provide specific information for defining the target volume for the radiosurgical treatment in patients with recurrent brain tumors, such as glioma, metastasis, and pituitary adenoma. This approach is particularly useful for optimizing target selection for infiltrating or ill-defined brain lesions. The use of PET scanning contributed data in 31 cases (93%) and information that was specifically utilized to adapt the target volume in 25 cases (74%). It would seem that the integration of PET data into GKS treatment planning may represent an important step toward further developments in radiosurgery: this approach provides additional information that may open new perspectives for the optimization of the treatment of brain tumors.

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Nicolas Massager, Philippe David, Serge Goldman, Benoît Pirotte, David Wikler, Isabelle Salmon, Nathalie Nagy, Jacques Brotchi and Marc Levivier

Object. In the management of brainstem lesions, the place of stereotactic biopsy sampling remains debatable. The authors compared the results of magnetic resonance (MR) imaging, positron emission tomography (PET) scanning, and histological studies obtained in 30 patients who underwent MR imaging— and PET-guided stereotactic biopsy procedures for a brainstem mass lesion.

Methods. Between July 1991 and December 1998, 30 patients harboring brainstem mass lesions underwent a stereotactic procedure in which combined MR imaging and PET scanning guidance were used. Positron emission tomography scanning was performed using [18F]fluorodeoxyglucose in 16 patients, methionine in two patients, and both tracers in 12 patients. Definite diagnosis was established on histological examination of the biopsy samples. Interpretation of MR imaging findings only or PET findings only was in agreement with the histological diagnosis in 63% and 73% of cases, respectively. Magnetic resonance imaging and PET findings were concordant in 19 of the 30 cases; in those cases, imaging data correlated with histological findings in 79%. Treatment based on information derived from MR imaging was concordant with therapy based on histological findings in only 17 patients (57%). Combining MR imaging and PET scanning data, the concordance between the neuroimaging-based treatment and treatments based on histological findings increased to 19 patients (63%). In seven patients who underwent biopsy procedures with one PET-defined and one MR imaging—defined trajectory, at histological examination the PET-guided samples were more representative of the tumor's nature and grade than the MR imaging—guided samples in four cases (57%). In 18 patients PET scanning was used to define a biopsy target and provided a diagnostic yield in 100% of the cases.

Conclusions. Although the use of combined PET and MR imaging improves radiological interpretation of a mass lesion in the brainstem, it does not accurately replace histological diagnosis that is provided by a stereotactically obtained biopsy sample. Combining information provided by MR imaging and PET scanning in stereotactic conditions improves the accuracy of targeting and the diagnostic yield of the biopsy sample; an MR imaging— and PET-guided stereotactic biopsy procedure is a safe and efficient modality for the management of mass lesions of the brainstem.

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Benoit Pirotte, Serge Goldman, Nicolas Massager, Philippe David, David Wikler, Maurice Lipszyc, Isabelle Salmon, Jacques Brotchi and Marc Levivier

Object. The aim of this study was to compare the contribution of the tracers 11C-methionine (Met) and 18F-fluorodeoxyglucose (FDG) in positron emission tomography (PET)—guided stereotactic brain biopsy.

Methods. Forty-five patients underwent combined Met-PET and FDG-PET studies associated with computerized tomography (CT)— or magnetic resonance (MR)—guided stereotactic biopsy. Each patient presented with a lesion that was in proximity to the cortical or subcortical gray matter. The Met-PET and FDG-PET scans were analyzed to determine which tracer offers the best information to guide at least one stereotactic biopsy trajectory. Histologically based diagnoses were rendered in all patients (39 tumors, six nontumorous lesions) and biopsies were performed in all tumors with the aid of PET guidance. When tumor FDG uptake was higher than that in the gray matter (18 tumors), FDG was used for target definition. When FDG uptake was absent or equivalent to that in the gray matter (21 tumors), Met was used for target definition. Parallel review of all histological and imaging data showed that all tumors had an area of abnormal Met uptake and 33 had abnormal FDG uptake. All six nontumorous lesions had no Met uptake and biopsies were performed using CT or MR guidance only. All tumor trajectories had an area of abnormal Met uptake; all nondiagnostic trajectories in tumors had no abnormal Met uptake.

Conclusions. When FDG shows limitations in target selection, Met is a good alternative because of its high specificity in tumors. Moreover, in the context of a single-tracer procedure and regardless of FDG uptake, Met is a better choice for PET guidance in neurosurgical procedures.

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Nicolas Massager, Philippe David, Serge Goldman, Benoît Pirotte, David Wikler, Isabelle Salmon, Nathalie Nagy, Jacques Brotchi and Marc Levivier

In the management of brainstem lesions, the place of stereotactic biopsy sampling remains debatable. The authors compared the results of magnetic resonance (MR) imaging, positron emission tomography (PET), and histological findings obtained in 30 patients who underwent an MR image– and PET-guided stereotactic biopsy procedure for a brainstem mass lesion.

Between July 1991 and December 1998, 30 patients harboring a brainstem mass lesion underwent a stereotactic procedure in which combined MR imaging and PET guidance was used. Positron emission tomography scanning was performed using [18F]-fluorodeoxyglucose in 16 patients, methionine in two patients, and with both tracers in 12 patients. Definite diagnosis was established on histological examination of the biopsy samples. Interpretation of MR imaging findings only or PET findings only were in agreement with the histological diagnosis in 63% and 73% of cases, respectively. Magnetic resonance imaging and PET findings were concordant in 19 of the 30 cases; in those cases, imaging data correlated with histological findings in 79%. In seven patients who underwent one PET-defined and one MR imaging–defined trajectory, at histological examination the PET-guided samples were more representative of the tumor's nature and grade than the MR imaging–guided samples in four cases (57%). In 18 patients PET scanning was used to define a biopsy target and provided a diagnostic yield in 100% of the cases.

Although the use of combined PET and MR imaging improves radiological interpretation of a mass lesion in the brainstem, it does not accurately replace histological diagnosis that is provided by a stereotactically obtained biopsy sample. Combined information provided by MR imaging and PET in stereotactic conditions improves the accuracy of targeting and the diagnostic yield of the stereotactically biopsy sample; an MR imaging– and PET-guided stereotactic biopsy procedure is a safe and efficient modality for the management of mass lesions of the brainstem.

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Benoit J. M. Pirotte, Alphonse Lubansu, Nicolas Massager, David Wikler, Patrick Van Bogaert, Marc Levivier, Jacques Brotchi and Serge Goldman

Object

In this paper, the authors' goal was to evaluate the impact of PET information on brain tumor surgery in children.

Methods

Between 1995 and 2007, 442 children were referred to the authors' institution for a newly diagnosed brain lesion. Of these, 85 were studied with FDG-PET and/or L-(methyl-11C)-methionine –PET in cases in which MR images were unable to assist in selecting accurate biopsy targets (35 patients) or to delineate tumors for maximal resection (50 patients). In surgical cases, PET and MR images were combined in image fusion planning for stereotactic biopsies or navigation-based resections. The preoperative planning images were compared postoperatively with MR imaging and PET findings and histological data for evaluating the clinical impact on the diagnostic yield and tumor resection.

Results

The PET data influenced surgical decisions or procedures in all cases. The use of PET helped to better differentiate indolent from active components in complex lesions (in 12 patients); improved target selection and diagnostic yield of stereotactic biopsies without increasing the sampling; provided additional prognostic information; reduced the amount of tissue needed for biopsy sampling in brainstem lesions (in 20 cases); better delineated lesions that were poorly delineated on MR imaging and that infiltrated functional cortex (in 50 cases); significantly increased the amount of tumor tissue removed in cases in which total resection influenced survival (in 20 cases); guided resection in hypermetabolic areas (in 15 cases); improved early postoperative detection of residual tumor (in 20 cases); avoided unnecessary reoperation (in 5 cases); and supported the decision to undertake early second-look resection (in 8 cases).

Conclusions

The authors found that PET has a significant impact on the surgical decisions and procedures for managing pediatric brain tumors. Further studies may demonstrate whether PET improves outcomes in children.

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Benoit J. M. Pirotte, Alphonse Lubansu, Nicolas Massager, David Wikler, Patrick Van Bogaert, Marc Levivier, Jacques Brotchi and Serge Goldman

Object

In this paper, the authors' goal was to evaluate the impact of PET data on the clinical management of incidental brain lesions in children.

Methods

Between 1995 and 2007, 442 children with a newly diagnosed brain lesion were referred to the authors' department. Of these, 55 presented with an incidental brain lesion and were selected for study because MR imaging sequences revealed limitations in assessing the tumor, its evolving nature, and/or the malignant potential of the lesion diagnosed. Thirteen children were studied using FDG-PET and 42 with L-(methyl-11C)-methionine (MET)–PET; 3 children underwent both FDG-PET and MET-PET but only the MET-PET results were used in the analysis. The PET and MR images were combined in image fusion navigation planning. Drawing on their experience with PET in adults, the authors proposed the following treatment plans: 1) surgery in children with imaging evidence of increased PET tracer uptake, which is highly specific of tumor and/or malignant tumor tissue; or 2) conservative treatment in children in whom there was little or no tracer uptake on PET. The authors compared the PET data with the MR imaging–based diagnosis and either 1) the results of histological examination in surgically treated cases, or 2) the long-term outcome in untreated cases. They studied PET and MR imaging sensitivity and specificity in detecting tumor and malignant tissues, and evaluated whether PET data altered their clinical management.

Results

Seventeen children had increased PET tracer uptake and underwent surgery. Tumor diagnosis was confirmed in all cases (that is, there were no false-positive findings). Cases in which there was little or no PET tracer uptake supported conservative treatment in 38 children. However, because PET was under evaluation, 16 of 38 lesions that were judged accessible for resection were surgically treated. Histological examination results demonstrated neither malignant nor evolving tumor tissue but yielded 9 indolent tumors (6 dysembryoplastic neuroectodermal tumors, 2 low-grade astrocytomas, and 1 low-grade astrocytoma and dysplasia) and 7 nontumoral lesions (3 cases of vasculitis, 3 of gliosis, and 1 of sarcoidosis). In 22 of the untreated 38 children, stable disease was noted during follow-up (range 18–136 months). Although an absence of PET tracer uptake might not exclude tumor tissue, PET did not reveal any false-negative findings in malignant or evolving tumor tissue detection in cases in which MR imaging showed false-positive and -negative cases in > 35 and 25% of the cases, respectively.

Conclusions

These data confirmed the high sensitivity and specificity of PET to detect tumor as well as malignant tissue. Regarding the treatment of the incidental brain lesions, the PET findings enabled the authors to make more appropriate decisions regarding treatment than those made on MR imaging findings alone. Therefore, the risk of surgically treating a nontumoral lesion was reduced as well as that for conservatively managing a malignant tumor. Nowadays, it is estimated that these data justify conservative management in incidental lesions with low or absent PET tracer uptake.

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Nicolas Massager, Ouzi Nissim, Carine Delbrouck, Isabelle Delpierre, Daniel Devriendt, Françoise Desmedt, David Wikler, Jacques Brotchi and Marc Levivier

Object

The purpose of this study was to measure the dose of radiation delivered to the cochlea during a Gamma knife surgery (GKS) procedure for treatment of patients with vestibular schwannomas (VSs), and to analyze the relationship between cochlear irradiation and the hearing outcome of these patients.

Methods

Eighty-two patients with VSs were treated with GKS using a marginal dose of 12 Gy. No patient had neurofibromatosis Type 2 disease, and all had a Gardner–Robertson hearing class of I to IV before treatment, and a radiological and audiological follow-up of at least 1-year after GKS. The dosimetric data of the volume of the cochlea were retrospectively analyzed and were correlated with the auditory outcome of patients.

Results

The mean radiation dose delivered to the cochlear volume ranged from 1.30 to 10.00 Gy (median 4.15 Gy). The cochlea received significantly higher radiation doses in patients with worsening of hearing after GKS. A highly significant association between the cochlear and the intracanalicular dose of radiation delivered during GKS was found.

Conclusions

During GKS for VSs, relatively high doses of radiation can be delivered to the cochlea. Worsening of hearing after GKS can be the consequence of either radiation injury to the cochlea or the irradiation dose delivered into the auditory canal, or both.