Benoît Pirotte

Regional glucose metabolism and histopathology of gliomas: A study based on positron emission tomography‐guided stereotactic biopsy

Positron emission tomography (PET) with 18F‐2‐fluoro‐2‐deoxy‐D‐glucose (FDG) is widely applied to the study of gliomas. The histology of most gliomas is regionally heterogeneous. The relationship between histologic features and glucose metabolism evaluated by PET with FDG may therefore vary within the limits of the tumor. PET with FDG integrated in the planning of stereotactic brain biopsy allows precise comparison between local FDG uptake and histology. Using this approach, the authors investigated whether glucose metabolism of gliomas is related to anaplasia, and whether PET with FDG detects metabolic heterogeneity that parallels histologic heterogeneity of gliomas.

Positron emission tomography-guided volumetric resection of supratentorial high-grade gliomas: a survival analysis in 66 consecutive patients.

OBJECTIVEIntegrating positron emission tomographic (PET) images into the image-guided resection of high-grade gliomas (HGG) has shown that metabolic information on tumor heterogeneity and distribution are useful for planning surgery, improve tumor delineation, and provide a final target contour different from that obtained with magnetic resonance imaging (MRI) alone in about 80% of the procedures. Moreover, PET guidance helps to increase the amount of tumor removed and to target image-guided resection to anaplastic tissue areas. The present study aims to evaluate whether PET-guided volumetric resection (VR) in supratentorial HGG might add benefit to the patients outcome. METHODSPET images using [18F]fluorodeoxyglucose (n=23) and [11C]methionine (n=43) were combined with MRI scans in the planning of VR procedures performed at the initial stage in 66 consecutive patients (43 M/23 F) with supratentorial HGG according to the technique previously described. In all cases (35 anaplastic gliomas [20 astrocytomas, 10 oligoastrocytomas, 5 oligodendrogliomas] and 31 glioblastomas [GBM]), level and distribution of PET tracer uptake were analyzed to define a PET contour projected on MRI scans to define a final target contour for VR. Maximal tumor resection was accomplished in each case, with the intention to remove the entire abnormal metabolic area comprised in the surgical planning. Early postoperative MRI and PET assessed tumor resection. Survival analysis was performed separately in anaplastic gliomas and glioblastoma multiforme according to the presence or absence of residual tracer uptake on postoperative PET and according to the presence or absence of residual contrast enhancement on postoperative MRI. RESULTSPreoperatively, metabolic information helped the surgical planning. In all procedures, PET contributed to define a final target contour different from that obtained with MRI alone. Postoperatively, 46 of 66 patients had no residual PET tracer uptake (total PET resection), 23 of 66 had no residual MRI contrast enhancement. No additional neurological morbidity due to the technique was reported. A total PET tracer uptake resection was associated with a significantly longer survival in anaplastic gliomas (P = 0.0071) and in glioblastoma multiforme (P = 0.0001), respectively. A total MRI contrast enhancement resection was not correlated with a significantly better survival, neither in anaplastic gliomas (P = 0.6089) nor in glioblastoma multiforme (P = 0.6806). CONCLUSIONSComplete resection of the increased PET tracer uptake prolongs the survival of HGG patients. Because PET information represents a more specific marker than MRI enhancement for detecting anaplastic tumor tissue, PET-guidance increases the amount of anaplastic tissue removed in HGG.

Results of positron emission tomography guidance and reassessment of the utility of and indications for stereotactic biopsy in children with infiltrative brainstem tumors

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 needles 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 was(18)F-2-fluoro-2-deoxy-D-glucose (FDG) in six cases, (11)C-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.

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 [11C]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. Tumor boundaries were ill-defined on MRI (including T2-weighted and fluid-attenuated inversion-recovery scans) and could not be clearly identified for allowing a complete, or at least a large, image-guided resection. The PET tracer Met was chosen because of its higher sensitivity and specificity than MRI to detect tumor tissue. The level and extension of MET uptake were analyzed to define the PET contour, subsequently projected onto MRI scans to define a final target contour for volumetric resection. The quality of tumor resection was assessed by an early postoperative MRI and Met-PET workup. RESULTS: In 20 of the 22 children with ill-defined LGBTs, PET improved tumor delineation and contributed to define a final target contour different from that obtained with MRI alone. Met-PET guidance allowed a total resection of Met uptake in 17 cases that were considered total tumor resections because the operative margin left in place contained nontumor tissue. CONCLUSION: These data suggested that Met-PET guidance could help to improve the number of total resections and the amount of tumor removed in infiltrative LGBTs in children.

Combined positron emission tomography and magnetic resonance imaging for the planning of stereotactic brain biopsies in children: Experience in 9 cases

Because brain tumors can be histologically heterogeneous, stereotactic brain biopsies (SBB) may lead to inaccurate diagnosis or grading. Positron emission tomography (PET) has been used in pediatric neuro-oncology to help in the understanding and management of brain neoplasms. We combined PET and magnetic resonance (MR) imaging in the planning of SBB in 9 children (5 males and 4 females, aged 2–14 years) with infiltrative, ill-defined brain lesions. Tracers used for PET were 18F-2-fluoro-2-deoxy-D-glucose in 4 cases, 11C-methionine in 2 cases and both tracers in 3 cases. Biopsy targets were selected in hypermetabolic areas. PET-guided SBB provided accurate histological diagnosis in all patients and allowed a reduction of the number of trajectories in lesions located in functional areas. It also helped in better understanding and management of complex cases. This preliminary series suggests that combining PET and MR imaging in the planning of SBB in children (1) improves the diagnostic yield of SBB in infiltrative, ill-defined brain lesions, (2) makes it possible to reduce the sampling in high-risk/functional areas and (3) improves the quality of therapeutic management of pediatric brain tumors.

Glucocorticoid-induced long-term remission in primary cerebral lymphoma: Case report and review of the literature

We report a 25-year old immunocompetent woman with a high grade primary non-Hodgkin‘s lymphoma of the central nervous system (PNHL-CNS) in whom the administration of dexamethasone alone during three months produced a complete clinical and radiological response lasting over four years. If complete remission of PNHL-CNS induced by glucocorticoids are well known, the opportunity to observe glucocorticoid-induced remission for a long period oftime without radio- and chemotherapy is rare. Only nine othercases of PNHL-CNS with complete remission induced by glucocorticoidslasting from 6 to 60 months, were found in the literature and aresummarized here. Duration of glucocorticoids therapeutic effect inPNHL-CNS is probably underestimated. Glucocorticoids cannotbe recommended as sole initial treatment for PNHL-CNS. However, we suggest standard therapies to be delayed in thosepatients responding completely to glucocorticoids where radio-and chemotherapy should be contraindicated (kidney, liver, bonemarrow failure, pregnancy).

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). fMRI data were analyzed with Statistical Parametric Mapping99 software (University College London, London, England; initial analysis threshold corresponding to P < 0.001), registered in a neuronavigation system, and correlated during surgery with iCM. The primary aim of this study was to improve the topographical precision of MCS. Matching of fMRI and iCM specifically was examined. RESULTS: Correspondence between the contour of the fMRI activation area and iCM in precentral gyrus (mean distance, 3.8 mm) was found in 17 (94%) of 18 patients. Eleven of them showed correspondence for more restrictive values of the analysis threshold (P < 0.0001); in six patients, the quality of the iCM was reduced by somatosensory wave attenuation and general anesthesia. In this group of six patients, a combination of both techniques was used for the final targeting. Correspondence was not found in one patient as the result of image distortion and residual motion artifact. At follow-up (4–60 mo), MCS induced significant pain relief in a total of 11 patients (61%). CONCLUSION: This study confirms the functional accuracy of fMRI guidance in neuropathic pain and illustrates the usefulness of combining fMRI guidance with iCM to improve the functional targeting in MCS. Because appropriate targeting is crucial to obtaining pain relief, this combination may increase the analgesic efficacy of MCS.

PET findings in a brain abscess associated with a silent atrial septal defect

Brain abscesses are classical complications of congenital heart disease (CHD) in children and adolescents. This association is rarely observed in adults. We report a 46-year-old man presenting a fronto-parietal abscess associated with an asymptomatic atrial septal defect. Positron emission tomography (PET) study revealed high uptake of L-[methyl-11C]methionine ([11C]methionine) and 2-[18F]fluoro-2-deoxy-D-glucose (FDG) around the brain abscess. We suggest (1) to exclude a silent cardiac malformation in the presence of a cerebral abscess of unknown source occurring in adults; (2) to consider the diagnosis of brain abscess in cases of high uptake of [11C]methionine and FDG in relation to a brain lesion.

Functional motor-cortex mapping using corticokinematic coherence.

We present a novel method, corticokinematic coherence (CKC), for functional mapping of the motor cortex by computing coherence between cortical magnetoencephalographic (MEG) signals and the kinematics of voluntary movements. Ten subjects performed self-paced flexion-extensions of the right-hand fingers at about 3 Hz, with a three-axis accelerometer attached to the index finger. Cross-correlogram and coherence spectra were computed between 306 MEG channels and the accelerometer signals. In all subjects, accelerometer and coherence spectra showed peaks around 3-5 Hz and 6-10 Hz, corresponding to the movement frequencies. The coherence was statistically significant (P<0.05) in all subjects, with sources at the hand area of the primary motor cortex contralateral to the movement. CKC appears to be a promising and robust method for reliable and convenient functional mapping of the human motor cortex.

Cerebral anaplastic pleomorphic xanthoastrocytoma with meningeal dissemination at first presentation.

IntroductionPleomorphic xanthoastrocytoma (PXA) is a rare brain glial tumour found in young patients. Most cases are reported as evolving low-grade neoplasms associated with a long survival after complete surgical resection. Some PXAs, however, can demonstrate secondary malignant transformation or progress with a short survival. Anaplastic histological features at first presentation or secondary meningeal dissemination have rarely been reported.Case reportWe describe the case of a cerebral PXA in a 7-year-old girl presenting with anaplastic histological features and craniospinal meningeal dissemination that progressed rapidly with a poor outcome.