Nicolas Massager

Université Libre de Bruxelles, Brussels, BRU, Belgium

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Publications (101)156.75 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The objective of the study was to assess the long-term radiological outcome of benign intracranial tumors (BIT) after Gamma Knife radiosurgery. We report the radiological outcome of 280 patients who underwent radiosurgical irradiation for BIT in a single center. Our series included 120 meningiomas, 139 vestibular schwannomas, 12 other schwannomas and 9 pituitary adenomas. Serial imaging studies were performed after irradiation for at least 5 years for all patients. The median tumor volume was 1.9 cc, and the median margin dose was 12 Gy. After a median follow-up of 6.8 years, the tumor control rate was 92.1 %: tumor decreased in 176 cases (62.9 %), remained unchanged in 82 lesions (29.3 %) and increased in 22 cases (7.9 %). The actuarial tumor control rate was 93.2 % at 5 years, 92.3 % at 7.5 years and 91.0 % at 10 years. No atypical or malignant transformation of irradiated tumors occured during the follow-up period. Gamma Knife radiosurgery provides a high rate of tumor control for BIT even in the medium to long-term.
    Acta neurologica Belgica. 05/2013;
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    ABSTRACT: BACKGROUND: Pharmacoresistant epilepsy can be treated by either resection of the epileptic focus or functional isolation of the epileptic focus through complete disconnection of the pathways of propagation of the epileptic activity. OBJECTIVE: To evaluate long-term seizure outcome and complications of temporal lobe disconnection (TLD) without resection for mesial temporal lobe epilepsy (MTLE). METHODS: Data of 45 patients operated on for intractable MTLE using a functional disconnection procedure have been studied. Indication of TLD surgery was retained after a standard preoperative evaluation of refractory epilepsy and using the same criteria as for standard temporal resection. RESULTS: Mean follow-up duration was 3.7 years. At the last follow-up, 30 patients (67%) were completely seizure-free (Engel-Ia/International League Against Epilepsy class 1) and 39 patients (87%) remained significantly improved (Engel-I or -II) by surgery. Actuarial outcome displays a 77.7% probability of being seizure-free and an 85.4% probability of being significantly improved at 5 years. No patient died after surgery and no subdural haematoma or hygroma occurred. Permanent morbidity included hemiparesis, hemianopia and oculomotor paresis found in three, five and one patient, respectively, after TLD. CONCLUSIONS: TLD is acceptable alternative surgical technique for patients with intractable MTLE. The results of TLD are in the range of morbidity and long-term seizure outcome rates after standard surgical resection. We observed a slightly higher rate of complications after TLD in comparison with usual rates of morbidity of resection procedures. TLD may be used as an alternative to resection and could reduce operating time and the risks of subdural collections.
    Journal of neurology, neurosurgery, and psychiatry 04/2013; · 4.87 Impact Factor
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    ABSTRACT: We analyzed the effects of stereotactic radiosurgery on tumour control and cranial nerve function in patients with vestibular schwannomas (VS) secondary to neurofibromatosis type 2 (NF2). Irradiation was performed with a Gamma Knife, model C equipped with a high-precision, robotized positioning system (APS). This study included 18 patients with 25 VSs secondary to NF2 that were treated from 2001 to 2010 with radiosurgery at our Gamma Knife Center. The radiosurgical procedure included high-resolution conformational dose-planning with multiple, small-diameter isocenters, a single-fraction, low-dose irradiation prescription, and highly accurate gamma rays delivery to the target with the APS. The median follow-up time was 4.4 y. For 16 tumours in 12 patients with available follow-up data, we observed an actuarial tumour control of 87.5% at 2 y and 80.2% at 5 y, based on the Kaplan-Meier method. No patient developed facial weakness. Serviceable hearing was preserved in 78% of cases. Patients treated for bilateral and unilateral tumours had similar outcomes. Radiosurgery could control tumour growth and preserve hearing function and facial weakness in patients with VS secondary to NF2. The enhanced techniques of radiosurgical irradiation provided with the Gamma Knife model C have improved the results of this treatment alternative to microsurgery.
    B-ENT 01/2013; 9(1):29-36. · 0.08 Impact Factor
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    ABSTRACT: Gamma Knife radiosurgery can be used as an alternative or complementary therapy to neurosurgery or radiotherapy for the treatment of some brain disorders or tumors of small volume. The most frequent indications are brain metastases, vestibular schwannomas, meningiomas, trigeminal neuralgia, arteriovenous malformations, some gliomas, and pituitary adenomas. Created in 1999, the Gamma Knife Center of the ULB remains currently the unique center in Belgium where a Gamma Knife radiosurgery treatment can be performed.
    Revue medicale de Bruxelles 09/2012; 33(4):367-70.
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    ABSTRACT: This prospective, bicentre, blinded, intention to treat study assessed the clinical added value of magnetic source imaging (MSI) in the presurgical evaluation of patients with refractory focal epilepsy (RFE). 70 consecutive patients with RFE (42 men; mean age 31.5 years, range 3-63) from two Belgian centres were prospectively included. All patients underwent conventional non-invasive presurgical evaluation (CNIPE) and a whole head magnetoencephalography recording (Elekta Neuromag). Equivalent current dipoles corresponding to interictal epileptiform discharges (IED) were fitted in the patients' spherical head model and coregistered on their MRI to produce MSI results. Results of CNIPE were first discussed blinded to the MSI results in respective multidisciplinary epilepsy surgery meetings to determine the presumed localisation of the epileptogenic zone and to set surgical or additional presurgical plans. MSI results were then discussed multidisciplinarily. MSI influence on the initial management plan was assessed. Based on CNIPE, 21 patients had presumed extratemporal epilepsy, 38 had presumed temporal epilepsy and 11 had undetermined localisation epilepsy. MSI showed IED in 52 patients (74.5%) and changed the initial management in 15 patients (21%). MSI related changes were significantly more frequent in patients with presumed extratemporal or undetermined localisation epilepsy compared with patients with presumed temporal epilepsy (p≤0.001). These changes had a clear impact on clinical management in 13% of all patients. MSI is a clinically relevant, non-invasive neuroimaging technique for the presurgical evaluation of patients with refractory focal epilepsy and, particularly, in patients with presumed extratemporal and undetermined localisation epilepsy.
    Journal of neurology, neurosurgery, and psychiatry 04/2012; 83(4):417-23. · 4.87 Impact Factor
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    ABSTRACT: We investigated variations in the distribution of radiation dose inside (dose inhomogeneity) and outside (dose falloff) the target volume during Gamma Knife (GK) irradiation of vestibular schwannoma (VS). We analyzed the relationship between some parameters of dose distribution and the clinical and radiological outcome of patients. Data from dose plans of 203 patients treated for a vestibular schwannoma by GK C using same prescription dose (12 Gy at the 50% isodose) were collected. Four different dosimetric indexes were defined and calculated retrospectively in all plannings on the basis of dose-volume histograms: Paddick conformity index (PI), gradient index (GI), homogeneity index (HI), and unit isocenter (UI). The different measures related to distribution of the radiation dose were compared with hearing and tumor outcome of 203 patients with clinical and radiological follow-up of minimum 2 years. Mean, median, SD, and ranges of the four indexes of dose distribution analyzed were calculated; large variations were found between dose plans. We found a high correlation between the target volume and PI, GI, and UI. No significant association was found between the indexes of dose distribution calculated in this study and tumor control, tumor volume shrinkage, hearing worsening, loss of functional hearing, or complete hearing loss at last follow-up. Parameters of distribution of the radiation dose during GK radiosurgery for VS can be highly variable between dose plans. The tumor and hearing outcome of patients treated is not significantly related to these global indexes of dose distribution inside and around target volume. In GK radiosurgery for VS, the outcome seems more to be influenced by local radiation dose delivered to specific structures or volumes than by global dose gradients.
    International journal of radiation oncology, biology, physics 05/2011; 81(4):e511-8. · 4.59 Impact Factor
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    ABSTRACT: Leksel Gamma Knife (LGK) radiosurgery is a safe and efficient therapeutic approach for vestibular schwannoma (VS) with low side effects. The goal of radiosurgery is not necessarily to cause significant tumour necrosis or to obtain a complete radiographic response, but to halt the tumour's growth permanently through its biological elimination. The 2 major aims of radiosurgery for VS are long-term tumour control and functional hearing preservation. The purpose of this study is to report our experience with LGK radiosurgery in the management of VS and to evaluate the hearing preservation rate after a minimum one-year follow-up. Between January 2000 and January 2011, 415 patients with unilateral VS underwent LGK radiosurgery at the University Erasmus Hospital of Brussels. There were 349 patients with previously untreated VS (86 grade I, 96 grade II, 141 grade III, 9 grade IVa, 17 unknown grades, according to Koos) and 66 patients with post-operative residual tumour. All patients in our series underwent evaluation with high resolution neurodiagnostic imaging including computed tomography and magnetic resonance imaging, and clinical evaluation as well as audiological tests that included tonal and speech audiometries. The Gardner Robertson (GR) classification is used to report the results of this study. We identified 276 patients treated for VS with LGK, tested and retested with speech and tonal audiometries by the same team, and followed for a minimum of one year. Before LGK, 144 patients had serviceable (85 GR class I and 59 GR class II) hearing; 95 (65.97%) of these patients had preservation of serviceable hearing (Pure tone average < or = 50 db and Speech discrimination > or = 50%) at minimum one-year audiological follow-up. It was observed that 44 of the 85 GR class I patients (51.76%) maintained their level of audition and 66 of these (74.64%) preserved serviceable hearing. In the 34 patients with preradiosurgery non-serviceable hearing (GR class III-IV) 25 of these patients (73.52%) maintained their hearing. The tumour was stable or declining in size in 90.44% of cases. LGK radiosurgery provides excellent tumour control in vestibular schwannomas and has low toxicity even after long-term follow-up.
    B-ENT 01/2011; 7 Suppl 17:77-84. · 0.08 Impact Factor
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    ABSTRACT: In this paper, the authors' goal was to evaluate the impact of PET data on the clinical management of incidental brain lesions in children. 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-(11)C)-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. 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. 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.
    Journal of Neurosurgery Pediatrics 05/2010; 5(5):479-85. · 1.63 Impact Factor
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    ABSTRACT: In this paper, the authors' goal was to evaluate the impact of PET information on brain tumor surgery in children. 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-(11)C)-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. 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). 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.
    Journal of Neurosurgery Pediatrics 05/2010; 5(5):486-99. · 1.63 Impact Factor
  • N. Massager, J. Brotchi, O. De Witte
    Neurochirurgie. 01/2010; 56(6):557-558.
  • Neurochirurgie. 01/2010; 56(6):534-535.
  • S. Lonneville, O. De Witte, N. Massager
    Neurochirurgie. 01/2010; 56(6):549-550.
  • Laurence Abeloos, Nicolas Massager
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    ABSTRACT: A 55-year-old man underwent a microvascular decompression procedure for a pharmacoresistant trigeminal neuralgia. Preoperative MRI showed a neurovascular conflict between the Vth nerve root and the superior cerebellar artery. Dissection of the intracisternal trigeminal root was undertaken, and a piece of Teflon was positioned between the artery and the nerve. Choroid plexus was found squeezing the root entry zone of the Vth nerve and partially removed. The patient did not improve after the vascular decompression procedure. Trigeminal neuralgia could be due to a mechanical irritation of the intracisternal nerve root. Since vascular decompression of the trigeminal root did not relieve the pain, we suggest that the presence of choroid plexus at the root entry zone of the nerve may have induced trigeminal neuralgia in this patient.
    Acta Neurochirurgica 09/2009; 152(4):717-9. · 1.55 Impact Factor
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    ABSTRACT: Integrating 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 patient's outcome. PET 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. Preoperatively, 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). Complete 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.
    Neurosurgery 04/2009; 64(3):471-81; discussion 481. · 2.53 Impact Factor
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    ABSTRACT: The role of radiation dose delivered to surrounding tissues outside target is often minimized in radiosurgery. We study histopathological effects of dose fall-offs outside the target using an experimental model of trigeminal nerve irradiation in the rat. Sixteen rats were irradiated with a Gamma Knife at the right trigeminal nerve using a 90-Gy dose and 4 different gradients of dose fall-off; the brainstem at the trigeminal nerve root entry was histologically analyzed 3 months after irradiation. Four specific histopathological reactions were found as a consequence of the irradiation. All these reactions were significantly related to the gradient of dose fall-off. Different dose distributions outside the target could produce various histological effects in the irradiated tissue that could influence the outcome of radiosurgical treatment. A more rapid fall-off of dose (higher selectivity) is associated with less risk of histological changes in tissues surrounding the target.
    Stereotactic and Functional Neurosurgery 04/2009; 87(3):137-42. · 1.46 Impact Factor
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    ABSTRACT: We report the results of an investigation carried out on the activity of functional neurosurgery of the cranial nerves in the French-speaking countries, based on the analysis of a questionnaire addressed to all the members of the SNCLF. Eighteen centers responded to this questionnaire, which showed that activities and indications varied greatly from one unit to another. The results appear homogeneous and comparable with those reported in the literature. The questionnaire sought to provide a global perspective, open to the comments and questions of all responders on the various techniques raised, with the objective of establishing a common decisional tree for these pathologies and providing if possible to a consensus for better dissemination of these therapies.
    Neurochirurgie 04/2009; 55(2):282-90. · 0.32 Impact Factor
  • Olivier De Witte, Sergio Hassid, Nicolas Massager
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    ABSTRACT: PROPOSE OF REVIEW: Surgical approaches of skull base tumors are complicated and invasive. We review all new therapeutic approaches that reduce the invasiveness of the surgery. RECENT FINDINGS: The development of minimal invasive surgery has completely changed the management of this kind of tumor and also the importance of the quality of life of the patient after surgery. Endoscopy and robotics represent the future of the surgery and therefore must increase resection and reduce complication. We review the articles in which new approaches were described and also the different steps of the procedure. New technologies are also reviewed. The second part is focused on stereotactic radiosurgery, and we review the principle of stereotactic radiosurgery and the results of large series with a long follow-up of tumor involving the skull base. SUMMARY: The knowledge of the new technology and also the result of stereotactic radiosurgery must help the physician in the choice of the treatment of skull base lesions.
    Current opinion in oncology 04/2009; 21(3):238-41. · 4.09 Impact Factor
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    ABSTRACT: Radiosurgery is currently performed with different systems of focused radiation providing different dose heterogeneities within the target volume. Here, we aimed to study histological consequences of different dose distributions inside the target area in an experimental model of Gamma Knife irradiation in the rat striatum. Twelve rats were irradiated by Gamma Knife at the same volume in the right striatum; the same margin dose of 45 Gy was prescribed for all rats. Three different dose distributions inside the target volume were applied. Brain sections at the level of the target area were histologically analyzed 3 months after irradiation. Of the 7 histopathological reactions found as a consequence of the irradiation, 6 of them were significantly related to the gradient of dose heterogeneity within the target volume. Dose distribution inside the target volume could influence the histological effects of radiosurgical irradiation on tissue included in the target. A high dose in the target volume is more likely to lead to the desired radiobiological result.
    Stereotactic and Functional Neurosurgery 03/2009; 87(2):82-7. · 1.46 Impact Factor
  • Neurochirurgie. 01/2009; 55(4):503-504.
  • Surgical Neurology - SURG NEUROL. 01/2009; 71(1):152-152.

Publication Stats

981 Citations
156.75 Total Impact Points


  • 1996–2013
    • Université Libre de Bruxelles
      • Gamma Knife Centre
      Brussels, BRU, Belgium
  • 1998–2011
    • University Hospital Brussels
      • • Department of E.N.T.
      • • Department of Neurosurgery
      Bruxelles, Brussels Capital Region, Belgium
  • 2009
    • Gamma Knife of Spokane
      Spokane, Washington, United States
  • 2008
    • University Hospital of Lausanne
      • Service de neurochirurgie
      Lausanne, VD, Switzerland
    • Pontifical Catholic University of Chile
      • División Medicina
      Santiago, Region Metropolitana de Santiago, Chile
  • 2007
    • Institut Jules Bordet
      Bruxelles, Brussels Capital Region, Belgium
    • Semmelweis University
      Budapeŝto, Budapest, Hungary
  • 2000–2001
    • Free University of Brussels
      • Department of Neurosurgery
      Brussels, BRU, Belgium