Impact of localisation of deep brain stimulation electrodes on motor and neurobehavioural outcomes in Parkinson's disease.

BACKGROUND: Deep brain stimulation (DBS) of the subthalamic nucleus (STN) represents a well-established treatment in advanced Parkinson's disease (PD) for motor signs, but it is still debated concerning psychiatric effects. OBJECTIVE: Exploration of relation between position of active electrode contacts and neuropsychological and motor change after STN DBS procedure for PD. METHODS: A cohort of 34 patients who underwent STN DBS was followed for 6 months. Preoperative and postoperative assessments included mood evaluation (depression and mania) and motor status. Active contact localisation was identified regarding position into the STN (4 groups: IN meant contacts were IN-IN IN-BORDER; OUT: OUT-OUT or OUT-BORDER; BORDER: BORDER-BORDER; IN-OUT: IN-OUT) and compared with clinical outcomes. RESULTS: STN DBS significantly improved motor scores and reduced dopaminergic medication when compared with baseline and active lead groups: the best result was seen with the IN group. At 3 and 6 months postsurgery, depression and manic scores do not significantly differ compared with baseline and between leads groups. Focusing on symptom domains and compared with baseline, a significant loss of appetite was observed for the IN group at M3 and a significant increase in appetite from baseline was observed at M3 for the OUT group. Graphic representations illustrate that postsurgery evolution parameters at M3 or M6 are very good discriminant variables and well differentiate all leading groups. CONCLUSIONS: Stimulation of zona incerta may influence appetite and weight gain. Our clinical results seem to support a personalised DBS-targeted Parkinson therapy including individual motor and non-motor parameters.

[Frameless trigeminal neuralgia radiosurgery with a dedicated linear accelerator: From equipment commissioning to initial clinical results]. / Radiochirurgie des névralgies trigéminales avec accélérateur linéaire dédié sans cadre invasif : de la mise en service de l'appareil aux premiers résultats cliniques.

PURPOSE: Radiosurgery for the treatment of trigeminal neuralgia delivers a very high dose in a single fraction, over a few millimeters, at a single isocenter placed along the nerve. We present here the different steps that have been performed to validate small beams by conical collimators, and report the clinical results of the first patients treated on Novalis Tx®, frameless. MATERIAL AND METHODS: First, the geometric accuracy of 4 and 6mm conical collimators was evaluated using Winston-Lutz tests; then dosimetric data acquisition was performed using high spatial resolution detectors (PTW 60019 microdiamond and a PTW 60017 E-diode). The corrective factors of the TRS 483 report were applied to calculate the collimator aperture factors. These dosimetric data were then compared with the data implemented in the iPlan® treatment planning system. Then end-to-end tests were performed to control the entire treatment process using an anthropomorphic phantom "STEEV". Between 2020 and 2022, 18 patients were treated for refractory trigeminal neuralgia on Novalis Tx®, frameless, with Exactrac® repositioning. A total of 17 patients were evaluated (one was lost to follow-up) using the BNI score for pain assessment and MRI with a median follow-up of 12 months. RESULTS: The quality criteria of geometric and dosimetric accuracy were met for the 6-mm cone but not for the 4-mm cone. All patients were treated with a 6-mm cone with a dose of 90Gy prescribed at the isocenter at the root entry zone. Initial pain control was obtained in 70.5% of our patients, and 53% maintained pain control with a median follow-up of 12 months. All recurrences occurred within 3 to 6 months after radiosurgery. No brainstem toxicity was observed. Six patients had non-disabling facial hypoesthesia, half of whom already had pretreatment hypoesthesia. CONCLUSION: The treatment of trigeminal neuralgia on a dedicated linear accelerator is a highly technical treatment whose accuracy and safety are paramount. The physical measurements allowed the commissioning of the technique with a 6mm cone. Our first clinical results are in accordance with the literature.

Neural correlates of consciousness and related disorders: From phenotypic descriptors of behavioral and relative consciousness to cortico-subcortical circuitry.

We report a review of medical aspects of the consciousness. The behavioral dimension, phenotypic descriptors, relative consciousness and neural correlates of consciousness and related disorders were addressed successively in a holistic and chronological approach. Consciousness is relative, specific to each individual across time and space. Historically defined as the perception of the self and the environment, it cannot be separated from behaviors, entailing an idea of conscious behavior with metapractic and metagnostic aspects. Observation of spontaneous and evoked overt behavior distinguishes three main types of disorder of consciousness (DoC): coma, vegetative state or unresponsive wakefulness, and minimally conscious or relationally impoverished state. Modern functional exploration techniques, such as imaging, increase the understanding of DoCs and consciousness. Whether consciousness is a superior function and/or an instrumental function is discussed. Neural correlates can be subdivided into two wakefulness pathways (superior thalamic cholinergic and inferior extra-thalamic), and cortico-subcortical circuitry. The deep brain structures are those described in the well-known sensorimotor, associative and limbic loops, as illustrated in the mesolimbic model of DoC. The cortices can be segregated into several overlapping networks: (1) a global workspace including thalamo-cortical loops; (2) the default mode network (DMN) and related intrinsic connectivity networks (i.e., central executive, medial DMN and salience networks); (3) a 3-fold network comprising the fronto-parietal control system and its dorsal and ventral attentional sub-networks, the fronto-parietal executive control network, and the cingulo-opercular salience network; (4) the internal and external cortices, respectively medial, turned toward the self, and lateral, turned toward the environment. The network dynamics is the reflection of consciousness, notably anticorrelations such as the decrease in activity of the posterior cingulate-precuneus regions during attentional tasks. Thanks to recent advances in DoC pathophysiology, further significative therapeutic progress is expected, taking into account the societal context. This depends notably on the dissemination of medical knowledge and its transfer to a wider public.

Functional and dysfunctional impulsivities changes after subthalamic nucleus-deep brain stimulation in Parkinson disease.

OBJECTIVES: We investigated changes of impulsivity after deep brain stimulation (DBS) of the subthalamic nucleus (STN) in Parkinson's disease (PD) patients, distinguishing functional from dysfunctional impulsivity and their contributing factors. METHODS: Data of 33 PD patients treated by STN-DBS were studied before and 6 months after surgery: motor impairment, medication (dose and dopaminergic agonists), cognition, mood and occurrence of impulse control disorders. Impulsivity was assessed by the Dickman Impulsivity Inventory, which distinguishes functional impulsivity (FI), reflecting the potential for reasoning and rapid action when the situation requires it, and dysfunctional impulsivity (DI), reflecting the lack of prior reasoning, even when the situation demands it. The location of DBS leads was studied on postoperative MRI using a deformable histological atlas and by compartmentalization of the STN. RESULTS: After STN-DBS, DI was significantly increased (mean pre- and postoperative DI scores 1.9±1.6 and 3.5±2.4, P<0.001) although FI was not modified (mean pre- and postoperative FI scores 6.2±2.7 and 5.8±2.6). Factors associated with a DI score's increase≥2 (multivariable logistic regression model) were: low preoperative Frontal Assessment Battery score and location of the left active contact in the ventral part of the STN. CONCLUSION: Our study suggests that STN-DBS may have a different impact on both dimensions of impulsivity, worsening pathological impulsivity without altering physiological impulsivity. The increase in dysfunctional impulsivity may be favoured by the location of the electrode in the ventral part of the STN.

Assessment of Maturational Changes in White Matter Anisotropy and Volume in Children: A DTI Study.

BACKGROUND AND PURPOSE: Anisotropy is a good indicator of white matter fascicle macrostructure and organization but the interpretation of its changes with age remains difficult. The increase of WM fascicle fractional anisotropy with time and its relationship with WM fascicle volume have never been examined during childhood. We studied the maturation of associative WM fascicles during childhood using MR imaging-based DTI. We explored whether the fractional anisotropy increase of the main WM fascicles persists beyond the period of brain growth and is related to WM fascicle volume increase. MATERIALS AND METHODS: In a series of 25 healthy children, the fractional anisotropy and volume of 15 associative WM fascicles were calculated. Several regression linear mixed models were used to study maturation parameters (fractional anisotropy, volume, and total telencephalon volume) considered as dependent variables, while age and sex were independent variables (the variable identifying the different WM fascicles was considered as a repeated measure). RESULTS: In children older than 8 years of age, WM fascicle fractional anisotropy increased with age (P value = .045) but not its volume (P value = .7) or the telencephalon volume (P value = .16). The time course of WM fascicle fractional anisotropy and volume suggested that each WM fascicle might follow a specific pattern of maturation. CONCLUSIONS: The fractional anisotropy increase of several WM fascicles after 8 years of age may not result from an increase in WM fascicle volume. It might be the consequence of other developmental processes such as myelination.

[Functional stereotactic radiosurgery: Indications and perspectives]. / Radiochirurgie fonctionnelle : indications et perspectives.

Stereotactic radiosurgery (SRS) is a non-invasive technique that enables to create brain focal lesions with a high precision and localization. Thus, functional brain disorders can be treated by SRS in case of pharmacoresistance or inoperability. To date, treatment of trigeminal neuralgia is the most described and known indication. Other indications will be developed in the future like movement disorders, refractory epilepsy, obsessive compulsive disorder and severe depression. We present here a review of actual and future indications of functional brain SRS with their level of evidence. All these SRS treatments have to be strictly conducted by trained teams with an excellent collaboration between radiation physicists, medical physicists, neurosurgeons, neurologists, psychiatrists and probably neuroradiologists.

Postoperative empyema following chronic subdural hematoma surgery: Clinically based medicine.

INTRODUCTION: Subdural empyema (SDE) is a rare complication of chronic subdural hematoma (CSDH) surgery. We introduced antibiotic prophylaxis (AP) for this procedure in 2014 following a morbidity-mortality conference (MMC) in our department. We report the results of retrospective data analysis to assess the effect of systematic AP and to identify risk factors for SDE. MATERIAL AND METHODS: Two hundred eight patients were recruited between January 2013 and December 2015; 5 were excluded for incomplete data: 107 without and 96 with AP (n=203). SDE was confirmed by clinical examination, imaging and bacteriological analysis. Comparisons between AP-(no cefuroxime) and AP+ (cefuroxime) groups were made with Chi2 test and Student's t-test. RESULTS: One empyema was found in each group, indicating that AP had no effect (P=1). The only criterion associated with SDE for these two patients was a greater number of reoperations for CSDH recurrence (P=0.013). DISCUSSION: The incidence of postoperative empyema was 1%, similar to the range of 0.2%-2.1% reported in the literature. This rare incidence explains why we found no significant effect of AP. The medical decision taken at the MMC did not help to reduce the rate of postoperative SDE. MMCs can help to define factors associated with adverse surgical events and identify opportunities for improvement. CONCLUSION: AP, introduced after an MMC, did not impact SDE rates. In practice, AP should be required only in case of reoperation for CSDH recurrence. However, we still continue to use AP following the MMC considering different parameters discussed in the manuscript.

Long-Term Outcomes After Linac Radiosurgery for Benign Meningiomas.

AIMS: Although several studies on outcomes following stereotactic radiosurgery (SRS) for benign meningiomas have been reported, Linac-based SRS outcomes have not been as widely evaluated. The aim of this retrospective institutional single-centre study was to determine long-term outcomes of Linac-based SRS for benign intracranial meningiomas. MATERIALS AND METHODS: From July 1996 to May 2011, 60 patients with 69 benign meningiomas were included. All patients were treated with single-fraction Linac-based SRS with four to five non-coplanar arcs, dynamic or not. The marginal dose prescribed for the periphery was 16 Gy. Prognostic factors associated with local control, progression-free survival (PFS) and overall survival were tested. RESULTS: The median follow-up was 128 months. No patient was lost to follow-up. The values observed at 1, 5 and 10 years were, respectively, 100%, 98.4% and 92.6% for local control, 94.9%, 93.2% and 78% for PFS and 100%, 94.7% and 92.7% for overall survival. In univariate analysis, local control after SRS was significantly higher for skull base and parasagittal meningiomas compared with convexity meningiomas (P = 0.031). Multivariate analyses showed significantly longer PFS when the minimum dose delivered to the tumour was greater than 10 Gy (P = 0.0082). No grade 5 toxicity was reported. CONCLUSION: Our long-term results from a large sample size of benign meningiomas treated with Linac-based SRS confirmed excellent local control (>90%) and good safety, which is in line with published studies on Gamma Knife surgery. Above all, we showed significantly poorer PFS if the minimum dose to the tumour was under 10 Gy.

New electrophysiological mapping combined with MRI in parkinsonian's subthalamic region.

The subthalamic nucleus (STN) is the main target for deep brain stimulation in Parkinson's disease. We analysed the relationships between magnetic resonance imaging (MRI) anatomy and spontaneous neuronal activity to confirm the potential of microelectrode recordings to assist in determining the optimal surgical target. Ten bilateral surgeries were performed after 1.5-T (T2-weighted) anatomical MRI identification of the STN, zona incerta (ZI), Forel's field H2 (H2) and substantia nigra (SN). Spontaneous neuronal activity was recorded simultaneously along the distal 10 mm on a central track (optimally covering the STN) and a 2-mm anterior track. We calculated off-line mean firing rate and burst frequency on 248 neurons clustered according to anatomical structure. Subjective visual analysis of signal was also realized on-line, during surgery, to classify patterns of activity. Mean firing rate and burst frequency increased from H2-ZI to SN. The mean firing rate was higher in SN only using paired comparison (SN vs. its neighbours). The burst frequency was lower in H2 than in SN; using comparison with neighbours, it was lower in H2 and ZI. An irregular high activity (type 2C) was more often detected in STN and SN than in H2 and ZI. Anatomical boundaries and unitary recordings appear to be linked, supporting the ability of MRI to provide a detailed anatomy. Electrophysiological mapping combined with MRI is a useful tool for precise targeting in the subthalamic region.

Overweight after deep brain stimulation of the subthalamic nucleus in Parkinson disease: long term follow-up.

OBJECTIVE: To assess the occurrence of weight gain in patients with Parkinson's disease, with an average 16 months of follow-up after subthalamic nucleus deep brain stimulation. METHODS: We used dual x ray absorptiometry to evaluate changes in body weight and body composition in 22 patients with Parkinson's disease (15 men and seven women) before surgery, 3 months after surgery and on average 16 months after surgery. RESULTS: No patient was underweight before surgery and 50% were overweight. By contrast, 68% were overweight or obese 3 months after surgery and 82% after 16 months (p<0.001). For men, the mean increase in body mass index (BMI) was 1.14 (0.23) kg/m(2) 3 months after surgery and 2.02 (0.36) kg/m(2) 16 months after surgery. For women, the mean increases in BMI at the same evaluation times were 1.04 (0.30) kg/m(2) and 2.11 (0.49) kg/m(2). This weight gain was mainly secondary to an increase in fat mass in both men and women. Three months after surgery, acute subthalamic deep brain stimulation induced an improvement in parkinsonian symptoms (evaluated by the Unified Parkinson Disease Rating Scale (UPDRS) part III) by 60.7 (2.9)% in the "off" dopa condition and a dramatic improvement of motor complications (dyskinesia duration: 82.8 (12.8)%, p<0.0001; off period duration: 92.7 (18.8)%, p<0.0001). CONCLUSION: Although subthalamic nucleus deep brain stimulation significantly improved parkinsonian symptoms and motor complications, many patients became overweight or obese. This finding highlights the necessity to understand the underlying mechanisms and to provide a diet management with a physical training schedule appropriate for patients with Parkinson's disease.

Fractionated radiotherapy and radiosurgery of intracranial meningiomas.

This review focuses on the role of radiosurgery and fractionated radiotherapy in the management of intracranial meningiomas, which are the most common benign intracranial tumors. Whenever feasible, surgery remains a cornerstone of treatment in effective health care treatment where modern radiotherapy plays an important role. Irradiation can be proposed as first-line treatment, as adjuvant treatment, or as a second-line treatment after recurrence. Stereotactic radiosurgery consists of delivering, a high-dose of radiation with high precision, to the tumor in a single-fraction with a minimal exposure of surrounding healthy tissue. Stereotactic radiosurgery, especially with the gamma knife technique, has reached a high level of success for the treatment of intracranial meningiomas with excellent local control and low morbidity. However, stereotactic radiosurgery is limited by tumor size,<3-4cm, and location, i.e. reasonable distance from the organs at risk. Fractionated radiation therapy is an interesting alternative (5 to 6weeks treatment time) for large inoperable tumors. The results of fractionated radiation therapy seem encouraging as regards both local control and morbidity although long-term prospective studies are still needed.

[Role of radiosurgery in the management of intracranial cavernomas. Review of the literature]. / Place de la radiochirurgie dans la prise en charge des cavernomes intracrâniens. Revue de la littérature.

From a review of the literature dealing with radiosurgery of cavernous malformations, we have analyzed its impact on hemorrhagic risk, epilepsy, histological modifications, morbidity and potential indications of treatment. Radiosurgery could significantly reduce the hemorrhagic risk, in a selected population with a high risk of hemorrhage, after an interval of about 2 years, but cannot provide protection against rebleeding. As for epilepsy related to the lesion, a significant reduction of seizures has been observed in certain cases, with better control in case of recent evolution and simple seizures linked to the site of the vascular malformation. Histologic lesions are vascular fibrosis, fibrinoid necrosis and ferrugination, without good correlation with results of CT scan or MRI. Morbidity of radiosurgery seems higher compared to other diseases with similar doses and target volumes. The rate of transient complications was about 25%, with permanent sequelae in 5 to 10% of patients. This would be due to a radiosensitizing effect of the hemosiderin halo around the lesion. Radiosurgery can be proposed for non-surgical lesions with a high risk of hemorrhage, nevertheless the superiority of the technique over conservative treatment has to be proven. Without long-term prospective studies, the efficiency of RS for cavernomas remains questionable and subject to debate. New imaging methods proving the obstruction of the cavernous malformation are needed.

[Derivation of cerebrospinal fluid: consequences on inner ear biomechanics in adult patients with chronic hydrocephalus]. / Dérivation du liquide cérébrospinal avec valve: ses conséquences sur la biomécanique de l'oreille interne chez les patients atteints d'hydrocéphalie chronique de l'adulte.

BACKGROUND AND PURPOSE: Patients suffering from hydrocephalus are often treated by the surgical placement of a shunt, directing the excess of cerebrospinal fluid towards another body compartment. However, the degree of clinical improvement is variable and the dynamics of cerebrospinal fluid pressure in shunted hydrocephalus is poorly understood. A recently developed noninvasive technique makes it possible to follow pressure variations: it is based on otoacoustic emissions, sounds naturally emitted by the cochlea and routinely detected in audiology. When cerebrospinal fluid pressure changes, emissions undergo a phase shift while crossing the oval window. The goal of this work is to study how this shift is affected by shunt placement. METHOD: Otoacoustic emissions were recorded repeatedly in 22 adult patients who suffered from chronic hydrocephalus. Their phase shifts were measured, in sitting and recumbent positions, before and after surgical placement of a ventriculo-peritoneal shunt (Sophysa SM8). RESULTS: Postural shift in normal subjects is a phase lead, and this outcome was found in 17 of 22 patients preoperatively. After shunt placement, the postural effect became a phase lag in 18 patients of 20. In a given posture, sitting or recumbent, phase shifts changed from pre to postoperative measurements in a systematic manner. CONCLUSION: Otoacoustic emissions respond in a characteristic way to posture changes in normal adults, and having received a shunt for chronic hydrocephalus reverses the effect, presumably in relation to the existence of a "vacuum" in the inner ear.

Manic behaviour induced by deep-brain stimulation in Parkinson's disease: evidence of substantia nigra implication?

We report the case of a patient who had benefited from bilateral subthalamic nucleus deep brain stimulation for Parkinson's disease and who presented acute and reproducible manic behaviour when stimulated mainly in the substantia nigra. A positron emission tomography scan showed an activation of the right dorsolateral prefrontal and inferior temporal cortex, the left anterior cingulate cortex and a deactivation of the left insula. This suggests that changes in cortical activation related to mania are subcortically driven, involving notably the substantia nigra.

[Hemorrhagic lumbar juxta facet cyst. A case report]. / Kyste lombaire hémorragique juxta-articulaire. A propos d'un cas.

We report the case of a hemorrhagic lumbar juxta facet cyst (L2-L3), revealed by a chronic right lumbocruralgia, in a 77-year-old woman treated by anticoagulants for cardiac arrhythmia. Computerized tomography and magnetic resonance imaging suggested the diagnosis of benign tumor. During surgical removal of the whole lesion, a hemorrhagic synovial cyst was evoked. The operation dramatically relieved the symptoms. The diagnosis was confirmed by the histopathological analysis confronted with the clinical and the radiological findings. This uncommon observation allows the discussion of the pathogenic mechanism and of the differential diagnosis.

[Subthalamic deep brain stimulation for severe idiopathic Parkinson's disease. Location study of the effective contacts]. / Stimulation sous-thalamique dans la maladie de Parkinson severe. étude de la localisation des contacts effectifs.

The subthalamic nucleus (STN) is the main target of deep brain stimulation (DBS) treatment for severe idiopathic Parkinson's disease. But there is still no clear information on the location of the effective contacts (used during the chronic phase of stimulation). Our aim was to assess the anatomical structures of the subthalamic area (STA) involved during chronic DBS. Ten patients successfully treated were included. The surgical procedure was based on direct STN targeting (stereotactic MRI based) pondered by the acute effects of intraoperative stimulation. We used a formaldehyde-fixed human specimen to compare by matching MRI images obtained at 1.5 Tesla (performed in clinical stereotactic conditions) and at very high field at 4.7 Tesla. This allowed accurate analysis of the anatomy of the STA and retrospective precision of the location of the center of effective contacts which were located within the STN in 4 patients, at the interface between the STN and the ZI and/or FF in 13, at the interface between ZI and FF in 2 and between the STN and the substantia nigra in one. These results were consistent with the literature, revealing the implication of neighboring structures, especially the zona incerta and Forel's Field, in the clinical benefit.

Personalized mapping of the deep brain with a white matter attenuated inversion recovery (WAIR) sequence at 1.5-tesla: Experience based on a series of 156 patients.

OBJECTIVE: Deep brain mapping has been proposed for direct targeting in stereotactic functional surgery, aiming to personalize electrode implantation according to individual MRI anatomy without atlas or statistical template. We report our clinical experience of direct targeting in a series of 156 patients operated on using a dedicated Inversion Recovery Turbo Spin Echo sequence at 1.5-tesla, called White Matter Attenuated Inversion Recovery (WAIR). METHODS: After manual contouring of all pertinent structures and 3D planning of trajectories, 312 DBS electrodes were implanted. Detailed anatomy of close neighbouring structures, whether gray nuclei or white matter regions, was identified during each planning procedure. We gathered the experience of these 312 deep brain mappings and elaborated consistent procedures of anatomical MRI mapping for pallidal, subthalamic and ventral thalamic regions. We studied the number of times the central track anatomically optimized was selected for implantation of definitive electrodes. RESULTS: WAIR sequence provided high-quality images of most common functional targets, successfully used for pure direct stereotactic targeting: the central track corresponding to the optimized primary anatomical trajectory was chosen for implantation of definitive electrodes in 90.38%. CONCLUSION: WAIR sequence is anatomically reliable, enabling precise deep brain mapping and direct stereotactic targeting under routine clinical conditions.

Modifications of spontaneous cerebral blood flow oscillations during cardiopulmonary bypass.

UNLABELLED: Spontaneous slow waves are present in the systemic circulation including the intracranial compartment. They are supposed to reflect the cerebral autoregulation. We hypothesised that in the absence of cardio respiratory variability, during cardiopulmonary bypass (CPB), we should reveal extreme physiologic controls. MATERIAL/METHODS: Ten patients were included. Arterial blood pressure (ABP, radial invasive), extracorporeal circuitry pressure and cerebral blood flow velocity (CBFV, middle cerebral artery) were recorded. We analysed the slow waves in the B (8 to 50) and the UB (>50 to 200) bands (in milli-Hz). The analysis, before and during CPB, was performed in the tine domain (correlation coefficient, entropy, mean quantity of mutual information, relative entropy) and in the frequency domain (spectrogram, frequency spectrum, coherence). RESULTS: CPB dramatically changed monitored signals decreasing their entropy and revealing a dominant CBFV 70 mHz-frequency and a dominant ABP 9 mHz-frequency. There was no association between the signals (p < 0.05). Before CPB we found complex patterns where B and UB waves were present. CONCLUSION: We hypothesised that CPB provoked a highly protective mechanism, reducing the fluctuations of CBF, by a deactivation of B waves, revealing monotonous UB waves.

[Oligodendrogliomas and radiosurgery]. / Place de la radiochirurgie dans le traitement des oligodendrogliomes.

Radiosurgery of oligodendrogliomas is not specific. It must be integrated into the overall treatment scheme for gliomas which remains to be strictly defined. Nevertheless, empirically, and in light of the limited constraints for the patient and the encouraging radiological and clinical benefits, radiosurgical teams usually propose this technique in the event of recurrence of malignant gliomas, as a second line treatment. Exceptionally radiation can be used for some small benign gliomas which could not be treated by open surgery and accurately defined radiologically. Radiosurgery can achieve local control of the lesion, mostly transitionally, with 15 to 18 Gy at the reference isodose. One of the key problems is the definition of the glioma boundaries. Despite progress in neuroimaging techniques most the limits of malignant forms are still not accessible. In routine practice, the nodular area, considered as the most active on MRI, i.e. the contrast enhanced area, is accepted as the target. Its widest dimension must be about 35-40 mm. Only patients with minimal disability can benefit from radiosurgery. Optimization of the target definition (in particular the most active zone) and prospective randomized studies should be helpful in clarifying indications for this technique.