[Parenchymal changes after radiosurgery of cerebral arteriovenous malformations. Clinical and MRI data]. / Réactions parenchymateuses après radiochirurgie des malformations artério-veineuses cérébrales. Données cliniques et IRM.

BACKGROUND AND PURPOSE: Purposes of this study are to describe different parenchymal changes seen after radiosurgery of cerebral arteriovenous malformations and the clinical symptoms which can be associated, and risk factors correlated with them. PATIENTS: and method. From the whole population of 705 patients with a cerebral arteriovenous malformations treated by radiosurgery between 1984 and 1998, clinical from 615 patients and post radiosurgery MRI data from 367 patients were reviewed. Neurological deficit occurred in 5.37% of cases and was still persistant in 1.46% of cases. Delay of occurrence of deficits ranged from 6 to 83 months (mean: 27 months, median: 15 months). Parenchymal changes seen in MRI were classified in 4 grades: 1 without parenchymal changes, 2 hypersignal in sp T2, 3=2 with homogenous enhancement with gadolinium, 4 with hyposignal in spT1 and annular irregular enhancement. Several parameters (size, volume, angioarchitecture of the cerebral arteriovenous malformation, dosimetric parameters) were studied and correlations were searched by uni and multivariate analysis with occurrence and delay of occurrence of deficits or parenchymal changes. RESULTS: In multivariate analysis, only size was significantly correlated with occurrence of parenchymal changes (p=0.0016); only size of the malformation was significantly correlated with delay of occurrence of parenchymal changes (p=0.0082); only grade 4 was correlated with occurrence of neurological deficit (p<0.00001). However, when only "a priori" parameters (known before radiosurgery) are introducted in logistic model, size taille (p=0.02) and hypoplasy of a sinus (p=0.0049) are significantly correlated with occurrence of neurological deficit. Only parenchymal changes grade 4 was significantly correlated with delay of occurrence of a neurological deficit (p<0.00001). However, when only a priori parameters (known before radiosurgery) are introducted in logistic model, only arterial steal (p=0.054) was significantly correlated with delay of occurrence of a neurological deficit. CONCLUSION: Parenchymal changes are various in expression, signification and clinical symptoms associated with them. They must be known and recognized for better prevention and symptomatic treatment as well.

Linac radiosurgery for cerebral arteriovenous malformations: results in 169 patients.

PURPOSE: To present the SALT group results using Linac radiosurgery (RS) for AVM in 169 evaluable patients treated from January 1990 thru December 1993. METHODS AND MATERIALS: Median age was 33 years (range 6-68 years). Irradiation was the only treatment in 55% patients. Other treatment modalities had been used prior to RS in 45%: one or more embolizations in 36%, surgery in 6%, and embolization and surgery in 3% patients. Nidus were supratentorial in 94% patients, infratentorial in 6% patients. Circular 15 MV x-ray minibeams (6-20 mm) were delivered in coronal arcs by a GE-CGR Saturne 43 Linac. Patient set-up included a Betti arm-chair, a Talairach frame. Prescribed peripheral dose was 25 Gy on the 60%-70% isodose (max dose 100%). Arteriographic results were reassessed in December 1997 at 48 to 96 months follow-up. RESULTS: The overall obliteration rate (OR) was 64% (108/169). AVM volumes ranged from 280 to 19,920 mm(3), median 2460 mm(3). OR was 70% for AVM

[Point of view of the radioneurologist]. / Le point de vue des neuroradiologues.

Since the 1970s, neuroradiology has benefited from significant advances and has become less and less invasive. SALT group (Saint-Anne-Lariboisière-Tenon), created in 1986, treats and follows patients presenting with arteriovenous malformation with surgery, embolization and/or radiosurgery. Treatment failures and complications are analyzed in order to better define indications and improve techniques of treatment which benefit from advances in equipment and software, as well as in radiobiology and genetics.

Single-fraction stereotactic radiotherapy: a dose-response analysis of arteriovenous malformation obliteration.

PURPOSE: Stereotactic radiotherapy delivered in a high-dose single fraction is an effective technique to obliterate intracranial arteriovenous malformations (AVM). To attempt to analyze the relationships between dose, volume, and obliteration rates, we studied a group of patients treated using single-isocenter treatment plans. METHODS AND MATERIALS: From May 1986 to December 1989, 100 consecutive patients with angiographically proven AVM had stereotactic radiotherapy delivered as a high-dose single fraction using a single-isocenter technique. Distribution according to Spetzler-Martin grade was as follows: 79 grade 1-3, three grade 4, 0 grade 5, and 18 grade 6. The target volume was spheroid in 74 cases, ellipsoid in 11, and large and irregular in 15. The targeted volume of the nidus was estimated using two-dimensional stereotactic angiographic data and, calculated as an ovoid-shaped lesion, was 1900 +/- 230 mm3 (median 968 mm3; range 62-11, 250 mm3). The mean minimum target dose (Dmin) was 19 +/- 0.6 Gy (median 20 Gy; range: 3-31.5). The mean volume within the isodose which corresponded to the minimum target dose was 2500 +/- 300 mm3 (median 1200 mm3; range 75-14 900 mm3). The mean maximum dose (Dmax) was 34.5 +/- 0.5 Gy (median 35 Gy; range 15-45). The mean angiographic follow-up was 42 +/- 2.3 months (median 37.5; range 7-117). RESULTS: The absolute obliteration rate was 51%. The 5-year actuarial obliteration rate was 62.5 +/- 7%. After univariate analysis, AVM obliteration was influenced by previous surgery (p = 0.0007), Dmin by steps of 5 Gy (p = 0.005), targeted volume of the nidus (< or = 968 mm3 vs. >968 mm3; p = 0.015), and grade according to Spetzler-Martin (grade 1-3 vs. grade 4-6; p = 0.011). After multivariate analysis, the independent factors influencing AVM obliteration were the Dmin [relative risk (RR) 1.9; 95% confidence interval (CI) 1.4-2.5; p < 0.0001] and grade distribution according to Spetzler-Martin (RR 1.4; 95% CI 1.1-1.7; p = 0.010). Delayed complications were observed in eight patients. The 5-year actuarial rate of delayed complications was 7.4%. CONCLUSION: After stereotactic radiotherapy delivered in a single high dose using a single-isocenter technique, the success rate for complete obliteration is independently correlated to Dmin but does not seem to be influenced by Dmax and the targeted volume of the nidus.

Episodic pain associated with a tumor in the parietal operculum: a case report and literature review.

We report a young woman suffering brief painful episodes in her right arm which sometimes spread to the whole right side of her body. The episodes were initially rare, but over 13 months they became increasingly frequent until occurring every 20 min. Neurological examination was normal. Magnetic resonance imaging revealed a lesion in the white matter of the parietal operculum. Lesions in the parietal operculum associated with persisting thalamic pain or loss of pain sensation have been reported, but rarely with episodic pain. Since episodic painful attacks have been described in association with various suprathalamic lesions, we conclude that paroxysmal pain attacks may be another consequence of the disturbance of the normal pattern of thalamocortical connections to the second sensory cortical area by a lesion, in our case, of the subcortical area of the parietal operculum.

[Stereotaxic radiotherapy of cerebral arteriovenous malformations: the role of neuroradiology]. / Radiothérapie stéréotaxique des malformations artério-veineuses cérébrales: place de la neuroradiologie.

The therapeutic approach to cerebral arteriovenous malformations has been modified with the availability of stereotactic radiosurgery, initially, the main indications of radiosurgery were limited, non surgical arteriovenous malformations. Indications are now much more diverse. Imaging plays an important role in the radiosurgical management of arteriovenous malformations and its evaluation. In this review, the different roles of neuroimaging are discussed; characterization of malformations, choice of the best indications, role of embolization, delimitation of the target, evaluation of results and complications of radiosurgery.

Parenchymal changes after radiosurgery of cerebral arteriovenous malformations. Preliminary report of a proposed classification.

Radiosurgery of cerebral arteriovenous malformations (cAVM) can induce parenchymal changes seen on MRI. The purpose of this study was to classify these changes and to correlate them to clinical outcome and obliteration of the cAVM. 142 patients with cAVM underwent radiosurgery with a linear accelerator between 1994 and 1995. 60 clinical records, MR images, and postradiation angiograms were reviewed. Signal abnormalities and contrast enhancements were correlated with clinical deterioration and size decrease of the AVM. The Spearman nonparametric test was used for statistical correlation. MR findings allowed to differentiate between four grades: grade 1 = no parenchymal changes; grade 2 = hypersignal on T2-weighted sequences, grade 3 = grade 2 + contrast enhancement on T1-weighted sequences; grade 4 = grade 3 + central hyposignal (necrosis-like) + peripheral hyposignal surrounding the AVM on T1-weighted sequences. Grade 4 was significantly related (p < 0.001) to clinical deterioration (deficit, seizures, increased intracranial pressure). All grade 4 patients, and only them, had clinical symptoms. Most of these symptoms regressed with corticoid treatment. Grade 4 was also related to the proportion of obliteration of the cAVM at 1 year after radiotherapy: mean proportion of obliteration was 12.5% for grade 2, 25% for grade 3 and 82.2% for grade 4 (p < 0.01). The size of T2-weighted MR images was related to clinical symptom appearance (p < 0.001). Finally, contrast enhancement was not predictive of the occurrence of the clinical symptoms. This proposed classification allows one to differentiate between the various MR images, and seems to predict clinical complications and response to radiotherapy of the cAVM.

[The rolandic line: a simple baseline for the identification of the central region. An MRI study and functional validation]. / La ligne rolandique: une ligne de base simple pour le repérage de la région centrale. Etude IRM et validation fonctionnelle.

INTRODUCTION: The identification of the central region--i.e. the central sulcus, the pre- and post-central gyri, the paracentral lobule--on MRI and angiographic images may be necessary prior to stereotactic procedures such as biopsies or resection of centrally located tumors, depth electrode recordings for presurgical evaluation of drug-resistant epilepsies, or radiosurgery of arteriovenous malformations. Stereotactic methods, such as the Talairach's proportional grid based on the bicommissural system, demonstrated the statistical position of the central sulcus according to the Ac-Pc, Vac and Vpc baselines. However, the course and the spatial position of this sulcus have remarkable individual differences that sometimes make the sulcus difficult to identify on serial sagittal MRI or lateral angiographic images. In order to facilitate this identification, the authors propose a new oblique baseline, the rolandic (R) line. MATERIAL AND METHODS: The stereotactic MRI and angiography of 22 patients were reviewed for this study. Eleven of these patients had stereotactic biopsies for a low-grade tumor located in the central region, while eleven others had multiple intracerebral electrodes implantation and depth EEG recording (SEEG: stereoelectroencephalography) in the presurgical evaluation of drug-resistant partial epilepsy, prior to epileptogenic cortex resection. The Ac-Pc, Vac, Vpc baselines and segments of the central sulcus were drawn from the mid-sagittal and lateral T1-weighted MRI images and reported on an individual graph. Surface and deep margins as well as axis of the central sulcus were also reported along with corpus callosum baselines as defined by Olivier et al.: horizontal plane, anterior and posterior callosal planes. The rolandic line was then traced from the graph:it joined the intersection point between the anterior callosal plane and an orthogonal line passing through the floor of the temporal fossa, and the intersection point between posterior callosal plane and an orthogonal line passing through the top of the hemisphere. The rolandic line was then superimposed on any sagittal MRI image or lateral stereotactic angiographic film. Finally, the spatial position of electrode contracts through which electrical stimulations elicited motor and/or sensory responses, either from central electrode implanted for motor fibers identification prior to stereotactic biopsies or from SEEG electrodes implanted for epileptogenic zone identification and cortical mapping, was reported on the individual graph. Angular and linear measurements were taken from the graph, between the rolandic line, the central sulcus axis, the Ac-Pc and callosal baselines, and the central sulcus limits (top, bottom, anterior and posterior margins). RESULTS: Graph measurements indicated that the rolandic line was significantly closer to the inferior part of the central sulcus than to its superior part (average distance between the line and the inferior point of the sulcus: 1.86 +/- 1.87 mm; average distance between the line and the superior point of the sulcus: 4.5 +/- 2.3 mm; p < 0.001-t test); similarly, the rolandic line was closer to the deep margin of the sulcus rather than to its superficial border (average distance between the line and the most anterior point of the sulcus: 11.43 +/- 3.16 mm; average distance between the line and the most posterior point of the sulcus: 7.95 +/- 4.14 mm; p < 0.01-t test). In 90% of the cases, the rolandic line followed the deep or middle part of the sulcus, with an average angle of 4.18 degrees +/- 2.53 degrees between the line and the sulcus axis. The spatial position of the electrode contacts that elicited motor/or sensory responses to stimulations correlated topographically well in all cases with the position of the motor and sensory fibers defined according to the central sulcus, baselines and reference to stereotactic atlases. (ABSTRACT TRUNCATED)

[Radiosurgical irradiation of 49 cerebral arteriovenous malformations using linear accelerator]. / Irradiation radiochirurgicale de 49 malformations artérioveineuses cérébrales au moyen d'un accélérateur linéaire.

During 1990 we treated 49 cases of arterio-veinous malformations (AVMs) using radiosurgery. We employed 15 MV X-Ray minibeams of a Saturne 43 Linac, eight additional collimators, 6-20 mm, the O Betti armchair and the Talairach stereotactic frame. Irradiation consisted of delivering 25 Gy at the periphery of the nidus corresponding to the 60-70% peripheral isodose range. We used the "Associated Target Methodology" and the three-dimensional treatment planning system Artemis-3D, both of which have been developed in our radiotherapy department. In December 1992, 44 out of 49 patients who had been treated were available for analysis with a 2-3-year follow-up. The overall obliteration rate was 33/44 (75%). According to the number of isocenters the obliteration rate was: 22/26 (85%) for one isocenter. In 18 multi-isocenters irradiation cases overall obliteration rate was 11/18 (61%). Two isocenters were used in nine of these 18 cases, the obliteration rate was 6/9; while when three isocenters were used it was 2/4 and in five cases of four isocenters irradiation the obliteration rate was 3/5. Obliteration rate for lesions < or = 4200 mm3 was 31/37 (84%). For greater volumes (5500 mm3 to 19000 mm3; median 9200 mm3) the obliteration rate was 2/7 whereas three others were partially (75 to 90%) obliterated and two remained inchanged. Before radiosurgery 21 cases received other treatment (mostly embolizations), the obliteration rate in this group was 15/21 (71.5%) while in previously untreated AVMs it was 18/23 (78%). A control arteriography was performed between 6 to 18 months after radiosurgery in 44 patients; three others refused the arteriography but are alive and well; two others had palliative irradiation, one of whom is dead. Out of 28 AVMs checked between 6 to 12 months 17/28 were obliterated (61%). In four cases, epilepsy was the first symptom; one has not suffered a further crisis whereas three others experienced a decrease in the number of crises. Two patients had recurrence of bleeding four and six months after irradiation (recurrence rate 2/44 = 5%). There were no lasting neurological consequences.

Methodology of "in vivo" anatomical study and stereo-electroencephalographic exploration in brain surgery for epilepsy.

Stereotactic implantation of deep SEEG electrodes performed as a prelude to surgery in some patients with drug-resistant focal epilepsy requires previous "in vivo" identification and localization of the cortical and subcortical structures to be explored, visualized "semi-directly" "or directly" by neuroradiological imaging techniques. Stereoscopic stereotactic teleangiography is a safety factor in transcutaneous electrode implantation and biopsies, but it also localizes the cortical sulci in a "semi-direct" manner by identifying vascular segments deeply buried in this sulci, which constitute their lamina vascularis. Although RMI greatly contributes to the study of the pallium, visualizing fragments of sulci and gyri does not necessarily mean that these structures can be identified with certainty, notably on the convexity of the brain. To solve this problem, RMI sections are enlarged by a photographic process, then combined with the images obtained from neuroradiological stereotaxis by means of anatomical landmarks that are common to both types of documents, using the bicommissural reference systems, bicallosal l/nl or vascular segments. This enables the angiographic laminae vascularis, which define the sulci in a "semi-direct" manner, to be used a kind of "Ariadne's clew" to identify cortical structures on RMI sections. In percutaneous stereotactic electrode implantation, the choice of the trajectories results from a compromise between the need to reach the desired anatomical structures, identified and localized within the stereotactic space, and the necessity to avoid the blood vessels displayed by stereoangiography. In some cases, the accuracy of anatomical definition can be verified during the SEEG study and/or by the evoked potential technique. Once the electrodes have been removed, their traces can be identified in a control RMI examination which constitutes a further verification.

Differential diagnosis between tumoural and non-tumoural intracranial lesions in children: a stereotactic approach.

The rational management of intracranial lesions should be based on the exact definition of the nature of the lesions and, when it is possible, on their spatial definition. Since External Radiotherapy (ERT) and cytostatic therapy are not free of undue effects, especially in children, such treatments should be used only when a "sure" diagnosis is obtained. The aim of this paper is to study the results allowed by the Talairach's stereotactic methodology in children. During the period January 1979-December 1986, 704 stereotactic procedures including serial biopsies, were performed at the S. Anne Hospital in Paris. One hundred forty-eight procedures (21%) concerned 134 children (78 M; 56 F) aged from 2 to 16 years. The interval between the occurrence of the first clinical symptoms and the stereotactic procedures varied between 1 and 180 months (m: 24 m). Fifty-two (40%) had previous therapeutic procedures without precise diagnosis. The lesions were hemispheric in 46 (34%) and deep seated in 88 (66%). The serial stereotactic biopsies proved the existence of a non-tumoural lesion in 20 children (14.9%): (cryptic vascular malformation: 5, cortical dysplasia: 3, haematoma: 3, ischaemia: 1, granuloma: 1, degenerative pathology: 2, cicatrix: 2, post-ERT alterations: 1, arachnoidal cyst: 2). Four were in the brain stem. In 3 patients (2%), a precise diagnosis was not obtained. The CT scan characteristics of the 20 non-tumoural lesions did not permit to establish a precise differential diagnosis. The therapeutic management was adapted to the diagnosis, avoiding potentially dangerous procedures in the 20 non-tumoural lesions.

MR visualization of CSF flow through a ventriculo-cisternostomy.

The MRI findings in a 6-year-old boy with an astrocytoma of the mesancephalon are reported. A ventriculocisternostomy had been performed in order to reduce the hydrocephalus. At the site of the ventriculocisternostomy, the T2-weighted images showed a low signal in the anterior part of the third ventricle, the interpeduncular and the pontine cistern. This was attributed to CSF flow void. We conclude that MRI can provide information about the precise location and normal functioning of a ventriculocisternostomy.

[Stereotaxic diagnosis and treatment of colloid cysts of the 3d ventricle. Apropos of 7 cases]. / Diagnostic et traitement stéréotaxique des kystes colloïdes du troisième ventricule. A propos de 7 cas.

The clinical and anatomical results of the treatment of 7 colloid cysts of third ventricle by stereotaxic aspiration are reported. A history of increased intracranial pressure was reported in all patients (4 females aged of 12, 16, 28, 38 years; 3 males aged of 36, 54, 59 years). A ventricular shunting device has been inserted in 4 patients. Pre-operative clinical findings were: signs of increased intracranial pressure (1 case), isolated memory disturbances (3 cases); motor weakness, memory disturbances and psychomotor slowness (2 cases); 1 of the 2 last cases had also thymic disturbances. Clinical examination was normal in 1 patient. CT-Scan revealed 5 hyperdense lesions, 3 with slight enhancement; 1 hypodensity encircled by an hyperdense ring without enhancement, 1 not enhancing isohypodensity. 6 colloid cysts were between the Foramens of Monro, 1 in the posterior third ventricle. Cyst volume ranged from 1.8 to 6.3 cc. (m: 3.4). Biventricular hydrocephalus was present in all but 1 patient. Stereotaxic aspiration of the cyst performed according to Talairach's system resulted in a release of C.S.F. circulation in all cases. 3 colloid cysts were aspirated completely, 4 were reduced to 3%, 11%, 12%, 33% of the initial volume. Post-operatively 2 patients presented with a transient meningeal reaction, 1 with a transient "myoclonic" syndrome. In 1 "completely aspirated" case a control CT-Scan showed, 5 years later, a small hyperdensity corresponding to 4% of the initial cyst volume. All patients lead a normal and useful life (Follow-up: 8-78 months, m: 45). Neurological examination is normal in 6 cases and shows a pre-existent facial asymmetry in 1. Ours results suggest that stereotaxic investigation should be the first safe procedure in order to achieve both diagnosis and treatment of colloid cysts of third ventricle.

[Value and technic of translating the data from x-ray computed tomography into the stereotaxic coordinates of the Talairach system]. / Intérêt et technique du transfert des données tomodensitométriques dans les coordonnées stéréotaxiques du système Talairach.

The neuroradiological stereotactic examinations provide indispensable information to localize many intracranial lesions: the data obtained by the CT-Scan are complementary of the stereotactic ones. The transfer of the routine CT-Scan transverse axial slices into the Talairach stereotactic system needs a precise definition of the inclination of the plan of the slices and a correct evaluation of the mean magnification factor. The inclination of the slices is appreciated using the bony, vascular and ventricular landmarks clearly identified on the CT-Scan and stereoscopic stereotactic images. We compared the spatial "reconstructed" CT-Scan data with the histopathological findings obtained by serial stereotactic biopsies in 48 tumor patients. The error varied from 1.5 to 4.6% (m: 2.7 +/- 1.2) on the sagittal plane; from 1.3 to 10% (m: 5.8 +/- 3.4) on the transversal plane; from 2.5 to 4.3% (m: 3.5 +/- 0.7) on the axial plane. The mean global error was 3.7% +/- 2.3. The CT-Scan directly performed under stereotactic conditions (acrylic frame) seems to be the more useful procedure. Nevertheless considering the good precision obtained with our methodology applied to the Talairach's system, we consider it suitable when: a) the gantry of the CT-Scan apparatus is too narrow for the acrylic frame; b) the exploitation of previous CT-Scan examinations is necessary; c) patient refuses the discomfort of the acrylic frame.

[Complementarity of x-ray computed tomography of staged stereotaxic biopsies and of stereo-electroencephalography in the spatial definition of intracranial lesions]. / Complémentarité de la tomodensitométrie des biopsies stéréotaxiques étagées et de la stéréo-électro-encéphalographie (SEEG) dans la définition spatiale des lésions intracérébrales.

This study concerns 180 patients (132 M; 48 F) (age: 2 to 69 years; m: 33 years) who underwent stereotactic procedures according to the methodology of Talairach and Szikla. Such procedures (stereotactic and stereoscopic angiography in all cases, and ventriculography in 81%) should permit a correct spatial definition of intracranial lesions. The informations provided by the angiography (normal in 7%) and by the ventriculography (normal in 11%) are complementary to those yielded by the TDM and permit an easier and safe stereotactic approach to the lesions. In 43% of patients the lesions were deep-seated (basal ganglia: 24; sellar region: 19; thalamo-peduncular: 13; brain stem: 6, etc.). The histological examination showed: low-grade gliomas in 43%; glioblastomas in 21%; non tumoral lesions in 17%. A precise diagnosis couldn't be obtained in 3.8%. The data provided by the stereo-EEG (in 11 patients suffering also of severe drug-resistant partial epilepsy) did not permit, alone, an histological diagnosis, excepted when electrodes explored a solid tumor. Two patients had a neurological impairment, and two died (one for extracerebral reasons). The authors consider that the TDM data and the informations given by the stereotactic procedures are complementary for obtaining valuable informations on the spatial organization of intracranial lesions and choosing the best treatment.

Serial stereotactic biopsies and CT scan in gliomas: correlative study in 100 astrocytomas, oligo-astrocytomas and oligodendrocytomas.

Histologic features of 100 supra-tentorial astrocytomas, oligodendrogliomas and oligo-astrocytomas obtained from serial stereotactic biopsies were compared with the corresponding CT scans. Topographic comparisons provided by visualization of the biopsy trajectories on post-biopsy CT scans were available in 24 cases. Areas of contrast enhancement and low attenuation were compared with the histologic grade of malignancy, tumor delimitation and structural type. The latter was determined as follows: Type I-solid tumor tissue without significant peripheral isolated tumor cells; Type II-solid tumor tissue associated with peripheral isolated tumor cells; Type III-isolated tumor cells only. There was a strong correlation between areas of contrast enhancement and tumor microvascularity. In addition, contrast enhancement occurred only in the solid tumor tissue component of the neoplasm. This correlation accounted for the relationship observed between CT images and the structural type of glioma. Contrast enhancement was constant in structural type I gliomas, inconstant in structural type II, and absent in structural type III. No correlation was found between malignancy and contrast enhancement. Contrast enhancement occurred in all grades of malignancy but was a constant feature of grade 4 gliomas. The volume of the tumors could not be reliably determined from CT images alone. Areas of low attenuation on contrast CT scans could correspond to either peritumoral edema or to edematous parenchyma infiltrated by isolated tumor cells. Serial stereotactic biopsies combined with calculations based on the CT scan provided a more precise definition of the tumor volume and identification of structural type. Such classification may prove useful in prospective analysis of various modes of therapy.

[Current significance of stereotactic exploration in the diagnosis and therapy of space-occupying cerebral processes]. / Heutige Bedeutung der stereotaktischen Exploration für die Diagnostik und für die Therapie bei raumfordernden cerebralen Prozessen.

To reach good functional results in patients with spaceoccupying processes--especially with those localized in the dominant hemisphere operative treatment should be planned individually, which is impossible if all diagnostic assessments are followed by the same surgical procedure. The choice of appropriate method of therapy in case of brain tumor depends on various factors, such as the histological nature, extent and volume, relationship to the brain structures and vessels, and spatial form of the growth. The synthesis of all neuroradiological information from stereotactic exploration, together with the histological findings from stereotactic serial biopsies yields a three-dimensional representation of the brain with the tumor. This method seems to offer the optimal basis for the choice of appropriate treatment--especially for gliomas--between surgery, radiotherapy (external or/and interstitial), endocavitary radiation therapy or drainage.

Correlation between stereo-EEG, CT-scan and stereotactic biopsy data in epileptic patients with low-grade gliomas.

Stereo-EEG activity, which was recorded precisely from the same location as stereotactic biopsies, was studied on 11 patients with low-grade glioma and severe partial epilepsy. The volume of the lesions varied from 6 to 72 cm3 (mean 23 cm3). A very depressed activity was recorded in all the 25 specimens of solid tumor and in more than half of infiltrated white matter. The background activity was still conserved in all 'normal' fragments, while it is never found in solid tumor; sometimes it could be found in the infiltrating tumors of white or gray matter. High voltage theta and delta activity was recorded in neither 'normal' nor solid tumors. We emphasize the importance of considering the stage of evolution when we evaluate the significance of the stereo-EEG activity.