[Postoperative assessment of the efficiency of the radical removal of glioblastomas in the cerebral hemispheres]

The paper analyzes the capacities of computed tomography (CT) and magnetic resonance imaging (MRI) in the postoperative period to evaluate the efficiency of surgical removal of the most malignant type of gliomas of the cerebral hemispheres. A total of 45 patients with different histological forms of cerebral hemispheral gliomas were examined, 37 of them with glioblastomas. Comparison of the results obtained by CT and MRI within the first 24 hours indicated that the latter was of greater informative value in all cases. At the same time only the use of a strict methodological approach to postoperatively estimating the remaining portions of glioblastomas makes it possible to apply these two methods as objective criteria for evaluating the efficiency of removal of a glioblastoma and hence the efficiency of subsequent therapeutic protocols. Contrast-enhanced MRI may be regarded as the method of choice in the primary assessment of patients with suspected recurrent glioblastoma.

[Access to the anterior cranial fossa through the frontal sinus]

In 1998 to 2001, the Academician N. N. Burdenko Research Institute of Neurosurgery operated on 15 patients aged 20 to 65 years who had bulky processes in the base of the skull and paranasal sinuses by applying an access through the frontal sinus. Most patients (n = 7) had meningiomas. The others had osteoma of the base of anterior cranial fossa (n = 2), chondroma (n = 2), angiofibroma (n = 1), fibroma (n = 1), esthesioneuroepithelioma (n = 1), and neurinoma (n = 1). The main criteria for choosing this access were the site and extent of a process, the sizes of the frontal sinus, and no signs of acute or chronic rhinosinusitis. The length of frontal sinuses in the most measurement was 3.5 to 5.0 cm, their width was 7 to 10 cm. All patients showed no progression of neurological symptoms. Three patients had a decrease in visual acuity from 1.0 to 0.8; with vascular therapy, visual disorders regressed during 2 months. Olfaction became worse in 4 cases, there was anosmia in 2 cases. Nasal liquorrhea was not observed. When there were tumors in the anterior cranial fossa, an access through the anterior wall of the frontal sinus permits radical removal of both intra- and extracranial parts of a tumor with closure of the defect with a periostal flap.

[Complex MR-diagnosis of brain abscesses]

Early diagnosis of brain inflammatory lesion is a basic factor in choosing treatment policy. The paper investigates the use and informative value of diffuse-weighed magnetic resonance imaging in the differential diagnosis of brain abscesses and processes of another origin. It also considers the application of MR spectroscopy and perfusion MRI to obtain additional information on an inflammatory processes. A series of observations covered 10 patients with brain abscesses at different sites. Diffusion-weighed image (DWI) revealed a drastic increase in a MR signal from the central abscess portions (a pyonecrotic area), which is suggestive of decreased diffusion of water molecules. The measured diffusion ratios (MDRs) were significantly lower in the central abscess area (p < 0.005) than those in the capsule and white matter of the brain at all values of the diffuse factor b (500, 1000 sec/mm2); the capsule was better visualized at the DWI at b = 500 sec/mm2. In addition, MDRs were significantly different within the annular contrasting area of abscesses and glioblastomas, in the abscess/tissue capsule, and edema (p < 0.01). Proton spectroscopy of the central abscess area (pus) revealed succinate, acetate, alanine, peaks of lactate and amino acid. Perfusion MR study (bolus contrasting and estimation of the tissue parameters rCBV and MTT) has indicated that the central abscess in relation to the medulla is a decreased perfusion area; perfusion in the abscess capsule is close to that in the medulla in its characteristics, but medullary time in this area is shorter than that in brain tissues; perifocal edema is also characterized by hypoperfusion. The analysis of complex MRI study in patients with brain abscesses has demonstrated that diffuse-weighed MRI enhances diagnostic specificity, diagnoses the development of a pyonecrotic abscess center at early stages of capsule formation; MR spectroscopy is an additional method of differential diagnosis of brain abscess and processes of another nature whereas perfusion MRI provides additional information on medullary hemodynamic changes.

[Disseminated craniofacial chondrosarcoma]

Chondrosarcomas are malignant mesenchymal tumors of chondroid nature. Less than 5% of all chondrosarcomas are localized in the head and neck. The paper analyzes a case of extensive chondrosarcoma of the skill base, which involves the anterior and median cranial fossa, ethmoidal, sphenoidal, right maxillary sinuses, and intratemporal fossa. A basal approach that is a combination of two-flapped subfrontal and orbitozygomatous accesses was used to remove the tumor. In doing so, the tumor could be excised and extensive defects of the skull base could be effectively closed with the flaps of the periostium and musculus temporalis, yielding a good functional and cosmetic effect.

[Use of the navigation system Stealth Station(TM) for removal of brain neoplasm]

The paper analyzes the authors' initial experience with the Stealth Station navigation system (Medtronic-Sofamor Danek, USA) during neurosurgery for intracranial tumors and outlines its techniques. Twenty eight patients with various brain tumors were operated on. Thirteen patients had tumors of the skull base (meningiomas, chordomas, paragangliomas, fibrous dysplasia). Twelve patients showed various intracerebral tumor-forming processes (gliomas, cavernous angiomas, and metastizing carcinomas). The navigation system ensured resection of these tumors. It was used in 2 other patients with gliomas and in 1 patient with cystic craniopharyngioma for their stereotactic puncture, biopsy, and drainage. The Stealth Station proved to be an effective tool for preoperative planning of cranial neurosurgical operations and their intraoperative guidance. Strict observance of the protocols of preoperative preparation ensures a high accuracy and facilitates search for and identification of anatomic guides. Only in 1 patient with surface glioma involving the central gyri, its resection was followed by hemiparesis that subsequently progressed. In the remaining 27 cases, the operation ran smoothly and caused no new neurological defect. The brain-shift phenomenon is the principal limitation of accuracy of the intraoperative system. This problem is less evident in skull-base surgery where the system was effectively used for critical structural location. Also, it can be safely employed for elimination of slight deep lesions to protect the brain and to minimize its injury via approach to a tumor through the brain parenchyma.

[Diagnosis of cerebral arterial aneurysms in acute and subacute subarachnoid hemorrhage]

The paper pools experience in using computed tomographic and magnetic resonance angiographies in patients with intracranial berry aneurysms in different periods following subarachnoid hemorrhage. The new low-invasive techniques for visualization of arterial vessels have been found to detect the aneurysm and to define its topographic and anatomic location in most cases (as high as 90%) by being on a par with direct cerebral angiography and to compare favourably with the latter. Based on the analysis of complex studies (angiography, CT- and MR-angiographies), the authors have developed algorithms for diagnosing intracranial aneurysms by the stage of subarachnoid hemorrhage.

[Mapping of the motor-sensory cortex by functional magnetic resonance tomography in frontoparietal tumors]

The potentialities of functional magnetic resonance imaging (FM-RI) in the preoperative mapping of the motor-sensory cortex of the brain in 24 patients with frontoparietal tumors and 5 healthy volunteers were studied. A good reproducibility of results was achieved while using a simple irritation paradigm as finger flexion-extension. The obtained activation maps were projected to the region of anterior and posterior central gyri and to the central sulcus. Imposition of the maps of motor-sensory cortical activation with routine T1-weighed images allows a surgeon to gain an insight into the mutual location of a tumor and a functionally significant portion of the cortex, by reducing the intraoperative risk of damage to this area. The intraoperative determination of the central sulcus by the evoked potential method in 4 patients confirmed the results obtained after FMRI. The relationship of the obtained activation maps to the presence of venous structures in the area concerned requires further studies on the modes of clarifying the site of functionally significant cortical areas in the brain.

[Diffusion-weighted image in the study of brain tumors and peritumoral edema]

The informative value of the technique of diffusion-weighted images (DWI) and diffusion maps was studied in diagnosing supratentorial tumors of the brain. Sixty four patients were examined. Among them there were 35 patients with glial brain neoplasms of varying malignancy [benign astrocytomas (asc) in 15 patients, anaplastic asc in 10, and glioblastomas in 10)], 15 patients with meningiomas, 5 with hydrocephalus, 9 with cerebral circulatory disorders. To obtain DWI, diffusion-weighted echo-planar impulse sequence was used. ADC was within (1.52 +/- 0.34) x 10(-3) mm2/sec for fibrillary astrocytomes. The anaplastic astrocytoma group showed variations in ADC values: ADC was higher in the contrasted part of the tumor than in the non-contrasted one and averaged (1.23 +/- 0.32) x 10(-3) mm2/sec. Glioblastomas were also noted for a higher variation in ADC that averaged (1.18 +/- 0.29) x 10(-3) mm2/sec. Meningiomas had a greater MR signal in response to DWI and low ADC values [(0.97 +/- 0.17) x 10(-3) mm2/sec]. Particular emphasis is laid on the study of different types of brain edema. ADC in the area of vasogenic (peritumoral), cytotactic (ischemic), and interstitial edema was (1.30 +/- 0.11) x 10(-3), (1.04 +/- 0.05) x 10(-3), and (1.91 +/- 0.1) x 10(-3) mm2/sec, respectively (p < 0.05) and sharply distinct in ADC maps.

[Proton magnetic resonance spectroscopy in diagnostics of tumorous and nontumorous lesions in brain]

Whether proton magnetic resonance spectroscopy (1H-MRS) can be used in the diagnosis of tumorous and nontumorous lesions of the brain was studied. The results of studies were analyzed in 80 patients, including 54 patients with brain tumors (astrocytomas and meningiomas), 20 with nontumorous lesions of the brain, and 6 apparently healthy individuals (controls). The nontumorous lesions of the brain involved cerebral circulatory disorders as ischemia (n = 14) and postradiation changes (n = 6). The studies were performed on a 1.5-T Signa-Horizont magnetic resonance tomograph by using the PROBE/SV programme package. The peak ratios of the following metabolites: N-acetylaspartate (NAA), choline (Cho), creatine, lactate (Lac), lipids (Lip) were examined in the spectra obtained. The spectra of astrocytomas showed a reduced peak of NAA, an elevated peak Cho; there was an increase in the peak of Lac along with higher tumor malignancy stage. The spectra of meningiomas presented a high peak of Cho along with a noticeable reduction in the peaks of other metabolites, the peak of NAA was not visualized. In ischemic lesion of the brain, the peak of Lac appeared within the first hours when the peaks of other metabolites were unchanged. A rise in the peak of Lac and a reduction in that of other metabolites were detectable with time. In radiation-induced lesions, the spectrum displayed a high peak of Lac and the peak of Lip appeared with virtually complete reduction in the peaks of other metabolites. 1H-MRS should be considered as an axillary technique used in combination with routine MRI in the diagnosis of various lesions of the brain, which can estimate chemical compositions, time-course of metabolic changes in the study tissue.

Correlation between the degree of contrast enhancement and the volume of peritumoral edema in meningiomas and malignant gliomas

Peritumoral edema and contrast enhancement of brain tumors are both thought to be due to breakdown of the blood-brain barrier (BBB); however, the exact mechanism by which these two phenomena occur and whether there is a quantitative or etiological relationship is not known. Our purpose was to determine whether the relationship between the breakdown of the BBB, defined radiologically as the degree of contrast enhancement, and the volume of surrounding edema is different for high-grade gliomas and meningiomas. We analyzed 13 meningiomas and 23 gliomas. A direct linear relationship between the degree of contrast enhancement (dC) and volume of peritumoral edema (V) with a high correlation coefficient (R = 0.66, P = 0.0006) was established for gliomas. A mathematical relationship between dC and V could not be established for meningioma. The findings for gliomas offer indirect radiological evidence that the defect in the BBB which causes edema is quantitatively and etiologically related to the defect in the BBB responsible for contrast enhancement. For meningiomas, the lack of a relationship between dC and V implies either that the mechanisms responsible for formation of edema and contrast enhancement are fundamentally different or that a physical barrier in certain meningiomas limits propagation of edema into the adjacent white matter.

[The computed and magnetic resonance tomographic anatomy of the normal hippocampal area and in neurosurgical pathology]

To make a correct diagnosis, a volumetric presentation of the anatomy of perihippocampal fluid spaces (PHFS) may be useful if there are abnormalities in the medial portion of the temporal region. Pathological processes in the region result in changes in the normal anatomy of PHFS. Hippocampal atrophy accompanied by enlarged PHFS is a sign of Alzheimer's disease (1081 patients). These changes are best detected on frontal MR images, but they can be seen at routine CT study. Hydrocephalus (88 patients) is characterized by dilatation of the lower horn of the lateral ventricles without increased dimensions of the transverse fissure. Normotensive hydrocephalus and Alzheimer's disease may be differentiated in evaluating the PHFS. The understanding of the anatomy of PHFS is useful in making a better assessment of the degree of both intra- and extracerebral tumors (in 296 patients) and arterioventricular malformations (in 12 patients) in the medial portions of the temporal regions.

[The prognostic importance of cancer-associated proteins and apoptosis in glioblastomas of the cerebral hemispheres]

Clinical and morphological studies were undertaken to examine 168 patients with glioblastomas of the cerebral hemispheres. They revealed that the longevity of the hemispheres was substantially influenced by three immunobiological criteria: the proliferative potential defined as a labelling index (LI) of proliferative cell nuclear antigen (PCNA), the expression of intracellular domain of epidermal growth factor receptor (EGFR) and the rate of apoptosis identified by ISEL. The risk for shorter survivals increases with higher PCNA LI and with the EGFR expression in the tumor. In contrast, the rate of apoptosis is a good predictor since the risk for shorter postoperative survivals progressively reduces with high apoptotic indices. The expression of cancer proteins p53 and bc12 in the glioblastomas produces no noticeable effect on the patients survival.

[Foci of pathological activity in the human brain and their influence on the spatial-temporal relationships of the EEG]

EEGs of 51 patients with focal brain lesions (tumor localized in brain hemispheres) were analyzed. Coherence functions were calculated between the EEG recorded from the intact and lesioned hemispheres and three-dimensional analysis of the delta-wave "source" localization was conducted. The revealed delta-wave "sources" localized in the perifocal region of the lesioned hemisphere demonstrated its dynamic properties and a tendency for fluctuations. Changes in the delta-wave "source" pattern were correlated with the EEG coherence values neither in the lesioned nor in the intact hemisphere. The focus of pathological activity produced the changes in EEG coherence and its interhemispheric asymmetry. In the majority of cases (72%), the mean level of intrahemispheric coherence at the side ipsilateral to the pathological focus was lower than the normal mean level, and the mean level of EEG coherence in the intact hemisphere was increased.

The use of hyperventilation in contrast-enhanced MR of brain tumors

Angiographic studies have demonstrated improved visibility of glial tumors after hyperventilation. The present study was undertaken to determine whether hyperventilation would change the MR enhancement characteristics of various glial tumors. Eighteen patients were studied twice: once with standard contrast-enhanced MR imaging and again with standard imaging plus hyperventilation. After hyperventilation, six low-grade astrocytomas showed no change and three showed a small decrease in relative enhancement (<10%). The ependymomas showed a 10% to 13% increase in the degree of enhancement, but no change in the area of enhancement. All the anaplastic astrocytomas showed an increase in the degree of enhancement (mean, 38%). Three of the anaplastic astrocytomas showed new foci of enhancement that were not seen on the nonhyperventilation study. Hyperventilation appears to be an inexpensive and safe method for increasing the conspicuity of abnormal areas of the blood-brain barrier.

MRI of high-grade glial tumors: correlation between the degree of contrast enhancement and the volume of surrounding edema

Contrast enhancement of malignant gliomas and the development of peritumoral edema are thought to be due to a breakdown of the blood-brain barrier (BBB). The degree to which these two factors are related to each other or to the degree of damage to the BBB is unknown. Our purpose was to quantitatively correlate the degree of enhancement with Gd-DTPA of anaplastic gliomas and glioblastoma multiforme with the volume of surrounding edema. In 14 patients, quantitative measurements of the volume of peritumoral edema and the degree of contrast enhancement were made. A high degree of correlation was found (r = 0.86, P < 0.01). These results can be viewed as indirect, radiological evidence that edema production is quantitatively related to the degree of breakdown of the BBB as determined by gadolinium enhancement. These results imply that the origin of the edema is in the area of breakdown of the BBB.

[Magnetic resonance angiography: a new diagnostic technique for neurosurgical abnormality]

The paper summarizes experience with magnetic resonance angiography (MRA) used in the diagnosis of neurosurgical diseases. The studies were performed on a Magnetom 42SP 1.0T tomograph (Siemens, Germany). The protocol included imaging in standard modes of T1-, T2- weighted images and different MRA techniques, depending on the nature of presumable changes. Based on 215 cases, the authors made a comparative analysis while using different MRA sequences in each type of abnormal changes. The potentialities and techniques in the detection of cerebrovascular diseases were defined. In addition to the efficiency of standard MRA techniques, that of paramagnetic contrasting used in the imaging of venous structures of the base of the skull was evaluated. The studies indicated that the technique was highly informative in detecting vascular diseases, such as arterial aneurysms, arteriovenous malformations, venous thromboses and occlusions of the brain, as well as dislocation changes in the vessels adjacent to tumors.

[Use of Omniscan (gadodiamide) in magnetic resonance studies of the central nervous system (results of a multicenter study)]

The aim the study: was to conduct first in Russia multicenter trial of gadodiamide in brain and spine MRI in adult patients. Open noncomparative multicenter (5 clinical centres) study. Brain and spine MRI was performed in 190 adult patients with signs of CNS disorders. Field strength of MR imagers was 0.04-1.5 T. Gadodiamide ("Omniscan", "Nycomed Imaging", Nycomed) was injected IV in dose 0.1 mmol/ml. Contrast enhancement was obtained in 74% cases. Gadodiamide allowed to detect more new lesions, better differentiate borders and internal structure of lesions, to differentiate them from oedema and surrounding structures. Contrast-enhanced MR images were superior to non-enhanced T1 and T2-weighted images and to CT images (before and after contrast enhancement). Use of gadodiamide increased confidence in diagnoses in 90.4% cases, changed the diagnosis in 30.3% cases. The general number of adverse events was 2.6%. Adverse reactions to gadodiamide were seen in 1.6%; all of them were of mild intensity without need for therapy. Gadodiamide is an effective and safe nonionic paramagnetic contrast media for brain and spine MRI in adult patients.

[The use of hyperventilation for improving the visualization of glial tumors of the brain in magnetic resonance tomography using the contrast substance Gd-DTPA]

This study was undertaken to evaluate the influence of hyperventilation (HV) as a test on the image contrast of brain glial tumors in enhanced magnetic resonance (MR) imaging. HV was performed for 2 min (30 breaths/min) before intravenous injection of Gd-DTPA (Magnevist), Schering AG, Germany, in a dose of 0.1 mmol/kg. A total of 19 patients with glial tumors of the brain were examined. After the functional test, the image contrast of tumor tissue was compared with tumor contrast after the standard enhanced MR imaging. Nineteen patients with brain tumors were assessed. The tumor types were histologically verified in all cases (nine malignancy degree I-II astrocytomas, six malignancy degree III astrocytomas, three ependymomas, one malignant oligodendroglioma). MRI was performed on a Magnetom 42 SP-1.0 T. There was an increase in the image contrast of degree I-II astrocytomas neither after the standard enhanced MRI nor after it in the presence of HV. On the contrary, in 2 cases there was an opposite effect--the tumor contrast decrease after the functional test. Ependymomas showed patterns of increases in contrast intensity from 10 to 13% as compared with the enhanced standard MRI in all cases. In these conditions the intrinsic structure and boundaries of tumors became more distinguished. Cases with malignant astrocytomas and oligodendroglioma had contrast enhancement increases as well. It is concluded that in cases with degree I-II astrocytomas, the use of HV does not improve the visualization of lesions. In ependymomas and anaplastic astrocytomas, HV aids in more significantly assessing the intrinsic structure and the extent of tumorigenesis and it may be useful as a functional test to assess the anaplastic extent of glial tumors of the brain and as a procedure enabling the contrast agent to be used in smaller dosages.

[Acoustic neurinomas. Magnetic resonance tomography using the contrast medium Gd-DTPA]

The contrast agent Gd-DTPA was used in the diagnosis of neurinomas of the VIII nerve. The analysis of the findings led to the conclusion that the use of the agent improved the visualization of auditory neurinomas and contributed to their differentiation from the brain stem and cerebellum and that its was more advisable to apply contrast enhancement in tumors located in the internal acoustic meatus (microneurinomas) or large (including bilateral) tumors with stem compression.

[Gd-DTPA in the diagnosis of brain metastasis]

The potentialities of present-day methods of imaging (computer-aided and magnetic resonance tomography) in the diagnosis of metastatic involvement of the brain are discussed. Besides routine scanning, the authors assess the efficacy of a contrast agent Gd-DTPA (Magnevist, Schering AG, Germany) used in magnetic imaging. The potentialities of reinforced-aided tomography, 0.04 and 1.0 Tesla magnetic imaging are compared on the basis of 23 cases. The results indicate that magnetic imaging at low-intensity magnetic field is approximately as effective as computer-aided tomography in the assessment of metastatic involvement of the brain; contrast reinforcement with Gd-DTPA appreciably improves the informative value of the method in comparison with reinforced computer-aided tomography. As for 1.0 Tesla magnetic imaging, it is highly informative and accurate in assessment of the type (single or multiple) of the pathologic process. Extra contrast staining with Gd-DTPA makes magnetic imaging still more reliable and superior to computer-aided tomography and 0.04 T magnetic imaging in the diagnosis of metastatic involvement of the brain. In this investigation authors performed analysis of 23 observations with metastases (22 cases were hystological verified) and estimated possibilities of modern diagnostic methods such as CT (+CM), standard MR imaging and MRI with Gd-DTPA (Magnevist, Schering AG, Germany). Authors have noticed that MR imaging with contrast enhancement is more efficient in diagnosis of brain metastases in comparison with CT. Metastases showed the signal intensity increase after Gd-DTPA injection. Small tumors and nodi situated nearly skull base and in cerebellum were more distinguished on MR imaging with contrast enhancement than before it.

[Magnetic resonance tomography in the diagnosis of intramedullary tumors]

The data of magnetic resonance imaging in 23 patients is hardly sufficient to characterize the histologic types of intramedullary tumors. However, the presence of cystous type of structure of intramedullary tumors on magnetic tomograms with nonhomogeneous (iso- or hypointensive) signal on T1-suspended tomograms or of hyper- or hypointensive signal on T2-suspended ones is to a great measure indicative of infiltration and diffuse growth of a tumor. A solid structure of intramedullary tumor with homogenous hyperintensive signals on both T1- and T2-dependent tomograms is more frequently indicative of a slowly growing tumor not involving the medulla, e.g. ependioma.

[The contrast enhancement of brain and spinal cord tumors using Gd-DTPA in magnetic resonance tomography with an extra-low magnetic-field intensity]

The contrasting agent Gd-DTPA (Magnevist, Schering AG, Germany) was tested when used in magnetic resonance tomography using extra-low (0.04 T) magnetic field intensity in 68 patients with various brain and spine tumors. The agent was injected intravenously in a dose of 0.1 mmol/kg. No complications were found. The tests showed its high efficiency in the diagnosis of brain neoplasms (particularly in malignant intracerebral disorders, meningiomas and neurinomas). Benign astrocytomas induced no noticeable signal intensification on post-contrasting T1-weighed tomograms. In all cases of spinal tumors, the application of Gd-DTPA could specify the extent of tumor invasions, the presence of cysts and identify accessory tumor nodes in one case.

[Magnetic resonance tomography in the diagnosis of spinal cord tumors]

The authors generalize experience in the examination of 245 patients with suspected disease of the spinal cord by means of the Acutscan magnetic resonance tomograph (Instrumentarium firm, Finland) with ultralow intensity of the magnetic field. The application of the new method in neuroradiologic diagnosis--magnetic resonance tomography (MRT) possessing certain advantages over computed tomography and myelography enables the authors to make the correct topical diagnosis in most cases and visualize the inner structure of the tumor and its relation with the structures of the spinal canal. Tumors of the spinal cord were detected in 102 patients: intramedullary in 24, extramedullary-intradural in 31, extradural in 13, and craniospinal in 34 patients. It was established from analysis of the results that MRT possesses high informativeness in cases of intradural tumors of the spinal cord.