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Les syndromes parkinsoniens sont une cause importante de handicap, en particulier chez les sujets âges. L’IRM a une place importante dans la prise en charge diagnostique et therapeutique de ces patients. Orientee par l’anamnese et l’examen clinique, l’IRM conventionnelle est habituellement normale dans la maladie de Parkinson alors que des anomalies evocatrices de pathologies neurodegeneratives (atrophie multi-systematisee, paralysie supra nucleaire progressive…) ou de diverses pathologies (hypoxiques, toxiques, familiales…) doivent etre recherchees. En recherche clinique, les techniques avancees (spectroscopie, diffusion, IRM fonctionnelle) offrent une etude anatomo-fonctionnelle et metabolique de la physiopathologie de ces affections.

Due to recent efforts in improving spatial and temporal resolution in imaging techniques, it is now possible to get relevant information about brain perfusion and metabolism in humans. This information can significantly impact on brain pathophysiology, diagnosis assessment and therapy options, particularly in patients having brain ischemia. Among these imaging and metabolism techniques are dynamic perfusion computed tomography, perfusion MRI, positron emission tomography and NMR spectroscopic imaging. The goal of this article is an overview of these four techniques, with their own technical description, advantages and drawbacks. Details are provided about brain parameters given by each technique and their clinical relevance, the accessibility of the technique in the emergency setting and the optimal window to use it during the patient's evolution.

Nuclear magnetic spectroscopy (MRS) is a useful method for noninvasively studying intracerebral metabolism. Proton MRS can identify markers of the neuronal viability (N-acetyl-aspartate, NAA), of the metabolism of cellular membranes (choline), of the cellular energy metabolism (creatine, lactate). In Phosphorus MRS, the peaks most readily identified are involved in the high-energy cellular metabolism (ATP, phosphocreatine, inorganic phosphate), and intracellular pH (pHi) can be determined using this method. MRS has been used in experimental models of traumatic brain injury (TBI), primarily to study the cellular metabolism and the relation between biochemical and histological changes after trauma. In trauma patients, significant changes in NAA, choline and pHi were found in both grey and white matter comparing with controls, and these alterations correlated with injury severity. Correlations have been reported between these biochemical changes (reduction in NAA, increase in choline) measured at 1 to 6 months after TBI and the clinical outcome of the patients. However, there are methodological issues which still impede to recommend MRS as a tool for predicting neurological outcome in the clinical setting.

To determine the perfusion-sensitive characteristics of cerebral dural metastases and compare them with the data on meningiomas. Twenty-two patients presenting with dural tumor underwent conventional and dynamic susceptibility-contrast MR imaging: breast carcinoma metastases, two patients; colorectal carcinoma metastasis, one patient; lung carcinoma metastasis, one patient; Merkel carcinoma metastasis, one patient; lymphoma, one patient; meningiomas, 16 patients. The imaging characteristics were analyzed using conventional MR imaging. The cerebral blood volume (CBV) maps were obtained for each patient and the relative CBV (rCBV) in different areas was calculated using the ratio between the CBV in the pathological area (CBVp) and in the contralateral white matter (CBVn). The differentiation between a meningioma and a dural metastasis can be difficult using conventional MR imaging. The rCBVs of lung carcinoma metastasis (1 case: 1.26), lymphoma (1 case: 1.29), breast carcinoma metastasis (2 cases: 1.50,1.56) and rectal carcinoma metastasis (1 case: 3.34) were significantly lower than that of meningiomas (16 cases: mean rCBV = 8.97±4.34, range 4–18). Merkel carcinoma metastasis (1 case: 7.56) showed an elevated rCBV, not different from that of meningiomas. Dural metastases are sometimes indistinguishable from meningiomas using conventional MR imaging. rCBV mapping can provide additional information by demonstrating a low rCBV which may suggest the diagnosis of metastasis.

Neurosurgery is in essence a field of application development for robots, based on multimodal image guidance. Specific motorized tools have already been developed and routinely applied in stereotaxy to position a probe holder or in conventional neurosurgery to hold a microscope oriented towards a given target. The potentialities of these approaches have triggered industrial developments which are now commercially available. These systems use databases, primarily coming from multimodal numerical images from X-ray radiology to magnetic resonance imaging. These spatially encoded data are transferred through digital networks to workstations where images can be processed and surgical procedures are pre-planned, then transferred to the robotic systems to which they are connected. We have been using a stereotaxic robot since 1989 and a microscope robot since 1995 in various surgical routine procedures. The future of these applications rely mainly on the technical progress in informatics, about image recognition to adapt the pre-planning to the actual surgical situation, to correct brain shifts (for instance), about image fusion, integrated knowledge such as brain atlases, as well as virtual reality. The future developments, covering surgical procedure, research and teaching, are sure to be far beyond our wildest expectations.

Sarcoidosis rarely presents as an intracranial mass lesion. We report the case of a patient presenting a disturbance of cognitive functions in whom CT and MRI demonstrated a large right fronto-temporal mass lesion with contrast enhancement and surrounding marked oedema, highly suggestive of a brain tumour. The diagnosis of neurosarcoidosis was made after stereotactic biopsy of the lesion.

The authors present oblique sections of the retroperitoneum adapted to the morphology of each patient, which affects both the liver and the organisation of the retroperitoneum. This original method involve two incidences for studying the left and right retroperitoneum separately with vertical sectional planes. The authors postulate that the orientation of the retroperitoneal viscera depends on the degree of hepatic development, so these incidences are chosen with reference to axial sections of the portal bifurcation and the middle hepatic v.: the two vascular landmarks of the liver. Anatomic and radiologic studies confirm the reliability of these landmarks and their easy application in modern imaging. Such new data improve our understanding of the classical topographic anatomy of the retroperitoneum. These oblique sections promote the radiologic study of the portal and systemic vessels, renal pedicles, suprarenal glands and pancreas.

A case of Lhermitte–Duclos disease is reported. Characterized by architectural disruption of the cerebellar folia with disorganization of the normal three layers, the lesion is easily identified using magnetic resonance imaging.

This study's purpose was to demonstrate a relationship between growth of stroke volume measured on Diffusion-Weighted MRI (DWI) at admission (baseline) and 24 hours later (follow-up) and functional outcome at 90 days evaluated by the modified Rankin Scale (mRS).DWI infarct volumes were calculated, using an Analyze Software. Clinical outcomes were assessed at 90 days by the mRS. Univariate regression analysis was performed to assess the relationship between changes in DWI lesion volume and mRS less or equal to 1.Sixty-nine cases had serial DWI scans with a measurable lesion at baseline and follow-up. The median baseline National Institutes of Health Stroke Scale (NIHSS) was 10, 5 and 7 at 24 hours. At 90 days, the proportion of patients with Rankin less or equal to 1 was 51.7%. The average baseline volume was 19.7 cm(3) and average follow-up volume was 46.1 cm(3). For each 10 cm(3) of growth in DWI infarct volume, the odds ratio for a mRS less or equal to 1 was 10,1 (IC 95%, 3-33.9).The results of this study provide evidence of a significant inverse relationship between infarct growth measured by DWI and good functional clinical outcome at 90 days.

Using computed tomography and magnetic resonance imaging, we prospectively studied 100 patients hospitalized with a lacunar infarct. Our aim was to evaluate the capabilities of magnetic resonance imaging in the detection and delineation of lacunes in a project of clinicotopographic correlations. Seventy-nine patients had a classic lacunar syndrome; 35 had pure motor stroke, 26 had ataxic hemiparesis, seven had sensorimotor stroke, and 11 had pure sensory stroke. A miscellaneous group of 21 patients had less typical lacunar syndromes, primarily with brainstem signs and symptoms. Among a total of 153 lacunes, magnetic resonance imaging detected at least one lacune appropriate to the symptoms in 89 patients. In 16 patients at least two lesions correlated with the clinical features, and precise clinicotopographic correlations were possible in 68 patients. Magnetic resonance imaging was more effective when it was performed a few days after the stroke. Lesions causing different types of lacunar syndromes had significantly different volumes, suggesting that the size of the lesion may influence clinical features. Magnetic resonance imaging may be the imaging technique of choice in the study of lacunar syndromes.

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In a few years, magnetic resonance imaging (MRI) has evolved from a morphology-based examination to one that encompasses metabolism and function.MRI is a well-established tool for the initial evaluation of brain tumors, but conventional MR sequences have some limitations. Conventional MRI is unable to distinguish high-grade glioma from metastasis and abscess, to define precisely the histopathological grade of gliomas, to determine exactly the limits of tumor extension, to characterize meningeal tumors. Differentiation of tumor recurrence from treatment-related changes may be difficult with standard MR imaging because the interpretation is essentially based on volume analysis.1H Spectroscopy, diffusion and perfusion imaging become possible with the development of MR imagers and can be routinely performed in clinical settings. They give complementary information about tumor metabolism and vascularity and allow a better analysis of post-treatment modifications. Functional and metabolic explorations should be used to characterize brain tumors.

In the last decade, functional MRI (fMRI) has become one of the most widely used functional imaging technique in neurosciences. However, its clinical applications remain limited. Despite methodological and practical issues, fMRI data has been validated by different techniques (magnetoencephalography, Wada test, electrical and magnetic stimulations, and surgical resections). In neurosurgical practice, fMRI can identify eloquent areas involved in motor and language functions, and may evaluate characteristics of postoperative neurological deficit including its occurrence, clinical presentation and duration. This may help to inform patients and to prepare postoperative care. fMRI may also identify epileptic foci. In neurological practice, fMRI may help to determine prognosis of recovery after stroke, appropriate medication, and rehabilitation. fMRI may help to identify patients at risk of developing Alzheimer disease. Finally, cerebrovascular reactivity imaging is an interesting approach that might provide new radiological insights of vascular function.

Perfusion MR Imaging is useful for initial diagnosis and follow up of brain tumors. Dynamic susceptibility contrast MR imaging is described. The limitations and advantages of this technique are discussed with respect to quantification and interpretation of results.

MRI has dramatically improved the management of cerebral tumors and consequently oligodendrogliomas. T1 and T2-weighted images and gadolinium enhancement are very useful for tumor detection and characterization. Tumor enhancement is of a great prognostic value because it is highly predictive of high-grade oligodendroglioma. Three-dimensional MR images provide, with high precision, the anatomical location and the relationships with functional structures (motor and language areas). The recent technical progress in MRI and the use of diffusion images in the screening of tumors lead to a better definition of the lesion. Comparative analysis of MRI images is helpful to detect eventual relapse and adverse effects of treatment.

MR spectroscopy (MRS) is a technique used to study a few metabolites in the brain or tumors in situ. This technique can provide information on tumor histological type and grade, and is helpful to identify tumor-like lesions, particularly abscesses. MRS can be used for treatment monitoring.

The present renewal of the surgical treatment of Parkinson's disease, almost abandoned for twenty Years, arises from two main reasons. The first is the better understanding of the functional organization of the basal ganglia. It was demonstrated in animal models of Parkinson's disease that the loss of dopaminergic neurons within the substantia nigra, at the origin of the striatal dopaminergic defect, induces an overactivity of the excitatory glutamatergic subthalamo-internal pallidum pathway. The decrease in this hyperactivity might lead to an improvement in the pakinsonian symptoms. The second reason is the improvement in stereotactic neurosurgery in relation with the progress in neuroimaging techniques and with intraoperative electrophysiological microrecordings and stimulations, which help determine the location of the deep brain targets. In the 1970s chronic deep brain stimulation in humans was applied to the sensory nucleus of the thalamus for the treatment of intractable pain. In 1987, Benabid and colleagues suggested high frequency stimulation of the ventral intermediate nucleus of the thalamus in order to treat drug-resistant tremors and to avoid the adverse effects of thalamotomies. How deep brain stimulation works is not well known but it has been hypothetized that it could change the neuronal activities and thus avoid disease-related abnormal neuronal discharges. Potential candidates for deep brain stimulation are selected according to exclusion and inclusion criteria. Surgery can be applied to patients in good general and mental health, neither depressive nor demented and who are severely disabled despite all available drug therapies but still responsive to levodopa. The first session of surgery consists in the location of the target by ventriculography and/or brain MRI. The electrodes are implanted during the second session. The last session consists in the implantation of the neurostimulator. The ventral intermediate nucleus of the thalamus was the first target in which chronic deep brain stimulation electrodes were implanted in order to alleviate tremor. This technique can be applied bilaterally without the adverse effects of bilateral thalamotomies. Like pallidotomy, internal globus pallidum stimulation has a dramatic beneficial effect on levodopa-induced dyskinesia but its effects on the parkinsonian triad are less constant and opposite motor effects are sometimes observed in relation with the stimulated contact. The inconstant results, perhaps related to the complexity of the structure led to the development of subthalamic nucleus stimulation. The alleviation of motor fluctuations and the improvement in all motor symptoms allows a significant decrease in levodopa daily dose and in levodopa-induced dyskinesia. Presently, deep brain stimulation is a fashionable neurosurgical technique to treat Parkinson's disease. Subthalamic nucleus stimulation seems to be the most suitable target to control the parkinsonian triad and the motor fluctuations. Because of the possible adverse effects it must be reserved for disabled parkinsonian patients. No large randomized study comparing different targets and different neurosurgical techniques has been performed yet. Such studies, including cost benefit studies would be useful to assess the respective value of these different techniques.

Although rare in non immunodeficient patients, the correct diagnosis of brain abscess is essential in order to initiate urgent medical and surgical treatment. We describe the imaging features including spectroscopy and diffusion MRI.

Functional MR angiography (fMRA) images have been generated from the brain of healthy volunteers, in response to a hand motor task. Two sets of 3D phase-contrast MR images were, therefore, acquired, one during a resting and one during a task activation period. The MR images measured during rest were subtracted from those measured during task performance. The fMRA images were eventually obtained by calculating maximum intensity projections from the set of subtraction images. The results confirm earlier observations that there is a significant functional response from pial veins to motor activity.

To assess the contribution of magnetic resonance (MR) cerebral blood volume (CBV) mapping in the initial evaluation of brain tumors.63 patients presenting a brain tumor underwent dynamic susceptibility-contrast MR imaging before surgery or biopsy: 28 high grade gliomas, 8 low grade gliomas, 2 pilocytic astrocytomas, 4 lymphomas, 12 metastases, 9 meningiomas. The CBV maps were obtained for each patient and the relative CBV (rCBV) in different areas was calculated using the ratio between the CBV in the pathological area (CBVp) and in the contralateral normal tissue(CBVn). The maximum rCBV (rCBVmax) for each tumor was determined and the mean values of rCBVmax in each group of tumors were compared using an unpaired Student t test (p=0.05).The rCBVmax for high grade gliomas (mean +/- SD: 2.6 +/- 1,2) was statistically different from low grade gliomas (0.9 +/- 0.4) (p0.001), lymphomas (0.7 +/- 0.2) (p=0.002), meningiomas (9.1 +/- 4.4) (p0.001) and kidney metastases (8.9 +/- 2.1) (p0.001). The two pilocytic astrocytomas had a much lower rCBVmax than high grade gliomas. No statistically significant difference was found between high grade gliomas and lung metastases (2.4 +/- 0.9) (p=0.72).CBV mapping provides additional information on the vascularity of the lesions, which is not available with conventional MR imaging. It might be useful for differentiating certain lesions showing contrast enhancement, mainly high grade gliomas from kidney metastases, meningiomas, lymphomas or pilocytic astrocytomas.

We performed conventional and dynamic susceptibility-contrast MRI imaging in 38 patients with brain tumours: 20 with metastases (breast carcinoma: two; renal carcinoma: five; colorectal carcinoma: one; lung carcinoma: seven; melanoma: five), and 18 with high-grade astrocytomas. We obtained cerebral blood volume (CBV) maps and calculated the relative CBV (rCBV) in different areas using the ratio between the CBV in the pathological area (CBVp) and in the contralateral white matter (CBVn). We calculated the maximum rCBV (rCBVmax) for each tumour and compared the mean rCBVmax in each group of tumours. The mean rCBV of melanoma metastases (5.35+/-2.32, range 3.14-9.23) and of renal carcinoma metastases (8.17+/-2.39, range 5.41-11.64) were significantly greater than those of high-grade astrocytomas (2.61+/-1.17, range 1.3-5.0) ( P=0.002 and

Summary: We report a case of Whipple disease involving the brain, optic chiasm, posterior fossa, and spinal cord. We evaluate the role of MR imaging for initial evaluation and for long-term follow-up of Whipple disease involving the CNS. We also discuss the semiologic characteristics of the lesions.

The purpose of this work was to demonstrate the feasibility of a new imaging technique called synchrotron radiation computed tomography (SRCT). This technique leads to a direct assessment of the in vivo concentration of an iodine- or gadolinium-labeled compound. Rats bearing C6 glioma were imaged by MRI prior to the SRCT experiment. The SRCT experiments were performed after a 1.3 g I/kg (n = 5) or a 0.4 g Gd/kg (n = 5) injection. Finally, brains were sampled for histology. The SRCT images exhibited contrast enhancement at the tumor location. Ten minutes after injection, iodine and gadolinium tissular concentrations were equal to 0.80 ( +/- 0.40) mg/cm3 and 0.50 ( +/- 0.10) mg/cm3, respectively in the peripheral area of the tumor (respective background value: 0.20 +/- 0.02 to 0.10 +/- 0.01). Correlation to MRI and histology revealed that the contrast uptake occurred in the most vascularized area of the tumor. The present study summarizes the feasibility of in vivo SRCT to obtain quantitative information about iodine and gadolinium-labeled compounds. Beyond brain tumor pathology, the SRCT appears as a complementary approach to MRI and CT, for studying iodine- and gadolinium-labeled compounds by the direct achievement of the tissular concentration value in the tissue.

NMR imaging allow specific study of contrast variations due to intravascular agents. It is possible to measure regional cerebral blood volume (rCBV). In brain tumor, this parameter allow to characterize tumoral vascularisation and blood brain barrier lesions. We use today 1st pass bolus technic. Easy to perform in clinical practice, it is useful for differential diagnosis, prebiopsic planning and follow up of lesions. That should be particularly interesting to evaluate the anti-angiogenic treatment efficiency.

It has been suggested that the switch to an angiogenic phenotype can separate the development of a tumor into two stages: the prevascular phase and the vascular phase. The purpose of the present work is to demonstrate the existence of an angiogenic switch in a longitudinal study of a brain tumor model during tumor growth by means of microvessel density measurements.The study was performed on 32 rats bearing C6 glioma. At different stages of tumor growth, the histological aspects were described and sections were immunostained for factor VIII-related antigen in order to highlight microvessel endothelial cells. Microvessels were counted at 400 magnification for different areas (central non necrotic area, peripheral area, contralateral grey and white matter area), using image analysis software.Vessel density was significantly higher at the tumor-brain interface than in the center of the tumor or in the contralateral cortex. The vessel density remains stable in the tumor during the first 3 weeks after cell implantation, after which a clear increase of vessel density can be observed.The present study demonstrates the presence of an angiogenic switch which is concomitant with the development of necrosis and pseudopalisading pattern.

The aim of this work was to evaluate the potential of T(2)-weighted, steady-state susceptibility-enhanced contrast magnetic resonance imaging (MRI), to characterize brain tumor heterogeneity and tumor vascularization. In vivo T(2)-weighted MRI experiments were carried out on normal rats (n = 11) and rats bearing C6 glioma (n = 17), before and after the injection of a remanent superparamagnetic contrast agent. The DeltaR(2) variations of the transverse relaxation rate due to the injection of the contrast agent were used to generate relative cerebral blood volume (CBV) maps. Contrast enhancement of the tumor was shown to reflect tissue vascularization rather than leakage of the blood-brain barrier. The quantitative results clearly show the heterogeneity of tumor vascularization and reveal a high vessel density in the peripheral area (CBV(per) approximately 17.2 +/- 2.3 sec(-1)) and a low vessel density in the central area of the tumor (CBV(cen) approximately 2.5 +/- 0.5 sec(-1)). Magn Reson Med 42:754-761, 1999.

Summary: This study reports the MR spectroscopic patterns of two patients with bithalamic glioma. In one patient, phosphorus ((31)P) MR spectroscopy was performed. In both patients, the proton MR spectroscopic scans showed an increased creatine-phosphocreatine peak in the tumor. In the patient who underwent (31)P-MR spectroscopy, an increased phosphocreatine peak was also observed. This group of thalamic tumors may be distinguished from other gliomas clinically, radiologically, and metabolically.

Neurosurgery is in essence a field of application development for robots, based on multimodal image guidance. Specific motorized tools have already been developed and routinely applied in stereotaxy to position a probe holder or in conventional neurosurgery to hold a microscope oriented towards a given target. The potentialities of these approaches have triggered industrial developments which are now commercially available. These systems use databases, primarily coming from multimodal numerical images from X-ray radiology to magnetic resonance imaging. These spatially encoded data are transferred through digital networks to workstations where images can be processed and surgical procedures are pre-planned, then transferred to the robotic systems to which they are connected. We have been using a stereotaxic robot since 1989 and a microscope robot since 1995 in various surgical routine procedures. The future of these applications rely mainly on the technical progress in informatics, about image recognition to adapt the pre-planning to the actual surgical situation, to correct brain shifts (for instance), about image fusion, integrated knowledge such as brain atlases, as well as virtual reality. The future developments, covering surgical procedure, research and teaching, are sure to be far beyond our wildest expectations.

Magnetic resonance spectroscopy (MRS) is a noninvasive means of obtaining metabolic information complementary to magnetic resonance imaging. Its potential is particularly interesting in tissue characterization and follow-up of brain lesions. We present here a review of clinical applications together with a short development of the fundamental principles. From a review of the literature, and our own experience, we discuss the role of MRS in clinical neuroimaging. Despite the small number of clinical applications validated to date, MRS is today a highly useful research tool.

Neurosurgery is by excellence a field of application for robots, based on multimodal image guidance. Specific motorized tools have been already developed and routinely applied in stereotaxy to position a probe holder or in conventional neurosurgery to hold a microscope oriented towards a given target. The potentialities of these approaches have triggered industrial developments currently commercially available. These systems use data bases, primarily coming from multimodal numerical images from X-ray radiology to magnetic resonance imaging. These spatially encoded data are transferred through digital networks to workstations where images can be processed and surgical procedures are preplanned, then transferred to the robotic systems to which they are connected. We have been using a stereotactic robot since 1989 and a microscope robot since 1995 in various surgical routine procedures. The future of these applications mainly rely on the technical progress in informatics, about image recognition to adapt the preplanning to the actual surgical situation, to correct brain shifts for instance, about image fusion, integrated knowledge such such as brain atlases, as well as virtual reality. The future developments, covering surgical procedure, research and teaching, will sure be far beyond our wildest expectations.

The same physical principles are the basis of magnetic resonance spectroscopy (MRS) and magnetic resonance imaging (MRI). Proton MRS is easily performed with clinical magnets (or = 1.5 T) and may be added to routine MRI studies to provide metabolic information on pathological tissues. It represents an important tool to detect several metabolic compounds. The article will review the current status of proton MRS with a particular emphasis upon its clinical utility for the diagnosis of brain tumors and for the evaluation of the efficacy of radiotherapy.

Synchrotron sources can provide intense, collimated and tunable X-ray beams suitable for medical imaging and research, allowing the use of monochromatic X-rays for human examinations. At the European Synchrotron Radiation Facility (ESRF), a beam line dedicated to medical research is under commissioning. Two imaging programs are being developed, for coronary angiography and cerebral CT. The new monochromatic imaging systems should improve image contrast and provide better image quantification. The properties of synchrotron radiation are described, as well as the instrumentation of the medical beam line and its 2 imaging programs. The new possibilities offered by synchrotron radiation for contrast media research are discussed, the improvement on concentration measurement precision achievable is underlined.

Sarcoidosis rarely presents as an intracranial mass lesion. We report the case of a patient presenting a disturbance of cognitive functions in whom CT and MRI demonstrated a large right fronto-temporal mass lesion with contrast enhancement and surrounding marked oedema, highly suggestive of a brain tumour. The diagnosis of neurosarcoidosis was made after stereotactic biopsy of the lesion.

A structural lesion of the brain is a frequent finding in intractable partial epileptic patients. We analyse anatomo-electro-clinical characteristics of 58 patients in which MR showed a lesion inside the temporal lobe. They are 29 males and 29 females with a mean age at surgery of 23.5 +/- 10.7 years (2.6-45.9). The mean epilepsy duration is of 13.4 +/- 8 years (1.3-35.5), with a mean seizure frequency of 28.7 +/- 43.6 per month, with a great inter-individual variability (from 3 per month to 15 a day). The minimum follow-up is 3.5 years. A video-EEG monitoring was performed in 21 cases, while a stereo-EEG investigation was judged mandatory in 26. On the basis of anatomo-electro-clinical correlations and of the results of presurgical investigations, the epileptogenic area was proved to be temporal in 49 cases, temporal but controlateral to the lesion in 1, and at least bilobar in 8 patients.

Brain tumor surgery, stereotactic or by resection, is based on the precise knowledge of the spatial position of the target and of their relationships with the normal brain structures. Modern computed neuroimaging allows image guidance of neurosurgical procedures, using robots driven by the coordinates of the target and of the entry point. We have developped a stereotactic robot as well as a robotized microscope which are guided from digitized images. They are used in routine daily practice and will become part of the standard neurosurgical equipment.

Nine patients with haemangioblastoma of the posterior cerebral fossa were explored by computerized tomography (CT), then by magnetic resonance imaging (MRI) with enhancement by gadolinium in 4 cases. Following a review of clinical and laboratory data, the radiological images are detailed and distributed into three forms: cystic with mural nodule, solid, and annular. The usefulness of the different imaging techniques is specified, and the stress it put on the need to look for multiple sites in the entire central nervous system.

In monkeys rendered parkinsonian, lesions and electrical stimulation of the subthalamic nucleus reduce all major motor disturbances. The effect of electrical stimulation of the subthalamic nucleus was assessed in three patients with disabling akinetic-rigid Parkinson's disease and severe motor fluctuations. Quadripolar electrodes connected to a pulse generator were implanted in the subthalamic nuclei on both sides. Patients were evaluated with the unified Parkinson's disease rating scale and timed motor tests. 3 months after surgery, activities of daily living scores had improved by 58-88% and motor scores by 42-84%. This improvement was maintained for up to 8 months in the first patient operated upon. One patient was confused for 2 weeks after surgery, and another developed neuropsychological impairment related to a thalamic infarction which improved over 3 months. In one patient, stimulation could induce ballism that was stopped by reduction of stimulation. This is the first demonstration in human beings of the part played by the subthalamic nuclei in the pathophysiology of Parkinson's disease.

A case of Lhermitte-Duclos disease is reported. Characterized by architectural disruption of the cerebellar folia with disorganization of the normal three layers, the lesion is easily identified using magnetic resonance imaging.

An impairment of muscle energy metabolism has been suggested as a predisposing factor for, as well as a consequence of exertional heatstroke (EHS). Thirteen young men were investigated 6 months after a well-documented EHS using 31Phosphorus Magnetic Resonance Spectroscopy (31P-MRS). The relative concentrations of ATP, phosphocreatine (PCr), inorganic phosphate (Pi), phosphomonoesters (PME), and the intracellular pH (pHi) were determined at rest, during a graded standardized exercise protocol (360 active plantar flexions) and during recovery. Also the leg tissue blood flow was determined by venous occlusion plethysmography during the MRS procedure. Sixteen age-matched healthy male volunteers served as control group. In resting muscle, there were no significant differences between the groups as regards pHi, Pi/PCr, and ATP/PCr+Pi+PME ratios. During steady state exercise conditions, effective power outputs were similar for both groups at each level of exercise: 20, 35, and 50% of maximal voluntary contraction (MVC) of the calf muscle. No significant differences were shown between the two groups in Pi/PCr, pHi, or changes of leg blood flow at each level of exercise. At 50% MVC, Pi/PCr was 0.48 +/- 0.08 vs 0.47 +/- 0.05 (P = 0.96), pHi was 6.94 +/- 0.03 vs 6.99 +/- 0.02, respectively (P = 0.13). Finally, the rate of PCr resynthesis during recovery was not significantly different between the two groups: t1/2 PCr = 0.58 +/- 0.07 vs 0.50 +/- 0.05 min, respectively (P = 0.35). Therefore, no evidence of an impairment of muscle energy metabolism was shown in the EHS group during a standardized submaximal exercise using 31P-MRS performed 6 months after an EHS.

The calf muscle energy metabolism of 8 stable chronic obstructive pulmonary disease (COPD) patients with chronic respiratory failure (arterial oxygen tension (Pao2) 7.7 +/- 0.4 kPa or 58 +/- 3 mmHg) was studied, using 31-phosphorus magnetic resonance spectroscopy (31P MRS). MRS spectra were acquired at rest and during the course of 360 pedal movements at 20, 35 and 50% of the maximal voluntary contraction (MVC) and during recovery. Eight healthy age-matched subjects served as the control group. No significant differences between groups were observed in resting muscle, as regards intracellular pH, Pi/PCr ratio (Pi: inorganic phosphate; PCr: phosphocreatine) and the relative ATP expressed as the ratio beta ATP/PCr + Pi + PME (PME: phosphomonoester). Although effective power outputs were similar for both groups at each work level, COPD patients exhibited a higher Pi/PCr ratio than health controls (3.34 +/- 0.89 vs 0.49 +/- 0.05 at 50% MVC; p less than 0.01) and a lower pHi (6.65 +/- 0.11 vs 7.06 +/- 0.02 at 50% MVC; p less than 0.01). PCr resynthesis during recovery was slower in patients than in control subjects (t1/2 PCr 1.27 +/- 0.26 min vs 0.47 +/- 0.05 min; p less than 0.05). These results suggest impairment of aerobic capacity in a non-ventilatory working muscle, which may be due to hypoxaemia in patients with chronic respiratory failure.

The authors have appplied magnetic resonance imaging (MRI) to the anatomic study of the liver by comparing cadaveric sections with those obtained with MRI. This study deals with sections oblique in relation to a sagittal or frontal plane, whose orientation is determined from landmarks visible on transverse sections. Oblique sections were made in 10 cadavers using an original method. First, adjacent transverse sections were made of the frozen trunk and two landmarks were located in these sections: the course of the middle hepatic v. and the direction of the division of the portal venous trunk. The transverse sections were then stacked and the block so reconstituted was refrozen and then cut in adjacent oblique sections oriented either along the plane of the middle hepatic v. (sagittal oblique sections) or along the plane of division of the portal venous trunk (frontal oblique sections). Oblique MRI sections were made in 15 healthy volunteers, mainly based on the same venous landmarks but sometimes on other landmarks visible on the transverse sections. Oblique MRI sections can be made in the plane of any anatomic structure located in the transverse sections in order to define its position. Sections based on identical landmarks differently oriented in different subjects allow for definition of the individual anatomy of the liver investigated. The frontal oblique sections clearly show the course of the trunk of the portal v. and the junctions of the hepatic vv. with the inferior vena cava. The sagittal oblique sections are particularly useful for investigating the thinnest part of the left side of the liver and also the caudate lobe. Moreover, these oblique sections reveal certain organs adjacent to the liver, notably the pancreas, from unusual angles. The oblique sections also make it possible to follow the curse of the veins participating in formation of the portal trunk remote from the liver. The new MRI techniques considerably decrease certain artifacts associated with study of the abdomen and should allow the most profitable use of oblique sections.