Modulatory effects on human sensorimotor cortex by whole-hand afferent electrical stimulation.

OBJECTIVE: To investigate the effect of electrical stimulation of the nerve afferents of the hand on cortical activity elicited by whole-hand subthreshold stimulation for sensation in healthy human subjects. METHODS: Ten healthy volunteers were studied using BOLD-fMRI with 1) a test motor-task with finger-to-thumb tapping of the left hand, 2) a whole-hand afferent electrical stimulation of the left hand below the sensory level for sensation for 30 minutes, 3) a second fMRI run with the same paradigm as in the test motor-task immediately after electrical stimulation, and 4) a final identical fMRI run 2 hours post-stimulation to test the cortical changes induced by electrical stimulation. Experiments were carried out on a 1.5 T MR scanner and for fMRI echoplanar sequences were used. Data analysis was performed with SPM99. RESULTS: An increase of movement-related responses was seen within the primary motor and primary somatosensory areas of both hemispheres when comparing the test motor-task with the motor-task after electrical stimulation relative to the baseline or sham stimulation. Two hours post-stimulation the modulatory effects of mesh-glove stimulation diminished to baseline level except within the contralateral primary motor region. CONCLUSIONS: The increased BOLD response spatially localized within the sensorimotor cortex reflects an increase in neuronal activity that may provide augmented neuronal excitability.

The natural course of Sneddon syndrome: clinical and magnetic resonance imaging findings in a prospective six year observation study.

Sneddon syndrome (SS) is increasingly recognised as a cause of ischaemic stroke in young adults. As the natural course of SS is not well defined, the authors performed a prospective six year clinical and neuroradiological follow up study. Thirteen patients with definite diagnosis of SS (livedo racemosa, characteristic skin biopsy, and history of stroke) entered a follow up programme that consisted of clinical examinations, two magnetic resonance imaging (MRI) investigations, and a comprehensive laboratory follow up protocol. The most frequent clinical findings during follow up had been headache (62%) and vertigo (54%). Seven patients (54%) suffered from transient ischaemic attacks, however, completed stroke has not been obtained during follow up. Progression of white matter lesions detected in MRI were present in 10 of 13 patients. Laboratory follow up protocol revealed transient antiphospholipid antibodies in two subjects. This prospective six year follow up study suggests a low incidence of territorial stroke but outlines progressive leucencephalopathy in patients with SS.

Noninvasive follow-up of GDC-treated saccular aneurysms by MR angiography.

The aim of this study was to determine sensitivity and specificity of magnetic resonance angiography (MRA) for the assessment of durable occlusion of intracranial aneurysms with Guglielmi detachable coils (GDC) and to point out the influence of MRA results in re-intervention strategies. Forty-five patients with 54 aneurysms that were previously treated by endovascular occlusion with GDC were selected for this study. All patients underwent digital subtraction angiography (DSA) and MRA examinations on the same day. The time-of-flight MRA studies were performed on a 1-T scanner. The MRA images were first read by radiologists who were not aware of the DSA results. In a second consensus reading by the neuroradiologists who had performed all interventional procedures of this series, the decision was made as to whether re-treatment was necessary. The distribution of aneurysm sizes, configurations and treatment results were sufficient for an unbiased evaluation. The first blinded evaluation revealed a sensitivity of 71% and a specificity of 95% for MRA assessment of aneurysm reperfusion. In the second consensus reading, the sensitivity increased to 92% and the specificity was 98%. The blinded reading indicates that MRA is a useful adjunct to DSA for the assessment of durable results after endovascular treatment of intracranial aneurysms. In the consensus reading it became obvious that sensitivity and specificity of MRA can be increased to 92 and 98%, respectively, if the results were evaluated by experienced neuroradiologists, including prior knowledge of all other examinations. We have already increased the follow-up intervals for DSA and use MRA intermittently, based on these results.

The impact of peak saturation of the arterial input function on quantitative evaluation of dynamic susceptibility contrast-enhanced MR studies.

PURPOSE: The purpose of this work was to investigate systematic errors in dynamic contrast-enhanced MR perfusion studies due to peak saturation of the arterial input function (AIF) and to introduce a simple correction algorithm. METHOD: Computer simulations were performed to evaluate the influence of AIF peak saturation and to demonstrate the effectiveness of the presented correction algorithm. To compare the computer simulations with real MR data, MR perfusion measurements were performed on volunteers. RESULTS: The computer simulations show that AIF peak saturation leads to a systematic overestimation of cerebral blood volume (CBV) and cerebral blood flow (CBF) values, which was confirmed by comparing the obtained MR data with PET results. With use of an improved calculation algorithm correcting for AIF peak saturation, a significant improvement of the obtained CBV and CBF values could be demonstrated. CONCLUSION: Our results suggest that AIF peak saturation leads to a significant systematic error in the determination of CBV and CBF values and has necessarily to be taken into account for dynamic contrast-enhanced MR perfusion studies.

Long-term outcome after local intra-arterial fibrinolysis of basilar artery thrombosis.

Thrombolytic therapy of acute basilar artery (BA) thrombosis has been shown to reduce mortality and avoid a fatal outcome. Objective of this study was to investigate the long-term clinical outcome following intra-arterial fibrinolysis of occlusions of the BA. We retrospectively analyzed the clinical records and neuroradiologic results of 20 consecutive patients who had intra-arterial fibrinolysis of acute occlusions of the BA between 1982 and 1990. All patients were followed neurologically for a period of up to 12 years, including assessment of the Barthel index (BI) and brain CT or MRI studies. At the time of treatment, 6 patients were somnolent and 14 comatose, and tetraparesis was present in 15. The time between the onset of symptoms and treatment ranged from 1 to 48 h. The mortality rate was 35% (7/20 patients). Functional outcome was excellent in 9, 78%, of 13 survivors (BI <85). During the cumulative follow-up period (125 patient years) there was 1 death from myocardial infarction and 1 death from pneumonia. Vascular events during follow-up were myocardial infarction (n = 3) and a single cerebral transient ischemic attack. Despite the fact that our series was biased towards patients with severe symptoms, 65% (13/20) survived, and 78% of the survivors reached independence in daily life. These results provide evidence that local fibrinolysis of BA occlusion reduces mortality, and the long-term prognosis of the survivors is better than previously thought. None of our patients had a further stroke during the follow-up period, which indicates that acute BA occlusion is not a strong indicator for advanced arteriosclerotic disease.

Accuracy of intravascular microcatheter pressure measurements: an experimental study.

Intravascular pressure measurements are considered useful for the monitoring and assessment of endovascular treatment effects in intracranial vascular malformations. Experimental data on the accuracy of these measurements are limited. A flow phantom with defined intraluminal pressures and pulsatility flow waveforms was used in this study. Microcatheters commercially available for neuroendovascular procedures (length 140-155 cm), with different outer (0.5-0.83 mm) and inner (0.3-0.53 mm) diameters, were introduced into the phantom in the direction of flow. In a static experiment, pressure values from 0 to 75 mmHg were applied, and in the dynamic part of the experiment mean pressure values from 25 to 65 mmHg, with a pulsatile amplitude from 70 to 170 mmHg were employed. In the static experiment, there was a linear relationship between the pressure values obtained through the microcatheters and the local transducer of the flow phantom. The pulsatile experiments showed increased damping of the pressure waveforms with decreasing inner diameter of the microcatheters. However, the mean pressure values remained accurate. This experimental study has shown that mean pressure values can be accurately measured through microcatheters from 0.3-0.5 mm inner diameter and more than 140 cm in length. In vivo pressure measurements during interventional procedures are therefore reproducible and can be used for monitoring of embolization effects in patients.

Image registration of MR and CT images using a frameless fiducial marker system.

A new system of fiducial stereotactic markers that can easily be adapted to various imaging modalities without losing image registration was developed and tested. Utilizing MR and CT imaging the accuracy of the new system was evaluated with phantom studies and preliminary patient studies. The markers are clearly visible without artifacts on both imaging modalities. The clear delineation of the marker dots on the images enables an accurate automated marker detection. Using the marker system, image registration was found to yield an accuracy of up to 1 mm, depending on the imaging modality and the employed marker arrangement. The presented marker system shall improve patient comfort in comparison to conventional fixed stereotactic frames if repeated, highly accurate registrations are necessary over longer periods.

MR volumetry for monitoring intramuscular bromocriptine treatment in macroprolactinomas.

OBJECTIVE: To assess volumetric changes of pituitary prolactinomas, we applied a threshold-based segmentation algorithm in two patients during intramuscular bromocriptine treatment. MATERIALS AND METHODS: Tumor volumes were calculated from contiguous slices of a 3D GE sequence and from conventional SE images. RESULTS: After a single 50 mg i.m. bromocriptine administration, the prolactinoma volumes decreased by 25 and 35% within 7 and 11 days, respectively. Volume calculations from 3D GE images were more accurate than calculations from 3 mm 2D SE images, especially for smaller tumors. A decrease of prolactinoma size was paralleled by a decrease of serum prolactin levels and correlated with an improvement of visual field and endocrine function in both patients. The end of the bromocriptine effect was indicated by a reincreasing tumor volume, which was observed after 30 days in the first patients and after 43 days in the second patient. CONCLUSION: Our results suggest that MR volumetry represents a useful tool to monitor changes of prolactinoma volume during bromocriptine treatment and may improve the clinical management of these patients.

MR imaging and proton spectroscopy of the brain in posttraumatic cortical blindness.

Magnetic resonance (MR) imaging and localized proton MR spectroscopy of the occipital lobes were performed in a patient with cortical blindness following brain trauma. Computed tomography (CT) scans and MR images of the visual cortex were normal in the acute stage. Six weeks after the trauma, MR images showed cortical lesions in both occipital lobes, while the spectra showed elevated lactate and decreased N-acetyl aspartate levels relative to those of healthy volunteers. One year later, visual acuity had improved and follow-up studies revealed an increase in the ratios of N-acetyl aspartate to choline and creatine. These results demonstrate that parenchymal lesions may develop in brain regions that appear normal at CT and MR imaging during the acute stage after trauma. Metabolic changes can be observed in these areas by means of localized proton MR spectroscopy.

[1H magnetic resonance spectroscopy in intracranial tumors and cerebral ischemia]. / 1-H-Magnetresonanzspektroskopie bei intrakraniellen Tumoren und zerebralen Ischämien.

Image-guided localized proton magnetic resonance can now increasingly be used with clinical 1.5T MR systems. To fuel the discussion on whether spectroscopy will become a routine modality or whether it will remain a research tool, we report on our experience with a stimulated echo sequence in 60 patients harboring intracranial tumors and 79 patients suffering from various forms of cerebral ischemia. Spectroscopy was incorporated into a routine imaging protocol, and the parameters of TR = 1500 ms, TE = 270 ms were kept constant over a 3-year period. Relative changes in the metabolite concentrations were estimated from peak height and area calculations compared with the spectra of 66 normal volunteers. The spectra of the volunteers did not show significant interindividual variations, and there were no changes during photic stimulation in a subgroup of 6 volunteers. All tumor patients' spectra were significantly different from those of normal controls. Low grade gliomas showed decreased levels of N-acetyl-aspartate and some had elevated levels of lactate. Oligodendrogliomas had higher choline levels than astrocytomas. High grade gliomas had higher levels of lactate and lower N-acetyl-aspartate ratios. Meningiomas were characterized by absence of N-acetyl-aspartate, and some metastases showed a lipid signal at 1 ppm. Spectra of ischemic brain tissue were also abnormal, revealing lowered N-acetyl-aspartate and elevated lactate. The changes paralleled the severity of ischemia and pronounced abnormalities were associated with an inferior outcome. Further technical improvements, including absolute quantification of metabolite concentrations and smaller sensitive volumes, will allow direct monitoring of treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Sneddon's syndrome: diagnosis by skin biopsy and MRI in 17 patients.

BACKGROUND AND PURPOSE: Sneddon's syndrome, characterized by generalized livedo racemosa and cerebrovascular lesions, is an underdiagnosed disease. We evaluated clinical, laboratory, histological, and neuroradiological findings in a series of 17 patients to improve diagnostic criteria for Sneddon's syndrome. METHODS: Patients with generalized livedo racemosa and cerebrovascular events were included in the study. All underwent neurological and dermatological examination, skin biopsy, computed tomographic scan, magnetic resonance imaging as well as magnetic resonance angiography, sonography of the extracranial arteries, and a comprehensive laboratory protocol. RESULTS: Completed stroke was present in eight patients, and 15 reported transient neurological deficits. Magnetic resonance imaging yielded cerebral abnormalities in 16 of 17, whereas computed tomographic scans were abnormal in only 12 of 16 patients. Magnetic resonance imaging revealed more lesions in individual patients than did computed tomography. Magnetic resonance angiography demonstrated patent intracranial vessels in 16 of 17 patients. Skin biopsy showed distinct histopathological findings in all patients. The involved vessels were small to medium-sized arteries at the border between dermis and subcutis. Early inflammatory reactions were followed by subendothelial proliferation and a late fibrotic stage. Laboratory examinations showed impaired creatinine clearance in eight patients, whereas all other laboratory tests, including antiphospholipid antibodies, were normal. CONCLUSIONS: In this series, magnetic resonance imaging and skin biopsy were useful for confirmation of the diagnosis of Sneddon's syndrome. Magnetic resonance findings were not specific, but the high sensitivity for detection of asymptomatic brain lesions helped to confirm the diagnosis in patients with transient symptoms. Histological features of skin biopsies were characteristic if appropriate techniques were employed.

Maple syrup urine disease: metabolic decompensation monitored by proton magnetic resonance imaging and spectroscopy.

Metabolic decompensation of maple syrup urine disease in a 3.5-year-old boy was monitored by means of proton magnetic resonance imaging and spectroscopy. In the acute stage, imaging showed diffuse cerebral edema. Proton spectra showed an elevation of lactate and a previously unassigned resonance at 1 ppm. This peak disappeared with normalization of branched-chain amino acids and oxoacids in the plasma and cerebrospinal fluid. In vitro spectroscopy of these metabolites at 1.5 T confirmed the chemical shift position of their methyl resonances at 1 ppm. The duration of lactate elevation correlated with the presence of brain edema and coma. These results demonstrate that magnetic resonance imaging can monitor therapeutic effects, and suggest that proton spectroscopy can detect cerebral accumulation of branched-chain amino acids and oxoacids in maple syrup urine disease.

Localized proton and phosphorus magnetic resonance spectroscopy following electroconvulsive therapy.

Animal studies show that cerebral lactate increases after electrically induced seizures. We investigated three adult psychiatric patients by means of localized proton and phosphorous magnetic resonance spectroscopy in order to evaluate if such effects can be observed after electroconvulsive therapy (ECT). None of the patients had changes in cerebral energy metabolism following ECT. Within the limitations of in-vivo spectroscopy in a clinical setting, our results suggest that if lactate production increases after ECT, this effect is either very short or increased perfusion causes an efficient efflux of cerebral lactate.

Combined magnetic resonance imaging and proton magnetic resonance spectroscopy of patients with acute stroke.

BACKGROUND AND PURPOSE: The prospect for a therapeutic window for treatment of ischemic stroke encourages the noninvasive investigation of metabolic changes in acute ischemia. Recently, localized proton spectroscopy became available at 1.5-T magnetic resonance systems. In this study we evaluated the usefulness of combined magnetic resonance imaging and spectroscopy on the diagnosis of acute and chronic infarctions. METHODS: Combined magnetic resonance imaging and spectroscopy investigations were carried out with a 1.5-T system in 16 volunteers, eight patients with chronic infarction (greater than 8 months), and 10 patients with acute ischemic stroke (less than 8 hours). We used a stimulated echo sequence to acquire localized spectra from image-guided volumes of interest (16-27 ml). RESULTS: There were no significant interindividual differences of choline, creatine, phosphocreatine, and N-acetyl aspartate resonances in the spectra from volunteers. In chronic infarctions, N-acetyl aspartate was decreased in relation to choline. Acute ischemic infarctions were characterized by decreased N-acetyl aspartate resonances and elevation of lactate. CONCLUSIONS: The study demonstrates the feasibility of proton spectroscopy in stroke patients. Metabolic alterations in ischemic tissue can be monitored and can distinguish acute from chronic lesions.

Corneal edema induced by cold.

We report on a patient, who regularly developed reversible corneal edema of the right eye after cold stress. Cycling tours in cold weather and windy conditions seemed to precipitate the edema. After a provocation test, we also observed transient, corneal edema. A few reports in the literature suggested that Raynaud's disease or trigeminal neuropathy might be responsible for cold-induced corneal opacification. None of these conditions was present in our patient, as proved by laboratory tests and magnetic resonance imaging. We found that contact lenses were an effective prophylaxis against corneal edema.