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Biomedical subjects

B Weder

Publications and source records attributed to B Weder.

At least 19 recordsLinked to original sources

Thrombolysis in stroke patients aged 80 years and older: Swiss survey of IV thrombolysis.

This databank-based, multicenter study compared all stroke patients with IV tissue plasminogen activator aged > or = 80 years (n = 38) and those < 80 years old (n = 287). Three-month mortality was higher in older patients. Favorable outcome (modified Rankin scale < or = 1) and intracranial hemorrhage (asymptomatic/symptomatic/fatal) were similarly frequent in both groups. Logistic regression showed that stroke severity, time to thrombolysis, glucose level, and history of coronary heart disease independently predicted outcome, whereas age did not.

Age Factors↗

Left and right superior parietal lobule in tactile object discrimination.

Tactile object discrimination is one of the major manual skills of humans. While the exploring finger movements are not perceived explicitly, attention to the movement-evoked kinaesthetic information gates the tactile perception of object form. Using event-related functional magnetic resonance imaging in seven healthy subjects we found one area in the right superior parietal cortex, which was specifically activated by kinaesthetic attention during tactile object discrimination. Another area with similar location in the left hemisphere was related to the maintenance of tactile information for subsequent object discrimination. We conclude that kinaesthetic information is processed in the anterior portion of the superior parietal cortex (aSPL) with a right hemispheric predominance for discrimination and a left hemispheric predominance for information maintenance.

Adult↗

Diffusion and perfusion MRI for the localisation of epileptogenic foci in drug-resistant epilepsy.

Drug-resistant epilepsy is an important clinical challenge, both diagnostically and therapeutically. More and more surgical options are being considered, but precise presurgical assessment is necessary. We prospectively studied eight patients with drug-resistant epilepsy, who underwent clinical examination, single photon emission computed tomography (SPECT) and interictal MRI, including diffusion- and perfusion-weighted echoplanar sequences. Lesions suspected on SPECT of being epileptogenic showed mild hypoperfusion, while the diffusion-weighted MRI (DWI) revealed increased apparent diffusion coefficients relative to the other side. However, these abnormalities were not visible on the corresponding maps. We showed that DWI and perfusion-weighted MRI could be used confirm the characteristics and site of an epileptogenic area in patients with drug-resistant epilepsy.

Adolescent↗

Hierarchical versus parallel processing in tactile object recognition: a behavioural-neuroanatomical study of aperceptive tactile agnosia.

The organization of the normal perceptual processing subserving tactile object recognition is poorly understood. While perceptual deficits associated with cases of tactile agnosia may pinpoint sites of critical interference with normal tactile information processing, the precise character of such deficits remains unclear. The aim of the present study was to explore the behavioural and neuroanatomical correlates of perceptual disturbances in two cases of unilateral aperceptive tactile agnosia. Perception of microgeometrical and macrogeometrical features was tested using an alternative forced choice paradigm. While both patients were impaired in the assessment of microgeometrical properties of objects (i.e. detecting subtle differences in grating profiles), one patient showed an additional deficit in the perception of macrogeometrical properties of objects (i.e. detecting differences in length of cuboids). The pattern of perceptual deficits for both patients suggested a severely compromised (if not totally lost) ability to recognize everyday objects. Perceptual performance improved when the patients had complementary tactile information (i.e. for intramodal comparison), despite a persistent inability to explicitly name the objects. That is, the patients were able to recognize objects, but only implicitly. Improved perceptual performance was also observed when complementary visual information was available (i.e. transmodal information transfer). In this case, the perceptual improvement was accompanied by a corresponding improvement in explicit object recognition. High resolution MRIs identified lesions in the postcentral gyrus in both patients, and additionally in the secondary somatosensory area (SII) and the posterior parietal cortex in the more severely affected patient. The results demonstrate that the underlying failure in tactile agnosia is mainly impaired perception of microgeometrical properties of objects due to a lesion of primary sensory cortex. The related neuroanatomical findings suggest a degradation of serial information processing within postcentral gyrus. In one case tactile agnosia was almost complete due to additionally impaired perception of macrogeometrical properties of objects, which correlated with the extension of lesion to the posterior parietal cortex. Importantly, the findings indicate traces of two distributed networks for tactile information processing and the associated parallel processing of complementary micro- and macrogeometrical information within postcentral gyrus and posterior parietal lobe.

Adult↗

Hyperperfusion of anterior cingulate gyrus in a case of paroxysmal nocturnal dystonia.

The authors report the clinical, EEG, and SPECT findings of a patient with nocturnal paroxysmal dystonia. Ictal and interictal scalp EEG showed epileptiform activity over both frontal lobes. Subtraction ictal SPECT co-registered to MRI indicated a bilateral significant hyperperfusion in the anterior part of the cingulate gyrus. These results support earlier electrophysiologic investigations by others suggesting that anterior cingulate epilepsy may manifest as nocturnal paroxysmal dystonia, and illustrate the usefulness of computer-assisted SPECT analysis.

Adult↗

Cerebral networks in sensorimotor disturbances.

Increasing evidence suggests that the human brain employs multiple, interconnected brain areas for information processing and control of behavior, including the performance of laboratory tasks. Brain diseases are expected to affect these networks directly by interference and indirectly as a consequence of deficit compensation. Covariance analyses applied to functional brain imaging data open the opportunity to study neural networks and their disease-related changes in the human brain. Here, we review our analytic approach based on principal component analysis (PCA) to address such questions. We will discuss its methodological foundations and applications in patients with sensorimotor disorders. We will show that PCA in combination with, both, hypothesis-driven testing and correlation statistics provides a powerful tool for elucidating disease-related abnormalities and postlesional reorganization of neural networks in the human brain.

Adult↗

SPECT during sleepwalking.

Sleepwalking is a dissociation between body sleep and mind sleep. We report single photon emission computed tomography (SPECT) in a man with a history of sleepwalking. Our findings suggest that this dissociation arises from activation of thalamocingulate pathways and persisting deactivation of other thalamocortical arousal systems.

Adolescent↗

Prediction of angiographic carotid artery stenosis indexes by colour Doppler-assisted duplex imaging. A critical appraisal of the parameters used.

The aim of our study was to establish colour Doppler-assisted duplex imaging (CDDI)-criteria to predict an angiographic internal carotid artery (ICA) stenosis of at least 70%, according to the North American Symptomatic Carotid Endarterectomy Trial (NASCET) and European Carotid Surgery Trialists (ECST) methods of measurement. In the following, we describe the findings in 79 patients who were screened for carotid endarterectomy by CDDI and further evaluated by digital subtraction angiography (DSA). In 158 carotid arteries, 107 stenoses of > 30% and nine occlusions were found. Receiver operator characteristic graphs were constructed in order to calculate sensitivities and specificities of the assessment by CDDI in the prediction of high-grade stenoses determined by angiography. Optimal cut-off points were defined by highest accuracy which reflects the combination of high sensitivity and specificity. The critical index of a high-grade ICA stenosis according to the ECST method could be predicted with an accuracy greater than 90% by a systolic peak velocitiy of 1.25 m/s or an area reduction by CDDI of 70%. Corresponding values, 1.6 m/s and 80% area reduction, predicted the stenosis indexes according to the NASCET method less reliably, with accuracies of between 80% and 90%. Flow velocity criterion was slightly less accurate than the area reduction criterion by CDDI. Finally, double-blind evaluation performed by two readers per examination modality showed that the measurement of area reduction in CDDI is at least as reliable as stenosis indexes according to ECST and NASCET methods.

Adult↗

Extracranial vertebral artery dissection causing cervical root lesion.

The authors report an unusual manifestation of extracranial vertebral artery dissection (VAD), presenting with a predominantly motor radicular manifestation. Cervical magnetic resonance imaging (MRI) revealed the intramural hematoma in the dissected vessel wall, compressing mainly the segmental motor root and, to a lesser degree, the sensory ganglion. In the digital subtraction angiography (DSA), a circumscribed narrowing of the incriminated vessel was demonstrated. Color-coded Duplex imaging (CDDI) revealed complete recanalization after a few days of anticoagulation treatment. Complete neurologic recovery was seen after 3 months. Considering the MRI data, the likely pathogenetic mechanism was compression of the nerve root by the intramural hematoma. The synopsis with similar cases in the literature points to the characteristic features, i.e., the association of neck pain with radicular motor deficit and the absence of degenerative disk disease. The respective syndrome should raise the suspicion of vertebral artery dissection, especially in young individuals.

Adult↗

Disturbed functional brain interactions underlying deficient tactile object discrimination in Parkinson's disease.

Somatosensory discrimination of cuboid objects was studied in a group of healthy volunteers and patients with Parkinson's disease using regional cerebral blood flow (rCBF) measurements obtained with positron emission tomography (PET) and 15O labeled water [H2 15O]. A 6-[18F]-fluoro-L-dopa (FDOPA) PET scan demonstrated that the patients may be grouped into those with normal and those with abnormally lowA FDOPA uptake in the caudate nucleus. The categorical group comparisons revealed that task-induced rCBF increases were deficient in bilateral motor and sensory cortical areas in the Parkinson patients. Moreover, deficient rCBF increases were evident in the mesial and right dorsolateral prefrontal cortex for patients in a more advanced disease state, who showed low FDOPA uptake in the caudate nucleus. A principal component analysis (PCA), performed on the rCBF data, identified three patterns (principal components, PCs) that differentiated patients from normals. The first PC represented a right-hemisphere dominant, bilateral group of brain areas known to be involved in tactile exploration. A second PC reflected a cortical-subcortical pattern of functional interactions, comprising cortical areas important for working memory processes. The third group-differentiating PC revealed a pattern of functional interactions involving bilateral temporo-parieto-occipital association cortices, which was consistent with a hypothesized supramodal network necessary for object discrimination. In an additional subgroup analysis, greater expression of the third PC pattern predicted greater caudate FDOPA uptake in patients. Our neuroimaging data revealed a disturbance of distinct patterns of brain functional interactions related to the sensorimotor deficit in Parkinson's disease and to deficits of cognitive information processing deficits in the more advanced stage of Parkinson's disease.

Adult↗

Neuroimaging findings in a patient recovering from global alexia to spelling dyslexia.

The authors report findings in a 67-year-old right-handed man who had an ischemic infarct in the territory of the left posterior cerebral artery. The clinical manifestation consisted mainly of total alexia without agraphia. The patient gradually recovered, subsequently showing the syndrome of spelling dyslexia. Cerebral MR-images revealed a circumscript infarction of medial and basal parts of left temporal lobe. In the acute stage [99mTc]HM-PAO SPECT was characterized by a diminished uptake in the definitely infarcted area and hyperfixation in the region of the left forceps major. Because high retention of HM-PAO indicates potentially salvageable tissue after an ischemic event, the depicted area might be correlated with the recovery of function. Thus, the authors' neuroimaging data give further support to the assumption that the left forceps major is a critical area for global alexia, whereas spelling dyslexia is due to involvement of the left medio-basal temporal lobe.

Aged↗

Somatosensory discrimination of shape: prediction of success in normal volunteers and parkinsonian patients.

Tactile discrimination of macrogeometric objects in a two-alternative forced-choice procedure represents a complex task including somatosensory and higher-order cognitive processing. The objects for somatosensory discrimination were rectangular parallelepipeds that differed in oblongness only. They were presented in sequential pairs to 12 normal volunteers and 13 parkinsonian patients. Owing to the dichotomy of the task, we calculated estimates of the probability of a correct answer by a binomial approach. The probability of a correct answer could be calculated on the basis of a logistic model ensuring that the probability values lie in the interval [0, 1]. The relationship between the probability of a correct answer and the difference in oblongness of the objects could be described solely by one coefficient determined by logistic regression. This coefficient summarized the effectiveness of the simultaneous and consecutive operations inherent in the task and allowed characterization of performances in groups and individuals.

Adult↗

Partial epileptic seizure with versive movements examined by [99m Tc] HM-PAO brain single photon emission computed tomography: an early post study analyzed by computerized brain atlas methods.

The consecutive steps of a seizure with leftward versive movements of the head and eyes were analyzed after video monitoring and correlated with findings on single photon emission computed tomography (SPECT) using [99m Tc] hexamethyl propylene amine oxime (HM-PAO). Evaluation included reconstruction of subtraction images from the early postictal state, obtained immediately after the video-monitored seizure, and the interictal baseline. Based on normalized perfusion indexes within voxels of Talairach space, we concluded that the primary epileptogenic focus was in the premotor cortex of the contralateral hemisphere. We then placed the functional data in an anatomic context by adapting a dedicated computerized brain atlas (CBA) to the patient's brain with the aid of magnetic resonance imaging (MRI) slices. By inverse transformation, the patient's data were aligned with the standard geometry of the brain atlas for comparison purposes with data from the literature. The validated activation field projected exactly onto the right precentral sulcus with the anterior border zone including the right frontal eye field.

Atlases as Topic↗

[Neurosarcoidosis of the central nervous system. Analysis of the long-term follow-up of 8 cases].

We present retrospective and follow-up data of eight patients with sarcoidosis involving the central nervous system (CNS). The diagnosis was established definitely by histological evidence in seven cases. Biopsies were taken directly from the CNS or the covering meninges in two of them. Additionally, we included a further case with the characteristic triad of arthralgia, erythema nodosum and pulmonary hilar adenopathy on X-ray, representing Löfgren's syndrome. Systemic manifestation of sarcoidosis was hardly recognized in some cases and sometimes became evident only in the long term after recurring manifestations. The symptomatology in our cases can be summarized as follows: Mostly, meningopolyneuritic and meningoencephalopathic syndromes occurred, with, in addition, one case of chronic meningitis and two cases of spinal involvement. In two cases, CNS symptoms represented the initial manifestation of the disease. Furthermore, the stringent interdependency of non-neurologic and neurologic episodes of the disease was not recognized easily. Under these circumstances, the histological confirmation was often difficult. Thus, the latency between the first neurological signs of the disease and the diagnosis of neurosarcoidosis may be long, as in our cases (mean 27 months). The course of the disease was followed for a mean 8.1 (range 1-15) years. Seven patients showed at least partial recovery from progressive disease after corticosteroid therapy. One patient developed, subacutely, a fatal pontine-medullary syndrome. The potentially poor prognosis emphasizes the importance of diagnostic efforts.

Adrenal Cortex Hormones↗

Deficient cerebral activation pattern in stroke recovery.

Specific cerebral activations induced by unilateral tactile discrimination of macrogeometric objects were identified in positron emission tomography images of regional cerebral blood flow in patients recovered from hemiplegic stroke and in healthy volunteers. Primary sensorimotor cortex, supplementary motor area, superior parietal lobule contralateral to moving hand, and premotor cortex on both sides were regularly activated in normals contrary to patients showing consistent activations only in the primary sensorimotor cortex. Furthermore, areas of activations in parietal association, premotor and midfrontal cortical areas were far less consistently activated in patients than in healthy subjects. These results demonstrated in correspondence to the clinical observations that the patients had regained their ability to move the fingers of the affected hand but remained impaired in tactile discrimination.

Adult↗

Tactile exploration of shape after subcortical ischaemic infarction studied with PET.

We studied the cerebral activations related to restitution of hand function in five patients with first hemiplegic subcortical stroke due to ischaemic infarction in the area of the basal ganglia or thalamus. In two subjects, involvement of the cortico-spinal tract was demonstrated by magnetic evoked potentials. The subjects were requested to discriminate rectangular parallelepipeda of identical mass with their affected hands. Regional cerebral blood flow (rCBF) was measured with PET after intravenous bolus injection of [15O]butanol, at rest and during task execution. Evaluation of the rCBF changes was based on pixel-by-pixel t statistics of spatially standardized and averaged PET images and on a statistical distribution analysis of regions of interest in the individual subjects. For anatomical localization of the significant rCBF changes, a computerized brain atlas (Greitz et al. J Comput Assist Tomogr 1991; 15: 26-38) and a matching procedure that directly aligns individual PET and high resolution magnetic resonance images were used. The rCBF at rest and the task-induced rCBF changes varied from subject to subject, as did the residual neurological deficits at the time of PET scanning. In all subjects there were large activation areas in the motor and the sensory hand area contralateral to the affected hand. Poor performance of the task was correlated with a low rCBF in the contralateral sensorimotor cortex at rest and a bilateral activation of the primary sensorimotor cortex during task performance. The premotor cortex, ipsilateral and anterior cerebellum, contralateral to the affected hand, were also significantly activated. Further activations were observed in the contralateral premotor cortex, supplementary motor area and bilaterally in the posterior cingulate cortex, but were less consistent among the subjects. Our data suggest that recovery from hemiplegic stroke is associated with a marked reorganization of the cerebral activation patterns, including common and subject-specific activation sites. With respect to task-specific information processing a lower discrimination rate of objects compared with controls was associated with diminished activations in parietal lobe.

Adult↗

Single photon emission computed tomography with 99mTc hexamethyl propylene amine oxime (HMPAO) and focal motor seizures.

The proper localization of regions of interest (ROIs) in Single Photon Emission Computed Tomography (SPECT) is an essential task. The limited spatial resolution makes it difficult to define regions by their structure. The particular problems are: 1) the difficulty to find the appropriate slice and its orientation in space; 2) the individual variation of the brain in dimension and shape. Referring to the basic work of Talairach and Szikla (1967), research is conducted to overcome these methodical problems in interpreting cranial computed tomography by using a proportional localization system. We analyzed four cases with focal motor seizures of different aetiology (tumour, hemorrhagic infarction, intracerebral hematoma, multifocal leukencephalopathy) by 99mTc HMPAO SPECT. The accumulation of the radiopharmacon was measured in ROIs which were delineated with the aid of the above mentioned system. The regions were selected in accordance to the autoradiographic study of penicillin induced epileptic seizures in animal experiments. Dependent on the severity of the clinical manifestation we were able to document the involvement of the supposed primary focus and of several related zones. We suggest that this approach should prove some usefulness in the examination of the interdependency of different brain areas.

Adult↗

In vitro and in vivo testing of the dopamine D1 ligand [123I]SCH 23982 with respect to its potential application in SPET investigations.

[123I]SCH 23982, a dopamine D1 ligand, was labelled in a large scale process and then tested in vitro for binding to rat brain sections and membranes. Because of the promising values of KD = 1.5 x 10(-10) M and Bmax = 0.7 x 10(-11) mol/g, in vivo evaluation was performed on rats and normal volunteers to test its possible usefulness for SPET imaging. In competition experiments, a higher binding in the presence of sulpiride was found while ketanserin displaced [123I]SCH 23982 only at a 10,000-fold excess. Differences between rats and men were seen with respect to their metabolism. SPET investigations failed because the washout of [123I]SCH 23982 was too rapid.

Aged↗