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U Knorr

Publications and source records attributed to U Knorr.

At least 19 recordsLinked to original sources
PubMed2002

[Extracorporeal shockwave therapy in symptomatic heel spurs. An overview].

Extracorporeal shock wave application (ESWA) has been successfully used for years in routine clinical management of plantar fasciitis. So far no clinical trails have shown the efficiency in placebo-controlled protocols. This paper presents an overview of conservative and operative treatment modalities with respect to their efficacy. Results of a prospective randomized placebo-controlled double-blind multicenter trial to show efficiency and safety of ESWT are presented. In patients treated conservatively without success, a single shock wave application can improve the condition significantly compared with placebo treatment (p = 0.0149). The Roles and Maudsley score also showed a significant improvement between the groups, with 61.6% good or excellent results in the verum group and 39.7% in the placebo group (p = 0.0128). Therapy-related side effects (local swelling, petechia) are rare. The data presented in this study led to FDA approval in January 2002 of the shock wave device used.

Adult↗
PubMed2001

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↗
PubMed2000

Corpus callosum size in children with developmental language disorder.

Using high-resolution in-vivo magnetic resonance morphometry of the midsagittal area of the corpus callosum (CC) and four callosal subareas in 21 children with developmental language disorder (DLD) of the phonologic-syntactic type we found no significant anatomical differences in comparison to an age- and gender-matched normal control group. There was also no significant between-group difference when the approximately 7% smaller forebrain volume among children with DLD was accounted for by relating CC measures to forebrain volume. Only a tendency towards a larger anterior and middle CC in relation to forebrain volume was found in DLD children. In our DLD children we found the same relationship between CC midsagittal size and forebrain volume as recently reported for normal adults, namely, that the CC area increases to the two-third power of forebrain volume.

Child↗
PubMed2000

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↗
PubMed1999

Reorganized cerebral metabolic interactions in temporal lobe epilepsy.

Patients with left temporal lobe epilepsy demonstrate language impairments that are not well understood. To explore abnormal patterns of brain functional connections with respect to language processing, we applied a principal component analysis to resting regional cerebral metabolic data obtained with positron emission tomography in patients with right- and left-sided temporal lobe epilepsy and controls. Two principal components were expressed differentially among the groups. One principal component comprised a pattern of metabolic interactions involving left inferior frontal and left superior temporal regions-corresponding to Broca's and Wernicke's areas, respectively-and right mesial temporal cortex and right thalamus. Functional couplings between these brain regions were abnormally enhanced in the left-sided epilepsy patients. The right thalamic left superior temporal coupling was also abnormally enhanced in the right-sided epilepsy patients, but differentially from that in the left-sided patients. The other principal component was characterized by a pattern of metabolic interactions involving right and left mid prefrontal and right superior temporal cortex. Although both the right- and left-sided epilepsy patients showed decreased functional couplings between left mid prefrontal and the other brain regions, a weaker right-left mid prefrontal coupling in the left-sided epilepsy patients best distinguished them from the right-sided patients. The two mutually independent, abnormal metabolic patterns each predicted verbal intelligence deficits in the patients. The findings suggest a site-dependent reorganization of two independent, language-subserving pathways in temporal lobe epilepsy.

Adolescent↗
PubMed1999

The role of diaschisis in stroke recovery.

BACKGROUND AND PURPOSE: Recovery from hemiparesis after stroke has been shown to involve reorganization in motor and premotor cortical areas. However, whether poststroke recovery also depends on changes in remote brain structures, ie, diaschisis, is as yet unresolved. To address this question, we studied regional cerebral blood flow in 7 patients (mean+/-SD age, 54+/-8 years) after their first hemiparetic stroke. METHODS: We analyzed imaging data voxel by voxel using a principal component analysis by which coherent changes in functional networks could be disclosed. Performance was assessed by a motor score and by the finger movement rate during the regional cerebral blood flow measurements. RESULTS: The patients had recovered (P<0. 001) from severe hemiparesis after on average 6 months and were able to perform sequential finger movements with the recovered hand. Regional cerebral blood flow at rest differentiated patients and controls (P<0.05) by a network that was affected by the stroke lesion. During blindfolded performance of sequential finger movements, patients were differentiated from controls (P<0.05) by a recovery-related network and a movement-control network. These networks were spatially incongruent, involving motor, sensory, and visual cortex of both cerebral hemispheres, the basal ganglia, thalamus, and cerebellum. The lesion-affected and recovery-related networks overlapped in the contralesional thalamus and extrastriate occipital cortex. CONCLUSIONS: Motor recovery after hemiparetic brain infarction is subserved by brain structures in locations remote from the stroke lesion. The topographic overlap of the lesion-affected and recovery-related networks suggests that diaschisis may play a critical role in stroke recovery.

Adult↗
PubMed1999

On two methods of statistical image analysis.

The computerized brain atlas (CBA) and statistical parametric mapping (SPM) are two procedures for voxel-based statistical evaluation of PET activation studies. Each includes spatial standardization of image volumes, computation of a statistic, and evaluation of its significance. In addition, smoothing and correcting for differences of global means are commonly performed in SPM before statistical analysis. We report a comparison of methods in an analysis of regional cerebral blood flow (rCBF) in 10 human volunteers and 10 simulated activations. For the human studies, CBA or linear SPM standarization methods were followed by smoothing and computation of a statistic with the paired t-test of CBA or general linear model of SPM. No standardization, linear, and nonlinear SPM standardization were applied to the simulations. Significance of the statistic was evaluated using the cluster-size method common to SPM and CBA. SPM employs the theory of Gaussian random fields to estimate the cluster size distributions; simulations described in the Appendix provided empirical distributions derived from t-maps. The quantities evaluated were number and size of functional regions (FRs), maximum statistic, average resting rCBF, and percentage change. For the simulations, the efficiency of signal detection and rate of false positives could be evaluated as well as the distributions of statistics and cluster size in the absence of signal. The similarity of the results yielded by similar methods of analysis for the human studies and the simulated activations substantiates the robustness of the methods for selecting functional regions. However, the analysis of simulated activations demonstrated that quantitative evaluation of significance of a functional region encounters important obstacles at every stage of the analysis.

Adult↗
PubMed1998

Multimodal output mapping of human central motor representation on different spatial scales.

1. Non-invasive mapping by focal transcranial magnetic stimulation (TMS) is frequently used to investigate cortical motor function in the intact and injured human brain. We examined how TMS-derived maps relate to the underlying cortical anatomy and to cortical maps generated by functional imaging studies. 2. The centres of gravity (COGs) of TMS maps of the first dorsal intersosseus muscle (FDI) were integrated into 3-D magnetic resonance imaging (MRI) data sets in eleven subjects. In seven of these subjects the TMS-derived COGs were compared with the COG of regional cerebral blood flow increases using positron emission tomography (PET) in an index finger flexion protocol. 3. Mean TMS-derived COG projections were located on the posterior lip of the precentral gyrus and TMS-derived COG projections were in close proximity to the mean PET-derived COG, suggesting that the two methods reflect activity of similar cortical elements. 4. Criteria for a reliable assessment of the COG and the number of positions with a minimum amplitude of two-thirds of the maximum motor-evoked potential (T3Ps) were determined as a function of the number of stimuli and extension of the stimulation field. COGs and T3Ps were compared with an estimate of the size of the human motor cortex targeting alpha-motoneurons of forearm muscles. This comparison suggests that TMS can retrieve spatial information on cortical organization below the macroanatomic scale of cortical regions. 5. Finally, we studied the cortical representation of hand muscles in relation to facial and foot muscle representations and investigated hemispherical asymmetries. We did not find any evidence for a different ipsi- or contralateral representation of the mentalis muscle. Also, no difference was found between FDI representations on the dominant versus the non-dominant hemisphere.

Adult↗
PubMed1998

Precentral glioma location determines the displacement of cortical hand representation.

OBJECTIVE: Low-grade brain tumors may remain asymptomatic in contrast to malignant gliomas. The mechanisms underlying the preservation of cerebral function in such gliomas are not well understood. METHODS: We used positron emission tomography and transcranial magnetic stimulation for presurgical monitoring of motor hand function in six patients with gliomas of the precentral gyrus. All patients were able to perform finger movements of the contralesional hand. RESULTS: Movement-related increases of the regional cerebral blood flow occurred only outside the tumor in surrounding brain tissue. Compared with the contralateral side, these activations were shifted by 20 +/- 13 mm (standard deviation) within the dorsoventral dimension of the precentral gyrus. This shift of cortical hand representation could not be explained by the deformation of the central sulcus as determined from the spatially aligned magnetic resonance images but was closely related to the location of the maximal tumor growth. Dorsal tumor growth resulted in ventral displacement of motor hand representation, leaving the motor cortical output system unaffected, whereas ventral tumor growth leading to dorsal displacement of motor hand representation compromised the motor cortical output, as evident from transcranial magnetic stimulation. In two patients, additional activation of the supplementary motor area was present. CONCLUSION: Our data provide evidence for the reorganization of the human motor cortex to allow for preserved hand function in Grade II astrocytomas.

Adult↗
PubMed1997

Representations of graphomotor trajectories in the human parietal cortex: evidence for controlled processing and automatic performance.

The aim of this study was to identify the cerebral areas activated during kinematic processing of movement trajectories. We measured regional cerebral blood flow (rCBF) during learning, performance and imagery of right-hand writing in eight right-handed volunteers. Compared with viewing the writing space, increases in rCBF were observed in the left motor, premotor and frontomesial cortex, and in the right anterior cerebellum in all movement conditions, and the increases were related to mean tangential writing velocity. No rCBF increases occurred in these areas during imagery. Early learning of new ideomotor trajectories and deliberately exact writing of letters both induced rCBF increases in the cortex lining the right intraparietal sulcus. In contrast, during fast writing of overlearned trajectories and in the later phase of learning new ideograms the rCBF increased bilaterally in the posterior parietal cortex. Imagery of ideograms that had not been practised previously activated the anterior and posterior parietal areas simultaneously. Our results provide evidence suggesting that the kinematic representations of graphomotor trajectories are multiply represented in the human parietal cortex. It is concluded that different parietal subsystems may subserve attentive sensory movement control and whole-field visuospatial processing during automatic performance.

Adult↗
PubMed1995

[Excess mortality of severely handicapped patients in mandatory health insurance].

The introduction of compulsory long term care insurance as of 1.1. 1995 has temporarily brought to an end a whole range of controversial discussions, which have been strongly coloured by party political interests. The originally planned expenditure figure of at least DM 30 billion represents an enormous outlay in these time of economic recession. It is already abundantly clear that the premium payments will not be sufficient in the long run, nor will it be possible to increase these premiums arbitrarily. This therefore elicits the question as to whether it is possible to calculate in advance the cost of treatment for those "in serious need of nursing care" on the basis of various factors such as age, sex, underlying illness, therapy and social integration. Up to now, there has been very little statistical analysis of these parameters. For this reason, the company MDK has carried out a preliminary survey (which so far has only looked at a limited number of cases) in order to obtain a general idea of the variations in the period required for long term care. This survey has shown that there are two main groups of cases requiring care, which can be differently assessed on the basis of age and sex. On the one hand, there are those in serious need of nursing care, who, due to a life-threatening disease or as a result of an acute deterioration of an existing chronic condition (e.g. severe KHK, cirrhosis of the liver, decompensated renal insufficiency) die a relatively short time after the application for care is made.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Large-scale plasticity of the human motor cortex.

The adult primate brain is capable of modifying rapidly the size of cortical receptive fields or motor output modules in response to altered synaptic input. We used positron emission tomography (PET) to map the regional cerebral blood flow changes related to voluntary finger movements in patients with tumours occupying the hand area of motor cortex. All patients showed activations solely outside the tumour. Compared with the unaffected side, the activations were shifted by 9-43 mm either along the mediolateral body representation of motor cortex or into premotor or parietal somatosensory cortex. These results provide evidence that slowly developing lesions can induce large-scale reorganization that is not confined to changes within the somatotopic body representation in motor cortex.

Adult↗
PubMed1994

Successive roles of the cerebellum and premotor cortices in trajectorial learning.

The structures of the human brain engaged during learning of unilateral trajectorial hand movements were mapped by measurements of regional cerebral blood flow. Trajectorial movement velocity accelerated moderately after short-term training p < 0.025 and increased further after long-term training p < 0.01. During the early phase of learning there was a significant activation p < 0.001 of the ipsilateral dentate nucleus. By contrast, after overlearning the premotor cortical areas in both cerebral hemispheres were maximally activated p < 0.001, while the dentate nucleus was no longer activated. It is suggested that learning of new movement trajectories involves the cerebellum, while overlearned trajectorial movements engage the premotor cortex.

Cerebellum↗
PubMed1994

[A panorama of rheumatic diseases].

The developments in our health care system mean that the significance of chronic, cost-intensive diseases is continually increasing in terms of diagnosis, treatment and prevention. Under this aspect, rheumatic diseases may be regarded as prime examples in that they generate expenditure in many areas of both social insurance and private insurance. Although many of the disorders classified as rheumatic diseases manifest themselves clinically in the form of complaints in the region of the skeletal system, it should not be forgotten that they are actually systemic disorders, i.e. they have immunological or metabolic causes. This aspect plays a significant role with regard to the possibility of long-term prognosis and hence with regard to life expectancy as well. It also exerts a major influence on the selection of therapeutic concepts which are hoped to slow down the progress of a disease or stop it altogether. Precise inquiries, careful diagnosis, patient-specific therapy, and not least growing health consciousness should be capable of exerting a positive influence on the course of even relatively severe rheumatic conditions. The consequences will be felt to a corresponding degree by the private insurers too.

Arthritis, Rheumatoid↗
PubMed1994

A neuromagnetic study of the functional organization of the sensorimotor cortex.

Movement-related neuromagnetic fields from eight healthy human subjects were investigated in a Bereitschaftspotential paradigm. The three conditions studied were right-sided mouth, index finger and foot movement. The neuromagnetic field patterns corresponding to the motor field and the movement-evoked field I were analysed using a moving dipole model. For both components a somatotopic organization was found: the estimated dipole locations for the mouth were more lateral and those for the foot more medial than the estimated dipole positions for the index finger movement. With regard to possible clinical applications, e.g. non-invasive mapping of the sensorimotor cortex and studies of plasticity of the motor function, the present results suggest that the investigation of movement-evoked field I for the index finger condition is most likely to yield further results.

Adult↗
PubMed1994

Inter-subject variability of cerebral activations in acquiring a motor skill: a study with positron emission tomography.

Cerebral structures activated during sequential right-hand finger movements were mapped with regional cerebral blood flow (rCBF) measurements by positron emission tomography (PET) in individual subjects. Nine healthy volunteers were examined twice; after initial learning and after practicing the finger movement sequence for more than 1 h. Task-specific activation sites were identified by statistical distributions of maximal activity and region size in rCBF subtraction images. A consistent task-specific activation in all nine subjects was detected in the contralateral sensorimotor cortex at an average movement rate of 3.2 Hz reached after practice. This corresponded to a significant increase of the mean rCBF in the left primary sensorimotor cortex in spatially standardised and averaged PET images. Additional task-specific activation sites detected by individual analysis were found in the lateral and medial premotor, parietal, and cingulate areas, and in subcortical structures including the basal ganglia of both cerebral hemispheres. These activations showed no or little spatial overlap from subject to subject, thus being obscured in the analysis of pooled data. The observed activity patterns were related to movement rate and accuracy in individual subjects. It is suggested that the rCBF changes associated with acquisition of a motor skill in individual humans may correspond to plasticity of sensorimotor representations reported in monkeys.

Adult↗
PubMed1994

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↗