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Cornelius Weiller

Publications and source records attributed to Cornelius Weiller.

At least 19 recordsLinked to original sources
PubMed2006

The effect of handedness on cortical motor activation during simple bilateral movements.

The neuronal correlates of handedness are still poorly understood. Here we used event-related functional magnetic resonance imaging to investigate the impact of handedness on neuronal activation of the primary sensorimotor cortex, supplementary motor area and dorsal premotor cortex during simple unilateral and bilateral finger movements. In 16 right-handed and 16 left-handed individuals, we mapped changes in regional neuronal activity while participants responded to four symbolic cues presented in a pseudorandom order. According to pre-specified cues, they pressed a button with their right, left or both index fingers or withheld a response. For unilateral right index finger button presses, reaction times, motor and premotor activity were the same for both right- and left-handers. Compared with right-handers, left-handers had shorter reaction times with unilateral left index finger button presses, along with greater activation of the supplementary motor area and right frontal opercular cortex. Simultaneous bilateral compared with unilateral button presses led to a relative increase of activity in the right and left dorsal premotor cortex and the right primary sensorimotor cortex in right but not left-handers. Neither right nor left-handers showed any tendency during bilateral button presses towards faster responses with the dominant hand and the reaction times were equal in the two groups. Therefore, we conclude that the relative increase of activity in dorsal premotor and right primary sensorimotor cortices in right-handers represents a genuine difference in bimanual motor control related to handedness.

Adult↗
PubMed2006

Iomazenil-single-photon emission computed tomography reveals selective neuronal loss in magnetic resonance-defined mismatch areas.

BACKGROUND AND PURPOSE: The mismatch of hypoperfused tissue on perfusion imaging and ischemic tissue on diffusion-weighted imaging is used as a surrogate marker for thrombolytic therapy in the extended time window. Mismatch tissue may recover completely, progress toward infarction, or proceed toward incomplete infarction with selective loss of cortical neurons. We used [(123)I]iomazenil-single-photon emission computed tomography (IMZ-SPECT) to characterize the neuronal integrity of reperfused "tissue at risk of infarction" that appeared morphologically intact on follow-up magnetic resonance imaging (MRI). METHODS: Twelve patients with acute stroke with striatocapsular (SC) infarctions were examined with multimodal MRI at days 0, 1, and 7; IMZ-SPECT was performed at days 5 to 15. The PI at day 0, fluid-attenuated inversion recovery (FLAIR) image at day 7, and IMZ-SPECT were coregistered and stereotactically normalized. The mismatch volume of interest (VOI) was defined as the initial PI lesion subtracted by the FLAIR lesion at day 7. An asymmetry ratio (AR) was computed by dividing the mean IMZ uptake of the mismatch VOI by the unaffected mirror VOI. The same AR was computed for signal intensity on FLAIR images at day 7. Three patients with cortical infarctions were included for calibration of the AR. In this group, the VOI consisted of the FLAIR lesion at day 7. RESULTS: All patients with SC infarctions had a large mismatch of initially hypoperfused (112+/-31 mL; mean+/-SD) and finally infarcted tissue (19+/-14 mL). Mean AR of cortical IMZ uptake was 0.85+/-0.01 in cortical infarctions and 0.95+/-0.03 in SC infarctions; thereby AR showed a continuous distribution from clearly reduced (0.89) to normal (1.01) in SC infarctions. Mean AR for FLAIR signal intensity was 1.84+/-0.14 for cortical infarctions and normal (1.01+0.03) for SC infarctions. CONCLUSIONS: IMZ-SPECT detected a selective loss of cortical neurons in patients with SC infarctions in transient hypoperfused tissue, which was morphologically intact on MRI.

Adult↗
PubMed2006

Oscillatory cerebral hemodynamics--the macro- vs. microvascular level.

The phase shift between oscillations of blood pressure (BP) and Doppler middle cerebral artery flow velocity (MCAFV) reflects continuous cerebral autoregulatory action. It is not known whether a similar phase shift exists for cortical hemodynamics ('microvascular level') assessed by near infrared spectroscopy (NIRS) and what the effects are of pathological conditions. This study investigates the phase relations between oscillations of BP, MCAFV and NIRS parameters in 38 healthy older adults and 28 patients with unilateral severe obstructive carotid disease. BP was recorded noninvasively by finger plethysmography. Stable 0.1 Hz oscillations of all hemodynamic parameters were induced by regular breathing at a rate of 6/min. Basic results were that: (1) BP-induced cortical microvascular oscillations (NIRS) follow those of macrovascular oscillations (MCAFV) with a phase of 80-90 degrees (corresponding to 2-2.5 s at 0.1 Hz), most likely reflecting a transit time phenomenon; (2) oxy- and deoxyhemoglobin thereby oscillate in counterphase; (3) hemodynamic compromise in carotid obstruction leads to (a) delayed NIRS oscillations in comparison to BP which are highly correlated to a shorter phase lead of MCAFV against BP and (b) a decoupling of the oxy-/deoxyhemoglobin counterphase to 240 degrees . Cortical hemodynamic responses to BP oscillations follow specific phase relationships due to cerebral autoregulatory action and circulatory transit times. With hemodynamic impairment, as in unilateral carotid obstruction, these phases are significantly changed reflecting disturbed autoregulation.

Aged↗
PubMed2006

Combined measurement of carotid stiffness and intima-media thickness improves prediction of complex aortic plaques in patients with ischemic stroke.

BACKGROUND AND PURPOSE: We hypothesized that for the prediction or exclusion of aortic thrombi or plaques >or=4 mm, the combination of intima-media thickness (IMT) and distensibility (DC) of the common carotid arteries would be superior to the measurement of IMT alone. METHODS: We prospectively included 208 stroke patients (mean age, 60 years) undergoing transesophageal echocardiography for screening of aortic plaques. IMT and DC were determined by ultrasound, and DC was quantified by measuring blood pressure and the common carotid arteries diameter change on M-mode ultrasound during the cardiac cycle. RESULTS: Negative predictive values of IMT <0.9 mm and DC >or=24x10(-3)/kPa for the exclusion of aortic atheroma >or=4 mm were similar (92.0% and 91.7%, respectively). However, negative predictive values increased to 98.2% and to 100.0% for the exclusion of aortic thrombi when both parameters were combined. Positive predictive values of IMT >or=0.9 mm and DC <24 were lower (46.3%, 41.1%; respectively), but they also increased in combination (54.3%). CONCLUSIONS: Our findings suggest that IMT and DC represent different vessel wall properties and that measuring both parameters provides optimized characterization of carotid atherosclerosis. Combining IMT and DC increases the predictive power of carotid ultrasound, making transesophageal echocardiography dispensable for assessment of the aorta for those with normal carotid arteries and indispensable for those patients with carotid atherosclerosis.

Adult↗
PubMed2006

The surround inhibition determines therapy-induced cortical reorganization.

Rehabilitation can induce cortical reorganization in chronic stroke patients. In this study we investigated the mechanisms underlying treatment-associated plasticity. Eight patients with a stroke >6 months earlier participated in a 4-week period of physiotherapy based on a forced use concept. Before and after treatment, focal transcranial magnetic stimulation over the affected hemisphere was used to assess the motor output map of the paretic first dorsal interosseous muscle. Using a paired pulse paradigm, intracortical inhibition was investigated at the center of the cortical output map (CoG) and one cm anterior, posterior, lateral and medial of that position. Motor function was evaluated with the Motor Activity Log and the Wolf Motor Function Test. After therapy, the cortical representation size of the affected hand muscle was increased. In each patient, the CoG moved in the direction where intracortical inhibition had been lowest prior to therapy. Significant correlations were found between motor function tests and changes of output map size and CoG shifts, respectively. We conclude that treatment-associated cortical reorganization is influenced by the distribution of inhibitory properties within the representation area prior to therapy, since the CoG moved in the direction of lowest inhibition. The correlations between motor functions and electrophysiological results indicate a functional relevance of the observed reorganization pattern.

Adult↗
PubMed2006

Dynamics of language reorganization after stroke.

Previous functional imaging studies of chronic stroke patients with aphasia suggest that recovery of language occurs in a pre-existing, bilateral network with an upregulation of undamaged areas and a recruitment of perilesional tissue and homologue right language areas. The present study aimed at identifying the dynamics of reorganization in the language system by repeated functional MRI (fMRI) examinations with parallel language testing from the acute to the chronic stage. We examined 14 patients with aphasia due to an infarction of the left middle cerebral artery territory and an age-matched control group with an auditory comprehension task in an event-related design. Control subjects were scanned once, whereas patients were scanned repeatedly at three consecutive dates. All patients recovered clinically as shown by a set of aphasia tests. In the acute phase [mean: 1.8 days post-stroke (dps)], patients' group analysis showed little early activation of non-infarcted left-hemispheric language structures, while in the subacute phase (mean: 12.1 dps) a large increase of activation in the bilateral language network with peak activation in the right Broca-homologue (BHo) was observed. A direct comparison of both examinations revealed the strongest increase of activation in the right BHo and supplementary motor area (SMA). These upregulated areas also showed the strongest correlation between improved language function and increased activation (r(BHo) = 0.88, r(SMA) = 0.92). In the chronic phase (mean: 321 dps), a normalization of activation with a re-shift of peak activation to left-hemispheric language areas was observed, associated with further language improvement. The data suggest that brain reorganization during language recovery proceeds in three phases: a strongly reduced activation of remaining left language areas in the acute phase is followed by an upregulation with recruitment of homologue language zones, which correlates with language improvement. Thereafter, a normalization of activation is observed, possibly reflecting consolidation in the language system.

Acute Disease↗
PubMed2006

Two different reorganization patterns after rehabilitative therapy: an exploratory study with fMRI and TMS.

We used two complementary methods to investigate cortical reorganization in chronic stroke patients during treatment with a defined motor rehabilitation program. BOLD ("blood oxygenation level dependent") sensitive functional magnetic resonance imaging (fMRI) and intracortical inhibition (ICI) and facilitation (ICF) measured with transcranial magnetic stimulation (TMS) via paired pulse stimulation were used to investigate cortical reorganization before and after "constraint-induced movement therapy" (CI). The motor hand function improved in all subjects after CI. BOLD signal intensity changes within affected primary sensorimotor cortex (SMC) before and after CI showed a close correlation with ICI (r = 0.93) and ICF (r = 0.76) difference before and after therapy. Difference in number of voxels and ICI difference before and after CI also showed a close correlation (r = 0.92) in the affected SMC over the time period of training. A single subject analysis revealed that patients with intact hand area of M1 ("the hand knob") and its descending motor fibers (these patients revealed normal motor evoked potentials [MEP] from the affected hand) showed decreasing ipsilesional SMC activation which was paralleled by an increase in intracortical excitability. This pattern putatively reflects increasing synaptic efficiency. When M1 or its descending pyramidal tract was lesioned (MEP from the affected hand was pathologic) ipsilesional SMC activation increased, accompanied by decreased intracortical excitability. We suggest that an increase in synaptic efficiency is not possible here, which leads to reorganization with extension, shift and recruitment of additional cortical areas of the sensorimotor network. The inverse dynamic process between both complementary methods (activation in fMRI and intracortical excitability determined by TMS) over the time period of CI illustrates the value of combining methods for understanding brain reorganization.

Aged↗
PubMed2006

Outcome and symptomatic bleeding complications of intravenous thrombolysis within 6 hours in MRI-selected stroke patients: comparison of a German multicenter study with the pooled data of ATLANTIS, ECASS, and NINDS tPA trials.

BACKGROUND AND PURPOSE: We compared outcome and symptomatic bleeding complications of intravenous tissue plasminogen activator (IV-tPA) within 6 hours of symptom onset in MRI-selected patients with acute middle cerebral artery infarction with the pooled data of the large stroke tPA trials. METHODS: Patients were examined by perfusion-weighted and diffusion-weighted imaging < or =6 hours. Within 3 hours, patients were treated according to Second European-Australasian Acute Stroke Study (ECASS II) criteria. After 3 to 6 hours, treatment with IV-tPA was performed based on MRI findings. Favorable outcome was assessed after 90 days using a dichotomized modified Rankin scale score of 0 to 1. Intracerebral bleeding complications were assessed on follow-up MRI or computed tomography. Data were compared with the pooled placebo and pooled tPA patients of the ATLANTIS, ECASS, and National Institute of Neurological Disorders and Stroke (NINDS) tPA trials. RESULTS: From 174 MRI-selected tPA patients, 62% (n=108) were treated in < or =3 hours and 38% (n=66) after 3 to 6 hours. Favorable outcome was more frequent in MRI-selected tPA patients (48% [95% CI, 39 to 54]) compared with pooled placebo (33% [95% CI, 31 to 36]; P<0.001) and pooled tPA patients (40% [95% CI, 37 to 42]; P=0.046). Odds ratios for favorable outcome in the MRI-selected tPA group were 1.82 (1.32 to 2.51) compared with the pooled placebo and 1.39 (1.01 to 1.92) compared with the pooled tPA group. The rate of symptomatic intracerebral hemorrhage in MRI-selected tPA patients (3% [95% CI, 0 to 5]) was lower than in the pooled tPA group (8% [95% CI, 7 to 10]; P=0.012) and comparable to the pooled placebo group (2% [95% CI, 1 to 3]; P=0.392). CONCLUSIONS: This study supports that it is safe and effective to expand the time window for IV-tPA up to 6 hours in patients with tissue at risk as defined by MRI.

Adolescent↗
PubMed2006

Role of functional imaging in neurological disorders.

Neuroimaging in recent years has greatly contributed to our understanding of a wide range of aspects related to central neurological diseases. These include the classification and localization of disease, such as in headache; the understanding of pathology, such as in Parkinson's disease (PD); the mechanisms of reorganization, such as in stroke and multiple sclerosis (MS); and the subclinical progress of disease, such as in amyotrophic lateral sclerosis (ALS). Apart from presurgical mapping, however, the clinical applications so far are limited. Nevertheless, functional imaging does enable the formulation of neurobiological hypotheses that can be tested clinically, and thus is well suited for testing classic clinical hypotheses about how the brain works. Understanding the mechanisms and sites of pathology, such as has been achieved in cluster headaches, facilitates the development of new therapeutic strategies.

Animals↗
PubMed2006

Elevated levels of neural recognition molecule L1 in the cerebrospinal fluid of patients with Alzheimer disease and other dementia syndromes.

In this study we surveyed a total of 218 cerebrospinal fluid (CSF) samples from patients with different neurological diseases including Alzheimer disease, non-Alzheimer forms of dementia, other neurodegenerative diseases without dementia and normal controls to quantitate by capture ELISA the concentrations of the immunoglobulin superfamily adhesion molecules L1 and NCAM, and characterized by immunoblot analysis the molecular forms of L1 and NCAM. We found a significant increase of L1 and a strong tendency for increase of the soluble fragments of NCAM in the CSF of Alzheimer patients compared to the normal control group. The proteolytic fragments of L1, but not NCAM were also elevated in patients with vascular dementia and dementia of mixed type. Higher L1 concentrations were observed irrespective of age and gender. NCAM concentrations were independent of gender, but positively correlated with age and, surprisingly, also with incidence of multiple sclerosis. Thus, there was an influence of Alzheimer and non-Alzheimer dementias and neurodegeneration on L1, whereas age and neurodegeneration influenced NCAM concentrations. These observations point to an abnormal processing and/or shedding of L1 and NCAM in dementia-related neurodegeneration and age, respectively, reflecting changes in adhesion molecule-related cell interactions.

Adult↗
PubMed2006

Cerebral vasculitis following oral methylphenidate intake in an adult: a case report.

Methylphenidate is structurally and functionally similar to amphetamine. Cerebral vasculitis associated with amphetamine abuse is well documented, and in rare cases ischaemic stroke has been reported after methylphenidate intake in children. We report the case of a 63-year-old female who was treated with methylphenidate due to hyperactivity and suffered from multiple ischaemic strokes. We consider drug-induced cerebral vasculitis as the most likely cause of recurrent ischaemic strokes in the absence of any pathological findings during the diagnostic work-up. We conclude that methylphenidate mediated vasculitis should be considered in patients with neurological symptoms and a history of methylphenidate therapy. This potential side-effect, though very rare, represents one more reason to be very restrictive in the use of methylphenidate.

Acute Disease↗
PubMed2005

Motor strokes: the lesion location determines motor excitability changes.

BACKGROUND AND PURPOSE: The purpose of this research was to investigate the impact of lesion location on motor excitability and motor performance. METHODS: We studied patients with pure motor strokes in 4 different brain areas: motor cortex lesions (n=7), striatocapsular lesions (n=13), lacunar lesions of the internal capsule (n=13), and paramedian pontine lesions (n=10). Motor performance tests included the 9-hole-peg test and grip strength recordings. Motor excitability was determined by transcranial magnetic stimulation. Motor thresholds, stimulus-response curves, silent periods, motor cortical inhibition, and facilitation were investigated. RESULTS: The 4 groups were clinically similar but showed major differences in motor excitability. Only motor cortex lesions had a loss of intracortical inhibition in the affected hemisphere. In the internal capsule lesion group and the pontine lesion group, stimulus-response curves were depressed on the affected side. All of the subcortical lesions showed a prolongation of the silent period in the paretic side. Motor thresholds were predominantly elevated in the lesioned hemisphere of patients with internal capsule or pontine lesions. Motor performance was correlated with silent period duration in internal capsule lesions and with motor thresholds in internal capsule and pontine lesions. CONCLUSIONS: Motor cortex lesions exhibited deficient inhibitory properties. In contrast, subcortical lesions displayed an enhancement of inhibition. Internal capsule and pontine lesions affecting the corticospinal tract on different levels particularly impaired neuronal recruitment. Our results suggest that the lesion location determines a specific pattern of motor excitability changes.

Aged↗
PubMed2005

Implementation of visuospatial cues in response selection.

We used functional magnetic resonance imaging to examine neuronal activity reflecting the dynamic interplay of external and internal guidance of action. Participants performed a choice reaction time task based on spatial visual cues with their right and left middle and index finger. In a given trial, the cue either fully determined the motor response (no-selection) or indicated the number and location of alternative responses (selection). Compared with fully determined responses, the selection among (two to four) alternative responses activated a widespread bilateral parieto-premotor-prefrontal cortical network along with the cerebellum. Within this network, task-related activity patterns allowed to delineate two sets of brain areas. In the anterior part of rostral dorsal premotor cortex (PMd), the rostral cingulate and supplementary motor area and the right dorsolateral prefrontal cortex, the increase in activity was independent of spatially defined restrictions. In contrast, there was an additional increase in activity in the posterior part of rostral PMd, superior parietal lobule and parieto-occipital sulcus bilaterally as well as in the right anterior intraparietal sulcus, when the visuospatial cue imposed specific constraints on response selection. We propose that the latter set of dorsal parieto-frontal areas subserves rapid implementation of spatial information during visually guided response selection.

Adult↗
PubMed2005

Reperfusion after severe local perfusion deficit precedes hemorrhagic transformation: an MRI study in acute stroke patients.

BACKGROUND: We applied magnetic resonance imaging to analyze the degree of local diffusion and perfusion abnormalities and the status of reperfusion in regions with subsequent hemorrhagic transformation (HT). METHODS: 51 patients with acute ischemic stroke were studied by diffusion- and perfusion-weighted imaging within 3.0 +/- 0.8 h, on day 1 and days 5-8. After realignment of the image data sets, the parameter maps of the apparent diffusion coefficient (ADC), cerebral blood flow (CBF) and cerebral blood volume (CBV), and mean transit time were analyzed in the area of subsequent HT. The degree of local diffusion and perfusion impairment in the HT area was compared with the entire diffusion and perfusion abnormality. Reperfusion status was separately assessed for the entire perfusion abnormality and the HT area. RESULTS: HT was observed in 19/51 patients (37.2%) within 8 days after symptom onset. Areas destined for HT revealed a more severe decrease in ADC (to 70 +/- 13%; p < 0.01), CBV (to 31 +/- 26%; p < 0.001) and CBF (to 28 +/- 19%; p < 0.001) compared to the entire perfusion abnormality. Local reperfusion in the HT area was seen in 18/19 patients. The presence of HT did not coincide with a worse clinical outcome. DISCUSSION: HT is the result of reperfusion in the region with the most severe local perfusion impairment and does not influence the neurological outcome.

Age Factors↗
PubMed2005

Distributed form of constraint-induced movement therapy improves functional outcome and quality of life after stroke.

OBJECTIVE: To evaluate the effectiveness of a distributed version of constraint-induced movement therapy (CIMT). DESIGN: Within-subjects control intervention study. SETTING: Outpatient rehabilitation center. PARTICIPANTS: Eleven persons with chronic stroke. All had active extension of at least 20 degrees at the wrist and at least 10 degrees for each finger of the more-affected hand. INTERVENTIONS: Intensive motor training of the more-affected arm for 3 hours a day for 20 days; restraint of the other arm for 9.3 hours daily to limit its use. This intervention provides the same amount of training as provided in the conventional CIMT therapy protocol (60 h) but distributes training time over twice the number of days. MAIN OUTCOME MEASURES: Real-world (Motor Activity Log) and laboratory motor activity (Wolf Motor Function Test, Frenchay Arm Test, Nine Hole Peg Test), strength (grip force) and spasticity (Ashworth Scale), and quality of life (QOL; Stroke Impact Scale) were assessed. RESULTS: Participants showed significant improvements in more-affected arm real-world motor activity, laboratory motor activity, strength and spasticity, as well as in some aspects of QOL, up to 6 months after treatment ( P .05). CONCLUSIONS: Distributed CIMT is a promising intervention for improving motor function and QOL in patients with chronic stroke.

Adult↗
PubMed2005

Contributions of occipital, parietal and parahippocampal cortex to encoding of object-location associations.

Events are stored in our episodic memory in varying degrees of accessibility for conscious retrieval and combined with varying amounts of associated information. A crucial aspect of episodic memory is to bind information together, e.g. linking an object to a certain location. Spontaneous or experimenter-induced variance in the allocation of attentional resources during encoding critically determines the strength of the resulting memory trace especially for associative information as measured in subsequent memory tests. The neural correlates of associative memory encoding were investigated by lesion, PET- and fMRI-studies. So far no study aimed to assess the memory for associative information in a non-categorical way. Such a parametric assessment opens the possibility for a closer inspection of the relationship between brain activity and memory trace formation. We established a novel associative object-location memory paradigm, together with a parametric assessment of subsequent memory performance for spatial location which allows: (i) to determine if associative information is retrieved in a continuous or discontinuous manner during recognition and (ii) to investigate the relationship between activity during encoding and the resulting memory trace. Such correlations were observed in the occipital, parietal and the parahippocampal cortex, areas known to be involved in processing either objects and/or locations. The analysis of response functions revealed for the majority of areas involved in encoding a continuous relationship between brain activity during encoding and the confidence in a subsequent memory test.

Adult↗
PubMed2005

Individual factors in constraint-induced movement therapy after stroke.

OBJECTIVES: Constraint-induced movement therapy (CIMT) has been shown to be effective in chronic stroke patients. It is worthwhile to investigate the influence of individual factors for two reasons: to find out whether they influence outcome and to see whether they support the theory underlying CIMT. METHODS: A group of 26 patients were treated with CIMT and followed over 6 months. In total, 14 individual factors were identified. Patients were assessed with 6 tests, including 2 commonly used after stroke (Frenchay Arm Test, 9 Hole Peg Test). RESULTS: There were individual differences, but as a group, patients improved after therapy. There were no individual factors that influenced improvement in more than one test. CONCLUSIONS: CIMT is an effective therapy in patients with moderate impairment after stroke, also in tests commonly used in stroke rehabilitation. Factors that could have expected to make a difference on the basis of the theory behind CIMT (e.g., time since stroke, previous therapy, sensory deficit) did not influence results. Patients with hemorrhagic lesions and those with a high level of performance (Motor Activity Log > 2.5) profit as well. Pairwise therapy is as effective as individual therapy.

Adolescent↗