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Biomedical subjects

O Jansen

Publications and source records attributed to O Jansen.

At least 19 recordsLinked to original sources
PubMed2006

Voxel-based morphometry shows no decreases in cerebellar gray matter volume in essential tremor.

OBJECTIVE: To investigate cerebellar gray matter volume in patients with essential tremor (ET). METHODS: We used voxel-based morphometry (VBM) based on high-resolution T1-weighted MRI to compare gray and white matter density between 27 patients with ET and 27 age- and sex-matched healthy control subjects. Fourteen patients had only postural tremor, whereas 13 patients showed additional intention tremor. RESULTS: VBM failed to demonstrate regional decreases in gray and white matter volume in patients with ET. There was, however, an expansion in gray matter depending on the type of tremor. Compared with age-matched control groups, patients with intention tremor showed a relative expansion of gray matter bilaterally in the region of the temporoparietal junction and the right middle occipital cortex. CONCLUSIONS: The lack of a consistent decrease in gray and white matter density argues against a progressive neurodegenerative process in essential tremor that leads to a substantial decrease in cerebellar gray matter volume. Patients with predominant intention tremor show a relative expansion of gray matter areas involved in higher order visuospatial processing, which might represent a long-term result of adaptive reorganization compensating the higher demands on the visuospatial control of skilled movements in case of trembling.

Adult↗
PubMed2006

30 day results from the SPACE trial of stent-protected angioplasty versus carotid endarterectomy in symptomatic patients: a randomised non-inferiority trial.

BACKGROUND: Carotid endarterectomy is effective in stroke prevention for patients with severe symptomatic carotid-artery stenosis, and carotid-artery stenting has been widely used as alternative treatment. Since equivalence or superiority has not been convincingly shown for either treatment, we aimed to compare the two. METHODS: 1200 patients with symptomatic carotid-artery stenosis were randomly assigned within 180 days of transient ischaemic attack or moderate stroke (modified Rankin scale score of < or =3) carotid-artery stenting (n=605) or carotid endarterectomy (n=595). The primary endpoint of this hospital-based study was ipsilateral ischaemic stroke or death from time of randomisation to 30 days after the procedure. The non-inferiority margin was defined as less than 2.5% on the basis of an expected event rate of 5%. Analyses were on an intention-to-treat basis. This trial is registered at Current Controlled Trials with the international standard randomised controlled trial number ISRCTN57874028. FINDINGS: 1183 patients were included in the analysis. The rate of death or ipsilateral ischaemic stroke from randomisation to 30 days after the procedure was 6.84% with carotid-artery stenting and 6.34% with carotid endarterectomy (absolute difference 0.51%, 90% CI -1.89% to 2.91%). The one-sided p value for non-inferiority is 0.09. INTERPRETATION: SPACE failed to prove non-inferiority of carotid-artery stenting compared with carotid endarterectomy for the periprocedural complication rate. The results of this trial do not justify the widespread use in the short-term of carotid-artery stenting for treatment of carotid-artery stenoses. Results at 6-24 months are awaited.

Aged↗
PubMed2006

Selective affection of hippocampal CA-1 neurons in patients with transient global amnesia without long-term sequelae.

The aetiology, pathomechanisms and anatomical correlates of transient global amnesia (TGA) still remain obscure. Recently, focal MR-signal diffusion-weighted imaging (DWI) changes in the hippocampus have been described in patients with TGA, but the exact localization, long term outcome and pathophysiological nature of these lesions still remain unknown. The topography and time course of hippocampal DWI lesions in 41 TGA patients was studied using serial 3 T high-resolution MR-imaging and correlated to clinical and neuropsychometric results. Of these, 29 patients showed 36 DWI lesions with corresponding T(2) lesions in the hippocampus within a time window of 48 h after onset. Almost all lesions (94%; 34/36) were selectively found in the CA-1 sector (Sommer sector) of the hippocampal cornu ammonis. Most DWI lesions (8/10) were already detectable in the peri-acute phase <6 h after onset of symptoms. A follow-up study 4-6 months after the episode did not show evidence for residual structural sequelae of these lesions (n = 20/20). A venous MR angiography of the intracranial dural sinus showed an asymmetric venous drainage in 21/24 (88%) patients. In 11/16 (69%) patients with unilateral lesions, the asymmetry corresponded to the side of the DWI lesion. Significant episodic verbal memory deficits in the acute phase (n = 14/18) were associated with lesions of the dominant hemisphere while impairment of visuospatial memory was associated with lesions of the non-dominant hemisphere. Persistent neuropsychological sequelae were not detected 4-6 months after the episode (n = 16). This is the first prospective study combining high-resolution imaging and neuropsychometry analysing the detailed functional anatomy and outcome of hippocampal DWI/T(2) lesions in TGA supporting the view the TGA being a benign transient disorder. The TGA can be considered a model for a focal transient perturbation of memory circuits in the temporo-mesial region.

Adult↗
PubMed2006

[Endovascular therapy of stroke].

Standard therapy of acute ischaemic stroke during the first three hours after symptom onset is intravenous thrombolysis. When contraindications exist, an endovascular approach might be possible. Intraarterial administration of thrombolytic drugs is the most common way. Additionally, there is an increasing use of mechanical tools that are expected to be faster and more effective. Three principles of mechanical thrombolysis are known: aspiration, extraction and fracturing of the thrombus. Different tools were tested clinically and some demonstrated its high efficiency. Larger studies are needed to compare those tools. Apart from recanalization of a cerebral vessel occlusion implantation of a stent might be necessary for prophylaxis of recurrent stroke.

Anticoagulants↗
PubMed2005

Unusual locations for cavernous hemangiomas: report of two cases and review of the literature.

Cavernous hemangiomas are most commonly found within the subcortical neural parenchyma near the fissura Rolandi, in the basal ganglia, or in the brain stem. Because of advancing neuro-imaging technology and thus resulting in a higher incidence of cavernous hemangiomas they have rising impact in neurosurgery. We present two unusual cases of extra-axial cavernous hemangiomas: one located at the frontal falx, the other within the bone of the right frontal bone. We discuss these and other cases in the literature with respect to the more common differential diagnoses and the appropriate therapy regimen for cavernous hemangiomas in these locations.

Adult↗
PubMed2005

[MRI of carotid stents: influence of stent properties and sequence parameters on visualization of the carotid artery lumen].

PURPOSE: To evaluate MR artifacts of carotid artery stents and to optimize stent properties and sequence parameters. MATERIAL AND METHODS: Four carotid artery stents - Wallstent (mediloy), Precise (nitinol), ACCULINK (nitinol) and a stent prototype (nitinol) - were investigated in a flow model of the cervical vessels. The model was made of silicon tubing and a flow pump that produces realistic flow curves of the carotid artery. To investigate the effects of magnetic susceptibility and radiofrequency induced shielding artifacts, turbo spin echo and gradient echo sequences as well as CE-MRAs were measured. To improve the visualization of the stent lumen in a CE-MRA, flip angle as well as geometry and covering of the stent prototype were altered. RESULTS: Susceptibility artifacts in stents of the carotid artery only influence the lumen visualization at the proximal and distal end of the braided mediloy stent. A change of stent coverings has no significant influence on radiofrequency artifacts, whereas a reduction in linking elements between stent segments and a change in diameter of stent struts improves visualization of the stent lumen. By increasing the flip angle in a CE-MRA, visualization of the stent lumen is possible in both mediloy and nitinol stents. CONCLUSION: The choice of stent material and changes in stent geometry as well as the optimization of the flip angle of the CE-MRA may reduce susceptibility and radiofrequency artifacts, rendering feasible the CE-MRA of a stented carotid artery.

Alloys↗
PubMed2005

[Infectious diseases of brain parenchyma in adults: imaging and differential diagnosis aspects].

Infectious diseases of the central nervous system have often to be considered in differential diagnosis, particularly in immunocompromised persons. Neuroimaging, specifically advanced techniques such as diffusion-weighted MRI and perfusion MRI contribute much to the differentiation of various brain infections and to delineation of brain infections from other, for instance, neoplastic diseases. In this review we present the imaging criteria for the most important brain infections in adults and discuss in detail differential diagnostic aspects.

Adult↗
PubMed2005

[Cortical reorganization in children with connatal spastic hemiparesis -- a functional magnetic resonance imaging (FMRI) study].

PURPOSE: We applied fMRI to investigate atypical cortical activation in patients with connatal spastic hemiparesis using voluntary movements of the hand, foot, and tongue. The relation between the findings from fMRI and the motor dysfunction was examined. MATERIALS AND METHODS: 11 patients with connatal spastic hemiparesis were studied. Eight of these patients had periventricular leukomalacia (PVL), and three patients had cortical-subcortical lesions. To evaluate the severity of motor impairment tests for the upper and lower limb were performed. fMRI data were obtained in a block design using hand, foot, and tongue movements. As a control group, 14 healthy volunteers were examined with the fMRI protocol. RESULTS: A laterally cortical representation of the paretic foot was found in three patients with PVL. In patients with cortical-subcortical lesions, tongue movements were associated with cortical activation restricted to the unaffected hemisphere. Movements of the paretic limb showed more ipsilateral activation in patients with PVL than in patients with cortical-subcortical lesions. CONCLUSION: Different types of structural damage such as PVL and cortical-subcortical lesions show differences in fMRI examination.

Adolescent↗
PubMed2004

The Stent-Supported Percutaneous Angioplasty of the Carotid Artery vs. Endarterectomy Trial.

The Stent-Supported Percutaneous Angioplasty of the Carotid Artery versus Endarterectomy (SPACE) Trial is investigating if both treatment modalities are equivalent in the treatment of severe symptomatic carotid stenoses. Patients with symptomatic (transient ischaemic attack or minor stroke) stenosis (above 50% following the North American Symptomatic Endarterectomy Trial criteria) eligible for both methods can be recruited into this trial. The primary endpoint is the incidence of an ipsilateral stroke or death between randomisation and day 30 after treatment. Surgeons as well as the interventionalists have to demonstrate their expertise prior to participation in the trial. Funding is mostly by public institutions (Federal Ministry of Education and Research and German Research Foundation). An external monitoring is applied. Thirty-two centres are currently taking part in the SPACE Trial that has been running in Germany, Austria and Switzerland for 3 years, and they have been able to recruit a total of around 670 patients. The definitive results of this study cannot be expected before 3-5 years.

Angioplasty↗
PubMed2003

Rate dependency of the human cortical network subserving executive functions during generation of random number series--a functional magnetic resonance imaging study.

In a random number generation (RNG) task subjects are instructed to generate the numbers 1-10 in a random fashion. RNG performance is assumed to involve executive functions, as it requires controlled response generation and suppression of habitual responses. To investigate cerebral structures involved in RNG associated executive functions we investigated functional magnetic resonance imaging in eight healthy subjects while performing an RNG task at two different response rates (1 and 2 Hz). During the 1 Hz condition an activation was detected bilaterally in the dorsolateral prefrontal cortex (BA 9/46), the lateral premotor cortex (BA 6), the anterior cingulate (BA 32), the inferior and superior parietal cortex (BA 7/40) and the cerebellar hemispheres. In the 2 Hz condition behavioural data showed higher counting tendencies reflecting poorer executive control. In parallel, a homogenous diminution of the activity in the involved cortical areas was obtained. This finding would support the theory of a cortical network involved in executive functions consisting of distinct brain regions working together rather than a distinct fronto-cortical functional localisation.

Adult↗
PubMed2003

[Evaluation of stent-protected angioplasty for theray of symptomatic stenoses of the carotid artery. SPACE and other randomized trials].

During recent years, stent-protected angioplasty of the carotid artery (SPAC) has become an alternative to endartectomy (CEA) in many centers. Despite many case reports, case series, and open records, it has not been proven that these therapeutical regimens are comparable regarding complication rates and long-term outcome. Until now, only three randomized trials were published on this theme, two of them only as abstracts. This is not sufficient for answering the question of whether SPAC is a good alternative to CEA. At present, four major, randomized, multicenter trials are being run (EVA3S in France, CREST in the US, ICSS in Great Britain and several other countries, and SPACE in Germany and Austria). About 7,300 patients will be included in these trials. At present, 24 centers are participating in the SPACE trial, recruiting about 350 patients. It has been prospectively agreed that EVA-3S, ICSS, and SPACE will combine their results after completion of initial randomization and follow-up to conduct a combined European meta-analysis of the data. Three to 5 years are needed until these trials' final results will be published. Until then, stent-protected angioplasty should be done only under the consideration that it has not been scientifically evaluated.

Angioplasty, Balloon↗
PubMed2003

Differentiation of multiple sclerosis plaques, subacute cerebral ischaemic infarcts, focal vasogenic oedema and lesions of subcortical arteriosclerotic encephalopathy using magnetisation transfer measurements.

Although multiple sclerosis (MS) plaques, subacute cerebral ischaemic infarcts, focal vasogenic brain oedema, and subcortical arteriosclerotic encephalopathy (SAE) often have typical radiological patterns, they are sometimes difficult to distinguish from each other. Our aim was to determine whether they can be differentiated by magnetisation transfer (MT) measurements. We measured MT ratios (MTR) in ten patients with plaques of MS, 11 with subacute ischaemic infarcts, 12 with focal vasogenic oedema, and ten with lesions of SAE and compared the mean MTRs statistically. The MTR of normal white matter was 47.3%; the lowest MTR was found in plaques of MS (mean 26.4%). With the exception of vasogenic oedema and subacute cerebral ischaemic infarcts the mean MTRs were significantly different between all groups. MT measurements can provide additional information for the differentiation of these conditions, but we could not distinguish vasogenic oedema from subacute cerebral ischaemic infarcts.

Adult↗
PubMed2003

Effector-independent representations of simple and complex imagined finger movements: a combined fMRI and TMS study.

Kinesthetic motor imagery and actual execution of movements share a common neural circuitry. Functional magnetic resonance imaging was used in 12 right-handed volunteers to study brain activity during motor imagery and execution of simple and complex unimanual finger movements of the dominant and the nondominant hand. In the simple task, a flexible object was rhythmically compressed between thumb, index and middle finger. The complex task was a sequential finger-to-thumb opposition movement. Premotor, posterior parietal and cerebellar regions were significantly more active during motor imagery of complex movements than during mental rehearsal of the simple task. In 10 of the subjects, we also used transcranial magnetic brain stimulation to examine corticospinal excitability during the same motor imagery tasks. Motor-evoked potentials increased significantly over values obtained in a reference condition (visual imagery) during imagery of the complex, but not of the simple movement. Imagery of finger movements of either hand activated left dorsal and ventral premotor areas and the supplementary motor cortex regardless of task complexity. The effector-independent activation of left premotor areas was particularly evident in the simple motor imagery task and suggests a left hemispherical dominance for kinesthetic movement representations in right-handed subjects.

Adult↗
PubMed2002

Serial analysis of the apparent diffusion coefficient time course in human stroke.

Acute cerebral ischemic injury can be rapidly detected on diffusion-weighted images. The apparent diffusion coefficient (ADC) depends on the stage of cytotoxic edema and water content in the infarcted parenchyma. The purpose of this study is to determine the time course of ADC during the first days of ischemic stroke. These data should make it possible to distinguish between multiple stroke and a single progressive infarction. Eight patients with clinically diagnosed acute cerebral ischemia were examined by diffusion-weighted MRI from 2 to 20 h after onset of symptoms. Daily control scans were performed for up to 10 days. ADC values were analyzed from 55 MRI studies. Furthermore, ADC was measured in the tissue which showed a hyperintense signal at the first examination and in the contralateral tissue. White and gray matter were analyzed separately. Data were expressed as the ratio ADC (rADC) of lesion to control region of interest. All patients showed a uniform reduction in rADC from the first hours of stroke and decreasing to the 3rd day. The rADC increased again from the 4th day up to the point of pseudo-normalization on day 9. The gray matter showed a slightly faster increase than the white matter. rADC shows significant changes in the first days after stroke, following a rather uniform time course. Together with T2-weighted MRI this makes it possible to differentiate between hyperacute, acute, and chronic stroke. Furthermore, the age of an ischemia can be determined and multiple strokes can be distinguished from a single progressive stroke.

Aged↗
PubMed2002

CT and diffusion-weighted MR imaging in randomized order: diffusion-weighted imaging results in higher accuracy and lower interrater variability in the diagnosis of hyperacute ischemic stroke.

BACKGROUND AND PURPOSE: Diffusion-weighted MRI (DWI) has become a commonly used imaging modality in stroke centers. The value of this method as a routine procedure is still being discussed. In previous studies, CT was always performed before DWI. Therefore, infarct progression could be a reason for the better result in DWI. METHODS: All hyperacute (<6 hours) stroke patients admitted to our emergency department with a National Institutes of Health Stroke Scale (NIHSS) score >3 were prospectively randomized for the order in which CT and MRI were performed. Five stroke experts and 4 residents blinded to clinical data judged stroke signs and lesion size on the images. To determine the interrater variability, we calculated kappa values for both rating groups. RESULTS: A total of 50 patients with ischemic stroke and 4 patients with transient symptoms of acute stroke (median NIHSS score, 11; range, 3 to 27) were analyzed. Of the 50 patients, 55% were examined with DWI first. The mean delay from symptom onset until CT was 180 minutes; that from symptom onset until DWI was 189 minutes. The mean delay between DWI and CT was 30 minutes. The sensitivity of infarct detection by the experts was significantly better when based on DWI (CT/DWI, 61/91%). Accuracy was 91% when based on DWI (CT, 61%). Interrater variability of lesion detection was also significantly better for DWI (CT/DWI, kappa=0.51/0.84). The assessment of lesion extent was less homogeneous on CT (CT/DWI, kappa=0.38/0.62). The differences between the 2 modalities were stronger in the residents' ratings (CT/DWI: sensitivity, 46/81%; kappa=0.38/0.76). CONCLUSIONS: CT and DWI performed with the same delay after onset of ischemic stroke resulted in significant differences in diagnostic accuracy. DWI gives good interrater homogeneity and has a substantially better sensitivity and accuracy than CT even if the raters have limited experience.

Acute Disease↗
PubMed2002

Effect of intravenous thrombolysis on MRI parameters and functional outcome in acute stroke <6 hours.

BACKGROUND AND PURPOSE: The goals of this study were to examine MRI baseline characteristics of patients with acute ischemic stroke (AIS) and to study the influence of intravenous tissue plasminogen activator (tPA) on MR parameters and functional outcome using a multicenter approach. METHODS: In this open-label, nonrandomized study of AIS patients with suspected anterior circulation stroke, subjects received a multiparametric stroke MRI protocol (diffusion- and perfusion-weighted imaging and MR angiography) within 6 hours after symptom onset and on follow-up. Patients were treated either with tPA (thrombolysis group) or conservatively (no thrombolysis group). Functional outcome was assessed on day 90 (modified Rankin Score; mRS). RESULTS: We enrolled 139 AIS patients (no thrombolysis group, n=63; thrombolysis group, n=76). Patients treated with tPA were more severely affected (National Institutes of Health Stroke Scale score, 10 versus 13; P=0.002). Recanalization rates were higher in the thrombolysis group (Thrombolysis in Myocardial Infarction criteria 1 through 3 on day 1; 66.2% versus 32.7%; P<0.001). Proximal vessel occlusions resulted in larger infarct volumes and worse outcome (P=0.02). Thrombolysis was associated with a better outcome regardless of the time point of tPA treatment (< or =3 hours or 3 to 6 hours) (univariate analysis: mRS < or =2, P=0.017; mRS < or =1, P=0.023). Age (P=0.003), thrombolytic therapy at 0 to 6 hours (P=0.01), recanalization (P=0.016), lesion volume on day 7 (P=0.001), and initial National Institutes of Health Stroke Scale score (P=0.001) affected functional outcome (mRS on day 90) positively (multivariate analysis). The time point of tPA therapy affected the recanalization rate (P=0.024) but not final infarct volume. CONCLUSIONS: In this pilot study, tPA therapy had a beneficial effect on vessel recanalization and functional outcome. Multiparametric MRI delineates tissue at risk of infarction in AIS patients, which may be helpful for the selection of patients for tPA therapy. tPA therapy appeared safe and effective beyond a 3-hour time window. This study delivers the rationale for a randomized, MR-based tPA trial.

Acute Disease↗