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Biomedical subjects

J Röther

Publications and source records attributed to J Röther.

At least 19 recordsLinked to original sources
PubMed2006

The amount of solid cerebral microemboli during carotid stenting does not relate to the frequency of silent ischemic lesions.

BACKGROUND AND PURPOSE: Carotid artery stent placement (CAS) may be associated with clinically silent cerebral lesions. We prospectively evaluated the association of the number of solid cerebral microemboli during unprotected CAS with the frequency of silent cerebral lesions as detected by diffusion-weighted MR imaging (DWI). METHODS: We performed multifrequency transcranial Doppler detection of solid microemboli in the ipsilateral middle cerebral artery (MCA) during CAS in 27 consecutive patients with symptomatic high-grade carotid stenoses. No embolus protection was used in any of the cases. DWI before and 24 +/- 2 hours after CAS was used to detect new ischemic lesions. RESULTS: We detected 484 solid microemboli in 17 patients (63%). On MR imaging 24 +/- 2 hours after CAS, 6 patients (22%) had developed 13 new clinically silent DWI lesions within the ipsilateral MCA territory. In patients with Doppler evidence of solid emboli during CAS, the incidence of new DWI lesions was higher (29%) than in patients without Doppler evidence of solid emboli during the procedure (10%); this difference was not statistically significant (P = .25). The number of solid microemboli during CAS in patients with new ipsilateral DWI lesions was not significantly different from that in patients without new ipsilateral DWI lesions. CONCLUSIONS: Solid microembolism is a common event during unprotected CAS; however, the frequency of procedure-related silent cerebral lesions appears to be independent of the number of solid cerebral microemboli during the procedure.

Adult↗
PubMed2005

Time course of wallerian degeneration after ischaemic stroke revealed by diffusion tensor imaging.

Wallerian degeneration (WD) after ischaemic stroke is a well known phenomenon following a stereotypical time course. Whereas conventional magnetic resonance imaging fails to detect signal intensity changes until four weeks after stroke, diffusion tensor imaging (DTI) reveals changes related to WD only after days. DTI was used to monitor the time course of Wallerian degeneration of the pyramidal tract from the early subacute to the late chronic stage of ischaemic stroke in two patients. A progressive decrease of fractional anisotropy was found along the pyramidal tract in the cerebral peduncle below the primary lesion resulting from progressive changes in the principal diffusivities, as well as a slight increase in the orientationally averaged diffusivity in the chronic phase. These signal changes reflect the progressive disintegration of fibre structures resulting from WD.

Anisotropy↗
PubMed2004

Magnetic resonance imaging criteria for thrombolysis in acute cerebral infarct.

BACKGROUND AND PURPOSE: Magnetic resonance imaging (MRI) selection of stroke patients eligible for thrombolytic therapy is an emerging application. Although the efficacy of therapy within 3 hours after onset of symptoms with intravenous (IV) tissue plasminogen activator (tPA) has been proven for patients selected with computed tomography (CT), no randomized, double-blinded MRI trial has been published yet. SUMMARY OF REVIEW: MRI screening of acute stroke patients before thrombolytic therapy is performed in some cerebrovascular centers. In contrast to the CT trials, MRI pilot studies demonstrate benefit of therapy up to 6 hours after onset of symptoms. This article reviews the literature that has lead to current controlled MRI-based thrombolysis trials. We examined the MRI criteria applied in 5 stroke centers. Along with the personal views of clinicians at these centers, the survey reveals a variety of clinical and MRI technical aspects that must be further investigated: the therapeutic consequence of microbleeds, the use of magnetic resonance angiography, dynamic time windows, and others. CONCLUSION: MRI is an established application in acute evaluation of stroke patients and may suit as a brain clock, replacing the currently used epidemiological time clock when deciding whether to initiate thrombolytic therapy. MRI criteria for thrombolytic therapy are applied in some cerebrovascular centers, but the results of ongoing clinical trials must be awaited before it is possible to reach consensus.

Brain↗
PubMed2003

Microvascular damage following experimental sinus-vein thrombosis in rats.

We evaluated effects of thrombosis of the superior sagittal sinus, its bridging and cortical veins (SVT) on the cerebral microvasculature in rats. Cryosections of brains ( n=7) were examined for venous infarction and microvascular basal lamina damage 3 h after SVT by immunohistochemical staining of microtubule-associated protein 2 and collagen type IV. Microvessels in the infarctions showed a decrease in the number (23.5+/-6.1%, P<0.002) and the total area (24.9+/-6.5%, P<0.011) of collagen type IV-positive vessels in contrast to control areas (21.7+/-12.4%, P<0.007; and 26.3+/-15.1%, P<0.026 in contrast to control areas of unoperated animals). This study showed a significant alteration of the cerebral microvasculature in SVT, which might contribute to edema and hemorrhagic transformation.

Animals↗
PubMed2003

[Spinal dural arteriovenous fistula: clinical and radiological findings in 54 patients].

PURPOSE: Presentation of the clinical and radiological findings in spinal dural arteriovenous fistulas (SDAVF) based on the experience in 54 patients. MATERIAL AND METHODS: Evaluation of patients' records and myelography (n = 23), MRI (n = 54) as well as conventional angiography (n = 54) with respect to history, symptoms, clinical and radiological results. RESULTS: Clinically, a long history (mean 20 months) with progressive ascending paresis (100 %), sensory deficits (93 %) and loss of control over bladder and bowel function (89 %) in male patients (78 %) of advanced age (mean 60 years) indicates the disease. Typical signs in MRI are central cord hyperintensity (100 %) with slight medullary distension (74 %), contrast enhancement (79 %) and distended perimedullary veins (89 %), the latter being disclosed by myelography in 78 % of cases. For diagnosis spinal angiography is necessary which most often shows a thoracic location of the fistula (69 %), more than one feeding artery (67 %) and caudal as well as rostral venous drainage (63 %). CONCLUSION: MRI is superior to myelography to detect diagnostic signs of SDAVF in patients with typical clinical presentation. For definitive diagnosis spinal angiography is still indispensable.

Adult↗
PubMed2002

Collateral circulation is an independent radiological predictor of outcome after thrombolysis in acute ischaemic stroke.

We tested the hypothesis that the type of vascular occlusion, recanalisation and collateralisation are predictive of outcome after thrombolytic therapy in acute ischaemic stroke. We carried out angiography and local intra-arterial (97) or systemic (14) thrombolysis within 6 h of the onset in patients with an ischaemic stroke in the territory of the internal carotid artery. Early ischaemic signs (EIS) on pretreatment CT and angiographic findings were classified and analysed in relation to clinical outcome at 3 months. A favourable outcome (Barthel index [BI]>/= 90) was found in 40% of patients with an occlusion of the middle cerebral artery trunk whereas intracranial occlusion of the internal carotid artery ("carotid T occlusion") was followed by death or severe disability (BI<50) in 87%. Significant univariate predictors of favourable outcome were occlusion type ( P<0.01), recanalisation ( P<0.01) and collateralisation ( P<0.01). However, multivariate analysis revealed a significant relationship only between collateralisation and favourable outcome (odds ratio 5.9, 95% confidence interval 1.3-26.7, P=0.02). EIS were not predictive in either case. Occlusion type and recanalisation, are related to outcome only if adequate collateralisation prevents infarction until recanalisation occurs.

Acute Disease↗
PubMed2002

[Endovascular therapy of high-degree stenoses of the neck vessels-stent-supported percutaneous angioplasty of the carotid artery without cerebral protection].

PURPOSE: Technical essentials and therapeutic results of carotid stenting without cerebral protection are presented. MATERIALS AND METHODS: In 161 patients, 167 high grade carotid stenoses were stented, followed by percutaneous transluminal angioplasty, with subsequent evaluation of the clinical and angiographic results. Diffusion-weighted MRI was carried out in 108 patients to detect cerebral sequelae. RESULTS: Endovascular therapy was successful (residual stenosis < 25 %) in 166 stenoses (99.4 %). Twelve patients (7.5 %) had cerebrovascular complications within the 30-day perioperative period, seven of which occurred during the procedure. After treatment, diffusion-weighted MRI disclosed at least one new cerebral lesion in 40 patients (37 %), which were symptomatic in six patients. CONCLUSION: Even without cerebral protection, high grade carotid stenosis can be safely treated with stent-protected percutaneous angioplasty. Microemboli detected by postoperative MRI are infrequently symptomatic.

Adult↗
PubMed2002

Experience with 123I-iomazenil SPECT in acute cerebral infarction.

Neuronal cells are susceptible to cerebral ischaemia. As gamma-aminobutyric acid(A) (GABA(A)) receptors are specific for neurones, functional receptor imaging using I-iomazenil (IMZ), a ligand to the GABA benzodiazepine receptor, has been proposed as an imaging modality for the assessment of neuronal integrity. However, there is only limited experience with IMZ in patients with acute cerebral infarction. Therefore, the aim of this study was to evaluate IMZ single photon emission computed tomography (SPECT) in patients with acute cerebral ischaemia. IMZ SPECT was performed in 21 patients with acute cerebral infarction 7-10 days after stroke onset. Eleven patients underwent systemic thrombolysis within 6 h after symptom onset (group 1), whereas 10 patients were treated conservatively (group 2). IMZ (150-200 MBq) was injected intravenously and imaging was performed using a dedicated four-head SPECT camera at 5 min (perfusion) and 90 min (receptor distribution) post-injection, with an acquisition time of 50 min each. Images were analysed by visual inspection. Four patients showed normal IMZ distribution, and 17 patients showed abnormalities of IMZ uptake on both early and late images. In six patients with regional uptake deficits, a crossed cerebellar diaschisis was observed on early images. Cerebellar inhomogeneity of tracer uptake was absent at the time of late images in all six patients. In eight patients, areas of hypoperfusion corresponded exactly to the regions of receptor deficiency (match). In five patients, preserved neuronal integrity was present in hypoperfused areas (mismatch). In four patients, normally or even hyperperfused areas exhibited regional receptor deficiency (inverse mismatch). In conclusion, IMZ SPECT demonstrated differences between regional perfusion and receptor distribution in about one-half of patients 7-10 days after acute cerebral ischaemia. Interesting patterns between the early phase (perfusion) and the late phase (receptor distribution) were found. These patterns are indicative of the heterogeneous development of cerebral ischaemia where, even days after stroke onset, areas of hypoperfusion but preserved neuronal integrity may be present. However, the evaluation of the potential clinical and therapeutic impact of individual IMZ distribution patterns requires further investigation.

Adult↗
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↗
PubMed2001

CT and MRI in the diagnosis of acute stroke and their role in thrombolysis.

Thrombolysis is an effective but potential deleterious therapy and should therefore be limited to patients with acute intracerebral vessel occlusion and salvageable tissue. MRI currently develops towards the new diagnostic standard for the selection of stroke patients eligible for acute thrombolytic treatment and acute stroke studies. Diffusion- and perfusion-weighed MRI provides diagnostic information not available from the neurological assessments or from CCT and conventional spin-echo MRI. As high-speed DWI and PWI protocols become standardized, a 15-minute integrated stroke protocol of employing echo-planar imaging (EPI) can be outinely performed in the setting of acute clinical stroke. The combination of these MR techniques is suitable to define tissue at risk of infarction that is potentially salvageable brain tissue (an estimate of the ischemic penumbra) and may respond to early recanalization even beyond 3 hours after stroke onset. The extension of the therapeutic window for thrombolytic therapy towards 6 hours in a subpopulation of acute stroke patients might open the way for the successful reperfusion therapy in more stroke patients.

Acute Disease↗
PubMed2001

Comparison of diffusion, blood oxygenation, and blood volume changes during global ischemia in rats.

Rapid diffusion, blood oxygenation, and blood volume weighted echo planar imaging was used to monitor global cerebral ischemia by cardiac arrest in rats. Serial CBV measurements used intravascular iron oxide contrast media (iron dextran). ADC dropped by 5% within 20 sec of cardiac arrest, then continued to decay slowly until a larger rapid drop after 2 min. After iron oxide injection, the initial 5% drop was not observed. The transverse relaxation rate (R(2), R(*)(2) no iron injection) increased rapidly after cardiac arrest, peaking at about 30 sec, then declining towards baseline. The CBV dropped by about 50% within 20 sec. The initial 5% ADC drop may be a vascular artifact. The rapidity of the CBV-weighted signal drop suggests a flow-mediated contribution to the iron oxide contrast mechanism. Magn Reson Med 45:10-16, 2001.

Animals↗
PubMed2001

Dysfunction of vasomotor reactivity in severe sepsis and septic shock.

OBJECTIVE: Perfusion abnormalities are an overall phenomenon in severe sepsis and septic shock, leading to organ dysfunction. We investigated whether carbon dioxide (CO2)-induced vasomotor reactivity (VMR) is impaired in septic patients, compared with values obtained outside sepsis. DESIGN: Prospective, clinical study. SETTING: Six-bed neurologic critical care unit of a university hospital. PATIENTS AND PARTICIPANTS: Eight consecutive patients with severe sepsis and septic shock. MEASUREMENTS AND RESULTS: CO2-reactivity was measured during and outside a period of severe sepsis or septic shock according to ACCP/SCCM criteria by means of transcranial Doppler sonography and near-infrared spectroscopy (NIRS). VMR was calculated as the percentage change of cerebral blood flow velocity (normalized CO2-reactivity, NCR) and absolute changes in concentration of oxygenated hemoglobin, deoxygenated hemoglobin, total hemoglobin (HbO2, Hb, HbT) and Hbdiff (difference between HbO2 and Hb) in micromol/l per 1% increase in end-tidal CO2 (CR-HbO2, CR-Hb, CR-HbT, CR-Hbdiff). NCR and NIRS-reactivities were significantly reduced during severe sepsis and septic shock compared with values outside sepsis (mean, SD, Wilcoxon): NCR 11.0 (7.1) versus 30.7 (13.0), p < 0.02; CR-HbO2 0.70 (0.61) versus 2.33 (1.11), p < 0.02; CR-Hb -0.17 (0.74) versus -1.42 (1.28), p < 0.04; CR-HbT 0.53 (0.48) versus 1.05 (0.40), p < 0.03; CR-Hbdiff 0.91 (1.33) versus 3.75 (2.33), p < 0.02. This indicates a severely disturbed VMR. CONCLUSIONS: In the advent of a disturbed cerebral autoregulation, critical drops in blood pressure during sepsis are transferred directly into the vascular bed, leading to cerebral hypoperfusion. This mechanism might contribute to the pathogenesis of septic encephalopathy.

Aged↗
PubMed2001

Apparent diffusion coefficient decreases and magnetic resonance imaging perfusion parameters are associated in ischemic tissue of acute stroke patients.

Perfusion-and diffusion-weighted magnetic resonance imaging scans are thought to allow the characterization of tissue at risk of infarction. The authors tested the hypothesis that the apparent diffusion coefficient (ADC) decrease should be associated with the severity of the perfusion deficit in ischemic tissue of acute stroke patients. Perfusion-and diffusion-weighted scans were performed in 11 patients with sudden onset of neurologic deficits within the last 6 hours and T2-weighted magnetic resonance imaging scans were obtained after 6 days. Parameter images of the maximum of the contrast agent concentration, time to peak, relative cerebral blood volume, relative cerebral blood flow, and relative mean transit time were computed from the perfusion-weighted data. A threshold function was used to identify tissue volumes with stepwise ADC decreases. An onionlike distribution of successively decreasing ADC values was found, with the lowest ADC in the center of the ischemic region. Correspondingly, tissue perfusion decreased progressively from the periphery toward the ischemic core. This effect was most pronounced in the time-to-peak maps, with a linear association between ADC decrease and time-to-peak increase. Apparent diffusion coefficient values decreased from the periphery toward the ischemic core, and this distribution of ADC values was strongly associated with the severity of the perfusion deficit.

Adult↗
PubMed2000

Hemodynamic assessment of acute stroke using dynamic single-slice computed tomographic perfusion imaging.

BACKGROUND: Stroke management would benefit from a broadly available imaging tool that detects perfusion deficits in patients with acute stroke. OBJECTIVE: To determine the role of dynamic, single-slice computed tomographic (CT) perfusion imaging (CTP) in the assessment of acute middle cerebral artery stroke. DESIGN AND PATIENTS: Imaging with CTP and CT within the first 6 hours of symptom onset and before the start of treatment in a consecutive clinical series of 22 patients (mean age, 68.3 years; 14 women; studied within 143 +/- 96 minutes of stroke onset). SETTING: A stroke unit in a university hospital. MAIN OUTCOME MEASURES: Area of the perfusion deficit (nAP(0)) from time-to-peak maps, hemispheric lesion area from follow-up CT (HLA(F)), final infarct volume, and stroke recovery (National Institutes of Health Stroke Scale scores). RESULTS: Eighteen patients had perfusion deficits in the middle cerebral artery territory and corresponding hypoattenuation in follow-up CT. Three patients with normal CTP findings showed lacunar infarctions or normal findings on follow-up CT. In 1 patient, CTP did not reveal a territorial deficit above the imaging slice. The overall sensitivity and specificity of CTP for the detection of perfusion deficits in patients with proven territorial infarction (n = 18) on follow-up CT were 95% and 100%, respectively. The nAP(0) was significantly correlated with the National Institutes of Health Stroke Scale score at admission (P<.003) and the HLA(F) (P<.001). Different stroke patterns were identified in patients with follow-up CTP (n = 10): (1) initial perfusion deficit and partial nutritional reperfusion (nAP(0)>HLA(F); n = 6), (2) initial perfusion deficit and nonnutritional reperfusion (nAP( 0)>/=HLA(F); n = 2), and (3) initial perfusion deficit without reperfusion (nAP(0)>/=HLA(F); n = 2). CONCLUSIONS: Computed tomographic perfusion imaging detects major perfusion deficits in the middle cerebral artery territory. Because CTP is broadly available, it may play a role in acute stroke management. Arch Neurol. 2000;57:1161-1166

Acute Disease↗
PubMed2000

["Spreading depression" and peri-infarct depolarizations. Relevant pathological events in migraine and stroke?].

Spreading depression is a fascinating phenomenon that can be provoked by chemical, electrical or mechanical stimuli of the cortex. Spreading depression-like transient depolarizations are observed in the peri-infarct tissue after focal ischemia. The reduction in electrical activity and a negative direct current potential shift propagating over the cortex with a rate of 2-5 mm/minute are the physiological hallmarks. It is thought that spreading depression and peri-infarct depolarizations might play a role in the pathogenesis of migraine and stroke. However, these events have never been detected in humans. This paper reviews the physiological characteristics of spreading depression and peri-infarct depolarizations and discusses their potential role in migraine and stroke.

Cerebral Cortex↗
PubMed2000

Reduced vasomotor reactivity in cerebral microangiopathy : a study with near-infrared spectroscopy and transcranial Doppler sonography.

BACKGROUND AND PURPOSE: Reduction of cerebral blood flow and vasomotor reactivity (VMR) are thought to play an important role in the pathogenesis of cerebral microangiopathy. The aim of our study was to determine whether near-infrared spectroscopy (NIRS) can detect a reduced VMR in patients with microangiopathy, whether NIRS reactivities correlate with VMR assessed by transcranial Doppler sonography (TCD), and whether the differing extents of patients' microangiopathy demonstrated on MRI or CT can be distinguished by both noninvasive techniques. METHODS: We compared the VMR of 46 patients with cerebral microangiopathy with 13 age-matched control subjects. Patients were classified with the Erkinjuntti scale. We monitored cerebral blood flow velocity (CBFV) in both middle cerebral arteries by TCD, changes in concentration of oxyhemoglobin (HbO(2)), deoxyhemoglobin (Hb) and blood volume (HbT) by NIRS, mean arterial blood pressure, and end-tidal CO(2) (EtCO(2)) during normocapnia and hypercapnia. VMRs were calculated as percent change of CBFV (NCR) and as absolute change in concentration of HbO(2), Hb, and HbT per 1% increase in EtCO(2) (CR-HbO(2), CR-Hb, CR-HbT). RESULTS: NCR and NIRS reactivities were significantly reduced in patients with cerebral microangiopathy. CR-HbO(2) and CR-Hb showed a close correlation with NCR, and NCR and NIRS reactivities were related to the severity of cerebral microangiopathy according to the Erkinjuntti scale. Validity of NCR and NIRS reactivities were similar. CONCLUSIONS: VMR is reduced in patients with cerebral microangiopathy and can be noninvasively assessed in basal arteries (with TCD) and brain parenchyma (with NIRS). Reduction of CO(2)-induced VMR, as measured by NIRS and TCD, may indicate the severity of microangiopathy.

Aged↗
PubMed1999

Serial magnetic resonance diffusion and hemodynamic imaging in a neonatal rabbit model of hypoxic-ischemic encephalopathy.

Dynamic changes in relative cerebral blood volume (rCBV) and apparent diffusion coefficient (ADC) were investigated, using high speed magnetic resonance imaging (MRI) in an acute neonatal rabbit model of hypoxic-ischemic encephalopathy (HIE). Serial rCBV imaging used a magnetic susceptibility blood pool contrast agent. Interleaved ADC and rCBV images were acquired with 9 s temporal resolution. Rabbits received unilateral common carotid artery (CCA) ligation followed by hypoxia. rCBV increased bilaterally within 1-2 min after the onset of hypoxia. A biphasic ADC decline was observed: a slowly declining phase (84 +/- 18% of baseline) followed by a rapid, focal drop to 55 +/- 8% of baseline in the ipsilateral cortex, which was paralleled by a rapid focal rCBV drop to 70 +/- 17% of baseline. ADC decline generally began in a small region of ipsilateral cortex and spread over the ipsilateral cortex, ipsilateral subcortical tissue and contralateral cortex. The initial ADC drop usually preceded the initial rCBV drop by approximately 60 s, however at later timepoints rCBV decline sometimes preceded ADC decline. Upon normoxia, rCBV recovered to about baseline values while ADC recovered to baseline or above. This method provides a sensitive means of non-invasively visualizing acute hemodynamic- and metabolic-related changes in HIE with good temporal and spatial resolution.

Animals↗