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Hermann Zeumer

Publications and source records attributed to Hermann Zeumer.

18 recordsLinked to original sources
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

Emergency carotid artery stenting in persistent hemodynamic deficit associated with severe carotid stenosis.

MR imaging in a 73-year-old man presenting with hemispheric stroke revealed a subcortical diffusion-weighted imaging lesion associated with a high-grade stenosis of the proximal internal carotid artery, which suggested hemodynamic infarction. Collateral supply was absent. After failure of conservative therapy, successful unprotected carotid artery stent placement (CAS) was performed followed by a complete neurologic recovery. Emergency CAS should be considered in acute stroke patients with severe hemodynamic impairment if conservative treatment options are not successful.

Aged↗
PubMed2005

Tissue at risk is overestimated in perfusion-weighted imaging: MR imaging in acute stroke patients without vessel recanalization.

BACKGROUND AND PURPOSE: The volume of decreased cerebral blood flow (CBF) in acute stroke perfusion-weighted imaging frequently overestimates final infarct volume. We hypothesized that surviving tissue exists even in patients without recanalization and tried to determine perfusion thresholds from initial MR imaging. METHODS: Stroke MR imaging including MR angiography was carried out at days 0, 1, and 7 after stroke onset in 19 patients without recanalization at least until day 1. The following lesions were defined: L0 = diffusion restriction at day 0; LG1 = lesion growth until day 1; LG7 = lesion growth until day 7; ST7 = initially hypoperfused, but surviving tissue. These lesions were transferred on initial MR imaging within 4.7 hours and perfusion values at day 0 were determined. RESULTS: Median lesion volume L0 at day 0 was 18.2 mL and increased to 39.4 and 43.8 mL at days 1 and 7. Volume of decreased rCBF not progressing to infarction was 148.5 mL (ST7). Mean ST7 perfusion values were different from L0 and LG1, but only mean relative cerebral blood volume (rCBV) was different from LG7, discriminating survival against death of tissue. A threshold value of 0.82 CBV for death versus survival was determined with a sensitivity of 0.56 and specificity of 0.95. Carotid T occlusions showed the greatest potential of lesion growth. CONCLUSION: Even when vessel occlusion persists, hypoperfused tissue on MR imaging does not necessarily progress toward infarction. The most conclusive inferences can be drawn from CBV images. The site of arterial occlusion also determines progression to infarction.

Adult↗
PubMed2005

Vascular occlusion sites determine differences in lesion growth from early apparent diffusion coefficient lesion to final infarct.

BACKGROUND AND PURPOSE: Occlusion of major cerebral arteries is the primary source of tissue damage in ischemic stroke and the target of thrombolytic therapy. We hypothesized that large infarcts in more proximal vascular occlusions correspond with substantially increased ischemic lesions shown on initial apparent diffusion coefficient (ADC) maps. METHODS: Initial ADC lesions in 120 patients with acute ischemic stroke were analyzed within 6 hours of stroke onset. Patients were categorized on the basis of vascular occlusion, as shown on MR angiography. Lesion volumes were determined by using manual delineation (ADC(man)) and a threshold method for ADC values (<550 x 10(-9) mm(2)/s(-1), ADC(<550)). Infarct volumes were analyzed by using T2-weighted (n = 109) or CT (n = 11) images obtained on days 5-8. RESULTS: Median lesion volumes for ADC(<550), ADC(man), and infarcts, respectively, were as follows: proximal internal carotid artery (ICA)/middle cerebral artery (MCA) occlusions, 10, 23, and 32 cm(3); carotid-T occlusions, 11, 37, and 138 cm(3); MCA trunk occlusions, 11, 27, and 44 cm(3)); and MCA branch occlusions 8, 27, and 21 cm(3). Initial ADC lesion volumes were different only between the carotid T and the MCA branch (P < .05). On days 5-8, infarct volumes decreased from proximal to distal sites (P < .05), with the exception of MCA trunk versus proximal ICA/MCA occlusions. Recanalization rate in carotid-T occlusion was significantly lower than those of all other occlusion types. CONCLUSION: Initial ADC lesions can be small, even in patients with proximal vascular occlusions. These patients develop considerably large infarctions, suggesting a high potential for infarct growth. This growth might be averted with improved early recanalization of proximal vascular occlusions.

Arterial Occlusive Diseases↗
PubMed2004

Are there time-dependent differences in diffusion and perfusion within the first 6 hours after stroke onset?

BACKGROUND AND PURPOSE: Stroke heterogeneity in computed tomography-based studies has been attributed as main cause for missing efficacy of intravenous tissue plasminogen activator (tPA) therapy within 3 to 6 hours. We investigated early time-dependent differences in acute stroke pathophysiology by multiparametric magnetic resonance imaging (MRI). METHODS: Stroke MRI of 112 acute ischemic stroke patients within <6 hours were dichotomized into a <3-hour group (n=52) and a 3- to 6-hour group (n=60). Infarct volume was determined on days 5 to 8. Lesion volumes were determined for apparent diffusion coefficient (ADC_man) and the subregion with ADC values <550x10(-9) mm/s2 (ADC <550), and for the time-to-peak (TTP) delay of 2 to 4 seconds, 4 to 6 seconds, 6 to 8 seconds, and >8 seconds. A subsample analysis was performed for occlusions of the middle carotid artery (MCA) trunk (n=36) and MCA branches (n=30), and for all patients treated by intravenous tPA (n=70). RESULTS: ADC and TTP lesion volumes were not different within <3 hours compared with volumes at 3 to 6 hours. In patients receiving intravenous tPA (n=70), there were no significant differences in ADC_man, TTP >2 seconds, and infarct volume (days 5 to 8) between the 2 groups. There was a greater proportion of ADC <550/ADC_man, which was most pronounced in patients with MCA trunk occlusions after 3 to 6 hours and a larger mismatch in the <3-hour group compared with that of the 3- to 6-hour group. In MCA branch occlusions, there was a less severe TTP delay after 3 to 6 hours. However, all differences missed the significance level (P=0.05) after correction for multiple testing. CONCLUSIONS: We observed no significant time-dependent differences within 6 hours after stroke onset in degree and volume of diffusion and perfusion impairment. An exclusion from intravenous tPA solely based on a rigid 3-hour time window seems unjustified in MRI-confirmed ischemic stroke.

Acute Disease↗
PubMed2004

Predictors of apparent diffusion coefficient normalization in stroke patients.

BACKGROUND AND PURPOSE: We sought to describe the frequency of normalization of apparent diffusion coefficient (ADC) values that are decreased in hyperacute stroke and to identify characteristics of tissue demonstrating normalization. METHODS: Sixty-eight acute ischemic stroke patients underwent MRI examination (including diffusion/perfusion imaging and MR angiography) within 6 hours (mean, 2.8 hours) after symptom onset, after 24 hours, and again 4 to 7 days later. Lesion volumes with decreased ADC and delayed time to peak in perfusion imaging were determined. In patients showing ADC normalization, volumes with ADC decrease graded as <50%, 50% to 60%, 60% to 70%, and 70% to 80% of the contralateral value were determined by thresholding. Patients were categorized as normalizers (demonstrating ADC normalization in >5 mL tissue with initially decreased ADC) or nonnormalizers (demonstrating ADC normalization in <5 mL tissue). RESULTS: Fourteen patients (19.7%) were classified as normalizers. Eleven of 31 patients (35.5%) initially imaged <3 hours after stroke onset and 3 of 37 (7.5%) of those imaged 3 to 6 hours after onset were normalizers. ADC normalization occurred predominantly in the basal ganglia and white matter after thrombolytic therapy in patients with more distal vessel occlusions. All normalizers demonstrated at least partial tissue reperfusion. Tissue with more severe initial decrease in ADC was less likely to demonstrate normalization. CONCLUSIONS: ADC normalization is not a rare event in acute stroke after tissue reperfusion. Brain tissue with initially decreased ADC, especially within 3 hours after stroke onset, may include "tissue at risk."

Acute Disease↗
PubMed2004

Cerebral perfusion impairment correlates with the decrease of CT density in acute ischaemic stroke.

Within the first 6 h of ischaemic stroke, changes on computed tomography (CT) scans are known as early ischaemic signs. We tested the hypothesis that the severity of perfusion impairment correlates with the degree of CT density decrease. Water uptake in ischaemic brain tissue results in a subtle decrease of CT density, and was quantified by delineation of the corresponding decrease of the apparent diffusion coefficient (ADC). Regions of decreased ADC and CT density in 29 acute-stroke patients were superimposed on the corresponding magnetic resonance perfusion images. Mean values of ADC and CT density decrease were correlated with the corresponding relative changes of cerebral blood flow (rCBF) and volume (rCBV), mean transit time (rMTT) and time-to-peak (rTTP). The decrease of CT density was 1.2 +/- 0.6 Hounsfield units and showed a linear correlation with rCBF (0.42, p < 0.01) as well as rCBV (0.62, p < 0.01), but not with the prolongation of rMTT (1.43, p = 0.78) or rTTP (1.34, p = 0.26). Therefore, the reduction of rCBF determines the severity of the early ischaemic oedema (EIOE) on CT, as well as reduction of the ADC. These findings provide a coherent view on the pathophysiology of the EIOE.

Adult↗
PubMed2004

Normal brain maturation characterized with age-related T2 relaxation times: an attempt to develop a quantitative imaging measure for clinical use.

OBJECTIVES: We studied age-related changes in T2 relaxation times from the normal maturating human brain under routine clinical MR examination conditions. MATERIALS AND METHODS: In 70 healthy subjects aged between 3 weeks and 39 years, T2 maps of the brain in which the intensity of each pixel corresponded to T2 relaxation times were generated based on magnetic resonance imaging data collected with a triple spin echo sequence. T2 relaxation times in white matter (WM) and gray matter (GM) were measured in 6 distinctive regions of interest of the T2 maps. The age dependence of the T2 values was mathematically simulated using a biexponential function. RESULTS: T2 values were largest at the age of 3 weeks (maximum: approximately 400 milliseconds for WM and 200 milliseconds for GM) and decreased continuously with increasing age, faster in the first few months and slower thereafter, until values achieved between 95 and 110 milliseconds for WM and 88 and 95 milliseconds for GM in adults. The relationship between T2 values and age could be well simulated using a biexponential function (R > 0.92). CONCLUSIONS: T2 relaxation time correlates well with the progress of brain maturation. The used biexponential function reflects the dynamic development of myelination in newborns and young children as well as the maturation of myelination during adolescence and could be used to develop a "normal" reference for neuroradiological diagnoses.

Adult↗
PubMed2003

Atypical focal MRI lesions in a case of juvenile Alexander's disease.

We present a juvenile case of Alexander's disease with atypical focal magnetic resonance imaging-detected lesions and elevated levels of lactate in cerebrospinal fluid. The diagnosis was based on the neuropathological finding of a diffuse accumulation of Rosenthal fibers within the brain and the spinal cord. The diagnosis was confirmed by detection of a mutation in exon 1 at nucleotide position 249 of glial fibrillary acidic protein cDNA, a finding previously reported in cases of infantile Alexander's disease.

Alexander Disease↗
PubMed2003

Local intra-arterial fibrinolysis in acute hemispheric stroke: effect of occlusion type and fibrinolytic agent on recanalization success and neurological outcome.

BACKGROUND: To evaluate the effect of occlusion type and fibrinolytic agent on recanalization success and clinical outcome in patients undergoing local intra-arterial fibrinolysis (LIF) in acute hemispheric stroke. METHODS: LIF was performed in 137 patients with angiographically established occlusion in the carotid circulation within 6 h of stroke onset. Retrospective analysis included recanalization success, recanalization time, type of occlusion and fibrinolytic treatment mode. Five types of occlusion were categorized: intracranial bifurcation (carotid 'T') of the internal carotid artery (ICA; n = 35); proximal segment of the middle cerebral artery (MCA; n = 66); distal segment of the MCA (n = 20); extracranial ICA with MCA embolism (n = 8); multiple peripheral branches of the anterior cerebral artery and the MCA (n = 8). Neurologic outcome was evaluated after 3 months by Barthel Index (BI) as good (BI >90), moderate (BI 50-90), poor (BI <50) or death. RESULTS: Recanalization was achieved in 74 patients (54%). Mean recanalization time in recanalized patients was 91 min. Neurologic outcome was good in 48 patients (35%), moderate in 34 (25%), poor in 30 (22%) and 25 died (18%). Outcome was significantly better in recanalized than in nonrecanalized patients (p < 0.001). Treatment results were significantly better in proximal and distal MCA occlusion than in carotid 'T' occlusions (p < 0.001). Recanalization success hardly differed between urokinase and rt-PA. Combined treatment with rt-PA and lys-plasminogen tended toward a faster recanalization. Parenchymal hemorrhage occurred in 13 patients (9%). CONCLUSION: The type of occlusion is of high prognostic value for successful fibrinolysis in the anterior circulation. However, recanalization is a time-consuming process even with an intra-arterial approach. Recanalization did not differ between type or dosage of plasminogen activators. Further innovative attempts are warranted towards hastening recanalization time in endovascular acute stroke treatment.

Adolescent↗
PubMed2003

Histological findings in ruptured aneurysms treated with GDCs: six examples at varying times after treatment.

BACKGROUND AND PURPOSE: A novel plastic embedding approach was used to histologically evaluate inflammatory changes and scar formation over time and to better visualize the mesh attenuation within the aneurysm lumen of acutely ruptured aneurysms after treatment with GDCs. METHODS: Autopsies were performed on six patients with acute subarachnoid hemorrhage who had died between 5 and 272 days after GDC treatment. The aneurysms containing the platinum coils were embedded in plastic along with the intact parent vessels, were sliced, and were ground to a thickness of 5 to 10 micro m. In addition, 250- micro m-thick sections were prepared. Histologic examinations were performed. Three exemplary cases representing the time lapse from treatment to death are discussed in detail. RESULTS: At the three exemplary time periods (5, 13, and 272 days) after coiling, a continuing healing process could be observed. At 5 days after placement of GDCs, a blood clot consisting of erythrocytes and fibrin was found throughout the cavity. Thirteen days after the procedure, large foamy macrophages were observed near the coils in the aneurysm cavity. Two hundred seventy-two days after the intervention, scar formation within the aneurysm appeared to be completed, with vascularized connective tissue filling the cavity and embedding the coils. Large foreign body giant cells were found adjacent to the coils. A layer of long slender cells, resembling endothelium, sealed the aneurysm neck. CONCLUSION: We postulate that within days after GDC treatment, blood clotting and thrombus formation prevent rebleeding and that solid scar formation covered by a layer of long slender cells, resembling endothelium, seals the aneurysm over time.

Adult↗
PubMed2003

Sensitivity and interrater agreement of CT and diffusion-weighted MR imaging in hyperacute stroke.

BACKGROUND AND PURPOSE: Previous acute stroke studies found diffusion-weighted (DW) imaging superior to CT for detection of early ischemic signs (EIS). However, these findings were confounded by a large time interval in favor of DW imaging. We compared DW images and CT scans obtained with a short time delay in patients with acute stroke to define the sensitivity and interrater agreement of both imaging techniques. METHODS: CT scans and DW images were obtained within 6 hours of symptom onset in 46 patients with acute stroke. Three neuroradiologists and three neurologists reviewed the images for EIS in five regions of the middle cerebral artery (MCA) territory and estimated the extent of EIS (< or > one-third of the MCA territory). RESULTS: The mean delay between imaging with both modalities was 24.5 minutes (range, 10-41 minutes). Forty-five of 46 patients had an ischemic stroke. EIS were seen on 33 of 45 CT scans (73% sensitivity; 95% confidence interval [CI]: 58-85%) and on 42 of 45 DW images (93% sensitivity; 94% CI: 82-99%). Interrater agreement was moderate (kappa = 0.57) for CT and excellent (kappa = 0.85) for DW imaging. CT studies had a moderate interrater agreement for estimation of EIS greater than one-third of the MCA territory (kappa = 0.40), whereas DW imaging showed good results (kappa = 0.68). Sensitivity for detection of greater than one-third of the MCA territory was equally poor (57%, 95% CI: 29-82%) for both CT and DW imaging. CONCLUSION: DW imaging helped identify EIS with higher sensitivity than that of CT. The interrater variability of the one-third rule was high for CT, and thus the clinical applicability of CT is limited. Our results support the application of stroke MR imaging for the treatment of patients with acute stroke.

Acute Disease↗
PubMed2002

Endovascular therapy of acute vertebrobasilar occlusion: early treatment onset as the most important factor.

In view of the poor prognosis for patients with acute intracranial vertebrobasilar occlusion (VBO), factors were sought that predict survival and good neurologic outcome after acute endovascular treatment by means of local intra-arterial fibrinolysis (LIF) and percutaneous transluminal angioplasty (PTA). LIF was performed in 83 patients with angiographically established acute VBO. A significant residual stenosis after LIF was treated by additional PTA in 8 patients. The types of occlusion were classified as either embolic occlusion (EO) or atherothrombotic occlusion (AO). Outcome was evaluated after 3 months by the Barthel Index (BI) as favorable (BI >90), unfavorable (BI <90) or death and compared for each of 3 diagnostic or treatment variables: recanalization success, occlusion type and time to treatment. Four fibrinolytic treatment modes [urokinase, low-dose and high-dose recombinant tissue-type plasminogen activator (rt-PA), rt-PA + Lys-plasminogen] were also analyzed. The outcome was favorable in 19 patients (23%), unfavorable in 14 (17%) and 50 died (60%). Recanalization was successful in 54 patients (66%). The neurologic outcome was better in recanalized than in nonrecanalized patients (favorable outcome: 30 vs. 10%, mortality: 54 vs. 72%; p = 0.118). The neurologic outcome was better in EO than in AO (favorable outcome: 31 vs. 17%, mortality: 47 vs. 70%, p = 0.112). Under combined treatment by LIF and PTA in 8 patients with AO, 4 survived, 3 with a favorable outcome (38%). Early treatment onset ( 6 h; favorable outcome: 36 vs. 7%, mortality: 52 vs. 70%, p = 0.005). Although no statistically significant differences were found between the types of fibrinolytic agents, treatment with rt-PA and Lys-plasminogen tended toward better results. Early treatment onset proved to be the most important factor for successful endovascular therapy in acute VBO, whereas recanalization and presence of an embolic occlusion also tended toward better results. Additional PTA may be a promising therapy in cases of significant residual stenosis after LIF.

Acute Disease↗
PubMed2002

Correlation of apparent diffusion coefficient and computed tomography density in acute ischemic stroke.

BACKGROUND AND PURPOSE: Diffusion-weighted MR imaging is very sensitive for the detection of restricted molecular water diffusion in acute ischemic stroke. CT is sensitive to net water uptake in ischemic edema. We compared the decrease in the apparent diffusion coefficient (ADC) in diffusion-weighted MR imaging with CT density changes to study the correlation between diffusion restriction and water uptake in acute stroke patients. METHODS: Twenty-five patients with acute ischemic stroke of the anterior cerebral circulation underwent MR and CT imaging 1.3 to 5.4 hours after symptom onset. ADC and CT data were transferred into a common 3-dimensional space, and regions of decreased ADC (dADC) were superimposed onto the corresponding CT. Mean values of ADC and Hounsfield units (HU) were determined in comparison with the nonaffected hemisphere. RESULTS: Mean decrease in ADC (dADC) was 170+/-53x 10(-6) mm2/s and corresponded to a decrease (dCT) in CT density of 1.3+/-0.7 HU. dCT showed a continuous linear decrease of 0.4 HU/h (r=0.55, P<0.01), whereas the decrease is ADC was almost complete after 1.5 hours. A correlation between the decrease in ADC and dCT was found (r=0.41, P=0.04). CONCLUSIONS: The severity of diffusion restriction correlates with net water uptake in acute ischemic stroke. However, the underlying pathophysiology and different time courses indicate a common reason rather than a direct causality for both phenomena. The time delay and low value of CT density changes provide a reasonable explanation for the higher sensitivity of MR imaging in ischemic stroke.

Acute Disease↗
PubMed2002

Cerebral blood flow predicts lesion growth in acute stroke patients.

BACKGROUND AND PURPOSE: We sought to study the role of MRI-derived cerebral blood flow (CBF) measurements for the prediction of lesion development in acute stroke patients. METHODS: Thirty-two patients were treated with tissue plasminogen activator. Diffusion-weighted (DWI) and perfusion-weighted MRI, T2-weighted imaging, and MR angiography were performed before treatment (2.8+/-0.9 hours after symptom onset) and on follow-up (days 1 and 7). CBF thresholds (12 and 22 mL/100 g per minute) were applied to bolus tracking MRI maps to determine predictive cutoff levels. RESULTS: In 21 patients (group A), the terminal lesion volume (T2-weighted imaging) was larger than the initial DWI lesion volume (89+/-93 versus 21+/-38 mL). In 11 patients (group B), the terminal lesion volume was smaller than the initial DWI lesion volume (7+/-27 versus 15+/-29 mL). The initial DWI lesion volume did not differ between both groups. The presence of a tissue volume > or =50 mL with a CBF value < or =12 mL/100 g per minute was predictive for lesion enlargement to day 7 in T2-weighted imaging (positive predictive value, 0.80). CONCLUSIONS: The presence of a tissue volume > or =50 mL with a CBF value < or =12 mL/100 g per minute predicts further lesion growth in hyperacute stroke patients. MRI-derived CBF values, with all their present limitations, are valuable in early estimation of prognosis of stroke patients.

Acute Disease↗
PubMed2002

Severe ADC decreases do not predict irreversible tissue damage in humans.

BACKGROUND AND PURPOSE: A mismatch between diffusion- and perfusion-weighted MRI is thought to define tissue at risk of infarction. This concept is based on the assumption that diffusion slowing of and decreases in the apparent diffusion coefficient (ADC) serve as indicator of tissue proceeding to infarction. We tested this hypothesis. METHODS: MRI (diffusion weighted, perfusion weighted, MRA, T2 weighted) was performed in 15 patients with acute stroke within 2.9+/-0.8 hours (mean+/-SD) of onset and on days 1 and 7. After intraindividual realignment of the ADC maps, the development of ADC range volumes and ADC values was determined. RESULTS: An increase (354%, group A1) in the total ADC-based lesion volume below a threshold of < 80% occurred in 4 patients on day 1, persisting on day 7 with a pronounced increase of ADC range volumes with low ADC values. An increase in total ADC-based lesion volume (201%, group A2) followed by a secondary drop to day 7 was found in 7 patients. A significant reduction in total ADC-based lesion volume (14%, group B) was found in 4 patients. ADC-based lesion volume increase was associated with persistent vessel occlusion in group A, whereas recanalization in group B resulted in ADC volume decrease. ADC normalization was observed independently from the degree of the initial ADC decrease on days 1 and 7 in group B. CONCLUSIONS: In line with results from animal experiments, ADC decreases do not reliably indicate tissue infarction Even severely decreased ADC values may normalize in human stroke, and it seems likely that ADC normalization depends on the duration and severity of ischemia rather than the absolute value.

Aged↗