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Biomedical subjects

T Neumann-Haefelin

Publications and source records attributed to T Neumann-Haefelin.

At least 19 recordsLinked to original sources
PubMed2006

[Long term follow-up after intracranial vertebro-basilar artery stenting].

PURPOSE: Recurrent ischemic symptoms attributable to intracranial high-grade vertebrobasilar artery stenoses are associated with a high risk of ischemic stroke, particularly if these occur in spite of aggressive medical treatment. Long term efficacy data for endovascular stent angioplasty of symptomatic intracranial stenoses are lacking. The purpose of this prospective study is to determine the rates of deaths, of ischemic events and of restenosis during long-term follow-up. MATERIALS AND METHODS: Between June 2001 and February 2004 twelve patients (11 male, 1 female; median 63 yrs; range, 46 - 75 yrs) with recurrent ischemic symptoms attributed to > or = 70 % intracranial vertebro-basilar artery stenoses, who had failed aggressive medical treatment, were included. Median follow-up was 24 months (range: 6 to 36 months). Intracranial stenoses were measured using 3D rotation angiography data sets and treated with balloon expandable stents. All patients were scheduled for follow-up including clinical (Barthel Index) and transcranial Doppler examinations and intraarterial angiography at 6 months after intervention. Clinical outcome was defined as the rate of stroke in any vascular territory or death during follow-up. Vascular outcome was determined by the rate of in-stent restenosis 50 % on follow-up as examined by intraarterial angiography at 6 months or by transcranial color-coded duplex sonography. RESULTS: Stent placement was technically successful in all patients. No patient had further cerebral ischemic symptoms; two patients died (1 myocardial infarct, 1 sudden death) during follow-up of median 24 months. The degree of stenoses was reduced from median 81 % (range 69 - 94 %) to 19 % (range 10 - 36 %) immediately after stent placement and to 32 % (range 22 - 48 %) after 6 months. No restenosis > or = 50 % occurred during follow-up. CONCLUSION: Based on this limited series, we believe that in patients, with recurrent symptoms despite aggressive medical treatment, endovascular stent placement in intracranial high-grade vertebrobasilar artery stenoses can be an effective and safe treatment option.

Aged↗
PubMed2005

Serum glial fibrillary acidic protein as a biomarker for intracerebral haemorrhage in patients with acute stroke.

BACKGROUND: Biomarkers of stroke are an evolving field of clinical research. A serum marker which can differentiate between haemorrhagic and ischaemic stroke in the very early phase would help to optimise acute stroke management. OBJECTIVE: To examine whether serum glial fibrillary acidic protein (GFAP) identifies intracerebral haemorrhage (ICH) in acute stroke patients. METHODS: A pilot study assessing 135 stroke patients admitted within six hours after symptom onset. Diagnosis of ICH (n = 42) or ischaemic stroke (n = 93) was based on brain imaging. GFAP was determined from venous blood samples obtained immediately after admission, using a research immunoassay. RESULTS: GFAP was detectable in the serum of 39 patients (34 of 42 (81%) with ICH, and five of 93 (5%) with ischaemic stroke). Serum GFAP was substantially raised in patients with ICH (median 11 ng/l, range 0 to 3096 ng/l) compared with patients with ischaemic stroke (median 0 ng/l, range 0 to 14 ng/l, p<0.001). Using receiver operating characteristic curve analysis, a cut off point of 2.9 ng/l provided a sensitivity of 0.79 and a specificity of 0.98 for the identification of ICH in acute stroke (positive predictive value 0.94, negative predictive value 0.91; p<0.001). CONCLUSIONS: Serum GFAP can reliably detect ICH in the acute phase of stroke. Further evaluation of the usefulness of GFAP as an early diagnostic marker of ICH is now required, with the aim of optimising cause specific emergency management.

Aged↗
PubMed2004

Hemi-spinal cord infarction due to vertebral artery dissection in congenital afibrinogenemia.

Isolated ischemia of the cervical spinal cord is an uncommon but increasingly recognized complication of vertebral artery dissection (VAD). The authors report a young patient with congenital afibrinogenemia, who developed VAD with extensive unilateral spinal cord infarction, probably caused by local compression of spinal radicular feeders at their origin by vertebral artery hematoma.

Adult↗
PubMed2004

Endovascular recanalization of acute atherothrombotic carotid artery occlusion holds up progressive stroke.

In acute carotid artery occlusion, hemodynamic compromise in addition to artery-artery thromboembolism is the mechanism of ischemia that may lead to a progressive clinical course with enlarging infarcts. The natural course of carotid artery occlusion with a progressive stroke is unfavorable with only about 10% of patients making a good recovery. We report on two patients in whom emergency recanalization of acute carotid artery occlusion with self-expanding stents restored cerebral blood flow and held up progressive stroke.

Carotid Artery Thrombosis↗
PubMed2003

Effect of incomplete (spontaneous and postthrombolytic) recanalization after middle cerebral artery occlusion: a magnetic resonance imaging study.

BACKGROUND AND PURPOSE: Early reperfusion is one of the best predictors of good outcome after acute middle cerebral artery (MCA) occlusion. The purpose of this study was to analyze the frequency and relevance of incomplete recanalization for tissue and clinical outcome. METHODS: From a larger acute stroke database (Kompetenznetzwerk Schlaganfall B5), all patients (n=82) with MCA main stem occlusion (excluding carotid T-occlusions) were selected. These patients had received a multiparametric stroke MRI protocol including diffusion- and perfusion-weighted imaging (DWI, PWI) and MR angiography (MRA) within 6 hours after symptom onset, at day 1 and after 1 week. Recanalization status was determined with MRA on day 1 (according to Thrombolysis In Myocardial Infarction flow grades) and used to group patients into those with persistent occlusion (0) or minimal (1), partial (2), or complete (3) recanalization. RESULTS: Incomplete recanalization according to MRI criteria was found in 39 patients (grade 1: n=20; grade 2: n=19), complete recanalization in 10, and persistent occlusion in 33. There was no statistically significant difference in any of the clinical (National Institutes of Health Stroke Scale score) or MRI baseline parameters (DWI lesion, PWI deficit, mismatch volume, mismatch ratio). However, lesion growth was smaller in patients with recanalization (even in patients with only minimal recanalization) and outcome was related to the degree of recanalization (mean modified Rankin score at 90 days: 3.36, 2.70, 1.79, and 1.44 for the groups with no, minimal, partial, and complete recanalization, respectively). Both incomplete and complete recanalization was more frequent in patients receiving thrombolysis. CONCLUSIONS: Incomplete recanalization on day 1 is a frequent MR finding after MCA main stem occlusion, indicating a more favorable clinical course than persistent occlusion. MR indicators of early recanalization could be useful surrogates of efficacy in thrombolytic trials.

Adult↗
PubMed2003

S100B as a surrogate marker for successful clot lysis in hyperacute middle cerebral artery occlusion.

OBJECTIVES: The astroglial protein S100B is a marker of cerebral tissue damage. This study investigated whether the serum kinetic of S100B may serve as a surrogate marker of successful clot lysis and early recanalisation (<6 hours) in hyperacute proximal middle cerebral artery (MCA/M1) occlusion. METHODS: The authors prospectively included 23 patients (mean (SD) age, 70.2 (11.0) years) presenting with MCA/M1 occlusion on magnetic resonance angiography (n=18), intra-arterial angiography (IA; n=2), or transcranial Doppler sonography (TCD; n=3) within five hours after symptom onset. Rates of recanalisation and their point of time were determined using TCD or IA. Individual S100B values were determined at hospital admission, every eight hours within the first three days, and at 12 hour intervals from day 4 to day 6. Additionally, the S100B area under the curve (AUC) and the S100B peak value were obtained. RESULTS: Early recanalisation (<6 hours after symptom onset, n=7) was associated with a significantly lower mean S100B AUC compared with no recanalisation (22.2 (40.1) versus 406.8 (284.4) micro g/l per hour; p<0.001). Using receiver operating calculations, a single S100B value obtained 48-96 hours after stroke onset of less than 0.4 micro g/l (cut off point) provided a 86% sensitivity and 100% specificity for sufficient MCA/M1 clot lysis <6 hours. The overall accuracy for a single S100B value obtained in the 48-96 hours time window was as high as for the AUC (95.7%). CONCLUSION: A single S100B value <0.4 micro g/l obtained 48-96 hours after stroke onset indicates successful clot lysis <6 hours in MCA/M1 occlusion with a high degree of accuracy. Thus, determination of a single S100B value may serve as a surrogate marker of early and sufficient MCA/M1 recanalisation in large scale thrombolytic studies.

Acute Disease↗
PubMed2003

[Recanalizing therapies in acute stroke].

Systemic thrombolysis with rt-PA within 3 hours after symptom onset has developed into a standard therapy for acute stroke patients. Recombinant t-PA is now licensed in Europe for this indication. Within 3 to 6 hours, no general therapeutic standard has been established yet. Currently, the available data are in favor of intra-arterial thrombolysis for patients with proximal occlusions of the middle cerebral artery. Systemic thrombolysis is not generally recommended in this time window, but is used in some centers for selected patients. In addition to thrombolysis and new strategies to improve thrombolysis (including patient selection with MRI), several interventional and surgical recanalization techniques are discussed.

Acute Disease↗
PubMed2001

Relationship between severity of MR perfusion deficit and DWI lesion evolution.

OBJECTIVE: To assess whether a quantitative analysis of the severity of the early perfusion deficit on MRI in acute ischemic stroke predicts the evolution of the perfusion/diffusion mismatch and to determine thresholds of hypoperfusion that can distinguish between critical and noncritical hypoperfusion. METHODS: Patients with acute ischemic stroke were studied in whom perfusion-weighted imaging (PWI) and diffusion-weighted imaging (DWI MRI) were performed within 7 hours of symptom onset and again after 4 to 7 days. Patients with early important decreases in points on the NIH Stroke Scale were excluded. Maps of cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) were created. These hemodynamic parameters were correlated with the degree of recruitment of the baseline PWI lesion by the DWI lesion. RESULTS: Twelve patients had an initial PWI > DWI mismatch of >20%. A linear relationship was observed between the initial MTT and the degree of recruitment of the baseline PWI lesion by the DWI lesion at follow-up (R(2) = 0.9, p < 0.001). Higher CBV values were associated with higher degrees of recruitment (rho = 0.732, p < 0.007). The volume of MTT of >4 (R(2) = 0.86, p < 0.001) or >6 seconds (R(2) = 0.85, p < 0.001) predicted final infarct size. CONCLUSION: Among patients who have had an acute stroke with PWI > DWI, who do not have dramatic early clinical improvement, the degree of expansion of the initial DWI lesion correlates with the severity of the initial perfusion deficit as measured by the mean transit time and the cerebral blood volume.

Adult↗
PubMed2001

MRI of subacute hemorrhagic transformation in the rat suture occlusion model.

In this study we investigated the utility of different MRI techniques for the detection and predictability of hemorrhagic transformation (HT) in a rat model of transient focal cerebral ischemia. Hemorrhagic infarction was reliably identified with gradient-echo sequences and developed between 2 and 7 days following the insult. None of the investigated early MRI features of the ischemic lesions (including the apparent diffusion coefficient and post-reperfusion blood-brain barrier damage) was a good predictor of HT severity at 7 days. This indicates that subacute HT at 2-7 days occurs independently of the severity of acute tissue and BBB damage.

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

Assessment of cerebrovascular reactivity with functional magnetic resonance imaging: comparison of CO(2) and breath holding.

Cerebral blood flow (CBF) and oxygenation changes following both a simple breath holding test (BHT) and a CO(2) challenge can be detected with functional magnetic resonance imaging techniques. The BHT has the advantage of not requiring a source of CO(2) and acetazolamide and therefore it can easily be performed during a routine MR examination. In this study we compared global hemodynamic changes induced by breath holding and CO(2) inhalation with blood oxygenation level dependent (BOLD) and CBF sensitized fMRI techniques. During each vascular challenge BOLD and CBF signals were determined simultaneously with a combined BOLD and flow-sensitive alternating inversion recovery (FAIR) pulse sequence. There was a good correlation between the global BOLD signal intensity changes during breath holding and CO(2) inhalation supporting the notion that the BHT is equivalent to CO(2) inhalation in evaluating the hemodynamic reserve capacity with BOLD fMRI. In contrast, there was no correlation between relative CBF changes during both vascular challenges, which was probably due to the reduced temporal resolution of the combined BOLD and FAIR pulse sequence.

Adult↗
PubMed2001

Reversal of early diffusion-weighted magnetic resonance imaging abnormalities does not necessarily reflect tissue salvage in experimental cerebral ischemia.

BACKGROUND AND PURPOSE: Diffusion-weighted MRI (DWI) can detect early ischemic changes and is sometimes used as a surrogate neurological end point in clinical trials. Recent experimental stroke studies have shown that with brief periods of ischemia, some DWI lesions transiently reverse, only to recur later. This study examined the histological condition of the tissue during the period of DWI reversal. METHODS: Rats underwent 30 minutes of middle cerebral artery occlusion followed by reperfusion. DWI images were obtained during ischemia and 3 to 5 hours, 1 day, and 7 days later. MRI scans were compared with histology (5 hours, n=5; 7 days, n=5) with the use of neuronal (microtubule-associated protein 2 [MAP2]) and astrocytic (glial fibrillary acidic protein [GFAP]) markers and heat-shock protein 72 (HSP72). RESULTS: DWI abnormalities reversed 3 to 5 hours after ischemia onset but recurred at 1 day. Four animals showed complete reversal of the initial DWI hyperintensity, and 6 showed partial reversal. When the 5-hour DWI was completely normal, there was significant loss of MAP2 immunoreactivity, comprising approximately 30% of the initial DWI lesion. However, GFAP staining revealed morphologically normal astrocytes. HSP72 immunoreactivity at 5 hours was extensive and corresponded to the initial DWI lesion. CONCLUSIONS: After brief ischemic periods, normalization of the DWI does not necessarily imply that the tissue is normal. Neurons already exhibit evidence of structural damage and stress. Normal GFAP staining suggests that other nonneuronal cell populations may partially compensate for altered fluid balances at the time of DWI reversal despite the presence of neuronal injury. These observations suggest that caution is warranted when relying solely on DWI for assessment of ischemic damage.

Animals↗
PubMed2000

Enhancement of whole cell calcium currents following transient MCAO.

Cerebral infarctions have been shown to cause widespread changes of neuronal excitability in non-infarcted tissue. Calcium currents are major determinants of neuronal behavior, and pathological modulation of Ca(2+)-channels is known to lead to altered excitability states in a variety of paradigms. In the present study we addressed the question to what extent whole cell calcium currents are altered after middle cerebral artery occlusion (MCAO) in both the ipsi- and contralateral sensory cortex. Transient middle cerebral artery occlusion was induced for 1 h in rats using the intraluminal thread model. After 7 or 28 days survival, whole cell patch clamp studies were carried out on freshly isolated neurons of the ipsi- and contralateral sensory cortex, and high voltage activated (HVA) calcium currents were examined. In lesioned animals, we found a significant increase of calcium current amplitude and maximal conductance in the sensory cortex contralateral to the infarcts. This was paralleled by a prominent positive shift of the potential of half-maximal activation (V(h,a)) in these cells. Changes were long-lasting and at least stable for the following 28 days. These alterations were present in animals with lesions of moderate size, but not in those with massive infarction, and only in the cortex contralateral to the lesion. Following cortical infarctions, changes of calcium current properties are selectively observed in neurons contralateral to the lesion. At the behavioral level, compensatory mechanisms involving the unaffected hemisphere may induce this alteration of calcium current properties.

Animals↗
PubMed2000

Diffusion- and perfusion-weighted MRI in a patient with a prolonged reversible ischaemic neurological deficit.

We report acute and follow-up diffusion- and perfusion-weighted MRI (DWI, PWI) findings in a patient with a prolonged reversible ischaemic neurological deficit. PWI 12 h after the patient was last seen to be without symptoms revealed a large perfusion deficit in the left posterior MCA territory with a relatively inconspicuous and much smaller abnormality on DWI. Follow-up showed resolution of abnormalities on both DWI and PWI, and conventional MRI was normal, apart from a very slight abnormality, visible only on FLAIR images, at the centre of the initially DWI-positive region. These findings demonstrate the utility of PWI when be used in combination with DWI to investigate the pathophysiology of transient ischemic syndromes.

Aged↗
PubMed2000

Surgical treatment of 50 carotid dissections: indications and results.

PURPOSE: This article analyzes the course of 48 patients with 49 chronic carotid dissections (who were treated surgically at our institution after a median anticoagulation period of 9 months because of a persistent high-grade stenosis or an aneurysm) and the course of one additional patient with acute carotid dissection (who underwent early operative reconstruction 12 hours after onset because of fluctuating neurologic symptoms). METHODS: All medical and surgical records and imaging studies were reviewed retrospectively. All histologic specimens were reevaluated by a single pathologist to assess the cause of dissection. Follow-up of 41 patients (85%) after 70 months (range, 1-190 months) consisted of an examination of the extracranial vessels in the neck by Doppler ultrasound scanning and a questionnaire about the patients' medical history and their personal appraisals of cranial nerve function. RESULTS: Seventy percent of the dissections had developed spontaneously; 18% were caused by trauma; 12% of all patients (22% of the women) had a fibromuscular dysplasia. Indication for surgery was a high-grade persisting stenosis and a persisting or newly developed aneurysm. Flow restoration was achieved by resection and vein graft replacement in 40 cases (80%) and thromboendarterectomy and patch angioplasty in three cases (6%). Gradual dilatation was performed and effective in two cases (4%). Five internal carotid arteries (10%) had to be clipped because dissection extended into the skull base. One patient died of intracranial bleeding. Five patients (10%) experienced the development of a recurrent minor stroke (ipsilateral, 4 patients; contralateral, 1 patient). Cranial nerve damage could not be avoided in 29 cases (58%) but were transient in most of the cases. During follow-up, one patient died of unrelated reasons, and only one patient had experienced the development of a neurologic event of unknown cause. CONCLUSION: Chronic carotid dissection can be effectively treated by surgical reconstruction to prevent further ischemic or thromboembolic complications, if medical treatment for 6 months with anticoagulation failed or if carotid aneurysms and/or high-grade carotid stenosis persisted or have newly developed.

Anticoagulants↗
PubMed2000

Periinfarct and remote excitability changes after transient middle cerebral artery occlusion.

Transient middle cerebral artery (MCA) occlusion results in substantially smaller cortical infarcts than permanent MCA occlusion if reperfusion is initiated within the first few hours. Only little information is available on the long-term functional outcome of the cortical regions "salvaged" by early reperfusion. To address this issue we examined basic electrophysiologic parameters in vitro using standard extracellular recording techniques at 7 and 28 days after transient MCA occlusion (1- and 2-hour ischemia) in rats. Both neocortical areas ipsi- and contralateral to MCA occlusion were systematically mapped to delineate the extent of periinfarct and remote alterations. In the periinfarct region we found a significant reduction of field potential amplitudes up to 3 mm when measuring from the infarct border at 7 days and up to 7 mm at 28 days. Paired-pulse inhibition, an indicator of GABAergic transmission, was only moderately impaired in this region at 7 days and not significantly different from control at 28 days. Remote effects were observed both ipsi- and contralaterally. Ipsilaterally they were restricted to a region close to the midline (presumably motor cortex) and were most likely attributable to the degeneration of corticostriatal connections. The extent of the contralateral excitability changes was clearly related to the size of the neocortical infarcts with large infarcts resulting in the widespread reduction of field potential amplitudes and an impairment of paired-pulse inhibition. The results show that there is a relatively large periinfarct region with decreased overall excitability after transient MCA occlusion which is likely to have a profound effect on perilesional processes involved in functional recovery. Remote excitability changes may contribute to the functional deficit and are probably related to deafferentation.

Action Potentials↗