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A Dörfler

Publications and source records attributed to A Dörfler.

At least 37 records · Page 2Linked to original sources
PubMed1999

Carotid endarterectomy and intracranial thrombolysis: simultaneous and staged procedures in ischemic stroke.

PURPOSE: The feasibility and safety of combining carotid surgery and thrombolysis for occlusions of the internal carotid artery (ICA) and the middle cerebral artery (MCA), either as a simultaneous or as a staged procedure in acute ischemic strokes, was studied. METHODS: A nonrandomized clinical pilot study, which included patients who had severe hemispheric carotid-related ischemic strokes and acute occlusions of the MCA, was performed between January 1994 and January 1998. Exclusion criteria were cerebral coma and major infarction established by means of cerebral computed tomography scan. Clinical outcome was assessed with the modified Rankin scale. RESULTS: Carotid reconstruction and thrombolysis was performed in 14 of 845 patients (1.7%). The ICA was occluded in 11 patients; occlusions of the MCA (mainstem/major branches/distal branch) or the anterior cerebral artery (ACA) were found in 14 patients. In three of the 14 patients, thrombolysis was performed first, followed by carotid enarterectomy (CEA) after clinical improvement (6 to 21 days). In 11 of 14 patients, 0.15 to 1 mIU urokinase was administered intraoperatively, ie, emergency CEA for acute ischemic stroke (n = 5) or surgical reexploration after elective CEA complicated by perioperative intracerebral embolism (n = 6). Thirteen of 14 intracranial embolic occlusions and 10 of 11 ICA occlusions were recanalized successfully (confirmed with angiography or transcranial Doppler studies). Four patients recovered completely (Rankin 0), six patients sustained a minor stroke (Rankin 2/3), two patients had a major stroke (Rankin 4/5), and two patients died. In one patient, hemorrhagic transformation of an ischemic infarction was detectable postoperatively. CONCLUSION: Combining carotid surgery with thrombolysis (simultaneous or staged procedure) offers a new therapeutic approach in the emergency management of an acute carotid-related stroke. Its efficacy should be evaluated in interdisciplinary studies.

Acute Disease↗
PubMed1999

[Endovascular therapy of cerebral aneurysms and vasospasm].

Major improvements have been achieved in endovascular treatment of cerebral aneurysms during the last twenty years. Initial techniques of selective balloon occlusion were progressively replaced by controlled packing of the aneurysmal sac with soft detachable platinum-coils (GDC). In some patients with large or giant aneurysms of the cavernous portion of the internal carotid artery endovascular parent vessel occlusion therapy with balloons is still necessary. In aneurysms of the proximal paraclinoidal segment of the internal carotid artery a combined endovascular and microneurosurgical approach, the "evacuation-trapping"-technique might be helpful. In patients with symptomatic cerebral vasospasm in whom conservative therapy has failed or is not possible balloon angioplasty and or the intra-arterial infusion of papaverine has become a valuable therapeutic alternative. Further follow-up studies are necessary to assess the value and long-term results of endovascular strategies.

Angioplasty, Balloon↗
PubMed1999

Surgically induced intracranial contrast enhancement: potential source of diagnostic error in intraoperative MR imaging.

BACKGROUND AND PURPOSE: Intraoperative MR imaging is being used increasingly during neurosurgical interventions. The aim of this study was to describe and classify different forms of surgically induced intracranial contrast enhancement observed during intraoperative MR examinations. METHODS: A total of 51 intraoperative MR examinations were performed to assess the extent of brain tumor removal. The intraoperative MR results (T1-weighted images, unenhanced and obtained serially after the IV administration of paramagnetic contrast material) were compared with preoperative and early postoperative MR findings. Animal experiments were conducted to obtain further evidence of the mechanism of surgically induced contrast enhancement. RESULTS: Four different types of surgically induced contrast enhancement were found: meningeal enhancement, increased enhancement of the choroid plexus, delayed enhancement at the resection margins, and immediate intraparenchymal contrast enhancement. The types of surgically induced contrast enhancement differ regarding their location, configuration, and time course. Their potential to be confused with contrast-enhancing, residual tumor also varies. Three of the four types of surgically induced contrast enhancement were reproducible in an animal model. CONCLUSION: Surgically induced contrast enhancement is a potential source of error in intraoperative MR imaging. Careful analysis of the location, configuration, and time course of intraoperatively observed intracranial enhancement is critical to avoid confusing surgically induced contrast enhancement with contrast-enhancing, residual tumor.

Animals↗
PubMed1998

Comparison of echo-planar sequences for perfusion-weighted MRI: which is best?

We compared gradient-echo (GRE), spin-echo (SE) and stimulated-echo (STE) echo-planar imaging sequences for perfusion-weighted imaging at different field strengths. Focal cerebral ischaemia was induced by endovascular occlusion of the middle cerebral artery in eight rats. MR was performed at 4.7 T or 2.35 T. With each sequence, we acquired data sets before, during and after bolus injection of Gd-DTPA with a time resolution of 1.2 s per image. The perfusion-weighted images were assessed with regard to image quality, artefacts, signal-to-noise ratio (SNR), and signal-at-tenuation-to-noise ratio (delta SNR) of the non-ischaemic tissue. Visual assessment showed GRE-EPI images acquired at 4.7 T to suffer from distortion due to susceptibility artefacts. Artefacts were less marked with the SE and STE series. The GRE-EPI sequence gave the highest SNR and delta SNR. At 2.35 T, the SNR of the STE sequences was less than 3 and therefore did not allow construction of reliable signal-time curves. SE-EPI was best suited for perfusion-weighted imaging at high field strength thanks to its minimal distortion artefacts and high SNR. Using lower field strengths (2.35 T and less), susceptibility artefacts are reduced; GRE-EPI sequences are then best suited, because they have the highest SNR and T2* sensitivity.

Animals↗
PubMed1998

Early carotid endarterectomy after non-disabling ischaemic stroke: adequate therapeutical option in selected patients.

OBJECTIVE: To evaluate neurological outcome and long-term results of early carotid endarterectomy (CEA) after non-disabling stroke. MATERIALS: Retrospective study between 1980 and 1995 of 56 patients undergoing CEA within 4 weeks of a transient (n = 15) or a permanent non-disabling (n = 41) ischaemic stroke. METHODS: Analyses of preoperative cerebral CT imaging, neurological outcome (mod. Rankin-scale) and long-term results (life-table analyses according to Kaplan-Meier). RESULTS: Incidence of early CEA increased from 1.7% (27 out of 1636) in the period 1980-1993 to 7.8% (29 out of 374) between 1994 and 1995. CEA was indicated after a neurological plateau phase was established (median interval 14 days). Fifty-seven per cent of the CEA patients had a minor ischaemic infarction (area < 2 cm), 18% showed a large territorial ischaemic infarction (area 2-5 cm) in cerebral CT imaging. Two patients deteriorated postoperatively (minor stroke rate 4%) but no major stroke or death occurred. Life-table probability of stroke-free survival (mean follow-up 42.7 months) was 94%, 90% and 84%, respectively, after 1, 2 and 5 years. Kaplan-Meier survival rates were 96%, 91% and 86% after 1, 2 and 5 years. CONCLUSIONS: Early CEA after non-disabling stroke is a safe procedure in selected patients.

Adult↗
PubMed1998

[Acute ischemic cerebral infarct: prospective serial observations by magnetic resonance imaging].

AIM: Serial observations of acute ischaemic cerebral infarcts by MRI in order to define signal patterns, contrast uptake, oedema and secondary haemorrhage over a period of three months. METHODS: Prospective serial examinations of 34 patients with acute cerebral ischaemia who were examined during the first 48 hours, on days 3 or 4, 7, 14, 21, 28 and after three months by MRI (spin echo TR/TE 2200/100/20, 500/20, +/- Gd). RESULTS: T2 weighted spin echo sequences showed the highest sensitivity (88%) during the first 8 hours of cerebral ischaemia when compared with other spin echo sequences. Parenchymal contrast enhancement showed a distinct peak during the second and third weeks. The use of contrast did not improve diagnosis of an infarct during any stage. 87% of lesions showed haemorrhage at some stage. Vascular enhancement was observed in 25% of infarcts during the first 24 hours and was still present after three months in 20%. Parenchymal and vascular enhancement, and haemorrhage correlate with the size of the infarct. CONCLUSION: Focal cerebral ischaemia produces an abnormality of the blood-brain barrier, oedema and finally necrosis, depending on the severity and duration of the lesion. Haemorrhage in 87% was considerably more common than has been described previously. Vascular enhancement is not an early sign of an infarct, contrary to what has been described in the literature.

Acute Disease↗
PubMed1998

[Follow-up monitoring with magnetic resonance tomography after decompressive trephining in experimental "malignant" hemispheric infarct].

Acute ischemia in the complete territory of the carotid or the middle cerebral artery may lead to cerebral edema with raised intracranial pressure and progression to coma and death. Although clinical data suggest benefit for patients undergoing decompressive surgery for massive space occupying hemispheric stroke, little data about the effects of this procedure on morbidity and outcome is available. The experimental data support an early surgical approach. For early and probably most effective treatment of severe, space-occupying cerebral ischemia, the "malignant" character of the brain edema has to be recognized early after onset of vessel occlusion. Hereby magnetic resonance imaging (MRI) may allow to determine the clinical significance of brain edema early after onset, simultaneously allowing to monitor the evolution of ischemia. We performed serial SE-MRI in rats with acute hemispheric infarctions treated by decompressive craniectomy. Focal cerebral ischemia was induced in 36 rats using an endovascular occlusion technique. Decompressive craniectomy was performed 4 and 24 hours after vessel occlusion in groups of 12 animals each. Twelve animals were not treated by decompressive craniectomy (control group). Four, 24, 48, 72 and 168 hours after MCAO all animals were examined with conventional T1- and T2-weighted SE-MRI. Shift of the midline structures and compression of the ventricles were scored. Changes in weight and neurological performance were measured daily. The infarction volume was calculated by triphenyltetrazolium chloride staining 168 hours after MCAO. While mortality in the untreated group was 33.3%, none of the animals treated by a decompressive craniectomy died (mortality 0%). Neurological behaviour, weight loss and infarction volume were significantly better in the animals treated by early decompressive craniectomy (p < 0.05). Four hours after MCAO all untreated animals showed a massive shift of the midline structures and a massive compression of the ventricles; only 7 of 12 animals treated early by craniectomy showed mild mass effects. Correlation of the histological brain damage with T2-weighted MRI 4 hours after MCAO was poor (r = 0.41); later than 24 hours there was a good correlation (r > 0.7). Our results suggest that decompressive craniectomy in malignant cerebral ischemia reduces mortality and significantly improves outcome. If performed early after vessel occlusion, it also significantly reduces infarction size. In the acute phase of hemispheric infarction conventional SE-MRI is not sensitive in estimation of infarction size. Later than 24 hours, conventinal SE-MRI proved to be useful in monitoring brain edema and infarction size in this rat model of malignant hemispheric stroke.

Animals↗
PubMed1998

[Computer-based training exemplified by the carotid artery].

The purpose of computer-based training (CBT) is interactive use of multimedia components, such as text, graphics, animation, sound, digital slide shows, and videos. This CD-ROM illuminates different aspects of carotid surgery: cerebrovascular insufficiency, sonographic and neuroradiological diagnostics, indications and results of carotid surgery in the literature, perioperative complications and new developments such as interventional procedures. Digital imaging (60 minutes of video sequences and 250 graphics) especially focus on operative standard procedures (conventional and eversion technique) and alternative methods. CBT is an evolving supplement to improve education programs in vascular surgery.

CD-ROM↗
PubMed1997

Haematoma evacuation does not improve outcome in spontaneous supratentorial intracerebral haemorrhage: a case-control study.

Surgical intervention in supratentorial intracerebral haemorrhage (ICH) is still controversial. We assessed the value of haematoma evacuation with a case-control study. 145 consecutive patients with supratentorial spontaneous ICH without tumour or vascular abnormalities were analysed. Haematoma evacuation was performed in 24 patients. Age, sex, Glasgow Coma Scale (GCS), level of consciousness, pupillary reaction on admission, localisation, aetiology and volume of the haematoma, presence of ventricular blood, and Glasgow Outcome Scale (GOS) on discharge were analysed. From statistical analysis 40 patients > 80 years and with haematoma volume < 10 ml, who were always treated conservatively, were excluded. Prognostic factors retained from a multiple regression model with the dichotomised GOS scale (GOS 1-3, 4 + 5) as response variable were GCS, haematoma volume and location. The only difference between all medically treated and "operated" patients was haematoma volume, which was larger in the "operated" patients. All 24 evacuated cases could be matched to a medically treated control regarding age, haematoma volume and location, GCS, and pupillary reaction. Significant differences between the two groups could not be detected. Outcome was not different between the two groups. After separating the sample into patients with and without ventricular haemorrhage, there was no different outcome between the two groups either. We conclude that haematoma evacuation did not improve outcome in supratentorial spontaneous ICH. Since haematomas were evacuated mainly in clinically deteriorating patients, our data suggest that the only effect of haematoma evacuation is to stop progressive deterioration rather than to improve overall clinical outcome.

Adult↗
PubMed1997

Craniectomy: an aggressive treatment approach in severe encephalitis.

BACKGROUND AND OBJECTIVE: Focal encephalitis may be associated with brain edema, which is often fatal. The control of intracranial pressure (ICP) is therefore crucial for further therapeutic strategies in space-occupying edema following encephalitis. However, aggressive treatment strategies such as hemicraniectomy have not been described in a larger series of patients. PATIENTS AND METHODS: We describe the clinical course and outcome in six patients who developed severe brain edema associated with acute encephalitis. All received maximum medical treatment for elevated ICP, but with signs of brainstem compression emerging, hemicraniectomy was performed to control ICP. RESULTS: All patients had a very severe encephalitic syndrome and were treated over the course of weeks in the neurocritical care unit (NCCU). However, all patients recovered almost completely and showed only mild or no neurologic deficit when reexamined after 4 months to 3 years. CONCLUSIONS: Hemicraniectomy should be considered in patients with severe brain edema following encephalitis as a potentially lifesaving therapeutic measure. Moreover, the initial neurologic deficit seems to have no impact on the long-term clinical outcome.

Adult↗
PubMed1997

[Carotid endarterectomy in the early phase after a non-disabling stroke: 1980-1995 results].

In 56 patients, carotid endarterectomy (CEA) was performed 14 days (median) after a non-disabling carotid-related stroke with a perioperative minor stroke rate of 3.6%. Even large ischemic brain infarcts on CT scan did not exclude patients from CEA, as long as the patient had reached a neurologic plateau. The data from this study indicate that CEA can be performed safely in properly selected patients, and might reduce the high risk of a recurrent stroke (5%-9.5% within 30 days).

Adult↗
PubMed1996

[Neuroradiological studies and findings in stroke].

This overview is about today's radiologic diagnostic possibilities in acute stroke. Despite many improvements in MR technology, CT is still the method of choice for most of these patients. Contrary to a long existing opinion, CT is a good diagnostic instrument even in the early phase of acute ischemic stroke. In combination with the new helical CT technique [CT angiography] all important questions regarding early therapeutic decisions can be answered. New MR perfusion techniques are just on the way to clinical application. Invasive angiography is only rarely indicated in acute ischemic stroke. The diagnosis of intracerebral hemorrhage is also mainly CT-based. MR and DSA are mandatory for further evaluation of the etiology of the hemorrhage. Nowadays, DSA is not longer mandatory for the diagnosis of cerebral venous sinus thrombosis. In some patients CT is already diagnostic; the combination of different MR and MRA techniques nearly always allows a definite diagnosis or exclusion of a venous thrombosis.

Brain Ischemia↗
PubMed1996

[Radiology of lumbar spinal canal stenosis].

Lumbar spinal stenosis is a frequent cause of low back pain. In this paper we discuss both the pathophysiology and clinical symptomatology of the disease. We also discuss advantages and limitations of plain film radiography, myelography, CT and MRI in its diagnosis. Following an analysis of the pertinent literature we try to determine the relative merit of the various radiologic procedures as to their true representation of clinical and intraoperative findings and faithful rendition of postoperative results. Until sufficient statistically valid data regarding the clinical significance of radiological findings have accumulated, surgery of lumbar spinal stenosis can only be performed after critical evaluation of the individual case.

Diagnostic Imaging↗
PubMed1994

MRI monitoring of experimental cerebral ischaemia: comparison of two models.

In experimental stroke research one of the key questions is whether animals models truly reflect human disease. One important reason for modelling stroke is to produce tissue changes that can be used to validate the correlation between the results of advanced radiological imaging and pathology. The aim of this study was to compare two minimally invasive rat models of focal ischaemic stroke as to their ability to simulate clinical stroke reproducibly. In one model a focal infarct was induced using the photochemical Rose Bengal technique. The second model was based on transvascular occlusion of the middle cerebral artery using a cervical approach. In all animals we performed MRI at different times with two different paramagnetic contrast agents. The time course of blood-brain-barrier disruption in the Rose Bengal model differed entirely from that in human brain ischaemia. The experimental stroke showed marked contrast enhancement in the first hour after the onset of ischaemia. On the other hand, the MRI changes in the suture occlusion model were very similar to the changes observed in human brain ischaemia: no early disruption of the blood-brain-barrier and increased T2-signal 4-6 h after the onset of stroke. We hope that the suture occlusion model will be used for research not only by basic and clinical scientists but also by radiologists, who, using modern imaging methods, may greatly influence the diagnosis as well as the management of this devastating disease.

Animals↗
PubMed1994

MRI in acute cerebral ischaemia: perfusion imaging with superparamagnetic iron oxide in a rat model.

An imaging technique capable of detecting ischaemic cerebral injury at an early stage could improve diagnosis in acute or transient cerebral ischaemia. We compared the ability of superparamagnetically contrast-enhanced MRI and conventional T2-weighted MRI to detect ischaemic injury early after unilateral occlusion of the middle cerebral artery in 12 male Wistar rats. Permanent vessel occlusion was achieved by a transvascular approach, which has the advantage of not requiring a craniectomy. At 45-60 min after the procedure, the animals had conventional T2-weighted MRI before and after administration of a superparamagnetic contrast agent (iron oxide particles). Unenhanced images were normal in all animals. After administration of iron oxide particles, the presumed ischaemic area was clearly visible, as relatively increased signal, in all animals; this high signal area corresponded to the area of ischaemic brain infarction seen on histological studies. Magnetic susceptibility effects of iron particles cause low signal in normally perfused cerebral tissue, whereas tissue with reduced or absent blood flow continues to give relatively high signal. Our results suggest that superparamagnetic iron particles may significantly reduce the interval between an ischaemic insult and the appearance of parenchymal changes on MRI.

Acute Disease↗