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Biomedical subjects

R Bachmann

Publications and source records attributed to R Bachmann.

At least 19 recordsLinked to original sources
PubMed2006

Mild mechanical traumas are possible risk factors for cervical artery dissection.

BACKGROUND AND PURPOSE: Cervical artery dissection (CAD) is a common cause of ischemic stroke in younger aged subjects. Retrospective studies suggest cervical manipulative therapy (CMT) and preceding infections as extrinsic risk factors for CAD. In a case-control study, we assessed a questionnaire with 7 mild mechanical traumas as potential trigger factors for CAD, including CMT and recent infections. PATIENTS AND METHODS: Forty-seven consecutive patients with CAD were compared with 47 consecutive patients of similar age with ischemic stroke due to etiologies other than CAD. Patients underwent a standardized face-to-face interview. We assessed head or neck pain and recent infection <7 days before symptom onset, as well as the following mechanical trigger factors <24 h and <7 days prior to symptom onset: (1) heavy lifting, (2) sexual intercourse, (3) mild direct or (4) indirect neck trauma, (5) jerky head movements, (6) sports activity, and (7) CMT. RESULTS: We found no association between any single one of the above risk factors and CAD. CMT (CAD, n = 10; non-CAD, n = 5) and recent infections (CAD, n = 18; non-CAD, n = 10) were more frequent in the CAD group but failed to reach significance. However, the cumulative analysis of all mechanical trigger factors revealed a significant association of mechanical risk factors as a whole in CAD <24 h prior to symptom onset (p = 0.01). CONCLUSION: Mild mechanical stress, including CMT, plays a role as possible trigger factor in the pathogenesis of CAD. CMT and recent infections alone failed to reach significance during the present investigation, presumably due to the relatively small sample size of the study cohort.

Adult↗
PubMed2005

Negative ultrasound findings in patients with cervical artery dissection. Negative ultrasound in CAD.

BACKGROUND: Cervical artery dissection (CAD) is a common cause of ischemic stroke in the younger age group. Modern imaging techniques allow the depiction of the mural hematoma, even in CADs with only subtle vessel alterations. The aim of this retrospective study was (1) to characterize the angiological features in CAD and (2) to determine the frequency of initially normal ultrasonography (US) findings. METHODS: 86 patients aged 44 +/- 11 years with CAD of the internal carotid (ICA), (n = 55) or the vertebral artery (VA), (n = 31), admitted to our hospital within 8 days (mean 1.6 days) of symptom onset, were included. CAD was confirmed either by CT-angiography, MRI of the neck, MR-angiography or digital substraction angiography (DSA) and was compared with the results of the initial as well as repeated US examinations of the arteries supplying the brain. RESULTS: In 75 patients (81.2 %) signs of vessel stenosis or occlusion were found while 11 patients (12.8%) with CAD of the ICA (n = 9) and the VA (n = 2) had normal US findings. The site of dissection in the US negative patients was highly variable without a predilection site. In 2 of 7 patients with repeated US examinations, complete vessel occlusion was found on follow-up, while in 5 patients again normal results were found. In four patients, there were changing findings in two alternative confirming imaging methods (MRI/DSA, CT/MRI) and in one patient conflicting findings (CT/MRI). Brain infarctions had occurred in 7 of the initially sonographically normal patients while the other 4 had suffered from transient (n = 2) or local (n = 2) symptoms only. CONCLUSION: Approximately 1 out of 8 patients with subsequently proven CAD has negative initial neurovascular US findings despite comprehensive examination. In patients with suspected CAD and negative US examination, repeated US examinations and further diagnostic imaging, especially MRI is necessary.

Adult↗
PubMed2005

Generalized arteriopathy in patients with cervical artery dissection.

OBJECTIVE: To make an ultrastructural comparison of superficial temporal artery (STA) biopsy specimens from patients with spontaneous cervical artery dissection (sCAD) and controls. METHODS: The authors used light microscopic examination of semithin sections and electron microscopic examination of ultrathin sections of STA biopsy specimens from patients with sCAD and controls. RESULTS: STA biopsy specimens from patients with sCAD taken around the time of the dissection showed a zone of connective tissue weakening with fissuring at the junction between the tunica media (TM) and the tunica adventitia (TA) in seven of nine specimens and erythrocyte infiltration in eight of nine specimens but in none of the control specimens. Light microscopy demonstrated transparent circular spots that, on electron microscopy, turned out to represent erythrocytes and other cellular components at different stages of degradation. Occasionally, scattered immune cells were found in specimens from patients with sCAD. In addition, smooth muscle cells of the synthetic phenotype, some of them showing extensive vacuolation were more common in the TM of STA biopsy specimens from patients with sCAD than in control specimens. CONCLUSIONS: Signs of tissue weakening along the TM/TA junction in STA biopsy specimens of patients with sCAD but not in controls suggest the presence of a generalized arteriopathy leading to impairment of the stability of the arterial wall in patients with sCAD. Limiting factors of the study are that some control biopsies were obtained from autopsies and that the anticoagulation status of patients and controls were not completely comparable.

Adult↗
PubMed2005

[Comparison of a T1-weighted inversion-recovery-, gradient-echo- and spin-echo sequence for imaging of the brain at 3.0 Tesla].

PURPOSE: The increased T1 relaxation times at 3.0 Tesla lead to a reduced T1 contrast, requiring adaptation of imaging protocols for high magnetic fields. This prospective study assesses the performance of three techniques for T1-weighted imaging (T1w) at 3.0 T with regard to gray-white differentiation and contrast-to-noise-ratio (CNR). MATERIALS AND METHODS: Thirty-one patients were examined at a 3.0 T system with axial T1 w inversion recovery (IR), spin-echo (SE) and gradient echo (GE) sequences and after contrast enhancement (CE) with CE-SE and CE-GE sequences. For qualitative analysis, the images were ranked with regard to artifacts, gray-white differentiation, image noise and overall diagnostic quality. For quantitative analysis, the CNR was calculated, and cortex and basal ganglia were compared with the white matter. RESULTS: In the qualitative analysis, IR was judged superior to SE and GE for gray-white differentiation, image noise and overall diagnostic quality, but inferior to the GE sequence with regard to artifacts. CE-GE proved superior to CE-SE in all categories. In the quantitative analysis, CNR of the basal ganglia was highest for IR, followed by GE and SE. For the CNR of the cortex, no significant difference was found between IR (16.9) and GE (15.4) but both were superior to the SE (9.4). The CNR of the cortex was significantly higher for CE-GE compared to CE-SE (12.7 vs. 7.6, p < 0.001), but the CNR of the basal ganglia was not significantly different. CONCLUSION: For unenhanced T1 w imaging at 3.0 T, the IR technique is, despite increased artifacts, the method of choice due to its superior gray-white differentiation and best overall image quality. For CE-studies, GE sequences are recommended. For cerebral imaging, SE sequences give unsatisfactory results at 3.0 T.

Brain↗
PubMed2005

[Incidence of cerebral ischemia in patients with suspected cervical artery dissection: first results of a prospective study].

PURPOSE: Aim of this prospective study was to investigate the incidence of spontaneous cervical artery dissection (sCAD) and cerebral ischemia in patients with suspected sCAD by using a combined head-neck MR-imaging protocol. MATERIALS AND METHODS: 51 consecutive patients (24 m, 27 f, mean age 39.5 years, range 18 - 55 yrs) admitted to our stroke unit with suspected sCAD according to clinical criteria and age < 55 years underwent a combined head and neck MR examination within 24 hours of admission (Gyroscan Intera 1.5 T, Philips). Head MRI included ax FLAIR, ax T (1), ax DWI and TOF angiography (imaging time 12 min). Neck MRI consisted of ax T1w-TSE, T2w-TSE, contrast enhanced T1w-TSE and CE-MRA (imaging time 17 min). Three radiologists assessed both studies in consensus with regard to the presence of sCAD and acute ischemia. RESULTS: One patient had to be excluded because of motion artefacts. In 17 of 50 patients sCAD was diagnosed, and in 20 of 50 patients cerebral ischemia. In 5 patients cerebral ischemia was caused by sCAD. CONCLUSION: The proposed combined MR protocol allows imaging work-up of patients with suspected sCAD within approximately 30 min, resulting in conclusive information about the status of the extracranial vasculature and the presence of ischemia. The high incidence of patients with definite sCAD and the low incidence of cerebral ischemia indicates the necessity of an early definite diagnosis in order to start timely anticoagulation to prevent development of stroke.

Acute Disease↗
PubMed2004

Superselective embolization of arterial bleeding as a late complication 3 months after nephron sparing surgery for renal cell carcinoma.

To our knowledge, this is the first case of an arterial bleeding as a late complication 3 months after nephron sparing surgery of renal cell cancer, presumably originating from an arteriocalyceal fistula. Superselective embolization of the feeding arterial branch was chosen for treatment of the hemorrhage and proved successful. The high efficacy of superselective embolization as a minimally invasive procedure in this and other cases of bleeding Vessels should be the preferred method instead of open surgery.

Carcinoma, Renal Cell↗
PubMed2004

Characterisation of materials causing discolouration in potable water systems.

Discoloured water is one of the main causes of customer complaints received by UK water suppliers. Flushing is recognised as a means of preventing red water events by mobilising material with the potential to cause discolouration. The understanding of the mechanisms and materials causing discolouration is limited. It is therefore necessary to characterise the materials mobilised by flushing, which are responsible for discolouration. The University of Sheffield and two UK water companies embarked on an in-depth programme of monitoring mains flushing. The programme involves collecting discrete samples during flushing of pipes of differing materials, diameters, age, source water and hydraulic regime. The results show iron to be the dominant material mobilised irrespective of pipe material. All samples indicate a direct correlation between turbidity, iron and manganese, and to a lesser extent with metals lead, copper, aluminium and zinc. Concentration of metals mobilised is independent of pipe material, diameter or age.

Color↗
PubMed2003

Magnetic resonance imaging protocols for examination of the neurocranium at 3 T.

The increasing availability of high-field (3 T) MR scanners requires adapting and optimizing clinical imaging protocols to exploit the theoretically higher signal-to-noise ratio (SNR) of the higher field strength. Our aim was to establish reliable and stable protocols meeting the clinical demands for imaging the neurocranium at 3 T. Two hundred patients with a broad range of indications received an examination of the neurocranium with an appropriate assortment of imaging techniques at 3 T. Several imaging parameters were optimized. Keeping scan times comparable to those at 1.5 T we increased spatial resolution. Contrast-enhanced and non-enhanced T1-weighted imaging was best applying gradient-echo and inversion recovery (rather than spin-echo) techniques, respectively. For fluid-attenuated inversion recovery (FLAIR) imaging a TE of 120 ms yielded optimum contrast-to-noise ratio (CNR). High-resolution isotropic 3D data sets were acquired within reasonable scan times. Some artifacts were pronounced, but generally imaging profited from the higher SNR. We present a set of optimized examination protocols for neuroimaging at 3 T, which proved to be reliable in a clinical routine setting.

Adult↗
PubMed2003

[Aneurysm of the subclavian artery after operatively corrected coarctation of the aorta: 20 years of follow-up and review of the current literature].

We report of long-term follow-up of a combined fusiform aneurysm of the right subclavian artery extending to the thyreocervical trunk (3.2 x 2.8 x 2.2 cm (width x height x depth)) in a 33-year old patient. As a newborn, the clinical diagnosis of an aortic isthmus stenosis was made without need for intervention at this stage. Further development of the child remained unremarkable until the age of eleven years when he experienced dizziness after sporting activities. Due to clinically proven progress, cardiac catheterization was performed and confirmed the initial diagnosis of a juxtaductale stenosis of the aortic isthmus, which was operated thereafter with an end-to-end anastomosis. Furthermore, an aneurysm of the right subclavian artery was revealed. Since then, non-invasive routine follow-up showed no significant worsening of this aneurysm, which extends to the thyreocervical trunk. The patient has been event free and completely asymptomatic. This case report illustrates the more than twenty years of follow-up of an asymptomatic combined fusiform aneurysm of the subclavian artery and thyreocervical trunk and provides a review of the literature on this topic.

Adolescent↗
PubMed2003

Selective hepatic artery ligation for hepatic haemangioendothelioma: case report and review of the literature.

Although benign, hepatic haemangioendotheliomas (HHE) are rare vascular tumours of the infant which have a high mortality rate secondary to high output congestive heart failure. The management of these tumours is still controversial and none of the different medical or surgical options has been unanimously accepted. We report the case of a neonate with congestive heart failure (CHF) due to a localized HHE, treated successfully by selective ligation of the left hepatic artery branch irrigating the tumour, under perioperative ultrasound Doppler control. A review of the literature showed 35 cases of HHE treated by hepatic artery ligation (HAL) with a survival rate of 80 %.

Female↗
PubMed2001

Phosphatidic acid-mediated mitogenic activation of mTOR signaling.

The mammalian target of rapamycin (mTOR) governs cell growth and proliferation by mediating the mitogen- and nutrient-dependent signal transduction that regulates messenger RNA translation. We identified phosphatidic acid (PA) as a critical component of mTOR signaling. In our study, mitogenic stimulation of mammalian cells led to a phospholipase D-dependent accumulation of cellular PA, which was required for activation of mTOR downstream effectors. PA directly interacted with the domain in mTOR that is targeted by rapamycin, and this interaction was positively correlated with mTOR's ability to activate downstream effectors. The involvement of PA in mTOR signaling reveals an important function of this lipid in signal transduction and protein synthesis, as well as a direct link between mTOR and mitogens. Furthermore, these studies suggest a potential mechanism for the in vivo actions of the immunosuppressant rapamycin.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Improving the detectability of focal liver lesions on T2-weighted MR images: ultrafast breath-hold or respiratory-triggered thin-section MRI?

The purpose of this study was to determine whether a respiratory-triggered (RT) T2-weighted turbo spin-echo (TSE) sequence with thin section can improve the detectability of focal liver lesions compared to a breath-hold (BH) T2-weighted TSE sequence. In 25 patients an RT TSE with 8-mm sections (8-TSE RT) and 5-mm sections (5-TSE RT) and a BH TSE sequence with 8-mm sections (8-TSE BH) were performed. Forty-one focal liver lesions (mean: 1.8 +/- 1.2 cm; 14 lesions < or =1 cm; 27 lesions >1 cm) were evaluated. The 5-TSE RT was significantly better in lesion detection compared to the 8-TSE BH sequence for all sizes of lesions (40/41 vs. 33/41; P = 0.014). For lesions >1 cm no relevant differences in the detection rate of the sequences were found (8-TSE RT, 26/27; 5-TSE RT, 26/27; 8-TSE BH, 25/27), for lesions < or =1 cm the 5-TSE RT provided significantly better sensitivity than the 8-TSE BH (14/14 vs. 8/14, P = 0.015). The results of this study suggest that lesion detection could be significantly improved by using an RT TSE sequence with thin sections compared with a BH TSE sequence.

Female↗
PubMed2001

Biliary atresia and orthotopic liver transplantation. 11 years of experience in Geneva.

Biliary atresia (BA) is a congenital malformation or an evolutive inflammatory process which, without treatment, leads to cirrhosis, hepatic failure and death within two years of birth. The literature gives a survival rate of 60% at five years and 25% to adulthood after an initial operation performed for BA. 30% of children do not survive beyond two years of age. BA has become the most frequent indication for liver transplantation (LT) in children. With LT, survival expectancy is 90%. Results of the operation designed for BA remain unsatisfactory, and seem to depend on the age of the infants, as well as on other factors such as liver histology, and centre experience. Since 1989, onset of the paediatric hepatic transplantation program in Geneva, to July 2000, 20 children have been referred for initial treatment of BA, and 26 for possible hepatic transplantation after initial treatment done in another centre. The aim of the current study is to analyse our own results of the initial operation and to present the results of liver transplantation in this particular group of patients. All the patients with a BA are included in this study. The initial operation for BA yielded 43% favourable outcome at five years and the survival in this group following LT reached 91.3% survival. The importance of the age of the patient at time of initial operation is underlined.

Biliary Atresia↗
PubMed2001

[Incidence and significance of small focal liver lesions in MRI].

PURPOSE: Analysis of the frequency and significance of small focal liver lesions (< or = 2 cm) detected on MRI in the presence or absence of a history of malignancy. METHODS: 628 MRI examinations of the liver performed during 1994-1996 were evaluated. The inclusion criterion into the study was the detection of a focal liver lesion with a size < or = 2 cm. The frequency, the size, the diagnostic proof, and the differential diagnosis of the focal liver lesions were analysed with regard to the patients history of a known malignant tumor. RESULTS: Overall, 179 of the 628 patients (28.5%) had focal liver lesions < or = 2 cm (n = 338). 58.9% of the lesions could be classified based upon follow-up studies by ultrasound, CT or MRI, or by biopsy. The remaining 41.1% of the lesions could not be classified due to the absence of follow-up examinations. 57.3% of all proven lesions were benign and 42.7% were malignant. A history of a malignant tumor was present in 76.7% of all patients with small liver lesions; however, lesions were benign in these patients in 50.6% of the cases. In patients with no known history of a malignancy, 75% of the lesions were benign and 25% were malignant. However, these malignant lesions were in 10/11 cases hepatocellular carcinomas in patients with liver cirrhosis. CONCLUSION: Even in the presence of a history of a malignant tumor, about 50% of the detected small liver lesions on MRI are benign. In the absence of a tumor history the probability of a small malignant liver lesion is very low, if the patients does not have liver cirrhosis where small hepatocellular carcinomas can be present.

Biopsy↗
PubMed2000

Co-operation at work: a process-oriented perspective on joint activity in inter-organizational relations.

In this paper the authors present a conceptual framework for analysing co-operation between organizations as a situated process, highlighting co-operation, co-ordination and co-construction as different modes of joint activity. Within this framework, the analysis of unexpected events becomes a crucial issue. The analytic power of reconstructing the (psycho-) logics of unexpected events in inter-organizational relations will be demonstrated in the presentation of selected outcomes of a research project on the dynamics of producer-supplier relationships in the German automobile industry. Also in this empirical part, the significance of trust and confidence in inter-organizational relations will be reflected.

Automobiles↗