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S Hähnel

Publications and source records attributed to S Hähnel.

At least 19 recordsLinked to original sources
PubMed2006

[Atypical monoclonal plasma cell hyperplasia. Infiltration of ZNS].

Atypical monoclonal plasma cell hyperplasia is extremely rare in the central nervous system without involvement of bone or other systemic disease. This neuropathological entity was first described by Weidenheim and colleagues in 1989. It is considered an inflammatory pseudotumor that can evolve into malignant myeloma. We report on an atypical monoclonal plasma cell hyperplasia with bilateral occipital and cerebellar involvement in a 38-year-old woman. The diagnosis was confirmed by brain biopsy immunohistochemical and molecular tests.

Adult↗
PubMed2006

3.0 Tesla contrast-enhanced MR angiography of carotid artery stents: in vitro measurements as compared with 1.5 Tesla.

BACKGROUND AND PURPOSE: To assess the appearance of carotid artery stents at 3.0 Tesla contrast enhanced magnetic resonance angiography (CE-MRA) as compared with 1.5 Tesla. METHODS: 19 stents (GUIDANT Acculink, GUIDANT Dynalink, BOSTON SCIENTIFIC SMART Neuroform, GUIDANT Omnilink, EV3 Protege, BOSTON SCIENTIFIC Carotid Wallstent, ABBOTT Xact) of different materials (nitinol, stainless steal, cobalt alloy) and different sizes (4.0 mm-10.0 mm) were investigated regarding their appearance on CE-MRA at 3.0 Tesla and at 1.5 Tesla. For each stent artificial lumen narrowing (ALN) was calculated based on a pixel-by-pixel profile of the contrast-to-noise-ratio giving an objective indicator for the size of the evaluable stent diameter. RESULTS: Only in two stents (Omnilink 7.0 mm, Omnilink 10.0 mm) was ALN higher at 3.0 Tesla relative to 1.5 Tesla. In all other stents ALN at 3.0 Tesla was the same or even lower as compared with 1.5 Tesla. In contrast to the ferromagnetic stents where ALN was typically higher than 85%, in most of the nitinol stents (Acculink, Dynalink, Neuroform, Protege) ALN was below 35%. In the Xact stents ALN was generally 100% at 1.5 Tesla and ranged between 31.8% and 100% at 3.0 Tesla. CONCLUSION: CE-MRA after carotid artery stenting is considerably impaired by ALN both at 1.5 Tesla and at 3.0 Tesla. Nevertheless, CE-MRA is well suited for the examination of carotid artery stents made of nitinol at both field strengths. Stent manufacturers should be aware of potential artifacts caused by their stents during noninvasive diagnostic methods such as CE-MRA.

Alloys↗
PubMed2006

Repeated digital substraction angiography after perimesencephalic subarachnoid hemorrhage?

BACKGROUND AND PURPOSE: In patients with perimesencephalic subarachnoid hemorrhage (pSAH) DSA is recommended to exclude aneurysms to due false negative findings in CT-angiography. However, whether a second DSA is indicated during the clinical course to exclude--in addition to aneurysms--fistulas, too, is still under debate. We aimed to evaluate the benefit of repeated DSA in patients with pSAH. METHODS: The source of data was a prospective database set up at the neurological, neurosurgical and neuroradiological departments in our institution. A total of 69 patients with pSAH were enrolled and analyzed by reviewing the medical records and neuroradiological findings. RESULTS: 68 patients presented with Hunt & Hess Grade I-II and one patient with Hunt & Hess Grade III. Median in-hospital stay was 8 days (3-22). In 2 patients mild vasospasm were diagnosed. DSA was performed in all patients at least once. DSA was repeated in 38 patients (55%) after a median of 7 (3-21) days. None of the repeated DSA did show any additional distinctive features with respect to the first DSA. CONCLUSIONS: In our opinion the procedure of repeating DSA in patients with pSAH is likely to become obsolete. One DSA should be performed prior to discharge--and subsequent to possible vasospasm--to exclude hemorrhage caused by aneurysms of the posterior circulation mimicking a perimesencephalic SAH pattern.

Angiography, Digital Subtraction↗
PubMed2006

[Trigeminal neuralgia: how often are trigeminal nerve-vessel contacts found by MRI in normal volunteers].

PURPOSE: To assess prospectively how often contacts are found between the trigeminal nerve and arteries or veins in the perimesencephalic cistern via MRI in normal volunteers. MATERIALS AND METHODS: 48 volunteers without a history of trigeminal neuralgia were examined prospectively (MRI at 1.5 T; T2-CISS sequence, coronal orientation, 0.9 mm slice thickness). Two radiologists decided by consensus whether there was a nerve-vessel contact in the perimesencephalic cistern. RESULTS: In 27 % of the volunteers, no contact was found between the trigeminal nerve and regional vessels, while in 73 %, such a contact was present. In 61 % of the cases, the offending vessel was an artery, in 39 %, it was a vein. In 2 volunteers, a deformation of the nerve was noted. CONCLUSION: Contrary to what has been suggested by retrospective studies, the majority of normal volunteers, if studied prospectively, do show a contact between the trigeminal nerve and local vessels. A close proximity between the nerve and regional vessels is thus normal and is not necessarily proof of a pathological nerve-vessel conflict.

Adult↗
PubMed2005

Hemorrhagic acoustic schwannoma: radiological and histopathological findings.

A 49-year-old man on anticoagulation treatment with phenprocoumon presented with acute right sided 7th and 8th cranial nerve palsy, acute hearing loss, headache, vertigo, and vomiting. CT and MRI revealed a cerebellopontine angle tumor 15mm in diameter and acute intratumoral hematoma. A cellular schwannoma composed predominantly of Antoni A tissue with dilated thin-walled vessels, surrounded by old hemorrhage with hemosiderin-laden macrophages was found histologically.

Cerebral Hemorrhage↗
PubMed2005

[Infectious diseases of brain parenchyma in adults: imaging and differential diagnosis aspects].

Infectious diseases of the central nervous system have often to be considered in differential diagnosis, particularly in immunocompromised persons. Neuroimaging, specifically advanced techniques such as diffusion-weighted MRI and perfusion MRI contribute much to the differentiation of various brain infections and to delineation of brain infections from other, for instance, neoplastic diseases. In this review we present the imaging criteria for the most important brain infections in adults and discuss in detail differential diagnostic aspects.

Adult↗
PubMed2004

Small vessel stents for intracranial angioplasty: in vitro evaluation of in-stent stenoses using CT angiography.

Our aim was to determine whether CT angiography is suitable for the evaluation of in-stent restenoses in small vessel stents for intracranial angioplasty. Therefore, we simulated stenoses with degrees of 25, 50, 75 and 90% in a total of 12 stents with different designs (MEDTRONIC AVE; ABBOT BioDivYsio, GUIDANT Neurolink, TERUMO Tsunami, COOK V-Flex Plus) and sizes (3.0 mm, 4.0 mm). For each stenosis, the apparent stenotic degree (ASD) was measured by CT angiography. Subjective (viewing at the CT images) and objective (acquisition of a density profile) evaluations were made after the stents were filled with a solution of 0.9% NaCl and with a diluted contrast medium. It was not possible to visualize the patent lumen in any of the stenotic stent segments by viewing at the CT images. After objective evaluation, the degree of the stenoses was generally overestimated. In the group with the 3.0-mm stents, ASD ranged from 73.6 to 100% in 25% degree stenoses. With the exception of one stent, stenoses with a degree of more than 25% appeared as vessel obstruction (ASD = 100%) in the 3.0-mm group. In the 4.0-mm group, the mean ASD was 60% for 25% degree stenoses, 76% for 50% degree stenoses, 91% for 75% degree stenoses and 96% for 95% degree stenoses. The minimum diameter of stents for differentiation between in-stent restenosis and vessel occlusion using CT angiography is 4.0 mm. In CT angiography, the degrees of in-stent stenoses are generally overestimated. The evaluation of in-stent restenoses only seems to be possible when CT angiographic images before and after contrast application are evaluated objectively by density profiles.

Angioplasty, Balloon↗
PubMed2004

[Current use and possible future applications of the magnetization transfer technique in neuroradiology].

Magnetization transfer (MT) imaging is a special MR technique used for selective suppression of the MR signal of protons bound on macromolecules. The most important applications in neuroradiology are (1) detection of subtle changes in otherwise normal-appearing cerebral white matter, for instance in multiple sclerosis (MS), Wallerian degeneration, and hydrocephalus, (2) differentiation of white matter lesions with high signal on T (2)-weighted MR-images, like MS plaques, brain infarctions, and brain edema, (3) follow-up of cerebral white matter diseases using volumetric MT techniques, and (4) improvement in delineating of contrast enhancing brain lesions, such as cerebral metastases. We describe the physical rationale of the MT technique and present the most important current and possible future applications of MT imaging to answer clinical and scientific questions in neuroradiology.

AIDS Dementia Complex↗
PubMed2004

The effect of quality of temporomandibular joint MR images on interrater agreement.

OBJECTIVES: Effects of calibration on interrater agreement in evaluating magnetic resonance (MR) images of the temporomandibular joint (TMJ) have already been examined. The objectives of the present study were to assess to what extent the quality of MR images of the TMJ influences interrater agreement and to evaluate interrater agreement with respect to image quality assessment. METHODS: Two non-calibrated medical radiologists and two general dentists evaluated sagittal images of 100 TMJs for both a rating of the image quality and the performance of five diagnostic tasks. The agreement between these raters with respect to the diagnoses was evaluated. Additionally, two additional raters, calibrated during a 5 h training including the evaluation of 70 MR images, also evaluated the diagnostic aspects and the image quality, on the basis of objective criteria. The agreement between the subjective diagnoses of the non-calibrated raters and the objective diagnoses of the calibrated raters was evaluated. Afterwards, the subjective and the objective quality assessments were compared using kappa statistics. RESULTS: When good quality images were evaluated, higher kappa values were obtained for all diagnostic categories by the non-calibrated raters (mean Deltak for making diagnoses >0.1). This finding was confirmed by the value obtained for the agreement between the non-calibrated and the calibrated raters. The non-calibrated raters were in good agreement (k=0.67, standard error +/-0.09) with the calibrated raters for assessment of image quality. CONCLUSION: The present study shows that it is possible even without calibration to obtain a better interrater agreement when higher quality MR images of the TMJ are evaluated.

Adult↗
PubMed2003

Differentiation of multiple sclerosis plaques, subacute cerebral ischaemic infarcts, focal vasogenic oedema and lesions of subcortical arteriosclerotic encephalopathy using magnetisation transfer measurements.

Although multiple sclerosis (MS) plaques, subacute cerebral ischaemic infarcts, focal vasogenic brain oedema, and subcortical arteriosclerotic encephalopathy (SAE) often have typical radiological patterns, they are sometimes difficult to distinguish from each other. Our aim was to determine whether they can be differentiated by magnetisation transfer (MT) measurements. We measured MT ratios (MTR) in ten patients with plaques of MS, 11 with subacute ischaemic infarcts, 12 with focal vasogenic oedema, and ten with lesions of SAE and compared the mean MTRs statistically. The MTR of normal white matter was 47.3%; the lowest MTR was found in plaques of MS (mean 26.4%). With the exception of vasogenic oedema and subacute cerebral ischaemic infarcts the mean MTRs were significantly different between all groups. MT measurements can provide additional information for the differentiation of these conditions, but we could not distinguish vasogenic oedema from subacute cerebral ischaemic infarcts.

Adult↗
PubMed2002

CT and diffusion-weighted MR imaging in randomized order: diffusion-weighted imaging results in higher accuracy and lower interrater variability in the diagnosis of hyperacute ischemic stroke.

BACKGROUND AND PURPOSE: Diffusion-weighted MRI (DWI) has become a commonly used imaging modality in stroke centers. The value of this method as a routine procedure is still being discussed. In previous studies, CT was always performed before DWI. Therefore, infarct progression could be a reason for the better result in DWI. METHODS: All hyperacute (<6 hours) stroke patients admitted to our emergency department with a National Institutes of Health Stroke Scale (NIHSS) score >3 were prospectively randomized for the order in which CT and MRI were performed. Five stroke experts and 4 residents blinded to clinical data judged stroke signs and lesion size on the images. To determine the interrater variability, we calculated kappa values for both rating groups. RESULTS: A total of 50 patients with ischemic stroke and 4 patients with transient symptoms of acute stroke (median NIHSS score, 11; range, 3 to 27) were analyzed. Of the 50 patients, 55% were examined with DWI first. The mean delay from symptom onset until CT was 180 minutes; that from symptom onset until DWI was 189 minutes. The mean delay between DWI and CT was 30 minutes. The sensitivity of infarct detection by the experts was significantly better when based on DWI (CT/DWI, 61/91%). Accuracy was 91% when based on DWI (CT, 61%). Interrater variability of lesion detection was also significantly better for DWI (CT/DWI, kappa=0.51/0.84). The assessment of lesion extent was less homogeneous on CT (CT/DWI, kappa=0.38/0.62). The differences between the 2 modalities were stronger in the residents' ratings (CT/DWI: sensitivity, 46/81%; kappa=0.38/0.76). CONCLUSIONS: CT and DWI performed with the same delay after onset of ischemic stroke resulted in significant differences in diagnostic accuracy. DWI gives good interrater homogeneity and has a substantially better sensitivity and accuracy than CT even if the raters have limited experience.

Acute Disease↗
PubMed2001

Loss of the Y chromosome is a frequent chromosomal imbalance in pancreatic cancer and allows differentiation to chronic pancreatitis.

In a study for the identification of genomic alterations in pancreatic cancer, representational difference analysis was used and led to the isolation of 2 distinct fragments, deleted on the Y chromosome in the xenografted tumor DNA of a male patient with an adenocarcinoma of the pancreas. Loss of Y chromosomal material was further studied in 11 pancreatic cancer cell lines of male origin, using PCR amplification of 5 sequence tagged sites (STSs) distributed along the Y chromosome; 8/11 cell lines exhibited a complete loss of the Y chromosome and 3 had deletions. To examine the status of the Y chromosome in situ, interphase FISH analysis was performed on paraffin sections from pancreatic carcinoma (n=7) and chronic pancreatitis (n=7) tissues, and the loss of Y-chromosomal STS-markers was studied in 6 xenograft tumors obtained from male pancreatic cancer patients. This analysis revealed that a loss of the Y chromosome occurs in vivo in primary pancreatic tumor cells, whereas the Y chromosome was intact in chronic pancreatitis. Our data suggest that loss of Y is a frequent event occurring in male pancreatic tumors. Although there is no evidence for a functional implication of Y chromosome loss, it effectively differentiates between a malignant and a benign condition as e.g. chronic pancreatitis. Thus, this genetic alteration may be of diagnostic use.

Animals↗
PubMed2001

Treatment planning in severe scoliosis: the role of MRI.

The use of magnetic resonance imaging (MRI) in the preoperative investigation of children with idiopathic scoliosis is controversial. Syringomyelia and other intraspinal lesions may be risk factors for neurological injury during surgical correction. Our purpose was to investigate whether pathology of the neuraxis is associated with scoliosis and to detect lesions which may threaten neurological sequelae during distraction and instrumented correction. We obtained T1- and T2-weighted images of 40 children (28 girls, 12 boys), mean age 12.7 years with severe idiopathic scoliosis (Cobb angle 50-70 degrees) obtained in coronal, sagittal and axial planes from the posterior cranial fossa to the sacrum, and these were assessed by two neuroradiologists and an orthopaedic surgeon prior to further treatment planning. Abnormalities of the neuraxis were found in 24 patients (60%); five (12%) had two or more lesions. No abnormalities of the neuraxis were found in 16 patients (40%). There were 15 patients (38%) with intraspinal abnormalities who deteriorated clinically and nine (22%) who showed no clinical changes. We transferred 16 patients (40%) from the orthopaedic to the neurosurgical department for further assessment. Our results suggest that one should investigate the neuraxis with MRI before contemplating orthopaedic surgical correction of severe idiopathic scoliosis, because the findings may lead to a change of procedure.

Adolescent↗
PubMed2001

CT and MRI findings in gliomatosis cerebri: a neuroradiologic and neuropathologic review of diffuse infiltrating brain neoplasms.

The aim of the study was to develop objective criteria that might be helpful for the diagnosis of gliomatosis cerebri (GC) with the highest possible probability based on both the neuroradiological and histopathological findings. Imaging findings in 14 patients with diffuse infiltrating brain neoplasms were studied by two neuroradiologists. Computed tomography and MRI scans were compared with each other side by side. The extent and kind of disease were graded on a scale of 1-5. Interexamination agreement between the two methods was calculated using a kappa analysis. Neither of the neuroradiologists performed the examinations and both were blinded to the histopathological findings, which were also available for all patients, based on biopsy as well as follow-up CT and MRI studies. A neuroradiological-neuropathological correlation was performed. A score system helped to differentiate the findings in three categories: 1 = suggestive of GC; 2 = GC cannot be excluded; and 3 = others. Both CT and MRI were performed in 14 patients with clinical signs and symptoms of an intracerebral tumor. All examinations had diagnostic quality and showed the involvement of at least two brain lobes. Stereotactic biopsy was carried out in all patients. In 2 patients the neuropathological diagnosis was suggestive of GC, in 1 patient glioblastoma, in 2 patients astrocytoma, and in 5 patients nonspecific astrogliotic proliferation. In the remaining 4 cases anaplastic tumor infiltration was diagnosed. The neuroradiological findings in 5 cases were suggestive of GC; in 6 cases a GC could not excluded; and in 3 patients only a slight probability of GC was found. In 2 cases was the neuropathological and the neuroradiological diagnosis of GC concordant. Magnetic resonance imaging is significantly more sensitive than CT in the diagnosis of GC. However, even with multiple, MRI-guided stereotactic biopsies in correlation with intraoperative analysis of the sample by smear preparations by a neuropathologist the antemortem diagnosis of GC is still difficult. Discussion of neuropathological and neuroradiological findings in each case in combination with a score system may help to resolve discrepancies.

Adolescent↗