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H Urbach

Publications and source records attributed to H Urbach.

At least 37 records · Page 2Linked to original sources
PubMed2004

[High field MR imaging: magnetic field interactions of aneurysm clips, coronary artery stents and iliac artery stents with a 3.0 Tesla MR system].

PURPOSE: To evaluate magnetic field interactions of commonly used biomedical implants at 3.0 Tesla. MATERIALS AND METHODS: Fourteen aneurysm clips designed for permanent placement in intracranial aneurysms, 19 coronary artery stents and 20 iliac artery stents were evaluated in an actively shielded compact 3.0 T MR system (Intera, Philips Medical Systems, Best, The Netherlands, length of magnet 1.57 m). The magnetic deflection forces (translational movement) were evaluated as follows: The implants were suspended by a fine string and placed in the magnet bore at the location of the maximum magnetic field gradient. The translational forces F (z) were calculated from the measured angle of deflection from the vertical axis. The magnetic field-induced torque (rotational forces) was evaluated as follows: Each implant was placed in the center of the magnetic bore parallel to the static magnetic field B0 (position 0 degrees ). Any possible displacement of the implant was noted on a millimeter scale and any torque qualitatively evaluated using a 5 point grading scale (0: no torque; + 4: very strong torque). The implant was turned in steps of 45 degrees, and the procedure was repeated to encompass a full 360 degrees rotation. RESULTS: In 52 of the 53 devices tested, the deflection force (deflection angle: range 0-21 degrees, translational force: range 0-3.8 mN) was less than the gravitational force (i.e., the implant's weight). These devices (n = 52/53) did not show any alignment to or rotation in the magnetic field at any of the various 45 degrees -increment positions corresponding to a qualitative torque evaluation of grade 0/4. One device (n = 1/53), an iliac artery stent made of stainless steel (Zenith, Cook, Mönchengladbach, BRD), was found to have deflection forces (deflection angle 88 degrees translational force 299 mN) greatly exceeding the gravitational force as well as a pronounced torque (grade 4/4). CONCLUSION: Out of 53 biomedical implants evaluated for magnetic field interactions at 3.0 T, one iliac artery stent made of stainless steel was found to be potentially unsafe based on ASTM criteria. MR imaging at 3.0 Tesla may be performed safely in patients with any of the other 52 different implants evaluated in this study with respect to magnetic field translational attraction and torque.

Alloys↗
PubMed2004

Immediate postoperative angiography after aneurysm clipping--implications for quality control and guidance of further management.

BACKGROUND: To determine the impact of postoperative angiography after aneurysm clipping on quality control and further management. METHODS: A recent consecutive series of n = 296 patients (186 females, 110 males, mean age 51 yrs) who underwent 324 craniotomies to clip 384 aneurysms was reviewed. New irregularities on postoperative angiographies were categorized as unrelated (e. g. vasospasm) or related (= vessel occlusion/residuum) to clipping and expected or unexpected by the surgeon. Therapies prompted by these findings as well as subsequent negative sequelae were analyzed. Factors related to negative events were identified by logistic regression (p < 0.05). RESULTS: Twenty-six (8%) unrelated findings prompted medical or intravascular therapy. Of 36 (9.4%) clip-related findings (n = 17 occlusions, n = 19 residua), 14 (3.6%) were unexpected (n = 9 occlusions, n = 5 residua). This was followed by 9 (2.3%, n = 4 occlusions, n = 5 residua) clip readjustments and 6 aggressive medical therapies. Nine patients were scheduled for angiographic follow-up, of which in five performed so far no change of aneurysm remnants was noted. Permanent sequelae from vessel occlusion occurred in 9 cases. Major premature rupture (p < 0.005), giant size/fusiform configuration (p < 0.001), posterior circulation aneurysms (p < 0.05) and ophthalmic segment location (p < 0.008) were significantly related to adverse postoperative findings. The use of microvascular Doppler significantly reduced the rate of unexpected vessel occlusion (3.3 vs. 0.9%). CONCLUSIONS: Apart from the need for quality control in aneurysm clipping--especially with respect to coiling--our results stress the importance of postoperative angiography, because a small, but significant subset of patients will benefit from immediate intervention and/or deserves long-term follow-up.

Angiography↗
PubMed2004

Planar brain surface reformations for localization of cortical brain lesions.

Cortical lesions close to the central region may be difficult to localize on orthogonal MRI slices, especially when space-occupying lesions distort the brain surface relief and obscure anatomical landmarks. The purpose of this study was to evaluate, whether localization can be improved with planar brain surface (Mercator or "pancake") reformations. Three independent MRI readers localized superficial brain lesions of 30 patients on orthogonal MRI slices and on planar brain surface views reformatted from a sagittal 3D T(1)-weighted gradient echo sequence. On orthogonal MRI slices 46% of lesions were considered easy to localize, 37% difficult and 17% could not be localized. Corresponding values for planar brain surface views were 82%, 16% and 2%, respectively. Evaluation of orthogonal MRI slices took 190 min compared to 100 min for planar brain surface views. Thus, planar brain surface reformations are a helpful and time-saving means to localize superficial brain lesions.

Adolescent↗
PubMed2004

Fusion of MRI and CT with subdural grid electrodes.

In patients with drug-resistant focal epilepsies subdural grid electrodes may be implanted to determine the seizure onset zone and eloquent cortex areas. Since the spatial relationship of the grid to the underlying brain is poorly visualized on MRI, we co-registered MRI before and CT after implantation of subdural grid electrodes. In this study we sought an appropriate algorithm to combine both imaging modalities. We compared six different co-registration algorithms including surface-oriented, mutual information-based and landmark-based methods. The resulting overlay matrices were analyzed by calculating rotational and translational shifts and by judging co-registered MRI and CT scans visually. A brain surface oriented method had the lowest rotational (axial 0.7 +/- 0.6 degrees; coronal 1.7 +/- 1.1 degrees; sagittal 1.9 +/- 1.8 degrees) and translational shifts (3.7 +/- 1.3 mm). It was judged visually to be the best, had a low intra- and inter-observer variability, and lasted approximately 15 minutes. This algorithm is recommended when co-registering MRI before and CT after implantation of subdural grid electrodes. Skin-, voxel-, and landmark-based algorithms are less accurate, which is most likely due to postsurgical deformation of extra- and intracranial soft tissue.

Adolescent↗
PubMed2004

Lesional mesial temporal lobe epilepsy and limited resections: prognostic factors and outcome.

OBJECTIVES: To evaluate the influence of clinical, investigational, surgical, and histopathological factors on postoperative seizure relief in patients with mesial temporal lobe epilepsy (MTLE) due to lesions other than ammonshornsclerosis (AHS). METHODS: Of 738 patients operated for TLE, 78 patients underwent limited resections for lesional MTLE (1990-2000). Seventy four patients with a follow up of more than one year were included. The preoperative clinical, neuropsychological, electroencephalogram, and neuroimaging characteristics were prospectively collected in a database. The histopathological material was re-examined. RESULTS: The mean follow up was 49 months. Fifty eight patients were classified as seizure free (78.4% Class I), and six as almost seizure free (8.1% Class II), grouped together as satisfactory seizure control (64 patients, 86.5%). Five patients (6.8%) were categorised in Classes III and IV, respectively. These were grouped as unsatisfactory seizure control (10 patients, 13.5%). Surgical procedures were: 32 amygdalohippocampectomies (AH), 17 partial anterior AH, 15 AH plus polar resection, seven AH plus basal resection, and three AH plus extended temporal lesionectomy. There was no mortality and 2.7% mild permanent morbidity. Seizure relief did neither differ significantly with these approaches, nor with different classes of pathological findings (43 developmental tumours, 12 glial tumours, 10 dysplasias, and nine others). Even operation of dysplasias resulted in 80% satisfactory seizure control. Seizure onset during childhood proved to be a negative predictor for seizure relief (p = 0.020). MRI revealed 73 suspected lesions (98.6%), one dysembryoplastic neuroepithelial tumour was missed, in four cases no structural abnormalities could be confirmed with histopathological exam. Additionally, multifactorial regression revealed the factors "seizure onset after 10 years of age", "presence of complex partial seizures", "absence of a neurological deficit", and a "correlating neuropsychological deficit" as predictive for satisfactory seizure control. CONCLUSIONS: "Preoperative tailoring" resulting in limit resections has proven to be safe and to provide a very good chance for satisfactory seizure relief in patients with lesional MTLE.

Adolescent↗
PubMed2004

Collateral brain damage, a potential source of cognitive impairment after selective surgery for control of mesial temporal lobe epilepsy.

BACKGROUND: Highly selective epilepsy surgery in temporal lobe epilepsy is intended to achieve seizure freedom at a lower cognitive risk than standard en bloc resections, but bears the risk of collateral cortical damage resulting from the surgical approach. OBJECTIVE: To investigate cortical damage associated with selective amygdalo-hippocampectomy (SAH). METHODS: 34 epileptic patients were evaluated. They were randomly assigned to SAH using either a sylvian (9 left/10 right) or a transcortical surgical approach (5 left/10 right). Postoperative MRI signal intensity changes adjacent to the approach were correlated with performance changes in serial word and design list learning. RESULTS: Losses in verbal learning and recognition memory were positively related to signal intensity changes, independent of the side of the resection, the surgical approach, or the extent of the mesial resection. Losses in consolidation/retrieval (memory) were greater after left sided surgery. Losses in design learning were related to right sided surgery and signal intensity changes. Seizure outcome (85% seizure-free) did not differ depending on the side or type of surgery. CONCLUSIONS: Collateral damage to cortical tissues adjacent to the surgical approach contributes to postoperative verbal and figural memory outcome after SAH. Controlling for collateral damage may clarify the controversial memory outcomes after SAH reported by different surgical centres.

Amygdala↗
PubMed2004

A new anti-neuronal antibody in a case of paraneoplastic limbic encephalitis associated with breast cancer.

Paraneoplastic neurological syndromes are rare remote effects of different types of cancer. Paraneoplastic limbic encephalitis is a specific syndrome, most often associated with small cell lung carcinoma. This report describes the case of a pure limbic encephalitis in association with breast cancer. An anti-neuronal antibody was found in the serum and CSF of the patient which has not been reported so far.

Antibodies↗
PubMed2003

Clinical and neuropsychological characteristics of pediatric epilepsy patients with atypical language dominance.

Studies on intracarotid amobarbital procedures (IAP) in pediatric patients are rare and mainly focus on practicability aspects. Very few studies have reported characteristics of children with atypical language dominance. We compared children with left-sided focal epilepsy and atypical (i.e., right or bilateral) versus left-sided language representation (n=12 versus 17). Our results indicate a higher incidence of left handedness, extratemporal lesions, an earlier onset of epilepsy, and a neuropsychological "crowding effect" with distinct nonverbal memory deficits in the atypical group. We conclude that atypical language representation in children with left-sided epilepsy is associated with similar characteristics as in adults. It is recommended that the possibility of a language shift in the presurgical workup of pediatric patients be considered, particularly if a left-hemispheric epileptic focus is suspected.

Adolescent↗
PubMed2003

[Preliminary experience with balloon kyphoplasty for the treatment of painful osteoporotic compression fractures].

PURPOSE: To describe the technique and to evaluate the safety and efficacy of percutaneous kyphoplasty as a new treatment in patients with painful osteoporotic vertebral body compression fractures of the lumbar and thoracic spine. MATERIALS AND METHODS: In this prospective study balloon kyphoplasty was performed in 34 consecutive patients (25 females, 9 males; mean age 75 years) with 56 painful osteoporotic vertebral fractures (from T6-L5), of which 22 showed a posterior wall involvement and retropulsion on preoperative CT. The median duration of symptoms was 9.7 weeks. Symptomatic levels were identified by correlating the clinical presentation with MRI, conventional radiographs and CT including bone-densitometry. Pre- and postoperative examinations (radiographs, CT) as well as Karnofsky and visual analogy pain scores (Visual Analog Scale = VAS) were documented and compared to evaluate the success of the procedure. RESULTS: The median Karnofsky score improved from 40 % (pre-) to 70 % (post-treatment). Simultaneously, median pain scores (VAS) decreased from 64 (pre-) to 21 (post-treatment) (p < 0.001). Perioperative morbidity included one transient L2 nerve root bruise. The procedure led to a partial restoration of the height of the vertebral body by reducing the median sagittal index from 11.5(3) to 5(3). In none of our patients, the procedure led to worsening of the fracture-induced narrowing of the spinal canal. Clinically asymptomatic cement leakage occurred in 10 cases, with leakage 4 times into the paraspinal space, 3 times into the spinal canal and 3 times into the disc space. CONCLUSION: Balloon kyphoplasty is a safe and effective procedure. It is applicable even in fractures with posterior wall involvement since it is a low-pressure technique in contrast to vertebroplasty and restores vertebral body height partially. It results in immediate clinical improvement of mobility and pain relief. While short-term results are excellent, follow-up data have to be awaited for the final judgment of this method.

Aged↗
PubMed2002

Local intra-arterial thrombolysis in the carotid territory: does recanalization depend on the thromboembolus type?

Little is known about whether recanalization of carotid territory occlusions by local intra-arterial thrombolysis (LIT) depends on the type of the occluding thromboembolus. We retrospectively analysed the records of 62 patients with thromboembolic occlusions of the intracranial internal carotid artery (ICA) bifurcation or the middle cerebral artery who were undergoing LIT with urokinase within 6 h of symptom onset. We determined the influence of thromboembolus type (according to the TOAST criteria), thromboembolus location, leptomeningeal collaterals, time interval from onset of symptoms to onset of thrombolysis, and patient's age on recanalization. The thromboembolus type was atherosclerotic in six patients, cardioembolic in 29, of other determined etiology in four, and of undetermined etiology in 23 patients. Thirty-three (53%) thromboembolic occlusions were recanalized. The thromboembolus location but not the TOAST stroke type nor other parameters affected recanalization. In the TOAST group of patients with cardioembolic occlusions recanalization occurred significantly less frequently when transoesophageal echocardiography showed cardiac thrombus. The present study underlines the thromboembolus location as being the most important parameter affecting recanalization. The fact that thromboembolic occlusions originating from cardiac thrombi had a lower likelihood of being resolved by thrombolysis indicates the thromboembolus type as another parameter affecting recanalization.

Carotid Artery Thrombosis↗
PubMed2002

Diagnosis and staging of Rasmussen's encephalitis by serial MRI and histopathology.

OBJECTIVE: To correlate MRI and histopathologic findings in patients with Rasmussen's encephalitis (RE). PATIENTS AND METHODS: MRI features of 10 patients with RE were studied on serial scans. In surgical specimens from these patients, densities of T lymphocytes, microglial cells and nodules, and reactive astrocytes were evaluated. RESULTS: Densities of T cells, microglial nodules, and astrocytes were inversely correlated to disease duration. MRI abnormalities had a focal onset and spread across one hemisphere. The following course of MRI abnormalities in a given brain region was observed: on very early scans, the cortex was swollen and showed a hyperintense T2/fluid-attenuated inversion recovery signal. Consecutively, progressive atrophy of the affected hemisphere occurred. Correlation of MRI features with quantitative histopathology revealed that there was a higher number of T cells and reactive astrocytes in the earlier MRI stages compared with the late (merely atrophic) stage. CONCLUSION: These data suggest a disease course in RE with the highest inflammatory intensity in the early stages and a subsequent decrease in inflammation. The MRI abnormalities and their characteristic sequence may help to identify patients with RE and to obtain informative biopsies.

Adolescent↗
PubMed2002

Time-efficient T2 relaxometry of the entire hippocampus is feasible in temporal lobe epilepsy.

OBJECTIVE: To test the clinical usefulness and reliability of a new dual-echo turbo-spin-echo (TSE) sequence for rapid and regional hippocampal T2 relaxometry. METHODS: Hippocampal T2 relaxation time (HRT) was determined by a TSE sequence on three to four consecutive coronal images in 16 control subjects and 12 patients with mesial temporal lobe epilepsy. HRT was related to neuropathology findings in hippocampal specimens including neuronal cell density (ND), results of visual analysis of MR images, clinical outcome after epilepsy surgery, and hippocampal volumetry. RESULTS: Rapid HRT differentiated patients from control subjects; all cases of hippocampal sclerosis (HS; n = 10) were correctly diagnosed. HRT showed a strong correlation with ND in CA1 (p < 0.02) and CA3 (p < 0.05). Diagnoses based on rapid relaxometry concurred fully with results of visual inspection. Mean HRT was prolonged ipsilaterally in all patients with excellent postoperative seizure outcome and bilaterally prolonged or normal in patients with poorer outcome. Rapid HRT was concordant with hippocampal volumetry in 10 of 12 patients. Regional HRT of control subjects revealed significantly higher values in the anterior than posterior hippocampus. In patients with unilateral HS, this gradient was absent. The gradient was also absent contralaterally to HS, although surgical outcome was excellent. CONCLUSIONS: Hippocampal dual-echo TSE-relaxometry can be regarded a reliable technique to detect and quantify HS. With a scan time of 3.31 minutes and immediate off-line analysis lasting a few minutes only, TSE-T2 relaxometry is easy to integrate in the routine diagnostic assessment of hippocampal morphology in large numbers of patients.

Adolescent↗
PubMed2002

Perfusion and molecular diffusion-weighted MR imaging of the brain: in vivo assessment of tissue alteration in cerebral ischemia.

The combined use of perfusion imaging (PI) and diffusion-weighted imaging (DWI) is opening a new window into the processes that occur during the first hours of ischemia. DWI detects changes in molecular diffusion associated with cytotoxic edema. PI characterizes the degree of regional hypoperfusion. Regions showing mismatches between DWI and PI, i.e. hypoperfused areas with normal diffusion behavior are considered potentially salvageable. We present results of 11 patients with an occlusion of the middle cerebral artery stem and spontaneous stroke evolution. Whereas the infarct was clearly visible on initial DWI and PI, surrounding tissue at risk of infarction was marked in all patients by an increased blood volume and transit time, but only in a subgroup (n = 3) where alteration were more pronounced this tissue at risk was progressively infarcted. These human DWI and PI data show alterations in the area of tissue at risk which correlates with infarct progression.

Adolescent↗