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Biomedical subjects

D Hellwig

Publications and source records attributed to D Hellwig.

At least 37 records · Page 2Linked to original sources
PubMed2000

Intrathecal baclofen alleviates autonomic dysfunction in severe brain injury.

Sympathetic storm phenomena are well known therapeutic problems in patients with severe brain injury. We have treated four patients with intrathecal baclofen (ITB) who suffered from severe hypertension, tachycardia and other sympathetic storm phenomena after different primary events. In all patients conventional therapy with sedatives and antiadrenergic medication had been taken to the upper limits before initiating ITB. Autonomic dysfunction immediately improved in three of four patients. In all patients ITB, via lumbar or ventricular route, proved safe and without complications. The anatomical and pharmacological basis of the GABA-B agonist action on such sympathetic storm phenomena are not yet fully understood. However, the positive results observed in three out of four patients are promising and require further investigation. ITB is a new therapeutic approach to control otherwise unresponsive sympathetic storm phenomena in severe brain injury.

Adult↗
PubMed2000

Relationships of virtual reality neuroendoscopic simulations to actual imaging.

Advances in computer technology have permitted virtual reality images of the ventricular system. To determine the relevance of these images we have compared virtual reality simulations of the ventricular system with endoscopic findings in three patients. The virtual fly-through can be simulated after definition of waypoints. Flight objects of interest can be viewed from all sides. Important drawbacks are that filigree structures may be missed and blood vessels cannot be distinguished clearly. However, virtual endoscopy can presently be used as a planning tool or for training and has future potential for neurosurgery.

Adult↗
PubMed2000

[Value of positron emission tomography with 18-fluorodeoxyglucose (FDG-PET) in diagnosis of recurrent bronchial carcinoma].

The aim of the present investigation was to evaluate the diagnostic accuracy of positron emission tomography with 18-fluoro-2-deoxyglucose (FDG-PET) in the detection of recurrent lung cancer. PET was performed using an ECAT ART scanner (Siemens CTI) after i.v. injection of 220 +/- 50 MBq 18FDG. PET data were analysed by visual interpretation of coronal, sagittal and transversal slices. PET scans were interpreted independently by two experienced nuclear medicine physicians without prior knowledge of the results of other imaging studies or clinical data. 40 patients (= 41 cases) who had undergone primarily curative tumour treatment, were evaluated. In 29 of 35 cases with recurrent tumour, diagnosis was verified by pathologic means. FDG-PET correctly identified tumour recurrence in 34/35 cases. In 5/6 cases without prevent tumour recurrence PET gave true negative results. The overall accuracy of FDG-PET was 39/41 = 95% (95%-confidence interval 83-99%). FDG-PET shows high diagnostic accuracy in detecting recurrent lung cancer in patients with prior curative tumour treatment, but cannot substitute the need for pathological diagnosis.

Aged↗
PubMed2000

Influence of diabetes mellitus on regional cerebral glucose metabolism and regional cerebral blood flow.

Previous studies have shown both increased and decreased regional cerebral glucose metabolism-blood flow (rMRGlu-rCBF) values in diabetes. We sought to elucidate the influence of diabetes on rMRGlu-rCBF in 57 patients with pure cerebral microangiopathy. Sixteen of 57 patients had diabetes requiring therapy (11 NIDDM, 5 IDDM). Using a special head-holder for exact repositioning, rMRGlu (PET) and rCBF (SPET) were imaged and measured in slices, followed by MRI. White matter and cortex were defined within regions of interest taken topographically from MRI (overlay). Diabetic and non-diabetic microangiopathy patients were compared to 19 age-matched controls. The diabetic patients showed significantly lower rMRGlu-rCBF values in all regions than controls, whereas non-diabetic patients did not. There were no significant NIDDM-IDDM differences. rMRGlu-rCBF did not depend on venous blood glucose levels at the time of the PET examination. However, analysis of variance with the factors diabetes, atrophy and morphological severity of microangiopathy showed that lowered rMRGlu-rCBF in the diabetic group was due to concomitant atrophy only (P < 0.005), while neither diabetes nor microangiopathy had any influence on rMRGlu-rCBF (all P > 0.2). These results were confirmed by multivariate factor analysis. It can thus be concluded that a supposed decrease in rMRGlu-rCBF in diabetes mellitus is in fact only an artefact produced by the concomitant atrophy. All previous studies failed to correct for atrophy, and a critical reappraisal is required.

Aged↗
PubMed2000

One-year follow-up of neuropsychology, MRI, rCBF and glucose metabolism (rMRGlu) in cerebral microangiopathy.

BACKGROUND: MRI shows lacunar infarctions (LI), deep white matter lesions (DWML) and atrophy in cerebral microangiopathy, which is said to lead to vascular dementia. In a first trial series on 57 patients with confirmed pure cerebral microangiopathy (without concomitant macroangiopathy), neuropsychological impairment and (where present) brain atrophy correlated with decreased rCBF and rMRGlu. LI and DWML did not correlate with either neuropsychological impairment or decreased rCBF/rMRGlu. This study was done one year later to detect changes in any of the study parameters. METHODS: 26 patients were re-examined for rCBF, rMRGlu, LI, DWML, atrophy and neuropsychological performance (7 cognitive, 3 mnestic, 4 attentiveness tests). Using a special head holder for exact repositioning, rCBF (SPECT) and rMRGlu (PET) were measured and imaged slice by slice. White matter/cortex were quantified using MRI-defined ROIs. RESULTS: After one year the patients did not show significant decreases in rCBF or rMRGlu either in cortex or in white matter (p > 0.05), nor did any patient show LI, DWML or atrophy changes on MRI. There were no significant neuropsychological decreases (p > 0.05). CONCLUSIONS: Cerebral microangiopathy ought to show progressive neuropsychological, functional (rCBF, rMRGlu) and morphological deterioration over periods > 1 year. It is unlikely that direct cortical damage (e.g., incomplete infarction) is responsible for neuropsychological impairment since one-year follow-up of our patients revealed no progression of brain atrophy or any other cortical damage.

Adult↗
PubMed2000

[Influence of single-photon emission scan duration measured with the ECAT ART PET scanner].

AIM: The aim was to study the influence of single-photon-transmission scan duration in 3D-PET on the quantitative values of attenuation coefficients and noise in transmission images and of activity concentrations and noise in attenuation corrected emission images of thorax phantom- and patient data. METHOD AND MATERIAL: Using dual collimated Cs-137 singles transmission sources (E gamma = 662 KeV, A = 2* 614 MBq) on an ECAT ART tomograph series of transmission scans of a thorax phantom were acquired pre- and post-injection of 18F. 17 patients underwent two transmission scans. The scan time of the short transmission was chosen according to the results of the phantom studies (noise of Poisson statistics less than 4%). Transmission and attenuation corrected emission images were evaluated with respect to estimated linear attenuation coefficients, noise and specific activities in organs. RESULTS: The phantom studies reveal little variation of the estimated linear attenuation coefficients as a function of scan duration. The estimates of the attenuation coefficients are found to be 1% lower than the expected values for pre- and up to 6.5% lower for post-injection transmissions. The noise level in the transmission images increases as expected for Poisson data. The noise level in the attenuation corrected emission images shows only little increase with decreasing transmission scan time whereas it is strongly influenced by a variation of emission scan time. In patient studies, less than 3% difference was found in the estimated linear attenuation coefficients as well as in the activity concentrations between short (pre or post-injection) and long transmission scans. The noise levels in transmission and emission images are 1% (pre-injection) and 4% (post-injection) higher for short transmission scans. CONCLUSION: Due to the high photon flux, single photon transmission offers good clinical performance with significantly reduced transmission scan durations (< 2 min/bed in pre-, < 4 min/bed in post-injection transmission).

Aged↗
PubMed1999

18F-deoxyglucose positron emission tomography (FDG-PET) for the planning of radiotherapy in lung cancer: high impact in patients with atelectasis.

PURPOSE: 18F-deoxyglucose positron emission tomography (FDG-PET) is increasingly applied in the staging of lung cancer (LC). This study analyzes the potential contribution of PET in radiotherapy planning for LC with special respect to tumor-associated atelectasis. METHODS AND MATERIALS: Thirty-four patients with histologically confirmed LC, who had been examined by PET during pretreatment staging, were included. All were irradiated after CT-based therapy planning with anterior/posterior (AP) portals encompassing the primary tumor and the mediastinum (CT portals, CP). The result of the PET examination was unknown in treatment planning. In retrospect, a PET portal (PP) was delineated and compared with the CP. RESULTS: In 12/34 cases, the shape and/or size of the portals were changed, primarily (n = 10) the size of the fields was reduced. The median area of CP was 182 cm2 versus 167 cm2 of PP. Seventeen of 34 patients had dys- or atelectasis caused by a central primary tumor. In these cases, differences between CP and PP were significantly more frequent than in the other patients (8/17 vs. 3/17, p = 0.03). CONCLUSION: In this retrospective analysis, the information provided by FDG-PET would have contributed to a substantial reduction of the size of radiotherapy portals. This applies particularly for patients with tumor-associated dys- or atelectasis.

Carcinoma, Non-Small-Cell Lung↗
PubMed1999

[Brain metastases of lung cancer: diagnostic accuracy of positron emission tomography with fluorodeoxyglucose (FDG-PET)].

The value of FDG-PET in oncology is currently investigated in clinical studies. There is only limited information on the usefulness of FDG-PET in the evaluation of distant metastases of lung cancer. The purpose of the present prospective investigation was to determine the diagnostic accuracy of FDG-PET in the detection of brain metastases of lung cancer. After intravenous injection of 220 +/- 50 MBq F-18-deoxyglucose PET acquisition was carried out using an ECAT ART scanner (CTI Siemens). Images were reconstructed using a filtered backprojection with a Hanning filter. PET data were analyzed by visual interpretation of coronal, sagittal and transversal slices. PET scans were interpreted by two experienced nuclear medicine physicians without prior knowledge of the results of other imaging studies or clinical data. Between March 1997 and July 1998 whole-body PET was performed in 417 patients with suspected lung cancer. 402 patients were used for statistical analysis. Based on conventional brain imaging with CT (occasionally MRI), brain metastases were suspected in 17 patients (prevalence 4.2%). For FDG-PET alone, sensitivity was 82% (14/17) and specificity 38% (14/37). Therefore, diagnostic accuracy of FDG-PET in detection of brain metastases was 93.5%. The low specificity of FDG-PET can be explained by reduced tracer uptake mainly due to brain infarction or vascular encephalopathy in this group of elderly patients. Our results indicate that due to its low specificity FDG-PET is not useful for the evaluation of brain metastases in the primary staging of patients with lung cancer.

Adult↗
PubMed1999

Intracranial dislocation of a lumbo-peritoneal shunt-catheter: case report and review of the literature.

We report on the dislocation of the tip of a lumbo-peritoneal shunting catheter into the cerebral parenchyma 10 months after insertion. The progressive migration towards the deep structures of the brain, once the catheter had left the peritoneal cavity, might have been caused by CSF-flow. Such hypothesis is supported by modern MRI technology visualizing CSF-flow in a spino-cerebral direction.

Brain↗
PubMed1999

Application of new electrosurgical devices and probes in endoscopic neurosurgery.

Complex demands and new indications in neurosurgery have led to the need for new electrosurgical generators (ESUs). For the first time, newly developed, automatically controlled ESUs make it possible to use extremely small and flexible instruments safely and to achieve reproducible microcuts and microcoagulations. These specifications make them suitable for neuroendoscopic interventions. In a series of more than one hundred patients with different intracranial and intraspinal pathologies the new electrosurgical devices and probes were used not only for coagulation but also for cutting. The main indications were endoscopic ventriculo-cisternostomy, ventriculo-cystostomy, and membranectomy. The electrosurgical generators as well as the bipolar microcoagulation and -cutting probes proved to be safe and effective for neuroendoscopic interventions.

Electrocoagulation↗
PubMed1999

Neuropsychological impairment correlates with hypoperfusion and hypometabolism but not with severity of white matter lesions on MRI in patients with cerebral microangiopathy.

BACKGROUND AND PURPOSE: Cerebral microangiopathy, indicated on MRI by lacunar infarctions (LI) and deep white matter lesions (DWML), is said to lead to vascular dementia. METHODS: Fifty-seven patients with proven cerebral microangiopathy were assessed for changes in regional cerebral blood flow (rCBF) and glucose metabolism (rMRGlu) and compared with 19 age-matched controls. The findings were correlated with results of extensive neuropsychological testing, as well as with MRI findings. A special head holder ensured reproducibility of positioning during rCBF (single-photon emission CT [SPECT]), rMRGlu (positron emission tomography [PET]), and MR imaging. White matter and cortex were quantified with regions of interest defined on MRI and superimposed to corresponding PET/SPECT slices. LI and DWML were graded by number and extent. RESULTS: Even with severe DWML and multiple LI, rCBF and rMRGlu values were not reduced. ANOVAs identified brain atrophy and neuropsychological deficits as the main determinants for reduced rCBF and rMRGlu values in both cortex and white matter. Neuropsychological deficits correlated well with decreased rCBF and rMRGlu, whereas MRI patterns such as LI and DWML did not. Factor analysis revealed no correlation of LI and DWML with rCBF, rMRGlu, atrophy, and neuropsychological deficits, showing instead positive correlations between rCBF, rMRGlu, and neuropsychological performance and negative correlations of the latter 3 with brain atrophy. CONCLUSIONS: From these data, we conclude that LI and DWML are epiphenomena that may morphologically characterize cerebral microangiopathy but do not in themselves indicate cognitive impairment. Dementia or neuropsychological deficits, by contrast, are reflected exclusively by functional imaging parameters (rCBF, rMRGlu) and cerebral atrophy.

Adult↗
PubMed1998

Correlation of neuropsychological, morphological and functional (regional cerebral blood flow and glucose utilization) findings in cerebral microangiopathy.

UNLABELLED: Cerebral microangiopathy, indicated in MRI by lacunar infarctions (LIs) and deep white matter lesions (DWMLs), is said to be accompanied by vascular dementia, which is reportedly caused by LI and DWML. METHODS: To confirm this assumption, 57 patients with cerebral microangiopathy were assessed for changes in regional cerebral blood flow (rCBF) and glucose utilization (rMRGlu) in both white matter and cortex, and these findings were correlated to the results of extensive neuropsychological testing (cognitive, mnestic and attentiveness tests), as well as to MRI findings. A special head holder ensured reproducibility of positioning during measurement of rCBF (99mTc-HMPAO SPECT) and rMRGlu (18F-FDG PET) and MRI. White matter and cortex were quantified with regions of interest defined on MRI and superimposed to corresponding PET/SPECT slices. The rMRGlu was calculated according to Sokoloff, and rCBF was determined from normalization to the cerebellum. LI and DWML were graded by number and extent. Brain atrophy was classified as no to slight inner and/or outer atrophy (Group A) or moderate-to-severe inner and outer atrophy (Group B). RESULTS: Even in severe DWMLs and in multiple LIs, rCBFs and rMRGlu values were not reduced. Analysis of variance identified atrophy and neuropsychological deficits as the main determinants for reduced rCBF and rMRGlu values (p < 0.05). However, 60% of patients (19 of 31) with neuropsychological deficits in attentiveness tests and 61% of patients (23 of 38) with mnestic deficits belonged to Group A and revealed decreased rCBF and rMRGlu values. Neuropsychological deficits correlated well with decreased rCBF and rMRGlu, whereas MRI patterns, such as LI and DWML, did not. CONCLUSION: We conclude that LI and DWML are epiphenomena that morphologically characterize cerebral microangiopathy. Dementia or neuropsychological deficits, however, are exclusively reflected by functional criteria (rCBF and rMRGlu), as long as cerebral atrophy does not occur.

Aged↗
PubMed1997

Endoscopic stereotaxy--an eight year's experience.

During the 10th meeting of the WSSFN in Maebashi in 1989, we discussed 'endoscopic stereotaxy', and presented our preliminary results. This technique was first designed to optimize stereotactic biopsy, but it proved to be effective for other neurosurgical indications as well, including endoscopic stereotactic evacuation of intraparenchymal and intraventricular space-occupying cysts, endoscopic stereotactic cystoventriculostomy, third ventriculostomy, evacuation of brain abscess and intracerebral hematoma, and retrieval of adherent or free-floating ventricular catheters. Our results with endoscopic stereotaxy in different indications are encouraging, compared to conventional microsurgical techniques and pure stereotactic techniques. From 1989 to 1997 we have performed more than 400 stereotactic endoscopic procedures. The mortality rate is below 1%, the operative morbidity is below 3%.

Biopsy↗
PubMed1997

[Comparison of findings with 18-FDG PET and CT in pretherapeutic staging of malignant lymphoma].

AIM: Comparison of diagnostic efficiency of FDG-PET and CT regarding localisation, histology, size and FDG-uptake of a lesion. METHODS: CT- and FDG-PET studies of 27 patients with histologically confirmed malignant lymphoma as primary disease or relapse were evaluated retrospectively. In CT lesions with a diameter (DCT) > 15 mm were regarded as positive. Focal accumulations of FDG, not explained by physiological metabolism, found by visual interpretation in iterative reconstructed PET-scans, were quantified for diameter (DPET) and corrected standardized uptake value (SUV), corrected for partial-volume-effect. Lesions were classified depending on histology and lesion quality (lymph nodes, bulks, extranodal lesions). RESULTS: CT detected 78 lesions in 26 patients, all confirmed by FDG-PET. PET localized 18 additional lesions (+23%); in high grade NHL +25%. Both methods were equally efficient in cervical lymph nodes and lung lesions, in all other regions of lymphatic nodules and in case of liver and spleen lesions PET localized more lesions. SUV was significantly higher in high-grade NHL (19.0) than in low-grade NHL and Hodgkin's disease (10.6 resp. 11.1). DCT and DPET correlated significantly (r = 0.75). CONCLUSION: Diagnostic efficiency of FDG-PET is equivalent or superior to CT in staging of malignant lymphoma before therapy. Qualitative interpretation seems sufficient for staging, quantitative analysis may add information about malignancy grade in NHL.

Fluorodeoxyglucose F18↗
PubMed1996

Endoscopic treatment of septated chronic subdural hematoma.

BACKGROUND: Chronic subdural hematomas are well delineated collections of fluid (blood) between the dura mater and the arachnoid space. Two types of encapsulated chronic subdural hematoma can be distinguished: the nonseptated and the septated form. The nonseptated form can be treated easily using the burrhole-drainage method, whereas treatment of septated chronic subdural hematoma remains a therapeutical problem. The main problem is the division of the hematoma by neomembranes into compartments, which hinder the efflux of the hematoma fluid through one or two burrholes. METHODS: Since 1991 we have operated on 14 patients with septated subdural hematoma using flexible steerable endoscopes through a burrhole approach. The flexible endoscopes are fixed and guided with the help of the Marburg Neuroendoscopy Fixation and Guiding System. For resection of neomembranes small microscissors or microforceps were used. This technique avoids blunt rupture of the membranes which may cause bleeding. A closed drainage system is applied temporarily to guarantee the efflux of the remaining hematoma. RESULTS: From January 1991 to May 1994, 14 patients with the septated variant of chronic subdural hematoma were operated on using the endoscopic technique. After the neuroendoscopic intervention 12 patients had a sufficient or complete hematoma evacuation. One patient had to be operated on a second time, and there was one postoperative subdural infection. Long term follow up of all patients shows no recurrence of the subdural hematoma. CONCLUSION: Treatment of membraneous septated CSH using an endoscopic operative technique combined with the application of a closed drainage system is a minimally invasive method and a therapeutic alternative to the craniostomy-membranectomy technique.

Adult↗
PubMed1995

Malignant transformation of benign gliomas during interstitial irradiation.

Interstitial curietherapy with 125-Iodine is an effective therapeutic option in the treatment of low grade gliomas. Four cases with astrocytoma grade II are presented, where tumour growth characteristics have changed to anaplasia during interstitial irradiation after a primary period of tumour regression. Anaplastic transformation could be due to a radiation effect or an insufficient therapeutic influence of interstitial irradiation on natural tumour progression of glioma growth due to genetic events.

Adult↗