PubMed Health⌕ Search

Biomedical subjects

V Rohde

Publications and source records attributed to V Rohde.

At least 37 records · Page 2Linked to original sources
PubMed2003

Measurement of motor evoked potentials following repetitive magnetic motor cortex stimulation during isoflurane or propofol anaesthesia.

BACKGROUND: Isoflurane and propofol reduce the recordability of compound muscle action potentials (CMAP) following single transcranial magnetic stimulation of the motor cortex (sTCMS). Repetition of the magnetic stimulus (repetitive transcranial magnetic stimulation, rTCMS) might allow the inhibition caused by anaesthesia with isoflurane or propofol to be overcome. METHODS: We applied rTCMS (four stimuli; inter-stimulus intervals of 3, 4, 5 ms (333, 250, 200 Hz), output 2.5 Tesla) in 27 patients and recorded CMAP from the hypothenar and anterior tibial muscle. Anaesthesia was maintained with fentanyl 0.5-1 microg kg(-1) x h(-1) and either isoflurane 1.2% (10 patients) or propofol 5 mg kg(-1) x h(-1) with nitrous oxide 60% in oxygen (17 patients). RESULTS: No CMAP were detected during isoflurane anaesthesia. During propofol anaesthesia 333 Hz, four-pulse magnetic stimulation evoked CMAP in the hypothenar muscle in 75%, and in the anterior tibial muscle in 65% of the patients. Less response was obtained with 250 and 200 Hz stimulation. CONCLUSIONS: In most patients, rTCMS can overcome suppression of CMAP during propofol/nitrous oxide anaesthesia, but not during isoflurane anaesthesia. A train of four magnetic stimuli at a frequency of 333 Hz is most effective in evoking potentials from the upper and lower limb muscles. The authors conclude that rTCMS can be used for evaluation of the descending motor pathways during anaesthesia.

Adult↗
PubMed2003

Focused high frequency repetitive transcranial magnetic stimulation for localisation of the unexposed primary motor cortex during brain tumour surgery.

OBJECTIVES: To investigate if intraoperative focused high frequency repetitive transcranial magnetic stimulation (rTMS) can localise the primary motor cortex without exposure of the cortical surface. METHODS: A high frequency train (357 Hz) of four suprathreshold magnetic stimuli was delivered transcranially to the region of the rolandic area during brain tumour operations in 12 patients. To induce a focal magnetoelectric field, the flat figure of eight coil (outer diameter of each loop 7 cm) was used. Motor evoked potentials (MEP) were recorded in eight muscles of the upper and lower contralateral extremities. The first stimulation site was 2.5 cm behind the bregma, the second site 2 cm, and the third site 4 cm dorsal to the first stimulation site. If no MEP were obtainable, stimulation was repeated in anteroposterior direction at more laterally located sites. Using neuronavigation, each positive stimulation site was correlated with the underlying cortical anatomy. RESULTS: Stimulation was performed at a total of 42 sites (in two patients, maximum stimulation at the three initial sites failed to evoke a motor response). In four patients, MEP were obtained only from one stimulation site. This site exactly overlayed the primary motor cortex. In eight patients, MEP could be elicited from more than one stimulation site. In seven of the eight patients, the site from which MEP with peak amplitudes were elicited, corresponded to the primary motor cortex. In total, the primary motor cortex was correctly identified on the basis of electrophysiological findings in 11 of 12 patients (92 %). In two patients, only the more lateral stimulation sites permitted MEP recording. CONCLUSION: Intraoperative focused rTMS is highly sensitive for localisation of the primary motor cortex. Focused rTMS as a localising instrument alleviates the need of motor cortex exposure and, thereby, can contribute to minimise the surgical approach to brain tumours in the rolandic area.

Adult↗
PubMed2003

Identification of milling parameters for manual cutting of bicortical bone structures.

Within the framework of the development of a new neurosurgical robot system, parameters of conventional manual neurosurgical bone milling had to be determined. These results were used as a reference for the design and validation of the robotic versus manual milling task. Bovine scapulae were used for the tests because their bicortical structure is similar to the bone structure of the skull. The exercise was to cut defined geometries that had been registered on the bone prior to the start of the milling operation. The geometries had to be milled with a depth of 3 mm, which corresponded to the radius of the ball of the cutter. Different parameters like tool position, rotary speed, temperature, forces and time were registered. Eleven experienced neurosurgeons with practical experience of 80-1200 skull operations participated in this study. First results show a large variation in depth along the line. The lateral deviation was up to 5 mm, the depth error up to 2.5 mm, the tool temperature was 22 degrees C to 65 degrees C, and rotary speed varied from 15,000 to 80,000 rpm. Registered forces had maxima of 16 N in the feed direction and 21 N normal to the surface; average forces were approximately 1-2 N.

Animals↗
PubMed2002

Virtual endoscopy combined with intraoperative neuronavigation for planning of endoscopic surgery in patients with occlusive hydrocephalus and intracranial cysts.

We assessed the clinical value of MR ventriculoscopy (virtual endoscopy, VE) combined with image-guided frameless stereotaxy for endoscopic surgery of occlusive hydrocephalus and intracranial cysts. VE was obtained in 20 patients with hydrocephalus and three with intracranial cysts. All surgical operations were endoscopic. The path of the rigid endoscope to the target point was planned using neuronavigation. VE was carried out along the same trajectory retrospectively in 20 cases and prospectively in three. The results were analysed for demonstration of anatomical landmarks and structures at risk. VE was successful in all patients. Possible obstacles to endoscopic access to the lamina terminalis and the basal cisterns and structures at risk, such as the basilar artery, were clearly shown in relation to the direction of the endoscope. However, the floor of the third ventricle and septum pellucidum were not clearly seen and possible abnormalities could therefore not be appreciated. VE can provide realistic simulation of endoscopic third ventriculostomy and cystostomy. The appropriate trepanation point and trajectory of the endoscope can be assessed with regard to the size of the foramen of Monro and the position of vulnerable structures. This simulated trajectory can be adapted to the field of operation by image-guided neuronavigation. This regime may potentially reduce the risk of damage to intracranial structures.

Adolescent↗
PubMed2002

Functional MRI and 18F FDG-positron emission tomography for presurgical planning: comparison with electrical cortical stimulation.

BACKGROUND: In patients with mass lesions near "eloquent" cortical areas different preoperative mapping techniques can be used. Two of the most widely used approaches include positron emission tomography (PET) and functional MRI (fMRI). We employed both methods in the same patients undergoing presurgical evaluation and compared the results to those obtained by direct electrical cortical stimulation (DECS). METHOD: 22 patients with tumours of different aetiology near the central region were investigated. FMRI was performed using a T2(*)-weighted gradient-echo BOLD sequence at 1.5 T, PET was performed after injection of 122-301 MBq (18)F-Fluorodeoxyglucose (18-FDG) under rest and activation conditions. DECS was performed in all patients with recordings of muscles primarily involved in the investigated tasks. FINDINGS: In 19 patients all three modalities could be compared, 1 patient demonstrated discordance between fMRI and PET with DECS speaking in favour of fMRI, 6 patients had neighbouring results of PET and fMRI (between 1-2 cm distance), 12 patients had overlapping results. INTERPRETATION: The high incidence of neighbouring results is presumably related to fMRI specific artefacts. Advantages of fMRI are: Higher spatial and temporal resolution, more and different functional runs, shorter examination time, wider availability, longitudinal examinations, non-invasiveness and cost-effectiveness, easy registration to anatomical images. Advantages of PET are: higher signal-to-noise ratio, lesser susceptibility to artefacts (motion, draining veins), evaluation of tumour metabolism. It is our opinion that the neurosurgeon has to decide on a case-by-case basis which study suits his specific needs in the presurgical evaluation of his patient.

Adult↗
PubMed2001

Virtual MRI endoscopy: detection of anomalies of the ventricular anatomy and its possible role as a presurgical planning tool for endoscopic third ventriculostomy.

BACKGROUND: Many anatomical anomalies have the potential to impair the efficacy of endoscopic third ventriculostomy (ETV) and increase the surgical morbidity. By virtual magnetic resonance imaging (MRI) endoscopy, the real endoscopic view into the ventricular system can be simulated. It was the objective of the present study to investigate if this simulation is sensitive enough to detect anatomical anomalies of the ventricular system. METHOD: In 18 hydrocephalic patients, first neuronavigationally guided ETV, then virtual MRI endoscopy were performed. This study design allowed for selection of a path for virtual MRI endoscopy, which was identical to that used during surgery, making the real and the virtual view on anatomical structures of the ventricular system highly comparable. It was investigated whether the intra-operatively identified anatomical anomalies could likewise be depicted on virtual MR endoscopic images. FINDINGS: Seven anatomical variants (not enlarged interventricular foramen n=2, atrophic corpus callosum and split fornical bodies n=1, narrow retroclival space n=1, prominent basilar tip n=1, opaque and thick/atypically declining third ventricular floor n=2) were encountered in 5 of the 18 patients during surgery. The five variants of the non-membraneous structures were identified by virtual MRI endoscopy (sensitivity 71%), whereas the anatomical variants of the third ventricular floor were missed. Both the normal as well as the variant third ventricular floor could not be visualised and appeared as a defect. Through this artefact, the anatomy of the major vessels in the interpeduncular cistern could be assessed. INTERPRETATION: The sensitivity of virtual MRI endoscopy for detection of anatomical variants of the ventricular system is low. Its potential usefulness as a presurgical planning tool inspite of this low sensitivity rate is discussed.

Adolescent↗
PubMed2001

Influence of intraventricular hemorrhage on outcome after rupture of intracranial aneurysm.

This study was performed to analyze the effect of intraventricular hemorrhage (IVH) on 14-day mortality, outcome at 6 months, and the occurrence of chronic hydrocephalus in patients with aneurysmal subarachnoid hemorrhage. Clinical grade of subarachnoid hemorrhage and the distribution of extravasated blood were evaluated in 219 patients with ruptured aneurysms. Computed tomographic scans performed within 72 h of hemorrhage were analyzed to determine the severity of intraventricular and subarachnoid hemorrhage and the volume of intracerebral hematomas. Outcome at 6 months was assessed using the Glasgow Outcome Scale. Intraventricular hemorrhage extension occurred in 109 of the 219 patients studied. Fourteen-day mortality increased from 7.3% in patients without IVH to 14.1% in those with moderate IVH (IVH score 1-6) and to 41.7% in those with more severe IVH (IVH score > 6). The corresponding figures for unfavorable outcome at 6 months are 19.8%, 30.5%, and 66.7%, respectively. According to logistic regression analyses, the severity of IVH was an independent predictor of mortality and functional outcome. The clinical outcome after aneurysm rupture is at least in part determined by the severity of IVH. Knowledge of the effect of IVH may help guide physicians in the care of patients with aneurysmal bleeding.

Adult↗
PubMed2001

The role of intraoperative magnetic resonance imaging for the detection of hemorrhagic complications during surgery for intracerebral lesions an experimental approach.

BACKGROUND: Intraoperative magnetic resonance imaging (MRI) for guided biopsy or microsurgical resection of intracranial lesions is gaining broader acceptance. It is not known whether intraoperative MRI has the potential to detect hemorrhagic complications of these surgical procedures, because scientific research has so far focussed on the signal characteristics of less acute clots. It is the objective of this experimental study to investigate whether MRI can visualise intracerebral blood within minutes after its occurrence. METHODS: In 26 pigs, a frontal hematoma was produced by injecting autologous blood. Twenty pigs underwent MRI 30 minutes after injection, and 6 pigs within the first 10 minutes. MRI scans were performed on a 1.5T system. T1-weighted spin echo (SE), T2-weighted turbo spin echo (TSE), T2-weighted fluid attenuated inversion recovery (FLAIR), and T2-weighted gradient echo (GE) images were acquired. Depending on the differences of the signal intensities of the hematoma and the surrounding brain, the detectability of the hematoma was rated as good, fair, or poor. RESULTS: None of the induced hematomas were rated to be clearly visible on T1-weighted sequences. Six of the 26 hematomas (23%) were easily detectable on FLAIR sequences, 18 hematomas (69%) on T2-weighted TSE sequences, and 23 hematomas (88%) on the T2-weighted GE sequences. CONCLUSION: Extravasated blood can be identified with a high reliability within minutes after its occurrence on MRI provided that T2-weighted GE sequences are used for imaging. In conclusion, intraoperative MRI is not only of value for guidance of neurosurgical procedures, but also for immediate detection of hemorrhagic complications.

Animals↗
PubMed2001

Navigated transcranial magnetic stimulation for presurgical planning--correlation with functional MRI.

PURPOSE: This paper describes the potential of navigated transcranial magnetic stimulation to map the motor cortex in patients with mass lesions near the primary motor cortex by comparing the results of this technique to those of functional MRI. MATERIAL AND METHODS: Ten patients with mass lesions near the central sulcus were studied preoperatively using a figure-of-eight transcranial magnetic stimulator attached to a neuronavigation system to allow for direct visualization of the stimulated brain region. Subsequently, in all patients a blood oxygenation level dependent 2D multislice multishot T2*-weighted gradient echo EPI sequence on a 1.5 T Philips Gyroscan during motor activation was performed. Results of both methods were coregistered and compared. RESULTS: The distances between the peak parenchymal fMRI activation and the cortical area where TMS elicited the maximum MEPs ranged between 0 and 1.2 cm (mean 0.6 cm, SD 0.4 cm). CONCLUSION: We conclude that navigated TMS is a reliable alternative for localizing the motor-related areas in the human brain preoperatively and therefore may be a useful adjunct or, in selected patients, even a helpful alternative to functional MRI.

Adult↗
PubMed2001

DNA of adeno-associated virus (AAV) in testicular tissue and in abnormal semen samples.

BACKGROUND: Human genital tissues, including spermatozoa, have been found to be frequently infected with the helper-virus dependent parvovirus, adeno-associated virus (AAV). METHODS: To assess the role of AAV infection in disorders of the male reproductive system, semen samples from 95 men (including 73 men attending a fertility programme) and testicular samples from patients with azoospermia (n = 38) or prostate cancer (n = 8) were analysed using polymerase chain reaction for the presence of AAV DNA. Semen quality was assessed according to World Health Organization guidelines and the grade of atrophy of testicular biopsies was determined histomorphologically. RESULTS: AAV DNA was detected in 38% (28/73) of ejaculates from men with abnormal semen analyses (oligoasthenozoospermia or asthenozoospermia) and in 4.6% of normal semen samples (1/22, P = 0.003). DNA from AAV helper-viruses (human papillomaviruses, cytomegalovirus) was detected at similar frequencies in normal and abnormal semen samples. In testes, AAV DNA was detected in 10 out of 38 biopsies from infertile men (26%), and in 2 out of 8 orchidectomy samples. CONCLUSION: The data show an increased incidence of AAV infection with abnormal semen analysis. Detection of AAV DNA in the testes might point to a role for AAV infection in male infertility, possibly by interfering with spermatozoa development.

Adolescent↗
PubMed2001

Functional MRI for presurgical planning: problems, artefacts, and solution strategies.

OBJECTIVES: Presurgical mapping of motor function is a widely used clinical application of functional (f) MRI, employing the blood oxygenation level dependent contrast. The aim of this study was to report on 3 years experience of 194 fMRI studies on the representation of motor function in 103 patients and to describe the problems and artefacts that were typically present. METHODS: An evaluation was carried out to determine whether the patients' age, type or location of the tumourous lesion, severity of the paresis, or the tasks used during the investigation have an effect on artefacts of fMRI studies and how these artefacts are best overcome. RESULTS: Functional MRI identified the motor regions in 85% of all investigated paradigms. In 11% of the investigated patients no information at all on functional localisation was obtained. A draining vein within the central sulcus was present in all patients that showed activation within the parenchyma of the precentral gyrus but also in three patients in whom no parenchymal activation was present. Head movement artefacts were the most frequent cause for fMRI failure, followed by low signal to noise ratio. Motion artefacts were correlated with the degree of paresis and with the functional task. Tasks involving more proximal muscles led to significantly more motion artefacts when compared with tasks that primarily involved distal muscles. Mean MR signal change during task performance was 2.5%. CONCLUSIONS: Most of the artefacts of functional MRI can be reliably detected and at least in part be reduced or eliminated with the help of mathematical algorithms, appropriate pulse sequences and tasks, and-probably most important-by evaluating the fMRI raw data-that is, the MR signal time courses.

Adolescent↗
PubMed2001

Metabolic and electrophysiological validation of functional MRI.

OBJECTIVES: Although functional MRI is widely used for preoperative planning and intraoperative neuronavigation, its accuracy to depict the site of neuronal activity is not exactly known. Experience with methods that may validate fMRI data and the results obtained when coregistering fMRI with different preoperative and intraoperative mapping modalities including metabolically based (18)F-fluorodeoxyglucose PET, electrophysiologcally based transcranial magnetic stimulation (TMS), and direct electrical cortical stimulation (DECS) are described. METHODS: Fifty patients were included. PET was performed in 30, TMS in 10, and DECS in 41 patients. After coregistration using a frameless stereotactic system, results were grouped into overlapping (<1 cm distance), neighbouring (<2 cm), or contradictory (>2 cm). RESULTS: Comparing fMRI with PET, 18 overlapping, seven neighbouring, and one contradictory result were obtained. In four patients no comparison was possible (because of motion artefacts, low signal to noise ratio, and unusual high tumour metabolism in PET). The comparison of TMS and fMRI showed seven overlapping and three neighbouring results. In three patients no DECS results could be obtained. Of the remaining 38 patients, fMRI hand motor tasks were compared with DECS results of the upper limb muscles in 36 patients, and fMRI foot motor tasks were compared with DECS results of the lower limb on 13 occasions. Of those 49 studies, overlapping results were obtained in 31 patients, and neighbouring in 14. On four occasions fMRI did not show functional information (because of motion artefacts and low signal to noise). CONCLUSIONS: All validation techniques have intrinsic limitations that restrict their spatial resolution. However, of 50 investigated patients, there was only one in whom results contradictory to fMRI were obtained. Although it is not thought that fMRI can replace the intraoperatively updated functional information (DECS), it is concluded that fMRI is an important adjunct in the preoperative assessment of patients with tumours in the vicinity of the central region.

Adult↗
PubMed2000

Novel amplification unit at chromosome 3q25-q27 in human prostate cancer.

BACKGROUND: In prostate carcinoma, amplification of the genes c-MYC, Her2/NEU, and the androgen receptor gene has been documented, with gene amplification being related to progressive tumor growth. Recently, using comparative genomic hybridization (CGH), we provided evidence for DNA copy number gains at chromosome 3q25-q26 in prostate cancer [Sattler et al.: Prostate 39:79-86, 1999]. METHODS: In this study, additional prostatic tumors were evaluated by CGH to determine the frequency of DNA overrepresentation at 3q. Comparative PCR and Southern blot analyses were applied to determine whether known genes are involved in DNA copy number gains. RESULTS: By CGH, DNA copy number gains, all of which involved chromosome region 3q25-q26, were disclosed in 50% of the prostate tumors analyzed. There was no evidence for high-level amplification. The analysis of 12 genes from 3q25-q27 by comparative PCR revealed amplification in 6 (35.3%) of 17 tumors tested. Amplification was detected for the genes IL12A, MDS1, SLC2A2, and SOX2, with coamplification of three genes in two tumors. IL12A was amplified as single gene in three tumors and in a subline of the DU145 cell line, SLC2A2 in one tumor. CONCLUSIONS: Our studies revealed a novel amplification unit at 3q25-q27 in prostate carcinoma, with the genes IL12A, MDS1, SLC2A2, and SOX2 being located within the amplification unit. A common region of amplification was evident spanning the IL12A gene locus at 3q25-q26.2. Possibly, IL12A indicates an adjacent, till now unidentified gene which is important in the development of prostate cancer.

Blotting, Southern↗
PubMed2000

Virtual pointer projection of the central sulcus to the outside of the skull using frameless neuronavigation -- accuracy and applications.

BACKGROUND: The purpose of this prospective study was to localize the central sulcus by frameless neuronavigation and to project this anatomical structure to the outside of the skull on the skin. This method was analyzed in respect to its practicability, accuracy, and potential applications. METHOD: In 27 patients investigated (28 unaffected hemispheres), the central sulcus was virtually projected to the outside of the skull using frameless neuronavigation and a virtual pointer elongation of 15 or 20 mm. The following parameters were measured on the scalp: 1. the distance between the bregma and the midline junction of the central sulcus, and 2. the angle between the central sulcus and the midline. These dada were compared with measurements based on the original axial MR images of these patients. Finally, a laboratory phantom study was designed in analogy to a patient's examination for estimation of the overall accuracy of the neuronavigation system in the experimental setup used in this study. FINDINGS: Virtual pointer projection of the central sulcus to the outside of the skull using frameless neuronavigation was found to be easily possible. The distance between the bregma and the midline junction of the central sulcus amounted to a mean of 55 mm on the left and 56 mm on the right. The angle between the central sulcus and the midline reached a mean of 63 degrees on the left and 60 degrees on the right. These data confirmed results of other studies with no frameless neuronavigation devices. The phantom study revealed a mean overall inaccuracy of 0.9 mm at a virtual pointer elongation of 15 mm. At a virtual pointer elongation of 20 mm, the mean overall inaccuracy of our study was 1.1 mm. These results correspond to the inaccuracy of frame based stereotaxy. INTERPRETATION: It is easily possible, valid, and reliable to virtually project the central sulcus to the outside of the skull with an acceptably low inaccuracy using frameless neuronavigation. This is important for research studies that correlate and integrate different functional imaging methods with the aid of frameless neuronavigation.

Adult↗
PubMed2000

Microsurgical treatment of spontaneous and non-spontaneous spinal epidural haematomas: neurological outcome in relation to aetiology.

BACKGROUND: This retrospective study evaluated the neurological outcome of 26 patients with spontaneous and non-spontaneous spinal epidural haematoma (SEH) who underwent microsurgical clot removal. It was the objective of the present study to investigate whether the aetiology of the SEH has an influence on the neurological outcome. METHODS: The medical records and radiological investigations of 26 patients with SEH were re-examined, and the latency between symptom onset and operation, and the size of the haematoma were determined. Motor and sensory function had been evaluated before surgery and 90 days after discharge. FINDINGS: Fourteen patients with non-spontaneous SEH and 12 patients with spontaneous SEH were identified. After surgery, neurological deficits improved in 9 of the patients with spontaneous (75%) and in 13 of the patients with non-spontaneous SEH (93%). In cases of spontaneous SEH, the median latency between symptom onset and operation was longer (72 hrs vs 7 hrs) and the median extent of the haematoma was larger (3.5 vs 2 spinal segments), than in the non-spontaneous cases. INTERPRETATION: Neurological outcome seems to be related to the aetiology of the SEH. Better outcome was observed in patients with surgically treated non-spontaneous SEH. Two explanations for this finding are worth considering. First, patients with non-spontaneous SEH usually are already under medical surveillance and can undergo medullary decompression more rapidly. Second, the compression of the spinal cord is possibly less severe in non-spontaneous SEH because of their smaller size.

Adolescent↗