Biomedical subjects

U Spetzger

Publications and source records attributed to U Spetzger.

At least 37 records · Page 2Linked to original sources

PubMed2000

Removal of adherent ventricular catheters by a modified sheath introducer system: technical note.

BACKGROUND/PURPOSE: A series of technical notes has been dedicated to the removal of retained intracranial shunt catheters, among which the intraluminal cautery proved to be the most accepted technique. However, several reports showed that these techniques still harbor potentially serious complications. METHODS: In this technique, a modified plastic sheath introducer system is passed over the retained ventricular catheter. While advancing the tube along the longitudinal axis of the catheter, circular movements of the tube around the longitudinal axis of the catheter are performed, allowing the tube to act as a spherical knife cutting the ingrown choroid plexus or ependymal adhesions. RESULTS: There were no procedure-related complications in any of the 9 patients treated by the technique described. The procedure proved to be easy and effective in all cases. In addition, in case a new ventricular catheter was needed at the same site, it could be placed via the same tube. CONCLUSIONS: The technique described seems to be an easy, safe, and effective alternative to other techniques for removal of retained ventricular catheters. However, considering the limited number of patients treated with the technique described and the great number of patients treated by the widely accepted intraluminal cautery, one cannot claim the one technique as superior to the other at this stage.

Cardiac Catheterization↗

PubMed2000

Virtual placement of frontal ventricular catheters using frameless neuronavigation: an "unbloody training" for young neurosurgeons.

OBJECTIVE: To evaluate virtually the reliability of freehand puncture of the anterior horn of the lateral ventricle and to provide realistic, but unbloody training for young neurosurgeons. METHODS: Virtual placement of ventricular catheters was performed repeatedly by neurosurgical doctors and thereafter controlled by neuronavigation. With the help of a frameless stereotactic navigation device they virtually had to hit the anterior horn of the lateral ventricle on the MRI of 29 brains with normal ventricular sizes and 60 pathological ventricles, respectively. The catheter placement was simulated using the pointer of the navigation system (EasyGuide Neuro). The monitor screen was blinded, so that on-line control was impossible. Virtual elongation of the pointer tip was performed on the workstation and the position of the virtual catheter was evaluated on a printout. RESULTS: Virtual freehand catheter placement was performed 145 times into the MRIs of the normal brains. In 66 cases (45%) the site of the catheter tip was judged as accurate as shown by the navigation system. No difference concerning the number of correctly placed catheters was observed when comparing more and less experienced doctors. The results in the 60 pathological MRIs of patients differed with respect to the size of the ventricles: in narrow ventricles an accurate placement succeeded in 7 of 22 cases (32%), moderately enlarged ventricles were accurately hit in 15 out of 32 cases (46%) and wide ventricles in 5 of 6 attempts (83%), respectively. CONCLUSION: This setup is a simple, practicable tool for neurosurgical education. The virtual freehand placement of ventricular drains controlled by neuronavigation provides an unbloody training of a routine neurosurgical procedure in a realistic setting without the risk of injuring a patient. Neuronavigation systems can serve therefore as a link between learning from observation and handling the real situation.

Adolescent↗

PubMed2000

High F-18 FDG uptake in a low-grade supratentorial ganglioma: a positron emission tomography case report.

PURPOSE: Positron emission tomography (PET) with fluorine-18 fluorodeoxyglucose (F-18 FDG) is used for the noninvasive monitoring and grading of primary brain tumors. Here the FDG uptake is positively correlated with the malignant extent of the lesion and thereby negatively correlated with patient survival. Little is known about the FDG PET features of primary brain tumors in children, such as mixed neuronal-glial tumors. METHODS: The authors describe a 13-year-old boy who had partial complex seizures since early childhood caused by a brain tumor in the left temporal lobe. RESULTS: Magnetic resonance and computed tomographic examinations yielded uncharacteristic results: mixed density, marked calcifications, little contrast enhancement, a nearly absent mass effect, and no edema. The FDG PET scan revealed a large hypermetabolic tumor, with a tumor: contralateral gray matter FDG uptake ratio of 1.45. In contrast to this intense hypermetabolism, the pathologic analysis after gross total resection revealed a low-grade ganglioglioma (WHO grade 1), which is usually associated with an excellent prognosis. CONCLUSIONS: Mixed neuronal-glial tumors such as gangliogliomas must be considered in making differential diagnoses by judging hypermetabolic FDG PET scans in young patients with brain tumors in the presence of uncharacteristic imaging features.

Adolescent↗

PubMed1999

Functional outcome after aneurysmal subarachnoid hemorrhage.

The introduction of the operating microscope, the principle of early surgery, specialized intensive care units, the calcium antagonist nimodipine, the sophisticated pre- and postoperative management and an aggressive antiischemic pharmacological management have substantially reduced morbidity and mortality after aneurysmal subarachnoid hemorrhage (SAH). In spite of this progress, many patients after rupture and surgical repair of an intracranial aneurysm exhibit substantial cognitive deficits and emotional problems although their neurological outcome was rated as good according to the Glasgow Outcome Scale (GOS = I). Therefore, a comprehensive neuropsychological examination is called for in order to evaluate the factual functional outcome after SAH. Neither focal brain damage associated with aneurysm location nor surgery but the hemorrhage itself and related events can be regarded as the most important causal factors for the late result after SAH. In contrast to the mild permanent effects of aneurysm surgery, the initial bleeding itself seems to have substantial lasting adverse neurobehavioral effects after. In concordance with other authors our own data stress the strong predictive power of the bleeding pattern such as the presence of intraventricular and/or intracerebral blood on the functional outcome after aneurysmal SAH.

Aneurysm, Ruptured↗

PubMed1999

Preoperative PET activation for assessment of motor cortex area in precentral chondroma.

BACKGROUND: A main problem in the preoperative planning for precentral tumors is the exact assessment of the spatial relationship between the tumor and the functionally relevant brain areas, which may be difficult using only morphologically oriented imaging (CT, MRI). Therefore, we applied motor activation PET and PET/MRI overlay in a patient with a precentral tumor. DESCRIPTION: We report the case of a 21-year-old woman suffering from progressive right-sided headache and intermittent dysesthesia of the left leg. MRI showed a hypointense tumor with inhomogenous contrast enhancement in the right precentral area. For preoperative assessment of the spatial relationship between the tumor and the motor cortex area, the patient underwent two F-18-fluorodeoxyglucose positron emission tomography (PET) scans (1. resting condition and 2. motor activation of the left leg) and subsequent calculation of subtraction images of activation minus rest. Fusion of PET and MRI data (PET/MRI overlay) was performed for bimodal function and morphology presentation. PET revealed an activation pattern behind and below the tumor, indicating that the motor cortex area was shifted to the back. PET findings were confirmed by intraoperative electrophysiology. Cortical stimulation combined with intraoperative neuronavigation localized the motor area of the left foot and leg exactly at the dorsal border, below and lateral to the lesion. After complete resection of the solid tumor, histopathological examination revealed a chondroma. The postoperative course was uneventful, and the patient was discharged without neurological deficits. CONCLUSIONS: This case shows that biomodal imaging (PET/MRI) provides a noninvasive exact assessment of functionally important cortex areas for preoperative planning in patients with cerebral lesions.

Adult↗

PubMed1999

Localization of the motor hand area using transcranial magnetic stimulation and functional magnetic resonance imaging.

OBJECTIVE: The anatomical location of the motor area of the hand may be revealed using functional magnetic resonance imaging (fMRI). The motor cortex representation of the intrinsic hand muscles consists of a knob-like structure. This is omega- or epsilon-shaped in the axial plane and hook-shaped in the sagittal plane. As this knob lies on the surface of the brain, it can be stimulated non-invasively by transcranial magnetic stimulation (TMS). It was the aim of our study to identify the hand knob using fMRI and to reveal if the anatomical hand knob corresponds to the hand area of the motor cortex, as identified by TMS, by means of a frameless MRI-based neuronavigation system. METHODS: Suprathreshold transcranial magnetic stimuli were applied over a grid on the left side of the scalp of 4 healthy volunteers. The motor evoked potentials (MEPs) were recorded from the contralateral small hand muscles, and the centers of gravity (CoG) of the MEPs were calculated. The exact anatomical localization of each point on the grid was determined using a frameless MRI-based neuronavigation system. In each subject, the hand area of the motor cortex was visualized using fMRI during sensorimotor activation achieved by clenching the right hand. RESULTS: In all 4 subjects, the activated precentral site in the fMRI and the CoG of the MEP of all investigated muscles lay within the predicted anatomical area, the so-called hand knob. This knob had the form of an omega in two subjects and an epsilon in the other two subjects. CONCLUSIONS: TMS is a reliable method for mapping the motor cortex. The CoG calculated from the motor output maps may be used as an accurate estimation of the location of the represented muscle in the motor cortex.

Adult↗

PubMed1999

Modification of a mechanical twist drill trephine for craniostomy in trauma patients.

A commercially available mechanical twist drill system was modified and evaluated in 35 craniotomies for frontal ventriculostomy in 31 trauma patients. The modified mechanical twist drill enabled faster and seemingly easier and safer craniotomy. It can be used as a safer alternative to common mechanical twist drill trephines, and is particularly recommended in difficult emergency conditions.

Adult↗

PubMed1999

Biomechanical modeling of the human head for physically based, nonrigid image registration.

The accuracy of image-guided neurosurgery generally suffers from brain deformations due to intraoperative changes. These deformations cause significant changes of the anatomical geometry (organ shape and spatial interorgan relations), thus making intraoperative navigation based on preoperative images error prone. In order to improve the navigation accuracy, we developed a biomechanical model of the human head based on the finite element method, which can be employed for the correction of preoperative images to cope with the deformations occurring during surgical interventions. At the current stage of development, the two-dimensional (2-D) implementation of the model comprises two different materials, though the theory holds for the three-dimensional (3-D) case and is capable of dealing with an arbitrary number of different materials. For the correction of a preoperative image, a set of homologous landmarks must be specified which determine correspondences. These correspondences can be easily integrated into the model and are maintained throughout the computation of the deformation of the preoperative image. The necessary material parameter values have been determined through a comprehensive literature study. Our approach has been tested for the case of synthetic images and yields physically plausible deformation results. Additionally, we carried out registration experiments with a preoperative MR image of the human head and a corresponding postoperative image simulating an intraoperative image. We found that our approach yields good prediction results, even in the case when correspondences are given in a relatively small area of the image only.

Biomechanical Phenomena↗

PubMed1998

Intraoperative localization of functional regions in the sensorimotor cortex by neuronavigation and cortical mapping.

Surgery of lesions within the central region requires exact intraoperative anatomical orientation and knowledge of the position of functional cortical regions to minimize the surgical trauma and to avoid postoperative neurological deficits. We combined somatosensory evoked potential (SSEP) phase reversal and/or cortical electrical stimulation with neuronavigation in 26 patients for localization and visualization of functional cortical areas and their anatomical site in relation to the lesion. After location of the central sulcus by means of SSEP phase reversal, the precentral gyrus was electrically stimulated to detect functional motor regions. Electrode position was documented, and the functional regions were related to the site of the lesion using a specially developed neuronavigation system. In 11 of 15 patients the central fissure was located with SSEP phase reversal. Electrical stimulation yielded motor evoked potentials in 23 of the total 26 patients. The anatomical site of these functional regions and their relation to the lesion were evaluated with the neuronavigation system. The precentral gyrus, central sulcus, and postcentral gyrus could be identified in all 23 cases. The combination of intraoperative electrophysiological mapping and neuronavigation provides safe and reliable localization of the sensorimotor cortex. This technique is a promising tool to minimize the risk of surgically caused sensory and motor deficits.

Adult↗

PubMed1998

Functional magnetic resonance mapping of sensory motor cortex for image-guided neurosurgical intervention.

PURPOSE: This paper describes the potentials of functional magnetic resonance imaging (fMRI) to map sensory motor cortex in patients with mass lesions near primary motor cortex and to guide neurosurgical procedures located close to eloquent brain regions. MATERIAL AND METHODS: 7 patients with mass lesions near the central sulcus and 10 healthy volunteers were studied using a blood oxygenation level dependent 2D multislice multishot T2* weighted gradient echo EPI sequence on a 1.5T Phillips Gyroscan during alternating epochs of rest and motor activation of hand, foot and tongue. Sites of neuronal activation were identified by statistical analysis of the signal time course using Kolmogorov Smirnov statistics. RESULTS: Neuronal activation following motor tasks consistently localised to the contralateral precentral gyrus and the supplementary motor area, even in the presence of local brain pathology. Additionally we could observe activation in primary sensory areas (post-central gyrus) and supplementary motor area (SMA) in some cases. CONCLUSION: fMRI is capable of mapping sensory motor cortex even in the presence of distorting brain lesions. Since this information will provide valuable information to the neurosurgeon during pre-operative planning, we consider this method for neurosurgical navigation a valuable tool in the routine diagnostic of intracerebral interventions.

Adult↗

PubMed1998

Endovascular coil embolization of microsurgically produced experimental bifurcation aneurysms in rabbits.

BACKGROUND: Endovascular treatment of cerebral aneurysms is a relatively new method, since only a few animal models and data are available. The present experimental study was performed in order to establish an appropriate aneurysm animal model, to determine the rate of permanent occlusion, and to correlate radiologic and morphologic findings. METHODS: End-to-side anastomoses of both common carotid arteries were performed microsurgically in 53 chinchilla rabbits. Venous pouches were adapted into the newly created bifurcation, resulting in berry-shaped aneurysms comparable to those in humans with regard to size and hemodynamics. Platinum and tungsten coils were used for endovascular embolization. The embolized aneurysms were investigated radiologically and morphologically. RESULTS: Twenty-three carotid bifurcation aneurysms remained for testing endovascular therapeutic approaches. The morphologic examinations of 13 embolized aneurysms revealed in no instance a complete obliteration, even in the three cases that were considered completely embolized according to angiographic criteria. CONCLUSIONS: The present animal model is an optimal tool for endovascular research. Analysis of the results of coil obliteration revealed a considerable discrepancy between radiologic and pathologic findings. The radiologic degree of aneurysm occlusion was overestimated.

Animals↗

PubMed1998

Minimally invasive bedside craniotomy using a self-controlling pre-adjustable mechanical twist drill trephine.

BACKGROUND: Craniotomy with a mechanical twist drill is a standard, minimally invasive procedure in neurosurgery, widely used for the drainage of chronic subdural hematomas and the placement of ventricular drains. Nevertheless, the use of a standard twist drill trephine bears the risk of causing cerebral lesions. METHOD: A commercially available mechanical twist drill system has been modified by a special self-controlling drill and a pre-adjustable distance holder that limits intracerebral penetration. After initial cadaver testing, the modified trephine has been used for 65 trephinations in patients (37 chronic subdural hematomas, 21 external ventricular drains, 6 frontal hygromas, 1 tumor cyst). RESULTS: There were no complications related to the modified trephine; cerebral lesions caused by drilling too deeply or by uncontrolled penetration were safely prevented. In our series no procedure related infections occurred, and the drilling time was reduced significantly. CONCLUSION: The described modified mechanical twist drill enables fast, easy, and safe craniotomy without jeopardizing the advantages of a mechanical twist drill. Therefore, it can be recommended particularly for difficult emergency conditions.

Brain Injuries↗

PubMed1998

Experience with a new multifunctional articulated instrument holder in minimally invasive navigated neurosurgery.

A new multifunctional articulated instrument holder for use in minimally invasive navigated neurosurgery is presented. The instrument holder is secured to the Mayfield clamp, yielding permanent fixation and guidance of instruments. Thus, surgical conditions with the advantages of both conventional and frameless stereotaxic neurosurgery are created without sacrificing the relevant advantages of both methods. Accuracy testing of the instrument holder in combination with the neuronavigation system EasyGuide Neuro demonstrated an error of 0.0 to 2.4 (mean 1.6) mm. In clinical testing, the device has been used for guided catheter insertions, pointer fixation for continuous intraoperative guidance and trajectory planning, navigated endoscopic procedures, and navigated intracerebral biopsies in totally 53 patients.

Equipment Design↗

PubMed1998

Treatment strategies and results in spinal vascular malformations.

We report the treatment strategies and results of 70 patients with spinal vascular malformations. Forty-six had dural arteriovenous fistulas, 12 spinal cavernous angiomas, nine intramedullary angiomas, and three intradural arteriovenous fistulas. The diagnosis was established for cavernomas by magnetic resonance images only and in the other cases by selective spinal angiography in patients whose neurological deficits, myelograms or magnetic resonance images suggested the presence of a spinal vascular malformation. All patients had symptomatic vascular malformations and were treated microsurgically. Intramedullary angiomas were operated when embolization seemed too dangerous or impossible and when they had a contact to the dorsal or lateral surface of the spinal cord. All but one were completely resected. In one angioma a small ventral residual fistula area was left. Complete obliteration of all fistulas was achieved. The cavernomas were primarily resected. Apart from one postoperative permanent deterioration with a paresis of the left arm in a patient with an intramedullary angioma, 16 cases presented only a transitory worsening of their neurological status after surgery. The long-term outcome of all these patients was good. Five patients had to be operated on again: three patients showed difficult localizations of dural fistulas which were still visible in the postoperative angiograms, one patient suffered a spinal epidural hematoma, and another patient showed a cerebrospinal fluid accumulation. We conclude that spinal dural arteriovenous fistulas, small intradural fistulas, spinal cavernomas, and symptomatic spinal angiomas with contact to the lateral or dorsal surface can be treated microsurgically with low perioperative morbidity.

Adult↗

PubMed1997

Unilateral laminotomy for bilateral decompression of lumbar spinal stenosis. Part I: Anatomical and surgical considerations.

A unilateral laminotomy for bilateral access to the lumbar spinal canal was investigated in human cadaver spine specimens to test its practicability in the treatment of spinal stenosis. Micro-surgical decompression was performed by partial resection of the ipsilateral facet, the medial portion of the laminar arch, the contralateral facet and by complete removal of the ligamentum flavum. Anatomical, radiological and morphometrical studies on 4 adult cadaver spine specimens have proved the feasibility of this unilateral approach. Complete bilateral flavectomy and partial bilateral facetectomy were the essential surgical steps for an adequate operative decompression.

Adult↗

PubMed1997

Unilateral laminotomy for bilateral decompression of lumbar spinal stenosis. Part II: Clinical experiences.

The surgical aim in the treatment of symptomatic lumbar spinal stenosis is the relief of the patient's complaints by an adequate neural decompression. Unilateral laminotomy and bilateral spinal canal decompression represents such a safe, effective and minimally invasive surgical method. This technique has been successfully used in the operative treatment of 29 patients with symptomatic mono- or multisegmental lumbar stenosis. There was no surgically induced neurological deterioration. In one patient, an inadvertent dural tear occurred, and due to unchanged symptoms another patient with a multisegmental stenosis had to be re-operated on at an additional level. Postoperatively, 25 of the 27 patients with neurogenic claudication (93%) demonstrated a marked improvement of the walking distance. The follow-up of 25 patients (mean follow-up time was 18 months) demonstrated an excellent result without pain in 7 patients (28%); a good outcome with mild residual pain, but a normal working capacity in 15 patients (60%); and a fair outcome with unchanged postoperative low-back pain but markedly improved working capacity and walking distance in 3 patients (12%). Postoperative morphometric evaluation as well as the clinical improvement of the patient's symptoms clearly demonstrated that bilateral ligamentectomy and recess decompression were adequately and successfully achieved via unilateral approach.

Adult↗

PubMed1997

Endovascular occlusion of experimental aneurysms with detachable coils: influence of packing density and perioperative anticoagulation.

OBJECTIVE: This study was designed to assess the intraluminal biological changes after endovascular coil occlusion of arterial aneurysms with detachable coils, to analyze the relationship between histological occlusion and mechanical packing density, and to evaluate the influence of perioperative anticoagulation on the occlusion rate. METHODS: In rabbits, 30 microsurgically produced arterial bifurcation aneurysms were occluded with coils (18 with platinum coils, electrically detached; 12 with tungsten coils, mechanically detached). Coils were placed until no further coils fit into the aneurysmal lumen and it was no longer filled with radiographic contrast material. The individual degree of occlusion was then determined by the "packing density" on the angiograms. Complete occlusion was considered only if no neck remnant was visible on the films. Anticoagulation during and 2 days after the treatment was performed in 11 cases. After an observation period ranging from 3 to 6 months, angiographic and histological analyses were performed to obtain control data. RESULTS: Complete occlusion was achieved in 9 cases, subtotal occlusion (i.e., > 95% occlusion, residual filling at the neck of the aneurysm) in 10 cases, and partial occlusion in 11 cases. Angiographically documented recanalization was detected in 14 aneurysms. In the remaining 16 aneurysms, the initially documented angiographic results were unchanged. A discrepancy between angiographic and pathological findings was frequently observed. Five of nine angiographically completely occluded aneurysms were recanalized. Endothelial-like tissue at the orifice of the aneurysm was able to be observed in only four of the nine initially completely occluded aneurysms. CONCLUSION: The results suggest that even dense packing does not always guarantee permanent occlusion, although there was a positive relationship between packing density and occlusion rate. Anticoagulation did not have any negative effect on the results.

Animals↗

PubMed1997

The computer-assisted localizer, a navigational help in microneurosurgery.

The computer-assisted-localizer (CAL) achieves a direct linkage between preoperative radiological images and individual intraoperative anatomical findings. Experiences with our system demonstrate that CAL improves the intraoperative orientation and facilitates the neurosurgical procedure. The system described here consists of a mechanical articulated robot arm with six degrees of freedom and a three-dimensional image processor. After calibration, the displayed image dynamically pointed out the exact intraoperative localization in three perpendicular sectional views. Meanwhile, CAL was successfully used in 73 selected microneurosurgical procedures.

Adult↗