Biomedical subjects

U Spetzger

Publications and source records attributed to U Spetzger.

At least 37 records · Page 2Linked to original sources

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↗

PubMed1997

Long-term angiographic and histopathologic findings in experimental aneurysms of the carotid bifurcation embolized with platinum and tungsten coils.

PURPOSE: To evaluate the long-term outcome of endovascular occlusion of arterial aneurysms effected with metal coils. METHODS: Microsurgical methods were used to produce carotid bifurcation aneurysms in 20 rabbits and the radiologic and histologic changes were examined. Eight of these aneurysms were occluded with electrically detachable platinum coils (Guglielmi detachable coils [GDCs] and nine were treated with mechanically detachable tungsten coils (mechanical detachable system [MDS]). Three aneurysms remained untreated and served as controls. One animal died of embolic complications 12 hours after endovascular treatment. After observation periods of 3 to 6 months, the remaining animals were examined by intraarterial digital subtraction angiography and subsequent fixation and light and electron microscopy. RESULTS: Large open spaces without signs of thrombosis were found between the loops of the coil baskets in 12 aneurysms (six treated with GDCs and six treated with MDS) regardless of the observation period. In very densely packed aneurysms (four cases with complete occlusion as determined by angiographic criteria), the coil surfaces were for the most part covered by thin cell layers; however, complete endothelialization was never seen. In aneurysms with an initial partial occlusion of 70% to 90%, coil compaction and/or recanalization was a consistent finding. A comparison of the radiologic findings with the histologic aspect revealed that the degree of occlusion was often overrated on the radiographs (in eight of 17 cases). In general, the fibrous tissue reaction appeared to be slightly more pronounced in aneurysms occluded with tungsten coils. CONCLUSIONS: Platinum and tungsten coils were not always effective in causing endoluminal thrombosis leading to long-term occlusion by organized thrombus.

Angiography, Digital Subtraction↗

PubMed1997

Cognition and quality of life in patients after transcallosal microsurgery for midline tumors.

OBJECTIVE: The transcallosal route has been propagated as a safe approach to midline tumors. The present study was performed in order to elucidate the neurobehavioral late sequelae in patients after transcallosal microsurgery on near-midline tumors. EXPERIMENTAL DESIGN: The present study was performed retrospectively with a delay between surgery and follow-up examination ranging from 2 to 36 months (mean 10.2 months). SETTING: The study was performed in the Department of Neurosurgery, University Hospital of the University of Technology (RWTH) Aachen, Germany. PATIENTS: A consecutive series of 18 patients treated for an intracranial lesion by transcallosal surgery was included into the study. The patients had to be not younger than 16 and not older than 67 years. The age mean was 38.9 years (range 16 to 65 years). INTERVENTIONS: The surgical approach was performed along the falx cerebi under microneurosurgical conditions with direct use of the microscope after opening the dura. MEASURES: Beyond neurological examinations, the patients were submitted to an extensive neuropsychological testing battery. Furthermore, quality of life was examined by means of a questionnaire. RESULTS: Surgery was performed without persistent new neurological deficits. Cognitive deficits were found in short- and long-term memory, motor fine-coordination, reaction time, divided attention and fronto-cortical capacity. The quality of life was particularly impaired in the area of cognitive capacity in daily life. These findings could be related to the duration of preoperative symptoms and to the tumor location. CONCLUSIONS: The deficits found cannot be explained by surgical damage to the corpus callosum itself. Rather, they seem to correspond to an extra-callosal pathology. Further studies with a prospective evaluation of larger patient samples are called for in the future.

Adolescent↗

PubMed1997

[Forum: Clips and coils in aneurysm treatment].

The treatment of cerebral aneurysms aims at the complete elimination of the aneurysm from the circulation. In the case of subarachnoid hemorrhage (SAH), early management prevents rebleeding and in incidental aneurysms, future rupture is to be prevented. Standardization of surgical techniques and optimized collateral measures have reduced the morbidity and mortality of early operations in SAH to 10% and 15%, respectively, in most series. As an alternative, endovascular techniques are being developed which attempt to obliterate the aneurysmal sack by packing it with detachable platinum-coils. A major difference between clipping and coiling is the closure of the aperture by the surgical clip which approximates the vessel walls. During coil embolization, that aperture stays open, allowing in some cases further compaction of the coils in subsequent months and years. Recanalization attributable to compaction depends on the size of the aneurysm and may necessitate repacking in up to 40% of the cases (aneurysms > 25 mm). As for the risk of rebleeding, a recanalized aneurysm is comparable to a partially clipped aneurysm. As the surgical results from early and delayed operations were obtained in randomized controlled studies, such randomized comparative studies will need to be applied to assess the value and risks and long-term results of endovascular strategies.

Aneurysm, Ruptured↗

PubMed1996

Hemangioblastomas of the spinal cord and the brainstem: diagnostic and therapeutic features.

Hemangioblastomas of the spinal cord and the brainstem make up 4% of all spinal tumors and are less common than cerebellar hemangioblastomas. CT and MRI are essential for preoperative diagnosis. Nevertheless, cerebral and spinal angiography are also mandatory, since they allow a detailed study of the vascular situation, which is decisive for exact planning of a surgical strategy. The purpose of this study was to evaluate the diagnostic and therapeutic factors which influence surgical morbidity and postoperative outcome. Twelve patients harbouring spinal(8 cases) or medullary (4 cases) hemangioblastomas, all symptomatic with sensorimotor deficits corresponding to the level of the lesion were evaluated. All patients were treated in our department between December 1989 and September 1994. Complete resection of the lesion was achieved in each case. Postoperatively, none of the patients showed deterioration. Nine patients had immediate postoperative improvement of neurological signs and symptoms; in three patients the initial neurological deficits remained unchanged during the in-patient period. Late postoperative outcome demonstrated a clear improvement; in only one patient was there no change of the clinical signs, while in the other 11 patients a significant improvement of pre-existing neurological deficits was experienced. We conclude that microsurgical resection of spinal and medullary hemangioblastomas with low morbidity is feasible.

Adult↗

PubMed1996

[Lumbar dislocation fracture with paraplegia after pelvic seat belt injury. Case report].

This report details a traumatic spinal column lesion due to a lap seat belt. A healthy 22-year-old woman was involved in a car accident and suffered a lumbar luxation fracture at the level L1-L2. She developed acute transsectional symptoms with paraplegia and severe hyperpathia in her legs. Plain radiographs (antero-posterior and lateral projection) and lumbar CT scans demonstrated an instable flexion-distraction fracture with ventral compression of the vertebral body of L2 and ventrolisthesis of L1 over L2. Surgical reposition of the luxation fracture and removal of a spinal epidural hematoma was performed 4 h after the trauma. Stabilization was achieved by monosegmental dorsal transpedicular spondylodesis with a fixateur interne. In follow-up the neurological deficits markedly improved. Six months after the trauma, the patient is able to walk, has no paresis and no genitourinary disturbances: only mild dysesthesia remains. This posttraumatic course confirms that spinal traumas below L1 which spare the conus have a favorable prognosis, because the peripheral nerves of the cauda equina are able to recover. This injured patient was the only one using a lap seat belt; the other four passengers in the same compact car-wearing lap and diagonal seat belts-suffered no harm. We conclude that lap seat belts are not acceptable as an adequate security standard in modern automobile technology.

Adult↗