Biomedical subjects

Ulrich Hubbe

Publications and source records attributed to Ulrich Hubbe.

8 recordsLinked to original sources

PubMed2006

Virtual reality augmentation in skull base surgery.

OBJECTIVE: Skull base anatomy is complex and subject to individual variation. Understanding the complexity of surgical anatomy is faster and easier with virtual models created from primary imaging data of the patient. This study was designed to investigate the usefulness of virtual reality in image guidance for skull base procedures. DESIGN: Primary volumetric image data from 110 patients was acquired using magnetic resonance, computed tomography (CT), and CT angiography. Pathologies included lesions in the anterior, middle, and posterior skull base. The data were transferred to an infrared-based image-guidance system for creation of a virtual operating field (VOF) with translucent surface modulation and optional "fly-through" video mode. During surgery, the target registration error for anatomical landmarks was assessed and the VOF was compared with the patient's anatomy in the operative field. RESULTS: Complex structures like the course of the sigmoid sinus, the carotid artery, and the outline of the paranasal sinuses were well visualized in the VOF and were recognized by the surgeon instantly. Perception was greatly facilitated as compared with routine mental reconstruction of triaxial images. Accurate assessment of the depth of field and very small objects was not possible in VOF images. CONCLUSION: Supported by sound anatomical knowledge, creation of a virtual operating field for a surgical approach in an individual patient offers a déjà vu experience that can enhance the capabilities of a surgical team in skull base approaches. In addition, application of this technique in image-guided procedures assists in targeting or avoiding hidden anatomical structures.

Journal Article↗

PubMed2005

Surgical treatment of hemangioblastomas of the central nervous system in pediatric patients.

OBJECTIVE: Hemangioblastomas are histologically benign lesions that occur sporadically or as a manifestation of von Hippel-Lindau disease (VHL). The treatment strategy of these neoplasms is complicated by their unpredictable growth patterns and the often irreversible neurological deficits they may cause. This study aims to outline the neurosurgical treatment options and to address the ongoing debate of surgical timing in pediatric patients with VHL. PATIENTS AND METHODS: Thirteen consecutive pediatric patients (mean age 15.1 years) who were surgically treated for intracranial (n=8) or spinal hemangioblastomas (n=5) were included in this study (range of clinical follow up 12-86 months). Ten patients were affected by von Hippel-Lindau and three were with sporadic tumors. Serial examinations, preoperative MRI studies, and operative findings were reviewed. RESULTS: Patients with cerebellar and intramedullary hemangioblastomas did not develop additional neurological deficits postoperatively. Two patients with brainstem tumors exhibited transient hemiparesis and caudal nerve palsy, respectively. Both patients recovered completely from their postoperative deficits. Preoperatively symptomatic patients with spinal tumors did not deteriorate nor improve after surgery. During the observed follow-up periods, no tumor recurrences were observed. CONCLUSION: Central nervous system (CNS) hemangioblastomas in pediatric patients can be surgically treated with low morbidity. Based on our experience, we recommend considering also the surgical removal of asymptomatic hemangioblastomas with proven radiological progression to prevent the development of permanent neurological deficits. Molecular screening of every pediatric patient and family is mandatory to enable the detection of extraneurological tumors and the development of an efficient therapeutic strategy.

Adolescent↗

PubMed2005

Dopamine release in human neocortical slices: characterization of inhibitory autoreceptors and of nicotinic acetylcholine receptor-evoked release.

The autoinhibitory control of electrically evoked release of [3H]-dopamine and the properties of that induced by nicotinic receptor (nAChR) stimulation were studied in slices of the human neocortex. In both models [3H]-dopamine release was action potential-induced and exocytotic. The selective dopamine D2 receptor agonist (-)-quinpirole reduced electrically evoked release of [3H]-dopamine, yielding IC50 and I(max) values of 23 nM and 76%, respectively. Also, the effects of several other subtype-selective dopamine receptor ligands confirmed that the terminal dopamine autoreceptor belongs to the D2 subtype. The autoinhibitory feedback control was slightly operative under stimulation conditions of 90 pulses and 3 Hz, with a biophase concentration of endogenous dopamine of 3.6 nM, and was enhanced under blockade of dopamine reuptake. [3H]-dopamine release evoked in an identical manner in mouse neocortical slices was not inhibited by (-)-quinpirole, suggesting the absence of dopamine autoreceptors in this tissue and underlining an important species difference. Also, nAChR stimulation-induced release of [3H]-dopamine revealed a species difference: [3H]-dopamine release was evoked in human, but not in rat neocortical slices. The nAChRs inducing [3H]-dopamine release most probably belong to the alpha3/beta2subtype, according to the potencies and efficacies of subtype-selective nAChR ligands. Part of these receptors may be located on glutamatergic neurons.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗

PubMed2004

Neuronavigation-assisted cranial reconstruction.

OBJECTIVE: Cranial defects resulting from congenital deformities, ablative resection of osseous tumors, traumatic injury, and destructive infectious lesions are often severe enough to warrant surgical reconstruction. In particular cases, satisfactory cosmetic results may be difficult to achieve because of the extent and location of the lesion. METHODS: We evaluated the role of neuronavigation for reconstruction of large cranial defects with prefabricated titanium and intraoperatively constructed neuronavigation-assisted polymethylmethacrylate implants. RESULTS: Neuronavigation-assisted cranial reconstruction was performed in 14 patients. Surgical procedure, illustrative cases, postoperative results, and apparent benefits of the technique are presented and discussed. In all patients, excellent cosmetic results were achieved. CONCLUSION: In cranial reconstruction, neuronavigation is of value not only for intraoperative determination of resection margins but also for preoperative assessment and planning. The combination of navigation techniques with prefabricated or intraoperatively constructed implants enables achievement of excellent cosmetic results.

Adult↗

PubMed2004

Complex visual hallucinations (Charles Bonnet syndrome) in visual field defects following cerebral surgery. Report of four cases.

The development of visual hallucinations after loss of vision is known as the Charles Bonnet syndrome. This phenomenon was first described in 1760 by Charles Bonnet and others during their observations of elderly patients with degeneration of the retina or cornea. To date a clear association between visual hallucinations and neurosurgical procedures has not been reported. Because of their clear demarcation, however, surgical lesions in the cerebrum offer a unique opportunity to determine the pathoanatomical aspects of visual hallucinations. During a 3-year period, 41 consecutive patients who acquired visual field defects after neurosurgery were examined for the occurrence of visual hallucination. Postoperatively, four of these patients experienced visual hallucinations. In two of them an upper quadrantanopia developed after the patients had undergone selective amygdalohippocampectomy. In the other two patients a complete hemianopia developed, in one case after resection of a parietal astrocytoma and in the other after resection of an occipital glioblastoma multiforme. The visual hallucinations were transient and gradually disappeared between 4 days and 6 months postoperatively. The patients were aware of the fact that their hallucinations were fictitious and displayed no psychosis. Electroencephalographic recordings were obtained in only two patients and epileptic discharges were found. Deafferentiation of cortical association areas may lead to the spontaneous generation of complex visual phenomena. In the present series this phenomenon occurred in approximately 10% of patients with postoperative visual field defects. In all four cases the central optic radiation was damaged between the lateral geniculate nucleus and the primary visual cortex. The complex nature of the visual hallucination indicates that they were generated in visual association areas.

Adult↗

PubMed2003

Perspectives and limitations of image-guided neurosurgery in pediatric patients.

INTRODUCTION: Progress in image-guided neurosurgery, and specifically in computer-assisted frameless navigation techniques and the application of robotic systems, has brought about many changes in the way we approach and treat pathologies involving the adult and pediatric central nervous system (CNS). Nevertheless, children are a patient group with special demands, in whom image-guided surgical techniques have certain limitations. In this article we address the common problem of registration accuracy in image-guided neurosurgery and assess both the reliability and the potential of ultrasound-based neuronavigation and robot-assisted neuroendoscopy in pediatric patients. METHODS AND RESULTS: We present our experience with new referencing and tracking techniques adapted to the needs of the pediatric patient. In addition, advantages and limitations of a 3D real-time ultasonography-based navigation system are demonstrated. Finally, we describe our experience with robot-assisted neuroendocopy and discuss the possible implications of the technique for the future. CONCLUSION: Image-guided techniques in pediatric neurosurgery are valuable tools and may open up new perspectives in the future. From our point of view, these tools enhance both intellectual and manual surgical skills, which does not mean that they should be considered as a replacement for such skills.

Adolescent↗

PubMed2003

Latent abscess formation adjacent to a non-functioning intraventricular catheter.

CASE REPORT: A 16-year-old male patient who had been treated at the age of 13 months with a ventriculoperitoneal (VP) shunt due to obstructive hydrocephalus was presented to our department for a routine follow-up examination. The patient had tolerated well a shunt disconnection in 1990 and the distal part had been removed. Six years later radiological evaluation revealed an intracerebral mass adjacent to the remaining intraventricular catheter. The mass, histologically classified as an abscess, had to be removed 3 years later due to disease progression, although the patient remained asymptomatic. DISCUSSION: This case is of particular interest because it demonstrates the extremely delayed onset and progressive course of a well-known complication of VP shunt systems in an asymptomatic patient. In addition, the reported case raises the question of whether a non-functioning shunt needs to be removed or not.

Adolescent↗

PubMed2003

Navigated transoral approach to the cranial base and the craniocervical junction: technical note.

OBJECTIVE: The transoral approach is an elegant reliable surgical procedure that provides anterior exposure of the cranial base and the craniocervical junction. Our objective was to demonstrate the advantages of neuronavigation in planning and performing the transoral approach. METHODS: Three patients with chordomas and one patient with rheumatoid atlantoaxial subluxation were considered for a neuronavigated transoral procedure. For image guidance, the Stryker navigation system (Stryker Instruments, Kalamazoo, MI) was used. Registration was performed with individually constructed occlusal splints with four markers. RESULTS: The transoral approach was successfully used for two patients with chordomas involving the cranial base and the upper spine and for one patient with dislocation of the dens and medullary compression. In one case, preoperative simulation of the approach and trajectory planning demonstrated that adequate resection could not be achieved via the transoral route, and a paracondylar suboccipital approach was used. The registration accuracy achieved with the occlusal splint was less than 1 mm. CONCLUSION: Neuronavigation is a useful tool for planning and performing a transoral approach. It optimizes preoperative planning, clarifies and secures resection limits, and reduces overall surgical morbidity. Registration with an occlusal splint with four markers proved to be an attractive alternative to conventional systems.

Adult↗