Biomedical subjects

Vassilios I Vougioukas

Publications and source records attributed to Vassilios I Vougioukas.

12 recordsLinked to original sources

PubMed2006

Monitoring motor function during resection of tumours in the lower brain stem and fourth ventricle.

OBJECTIVES: Even in the days of modern microsurgery, the removal of a brain stem lesion remains a surgical challenge. Especially when operating on children, the prognosis is directly related to the radicality of the resection; however, a radical resection is often associated with surgical morbidity. Intraoperative neuromonitoring could help to minimise the surgical morbidity, but few studies have been performed to clarify the value of this monitoring. We investigated a prospective series of 21 patients with lesions involving the brain stem for the prognostic value and benefits of neuromonitoring. METHODS: We performed intraoperative neuromonitoring of cranial nerve function by electromyography (EMG) and motor evoked potential (MEP). The results were correlated with postoperative neurological deficits. CONCLUSIONS: There is a good correlation between intraoperative neurophysiological events and postoperative neurological deficits in patients with lesions of the brain stem. In general, transient, prolonged, spontaneous activity in EMG is associated with a transient paresis of the respective muscle, whereas a permanent spontaneous activity is associated with a permanent deficit. Intraoperative neuromonitoring reliably predicts postoperative neurological function in patients with tumours of the lower brain stem and fourth ventricle. This neuromonitoring guides the neurosurgeon in the operation and may decrease surgical morbidity. We recommend using monitoring of MEP and EMG of the lower cranial nerves in surgery on all patients with lesions involving the lower brain stem and fourth ventricle.

Adolescent↗

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

Far lateral supracerebellar infratentorial approach for the treatment of upper brainstem gliomas: clinical experience with pediatric patients.

OBJECTIVE: Surgical exposure of intrinsic lesions located lateral to the brainstem still represents a challenging task. The aim of this study was to assess the feasibility of the extracerebral far lateral supracerebellar infratentorial (FLSI) approach for the treatment of gliomas located in the upper brainstem in the pediatric population. METHODS AND RESULTS: Between 1992 and 2002, seven patients (mean age 8.7 years) with tumors of glial origin (WHO I-IV) located mainly in the pontomesencephalic region were operated with the FLSI approach in a sitting position. Satisfactory extent of resection without additional morbidity was achieved. CONCLUSION: In a carefully selected pediatric patient population, the FLSI approach proved to be a feasible and effective surgical route for the treatment of upper brainstem gliomas.

Adolescent↗

PubMed2005

Characterization of hemangioblastomas of spinal nerves.

OBJECTIVE: Hemangioblastoma is classified as a benign tumor of the central nervous system. Peripheral nervous system hemangioblastomas to date have been described only in a few case reports. Experience in treating patients with these rare lesions, which harbor diagnostic and therapeutic pitfalls, is limited. METHODS: To characterize these lesions better, we reviewed our hemangioblastoma database for patients who underwent surgery for extradural hemangioblastoma of the spinal nerve. RESULTS: Between 1983 and 2003, six patients underwent surgery for spinal nerve hemangioblastomas at our institution. These tumors occurred in 2% of all patients with hemangioblastomas of the central nervous system, or 6% of all patients with spinal hemangioblastomas. The occurrence did not differ in von Hippel-Lindau disease cases versus sporadic cases. Radiographically, the tumors easily could be mistaken for schwannomas or metastases; however, they did have some typical features. If a hemangioblastoma was not suspected primarily, profuse bleeding could complicate surgery. Most of the tumors arose from the dorsal sensory fascicles. The vascular supply was from extradural circulation. In general, the surgical outcome of these lesions was good, and permanent neurological deficit was rare. However, local recurrence was observed in three of six patients. CONCLUSION: These tumors harbor diagnostic and therapeutic pitfalls. In general, the tumors are surgically more challenging, and clinically significant bleeding as well as local tumor recurrence is more common than in intradural hemangioblastomas, mostly because of the frequency of incorrect initial radiographic diagnosis. We suggest that because of the surgical consequences, hemangioblastoma should always be considered to be an important radiological differential diagnosis for nerve sheath tumors. Angiography can bring clarification to ambiguous cases.

Adult↗

PubMed2005

Clinical and radiological results after parapedicular screw fixation of the thoracic spine.

OBJECT: The proximity of thoracic pedicles to the spinal cord and neurovascular structures has prompted numerous efforts to obtain proper screw placement. The aim of this study was to evaluate the feasibility and efficacy of thoracic parapedicular (intercostovertebral) screw fixation by following anatomical landmarks and using fluoroscopy. METHODS: Thoracic parapedicular screw fixation was performed in 41 patients (328 screws). Postoperative computerized tomography scans were obtained in all cases to analyze the position of each screw with respect to the pedicle rib unit, the spinal canal, and the vertebral body (VB) according to a proposed novel grading system. Additionally, screw convergence angles were calculated for each instrumented level. There was no additional morbidity associated with parapedicular screw insertion. In a single case a screw suspected of entering the spinal canal was revised without causing neurological damage. The remaining screws were placed entirely within the pedicle rib unit and VB without breaching the neural foramina, pleura, or vascular structures. CONCLUSIONS: Thoracic and thoracolumbar instability can be treated adequately and safely by using parapedicular screw fixation guided by anatomical landmarks and fluoroscopic imaging. The use of computer-aided navigation may be beneficial but does not appear to be mandatory.

Aged↗

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

Inverse correlation of epidermal growth factor receptor messenger RNA induction and suppression of anchorage-independent growth by OSI-774, an epidermal growth factor receptor tyrosine kinase inhibitor, in glioblastoma multiforme cell lines.

OBJECT: Quantitative and qualitative alterations in the epidermal growth factor receptor (EGFR) commonly occur in many cancers in humans, including malignant gliomas. The aim of the current study was to evaluate molecular and cellular effects of OSI-774, a novel EGFR tyrosine kinase inhibitor, on nine glioblastoma multiforme (GBM) cell lines. METHODS: The effects of OSI-774 on expression of EGFR messenger (m)RNA and protein, proliferation, anchorage-independent growth, and apoptosis were examined using semiquantitative reverse transcription-polymerase chain reaction, immunocytochemical analysis, Coulter counting, soft agar cloning, and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling/fluorescence-activated cell sorting, respectively. All p53 genes were completely and bidirectionally sequenced. Suppression of anchorage-independent growth by OSI-774 was inversely correlated to the induction of EGFR mRNA during relative serum starvation (r = -0.74) and was unrelated to p53 status. Overall, suppression of anchorage-independent growth was a considerably stronger effect of OSI-774 than inhibition of proliferation. The extent of OSI-774-induced apoptosis positively correlated with both proliferation and anchorage-independent growth of GBM cell lines (r = 0.75 and 0.79, respectively). In a single cell line derived from a secondary GBM, exposure to concentrations of greater than or equal to 1 micromol/L resulted in a substantial net cell loss during proliferation studies. CONCLUSIONS: The induction of EGFR mRNA may constitute a cellular mechanism to counteract the inhibitory effect of OSI-774 on the anchorage-independent growth of GBM cells. In contrast, no considerable correlation could be established between baseline expression levels of EGFR (both mRNA and protein) in GBM cell lines and their biological response to OSI-774. The OSI-774 induced greater (p53-independent) apoptosis in more malignant GBM phenotypes and may be a promising therapeutic agent against secondary GBM.

Actins↗

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↗

PubMedDate not supplied

Uniform MDM2 overexpression in a panel of glioblastoma multiforme cell lines with divergent EGFR and p53 expression status.

BACKGROUND: Overexpression and deletion mutation of the epidermal growth factor receptor (EGFR) gene, as well as murine double minute 2 (MDM2) overexpression have been linked to the absence of p53 gene mutations in human glioblastoma multiforme (GBM). MATERIALS AND METHODS: EGFR and MDM2 messenger (m)RNA expression profiles and p53 status were examined by reverse transcription-polymerase chain rection (RT-PCR) and gene sequencing, respectively, in a set of human wild-type (wt) p53 GBM cell lines (U-87MG, U-87MG.wtEGFR and U-87MG.deltaEGFR) that exclusively differ in EGFR expression (endogenous wt EGFR expression, exogenous wt EGFR overexpression and exogenous 801-bp deletion-mutant [delta] EGFR overexpression, respectively), as well as in two human mutant p53 GBM cell lines that differ approximately two-fold in endogenous wt EGFR mRNA expression. RESULTS: Regardless of the underlying heterogeneity in EGFR mRNA expression and p53 status, MDM2 was similarly overexpressed among the cell lines. CONCLUSION: These data suggest that in human GBM (i) overexpression of wt or deltaEGFR and of MDM2 may constitute independent genetic events, (ii) overexpression of wt EGFR and mutation of p53 in GBM, although considered mutually exclusive in vivo, are not reciprocally prohibitive per se, and (iii) p53 mutations do not necessarily preclude MDM2 overexpression. In addition, this set of human GBM cell lines may constitute a suitable model for evaluating MDM2-targeted therapies in the context of various accompanying genetic alterations.

Brain Neoplasms↗