ISSN:0148-396X    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

OBJECTIVEThe ability to visualize median-sagittal brain structures by magnetic resonance imaging (MRI) improves the planning for surgical removal of lesions located in and around the third ventricle. The transcallosal approach is the most appropriate path to the anterior part of the third ventricle. The present study was undertaken to obtain normative morphometric data, derived from sagittal MRI scans, which are necessary for operation planning that takes into account the surgical microanatomy and landmarks encountered during this approach.METHODSThe morphometric evaluation was performed on 72 median-sagittal MRI scans. The surface landmarks for the corridor were the two points, P5 and P7, located 5 and 7 cm anterior to the central sulcus, respectively. With these two points on the cortical surface as references, a variety of measurements were made to provide quantitative information about distances between brain structures encountered during the surgical approach. In addition, various parameters were determined to characterize the different shapes of the fornix and the different types of forniceal insertion.RESULTSThe following measurements (means) were obtained: 1) the distance between P5/P7 and the cingulate sulcus was 25.76 mm (range, 17.113–42.73 mm) with reference to P5, and 25.41 mm (range, 12.91–36.29 mm) with reference to P7; 2) the distance between the cingulate sulcus and the corpus callosum was 12.91 mm (range, 7.19–22.60 mm) with reference to P5, and 12.92 mm (range, 6.75–23.37 mm) with reference to P7; 3) the height of the corpus callosum was 6.22 mm (range, 3.07–9.00 mm) with reference to P5, and 6.92 mm (range, 3.50–13.57 mm) with reference to P7; 4) the distance between the anterior commissure and the foramen of Monro was 6.78 mm (range, 1.86–14.57 mm), independent of P5 and P7; 5) the distance between the lower margin of the corpus callosum and the upper insertion point of the fornix was 12.44 mm (range, 2.71–26.13 mm) with reference to P5, and 13.34 mm (range, 3.74–27.58 mm) with reference to P7; 6) the distance between the lower margin of the corpus callosum and the lower insertion point of the fornix was 18.08 mm (range, 9.47–29.71 mm) with reference to P5, and 18.58 mm (range, 10.48–30.40 mm) with reference to P7; and 7) the distance between the lower margin of the corpus callosum and the anterior commissure was 23.46 mm (range, 11.98–32.70 mm) with reference to P5, and 22.89 mm (range, 11.05–33.04 mm) with reference to P7. Four different insertion types between the fornix and the corpus callosum were noted and classified.CONCLUSIONMorphometric data concerning the surrounding structures of the third ventricle have received very little attention in the literature. This morphometric study permitted definition of the surgical corridor to the third ventricle by preserving important anatomic structures such as the motor strip, genu of the corpus callosum, forniceal commissure (hippocampal commissure), anterior commissure, and forniceal columns. The detailed morphometric data obtained on median-sagittal MRI scans of the brain structures involved in the transcallosal interforniceal and/or transcallosal transforaminal approach allow for exact planning of the surgical approach.

ISSN:0148-396X    

出版商:OVID    

年代:1999

数据来源: OVID

ISSN:0148-396X    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

OBJECTIVEIn this study, a nonimmunogenic, acellular, dermal collagen matrix termed XenoDerm (LifeCell Corp., The Woodlands, TX) was examined for use as a dural replacement material in a porcine model. This model was used to investigate whether AlloDerm (LifeCell), an almost identical material made from human dermis, could be safely used in neurological surgery.METHODSBilateral temporoparietal dural defects were surgically created in 12 Yucatan minipigs. One side was repaired with autologous pericranium, and the other was repaired with XenoDerm. The pigs were killed after 1, 3, or 6 months, and the areas of dural repair were collected and examined macroscopically and histologically. XenoDerm is derived from porcine skin collected in thin sheets. It is processed so that the epidermis and all dermal cells are removed without disruption of the collagen matrix, rendering the material immunogenically inert and resistant to calcification. It is packaged as a freeze-dried sheet and is easily rehydrated at the time of surgery.RESULTSThere were no postoperative complications, and all pigs survived. Both grafts performed well as dural replacements in all cases. There was no macroscopic evidence of inflammation or cerebrospinal fluid leakage. The XenoDerm grafts were intact, retained their original dimensions, and resembled the surrounding dura. The autologous pericranial grafts, in contrast, were thicker than when implanted and had bony excrescences firmly adhering to their surfaces. Again, however, there was no evidence of cerebrospinal fluid fistulae. There was no gross adherence to the underlying meninges or brain tissue in any specimen. Repopulation by fibroblasts and neovascularization were evident in the XenoDerm grafts as early as 1 month after surgery; by 3 months, the XenoDerm had been remodeled to assume the connective tissue appearance of the surrounding dura.CONCLUSIONIn this porcine model, an allograft of acellular dermis is a nearly ideal dural replacement. AlloDerm, the human equivalent of XenoDerm, would be an allograft of acellular dermis after implantation in human subjects. On the basis of this study and previous work with AlloDerm in other reconstructive applications, it is proposed that this material could be similarly used for duraplasty in human subjects.

ISSN:0148-396X    

出版商:OVID    

年代:1999

数据来源: OVID

ISSN:0148-396X    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

OBJECTIVEMurine models using intraluminal occluding sutures to establish transient focal cerebral ischemia are becoming increasingly widespread, because of advances in transgenic technology and the advent of cerebroprotective strategies to ameliorate postischemic cerebrovascular no-reflow. We hypothesize that the degree of postischemic hypoperfusion is directly related to the severity of the initial ischemic insult.METHODSTransient ischemia of 45-minute duration was produced using middle cerebral artery occlusion with 10-0 (n = 5), 9-0 (n = 5), 8-0 (n = 6), 7-0 (n = 8), 6-0 (n = 30), or 5-0 (n = 5) sutures. In separate experiments, transient vessel occlusion with 6-0 sutures was performed for 15 (n = 17), 30 (n = 16), or 45 (n = 30) minutes. Sequential laser Doppler measurements of relative cerebral blood flow were obtained, and stroke severity was assessed using neurological deficit scores and infarction volumes.RESULTSAlthough relative cerebral blood flow at the time of occlusion and 24 hours thereafter was diminished in parallel with increasing suture diameters, only the use of larger sutures resulted in postischemic no-reflow. As the suture diameter was increased, the resultant reflow was decreased and the stroke outcome worsened. A more than twofold increase in infarction volume (8.0 ± 3 versus 19.7 ± 3%,P< 0.05) resulted when ischemia duration was increased from 30 to 45 minutes.CONCLUSIONTitration of the initial ischemic insult leads to corresponding variations in the magnitude of postischemic no-reflow and tissue damage. Therefore, critical control of the severity of the initial injury in studies using intraluminal suture occlusion is warranted.

ISSN:0148-396X    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

OBJECTIVEFluid shear stress (the frictional force resulting from blood flow) is a principal regulator of endothelial nitric oxide synthase (eNOS) expression. We examined the responses of eNOS messenger ribonucleic acid (mRNA) levels to dynamic shear stimuli in the presence of pathological risk modifiers.METHODSConfluent bovine aortic endothelial cells were subjected in vitro to shear stress (using a cone-plate viscometer) and to hydrostatic pressure (using a custom-built pressure chamber device). eNOS mRNA levels were quantitated by densitometric analysis of Northern blots.RESULTSIn contrast to steady laminar shear stress, which elevated eNOS mRNA levels in a time- and dose-dependent manner (2.9- and 3.6-fold after 6 h at 4 and 20 dyn/cm2, respectively), steady hydrostatic pressure of 150 mm Hg decreased eNOS mRNA levels by 46%. eNOS mRNA up-regulation by shear stress was reversible after cessation of flow, although it was not influenced by previous shear exposure, and it was not mediated by a stable transferable factor. eNOS mRNA up-regulation by sinusoidal shear stress was frequency-dependent, with a moderate response at 1-Hz oscillating shear and no change at 0.3 Hz. Hypoxia (3% O2) suppressed eNOS mRNA expression by 78% under static conditions and by 72% under shear conditions but did not alter the fold induction by shear. Elevated glucose concentrations reduced eNOS mRNA levels in both resting and shear stress-exposed cells but did not reduce the fold induction by shear; the protein kinase C inhibitor calphostin C was without effect. Shear-induced up-regulation of eNOS mRNA was unaffected by changes in the medium partial pressure of CO2/pH, by the Na+/H+-exchanger inhibitor HOE694, or by aspirin. In contrast, the shear response was potentiated by homocysteine.CONCLUSIONBoth physical and chemical stimuli regulate eNOS mRNA levels in endothelial cells. Although eNOS mRNA expression is increased by shear stress, it is decreased by hydrostatic pressure, hypoxia, and elevated glucose levels. The effect of shear on eNOS mRNA expression involves a reversible, frequency-dependent process. These in vitro findings suggest possible contributions of the eNOS flow response to atherosclerosis, in the presence of systemic risk factors.

ISSN:0148-396X    

出版商:OVID    

年代:1999

数据来源: OVID

ISSN:0148-396X    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

OBJECTIVEThe recent successful development of chronic stimulation of the motor cortex as a treatment for neuropathic and central pain does not exclude the possibility of eventual side effects, such as epileptic seizure or a lowering of the epileptic threshold. This study evaluates the behavioral and electroencephalographic impact of this treatment in three normal monkeys.RESULTSNone of the monkeys presented epileptic behavior or abnormal electroencephalographic activity at parameters of stimulation currently used in clinical series, i.e., frequency and pulse duration of approximately 40 Hz and 90 microseconds, respectively, and an intensity just under the threshold for inducing muscle twitch in painful areas. Higher intensities did, however, induce reversible epileptic seizure. There was, nonetheless, no modification of the epileptic threshold, because even after these seizures, intermittent light stimulation elicited no abnormal electroencephalographic activity.CONCLUSIONIt thus seems that motor cortex stimulation does not induce epileptic complications when the classic clinical criteria of stimulation are respected. Nevertheless, it would be wise to subject candidates for implantation to intermittent light stimulation before and after a period of stimulation to ascertain the innocuousness of the cortical stimulation.

ISSN:0148-396X    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

PURPOSEAn alternative endovascular treatment to conventional transarterial embolization of cerebral arteriovenous malformations (AVMs) is proposed.CONCEPTAccording to this proposed treatment, selected AVMs could undergo transvenous retrograde nidus sclerotherapy under controlled hypotensive anesthesia (TRENSH).RATIONALEIt is hypothesized that TRENSH may provide the means of avoiding delivery of embolic agents via arterial feeders (thus preventing ischemic complications), in addition to a possible more complete permeation of an AVM nidus with a sclerosant than can otherwise be obtained with current agents via arterial feeders.DISCUSSIONInstead of relying on access to an AVM nidus from the arterial side (with its usual complexity), TRENSH would require retrograde access to the lesion via much larger and anatomically simpler draining veins. Retrograde permeation of the AVM nidus may then be possible with a liquid sclerosant (to effect a “chemical embolization”) provided that the arterial inflow is reduced sufficiently by temporary controlled systemic hypotension, with or without the aid of temporary balloon occlusion of the main arterial feeder(s). Retrograde spread of sclerosant within the nidus that falls short of filling arterial feeders and their branches to normal brain tissue may then be possible. Angioarchitectural and hemodynamic considerations are addressed, as are the potential role and limitations of TRENSH in the management of cerebral pial AVMs. Future implementation of this new technique in some specific selected cases in which the anatomic configuration of the AVM and its draining veins might be favorable could prove to be a potentially useful addition to the armamentarium of AVM therapies, which currently includes microsurgery, radiosurgery, and transarterial embolotherapy. Experimental studies directed at assessing the feasibility of TRENSH before potential future clinical application seem justified.

ISSN:0148-396X    

出版商:OVID    

年代:1999

数据来源: OVID