摘要:

OBJECTIVE:The angle of arteries at bifurcations, as well as the blood flow, are factors of hemodynamic stress on the apical region, where aneurysms often develop. Using images obtained with three-dimensional computed tomographic angiography, we sought to determine the angles between the A1 and A2 segments of the anterior cerebral artery of the anterior communicating artery (ACoA) complex associated with aneurysms. These angles cannot be detected by conventional cerebral angiography.METHODS:The course of the anterior cerebral artery was studied using three-dimensional computed tomographic angiography in 42 consecutive patients with ACoA aneurysms. Twenty-one other subjects, randomly chosen from patients without aneurysms, served as controls. Bilateral A1–A2 angles of the contrast-opacified anterior cerebral artery were measured by three-dimensional computed tomographic angiography in patients with normoplastic A1 segments, and the relationship between the angle and the association of aneurysms was analyzed using cerebral angiography.RESULTS:Of the 42 patients with ACoA aneurysms, 19 patients showed hypo- or aplastic A1 segments, as did only 2 of the 21 patients without ACoA aneurysms. The average A1–A2 angle was determined to be 116 ± 24 degrees (mean ± standard deviation) in 18 patients having ACoA complexes with normoplastic A1 segments with aneurysms; 17 patients without aneurysms had A1–A2 angles measuring 143 ± 14 degrees (P< 0.0001). The A1–A2 angle associated with ACoA aneurysms was 103 ± 20 degrees, which was much smaller than that of the non-aneurysm side in the former group (128 ± 20 degrees) (P= 0.0036).CONCLUSION:ACoA aneurysms are associated with the smaller A1–A2 angle junction of the ACoA complex, where higher hemodynamic stress may occur in patients with normoplastic A1 segments.

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:

OBJECTIVE:The far lateral extension of the classic suboccipital craniectomy has been found to reduce the depth of the field and improve the angle of surgical perspective to the ventrolateral clivus. The goal of the present study is to determine and compare the dimensions of the far lateral transcondylar approach with the suboccipital craniectomy.METHODS:Ten cadaveric specimens were used to study the anatomy at the foramen magnum (FM), occipital condyle (OC), and vertebral artery. The distances from the posterior midline of the FM to the medial and lateral borders of the OC were measured. The distance of the vertebral artery from the transverse foramen of C1 to its dural entry and the distance from the dural entry to the posteroinferior cerebellar artery were measured. The amount of OC removal that was necessary to expose the contralateral jugular tubercle was determined. A reference line was constructed from the posterior margin of the FM to the border of the OC. From this line, the angle of surgical approach provided by each exposure was measured.RESULTS:The mean distance of the vertebral artery from the transverse foramen of C1 to its dural entry was 22 ± 3 mm (standard deviation), and the distance from the dural entry to the posteroinferior cerebellar artery was 17 ± 8 mm. The distance from the posterior midline of the FM to the medial border of the OC was 27 ± 0.5 mm; the distance from the posterior midline of the FM to the lateral border of the OC was 40 ± 0.4 mm; and the long axis of the OC was 30 ± 0.4 mm. The amount of OC removal to expose the contralateral jugular tubercle without brainstem retraction was 17 ± 1 mm. The angle of surgical approach versus the reference line decreased from 88 ± 2 degrees with the suboccipital craniectomy alone to 47 ± 2 degrees for the far lateral transcondylar exposure (P< 0.001). This angle decreased an average of 2.4 degrees per millimeter of OC removal.CONCLUSION:Understanding the dimensions of the craniovertebral junction has clear implications for surgery in this area. If a lesion may be approached through a perpendicular exposure, the suboccipital craniectomy alone may be sufficient. Additional exposure of the ventrolateral clivus without brainstem retraction requires condylar removal. A more limited condylar removal than the 17 mm described in this report may be adequate if the entire 47-degree angle is not needed.

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:

OBJECTIVE:The purpose of this study was to analyze the outcomes of five commonly performed pediatric neurosurgical operations: 1) initial shunt insertion; 2) first shunt revision; 3) craniotomy for brain tumor; 4) correction of sagittal synostosis; and 5) release of tethered cords. A second purpose was to analyze the neurological outcome data after tethered cord releases.METHODS:Morbidity and mortality records, patient charts, and operative records were reviewed to determine length of hospitalization and, for each disorder, the pertinent outcomes such as duration of shunt function and incidence of infection or neurological morbidity.RESULTS:Many outcome data were expected, such as a high long-term shunt function rate after primary shunt insertion (65% at 5 yr), a low mortality rate (1%) and permanent morbidity rate (10%) after craniotomy for brain tumor, and a low frequency of transfusion (20%) for sagittal synostosis operations. The outcomes among the three neurosurgeons varied more than expected, e.g., the duration of hospitalization after sagittal reconstructions ranged from 3.1 to 5.8 days; the frequency of infections of primary shunt revisions ranged from 0 to 15%; and the neurological morbidity after tethered cord releases ranged from 0 to 12%, with all neurological morbidity occurring in patients undergoing their second or third tether release.CONCLUSION:The data may serve as a basis for outcome comparisons for these procedures. Outcome data allow us to analyze factors to improve patient care, but outcome analysis is complex.

ISSN:0148-396X    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

OBJECTIVE:A computer simulation based on the finite-element method was used to study the biomechanics of acute obstructive hydrocephalus and, in particular, to define why periventricular edema is most prominent in the anterior and posterior horns.METHODS:Brain parenchyma was modeled as a two-phase material composed of a porous elastic matrix saturated by interstitial fluid. The effects of the cerebrovascular system were not included in this model. The change in the shape of the ventricles as they enlarged was described by two variables, i.e., the stretch of the ependyma and the concavity of the ventricular wall. The distribution of stresses and strains in the tissue was defined by two standard mechanical measures, i.e., the mean effective stress and the void ratio.RESULTS:With obstruction to cerebrospinal fluid flow, the simulation revealed that the degree of ventricular expansion at equilibrium depended on the pressure gradient between the ventricles and the subarachnoid space. Periventricular edema was associated with the appearance of expansive (tensile) stresses in the tissues surrounding the frontal and occipital horns. In contrast, the concave shape in the region of the body of the ventricle created compressive stresses in the parenchyma. Both of these stresses seem to be direct consequences of the concave/convex geometry of the ventricular wall, which serves to selectively focus the forces (perpendicular to the ependyma) produced by the increased intraventricular fluid pressure in the periventricular tissues.CONCLUSION:The distribution of periventricular edema in acute hydrocephalus is a result not only of increased intraventricular pressure but also of ventricular geometry.

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:

OBJECTIVE:The present study was undertaken to explore the relationship between the characteristic geometry of aneurysms prone to rupture and the blood flow patterns therein, using microsurgically produced aneurysms that simulated human middle cerebral artery aneurysms in scale and shape.METHODS:We measured in vivo velocity profiles using our 20-MHz, 80-channel, Doppler ultrasound velocimeter. We produced small (≤5 mm, 5 cases) and large (6–13 mm, 12 cases) aneurysms with round, dumbbell, or multilobular shapes.RESULTS:The fundamental patterns of intra-aneurysmal flow were composed of inflow, circulating flow, and outflow. The inflow, which entered the aneurysm only during the systolic phase, was strongly influenced by the position and size of the neck and the flow ratio into the distal branches. The outflow was usually nonpulsatile and of low velocity. The circulating flow depended on the aspect ratio (depth/neck width). A single recirculation zone was observed in aneurysms with aspect ratios of less than 1.6. This circulation did not seem to extend to areas with aspect ratios greater than this value; in aneurysms with aspect ratios of more than 1.6, a much slower circulation was observed near the dome. Furthermore, in the dome of dumbbell-shaped aneurysms and daughter aneurysms, no flow was detected. Intra-aneurysmal flow was determined by the aspect ratio, rather than the aneurysm size.CONCLUSION:The localized, extremely low-flow condition that was observed in the dome of aneurysms with aspect ratios of more than 1.6 is a common flow characteristic in the geometry of ruptured aneurysms, so great care should be taken for patients with unruptured intracranial aneurysms with aspect ratios of more than 1.6.

ISSN:0148-396X    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

OBJECTIVES:Recent work has established that the remote injection of attenuated adenoviral vectors may result in central nervous system (CNS) gene expression. These studies suggest that virus passes through peripheral nerves into the CNS. The present experiment attempts to characterize this phenomenon systematically.METHODS:Spinal cord cells staining for the reporter gene &bgr;-galactosidase were histologically quantified after microinjection of the viral vector Ad5RSVntLacZ into rat footpad, muscle, or sciatic nerve. The effects of injection location, titer, and time, as well as nerve crush and dexamethasone, were examined.RESULTS:Sciatic nerve viral vector injection results in significantly higher CNS uptake than intramuscular and subcutaneous injections (P< 0.05). Nerve crush injury caused a time-dependent reduction in spinal cord gene uptake after sciatic nerve adenoviral injection (P< 0.05). Neuronal staining reaches its peak at 6 days after injection (P< 0.002). Peripheral nerve delivery to the CNS increases with augmented titers (P< 0.03). Finally, gene expression is augmented by administration of dexamethasone (P< 0.0001).CONCLUSION:Remote adenoviral vector injection represents a potential method for spinal cord gene therapy that avoids any manipulation of CNS tissue.

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