Biomedical subjects
P E Stieg
Publications and source records attributed to P E Stieg.
Carotid-coronary artery bypass graft conundrum.
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Computer-assisted surgical planning for cerebrovascular neurosurgery.
OBJECTIVE: We used three-dimensional reconstructed magnetic resonance images for planning the operations of 16 patients with various cerebrovascular diseases. We studied the cases of these patients to determine the advantages and current limitations of our computer-assisted surgical planning system as it applies to the treatment of vascular lesions. METHODS: Magnetic resonance angiograms or thin slice gradient echo magnetic resonance images were processed for three-dimensional reconstruction. The segmentation, based on the signal intensities and voxel connectivity, separated each anatomic structure of interest, such as the brain, vessels, and skin. A three-dimensional model was then reconstructed by surface rendering. This three-dimensional model could be colored, made translucent, and interactively rotated by a mouse-controlled cursor on a workstation display. In addition, a three-dimensional blood flow analysis was performed, if necessary. The three-dimensional model was used to assist in three stages of surgical planning, as follows: 1) to choose the best method of intervention, 2) to evaluate surgical risk, 3) to select a surgical approach, and 4) to localize lesions. RESULTS: The generation of three-dimensional models allows visualization of pathological anatomy and its relationship to adjacent normal structures, accurate lesion volume determination, and preoperative computer-assisted visualization of alternative surgical approaches. CONCLUSION: Computer-assisted surgical planning is useful for patients with cerebrovascular disease at various stages of treatment. Lesion identification, therapeutic and surgical option planning, and intraoperative localization are all enhanced with these techniques.
Cerebral arteriovenous malformation feeding artery aneurysms: a theoretical model of intravascular pressure changes after treatment.
OBJECTIVE: A quantitative model may be used to estimate the magnitude of expected pressure changes along the vascular tree with shunt ablation and may provide information to assess the hemodynamic risk of arteriovenous malformation (AVM) treatment. METHODS: A computer model of the cerebral circulation was applied to estimate the changes in intravascular pressure, velocity, biomechanical stress, and shear stress that might be expected from either endovascular or surgical ablation of AVMs. Two AVM sizes and two feeding artery constellations were simulated. The effect of different shunt flows on vascular pressure was modeled. In each simulation, AVMs were occluded in a stepwise fashion. The effects of systemic hypertension and hypotension in various vascular zones were also simulated. RESULTS: As large (1000 ml/min) AVMs were occluded, the mean feeding arterial pressure increased from 18 to 68 mm Hg; the percent-occlusion at half-maximal pressure increase was 92%. For medium (500 ml/min) AVMs, feeding arterial pressure increased from 37 to 66 mm Hg; the percent-occlusion at half-maximal pressure increase was 71%. During manipulation of systemic pressure, hemodynamic changes in the circulation close to the nidus were proportionally less than changes in systemic pressure; the degree of proportionality depended on the magnitude of AVM shunt flow. CONCLUSION: In this simulation, shunt obliteration increased pressure in the nidus and feeding arteries with little effect on the proximal circulation. The shunt provided a "buffering" effect, i.e., higher flow fistulas were exposed to smaller variations in intravascular pressure in feeding artery and nidal pressures during manipulation of systemic pressure.
Synostotic frontal plagiocephaly: anthropometric comparison of three techniques for surgical correction.
Surgical correction of synostotic frontal plagiocephaly ("unilateral coronal synostosis") focuses on distortions of the forehead and orbits. Technical variations include unilateral versus bilateral fronto-orbital positioning. Surgical alignment of the deviated nasal root was introduced in our unit. Anthropometry was used to assess anatomic outcome, and results were compared in 22 children with synostotic frontal plagiocephaly who had either (1) unilateral fronto-orbital advancement ("canthal advancement") (n = 8), (2) bilateral fronto-orbital advancement/ modeling without nasal straightening (n = 7), or (3) bilateral fronto-orbital advancement/modeling with closing wedge nasal osteotomy (n = 7). Postoperative fronto-orbital asymmetry was most marked in the group I patients wherein the ipsilateral supraorbital rim was retruded 3.9 mm and elevated 2.6 mm, on average relative to the corneal apex, compared with the normal side. Group II children averaged 2-mm orbital retrusion and 2.2-mm elevation. Group III patients averaged 1.4-mm orbital retrusion and 2.9-mm elevation. These differences in orbital rim measurements among the three groups were not statistically significant. Postoperative nasal root angulation of 4 degrees or more was found in more than 50 percent of children who had either a unilateral or a bilateral procedure, without nasal correction. In contrast, primary nasal osteotomy resulted in a nasal cant of 3 degrees or less in all children. This difference in nasal angulation among the three groups was statistically significant (p = 0.035). Group III had a straighter nasal angle than groups II and I (in that order). Measurement of the distances from nasion to inner and to outer canthi also reflected persistent deviation of the nasal root. Group III children had a more central radix than either group I or II (p = 0.05). The data in this study support an operative strategy of bilateral (parallelogrammic) positioning of the forehead/ superior orbits with primary correction of nasal root angulation.
Cerebral hemorrhage in a patient taking fenfluramine and phentermine for obesity.
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Computer-assisted interactive three-dimensional planning for neurosurgical procedures.
We have used three-dimensional reconstruction magnetic resonance imaging techniques to understand the anatomic complexity of operative brain lesions and to improve preoperative surgical planning. We report our experience with 14 cases, including intra- and extra-axial tumors and a vascular malformation. In each case, preoperative planning was performed using magnetic resonance imaging-based three-dimensional renderings of surgically critical structures, such as eloquent cortices, gray matter nuclei, white matter tracts, and blood vessels. Simulations, using the interactive manipulation of three-dimensional data, provided an efficient and comprehensive way to appreciate the anatomic relationships. Interactive three-dimensional computer-assisted preoperative simulations provided otherwise inaccessible information that was useful for the surgical removal of brain lesions.
Surgery of the Soul's cistern.
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A case of acute vertigo with incidental aneurysms.
It is essential to decrease the risk to the patient to an absolute minimum when prophylactic procedures are offered against a relatively unpredictable (for the individual patient) natural history risk. Very careful preoperative planning and intraoperative execution are mandatory to maximize the chances of the patient for a successful outcome.
Acute presentation of an intracranial mass.
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Evaluation of cerebral aneurysms with helical CT: correlation with conventional angiography and MR angiography.
PURPOSE: To evaluate detection of intracranial aneurysms with helical computed tomography (CT) and compare the results with those of conventional angiography and magnetic resonance (MR) angiography. MATERIALS AND METHODS: Twenty-one patients with 30 intracranial aneurysms were studied with helical CT and conventional angiography; 17 of the patients (24 aneurysms) also underwent MR angiography. RESULTS: All aneurysms 3 mm or larger in greatest dimension were seen with helical CT and MR angiography; no aneurysms smaller than 3 mm were apparent with either modality. Of the 21 aneurysms demonstrated with both helical CT and MR angiography, 11 were seen equally well with both techniques; six were seen better with helical CT owing to flow-related or motion artifact at MR angiography, and four were seen better with MR angiography because calcium partially obscured them at helical CT. CONCLUSION: Helical CT is a promising noninvasive method of imaging the intracranial vasculature and is comparable with standard MR angiographic techniques in demonstrating aneurysms.
"Acquired" Chiari I malformation after multiple lumbar punctures: case report.
The authors present the history of a patient with a Chiari I malformation "acquired" after multiple traumatic lumbar punctures. The genesis of tonsillar descent is believed to be related to persistent leakage of cerebrospinal fluid secondary to the multiple traumatic lumbar punctures. The topic of acquired Chiari I malformations and complications of lumbar puncture is reviewed.
Common carotid artery bifurcation: evaluation with spiral CT. Work in progress.
To determine the utility of spiral computed tomography (CT) in evaluation of carotid artery stenosis, spiral CT images of 20 patients were compared with images obtained with conventional angiography (20 patients), ultrasound (US) (15 patients), and magnetic resonance (MR) angiography (six patients). The category of stenosis was determined for each internal carotid artery on the basis of the percentage of narrowing: mild = less than 30%, moderate = 30%-69%, and severe = 70%-99%. Occlusions were also noted. The degree of carotid stenosis determined with spiral CT correlated with that determined with conventional angiography in 92% of cases, with that determined with US in 97% of cases, and with that determined with MR angiography in 100% of cases. Calcifications and large ulcers were also well delineated. Spiral CT provided an accurate anatomic depiction of the carotid bifurcation, which could be helpful in preoperative evaluation. The major disadvantage of the technique was the need to postprocess data to remove veins, calcifications, and bone structures from the images.
Neurosurgical complications in craniofacial surgery.
A retrospective review of the neurosurgical complications that occurred between 1980 and 1989 at The Children's Hospital in Boston is described. The results are compared with reports from other craniofacial centers. A total of 355 cases are analyzed, with an overall complication rate of 8.6%. Infection and cerebrospinal fluid leaks are the most common problems. This article discusses techniques incorporated into personal methods to reduce the incidence of these complications.
Rapid increase in enzyme and peptide mRNA in sympathetic ganglia after electrical stimulation in humans.
Thoracic ganglia in humans were studied after electrical, preganglionic stimulation using in situ hybridization with synthetic oligonucleotide probes against the catecholamine-synthesizing enzymes tyrosine hydroxylase (EC 1.14.16.2) and dopamine beta-hydroxylase (EC 1.14.17.1) and neuropeptide tyrosine. Immunohistochemical analysis was also performed. Following short peroperative stimulation a severalfold increase in all three mRNAs was found in principal ganglion cells, whereas no definite changes could be detected in enzyme or peptide levels with immunohistochemistry. The results suggest a very rapid and sensitive regulation of genes involved in signal transmission in the sympathetic nervous system of humans. Moreover, they indicate that electrical stimulation of neurons and/or pathways combined with in situ hybridization may be used as a method to define neuronal projections by visualizing increases in mRNAs for transmitter enzymes and/or peptide in target cells.
Immunocytochemical and biochemical analysis of carbonic anhydrase in primary astrocyte cultures from rat brain.
Carbonic anhydrase (CA) was studied in primary monolayer cultures from neonatal rat cerebral hemispheres with both immunocytochemical and biochemical techniques. In such cultures, which consist predominantly of astrocytes, immunocytochemical staining for CA using antibody raised against the type II enzyme from rat erythrocytes resulted in positive staining of the flat, glial fibrillary acidic protein-positive, astrocytic monolayer. Smaller, process-bearing, round cells that grew on top of the astrocytes stained intensely for CA. We estimated that these cells represented 1% or less of the total cells in the cultures, and they have been identified by others as oligodendrocytes. The intensity of the staining of astrocytes for CA could be increased to that observed in oligodendrocytes when the astrocytes were made to round up and form processes by treatment with 2',3'-dibutyryl cyclic AMP. Enzymatic assays showed that CA activity of the cultures after 3 weeks of growth was 2.5- to 5-fold less than that found for cerebral homogenates from perfused 3-week-old rat brains. However, both activities were totally inhibited by acetazolamide with an I50 of 10(-8) M, confirming that both rat brain and the astrocyte cultures possess the high-activity type II enzyme. CA-II activity was unaffected by treatment of the cultures with a method reported to remove oligodendrocytes. Thus, the immunocytochemical and biochemical studies reported here demonstrate that astroglial cells in primary cultures from neonatal rat brain contain CA-II.
Distribution of glial fibrillary acidic protein and fibronectin in primary astroglial cultures from rat brain.
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