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Biomedical subjects

A M Norbash

Publications and source records attributed to A M Norbash.

At least 37 records · Page 2Linked to original sources
PubMed1998

Coexistence of occult vascular malformations and developmental venous anomalies in the central nervous system: MR evaluation.

PURPOSE: We sought to determine the prevalence of coexistent occult vascular malformations (OVMs) and developmental venous anomalies (DVAs) and to investigate the relationship between them. METHODS: One hundred two patients with OVMs were examined with precontrast and postcontrast T1-weighted MR imaging and with noncontrast T2-weighted MR imaging. Seventy-two patients had surgery, with subsequent pathologic confirmation of the final diagnosis. RESULTS: Coexistent DVAs and OVMs were present in 23 (23%) of 102 patients. Seventy-nine patients had OVMs without DVAs, and in this population, multiple OVMs (from two to 10 or more) were seen in 13 patients (16%). In contrast, multiple OVMs were seen in 10 (43%) of 23 patients with coexisting OVMs and DVAs. Twenty-five (83%) of 30 OVMs coexisting with DVAs were infratentorial. In 72 patients with surgically resected OVMs, 49 (68%) had pathologically confirmed cavernous malformations. Among the patients with coexistent DVAs, seven (46%) had cavernous malformations, four (27%) had thrombosed arteriovenous malformations, and four (27%) had vascular malformations that were not classifiable. CONCLUSION: Our study revealed a high prevalence of OVMs with coexistent DVAs, and a high percentage of these were in the posterior fossa. Contrast-enhanced MR imaging may increase the probability of finding these lesions, and therefore should be considered part of the preoperative evaluation, since the finding of unexpected coexistent lesions may affect surgical management.

Adolescent↗
PubMed1997

Virtual endoscopy of the paranasal sinuses using perspective volume rendered helical sinus computed tomography.

Our goal was to use three-dimensional information obtained from helical computed tomographic (CT) data to explore and evaluate the nasal cavity, nasopharynx, and paranasal sinuses by simulated virtual endoscopy (VE). This was done by utilizing a new image reconstruction method known as perspective volume rendering (PVR). Thin-section helical CT of the nasal cavity, nasopharynx, and paranasal sinuses was performed on a conventional CT scanner. The data were transferred to a workstation to create views similar to those seen with endoscopy. Additional views not normally accessible by conventional endoscopy were generated. Key perspectives were selected, and a video "flight" model was choreographed and synthesized through the nasal cavity and sinuses based on the CT data. VE allows evaluation of the nasal cavity, nasopharynx, and paranasal sinuses with appreciation of the relationships of these spatially complex structures. In addition, this technique allows structural visualization with unconventional angles, perspectives, and locations not conventionally accessible. Although biopsies, cultures, and lavages routinely done with endoscopy cannot be performed with VE, this technique holds promise for improving the diagnostic evaluation of the nasal cavity, the nasopharynx, and the paranasal sinuses. The unconventional visual perspectives and very low morbidity may complement many applications of simple diagnostic endoscopy.

Endoscopy↗
PubMed1997

Intracavernous anterior cerebral artery origin with associated arteriovenous malformations: a developmental analysis: case report.

OBJECTIVE AND IMPORTANCE: This case demonstrates an unusual association between arteriovenous malformations and an intracavernous anterior cerebral artery origin. To the best of our knowledge, this relationship has not been previously described. Identification and understanding of this relationship are important in pre-embolization and surgical planning and in offering some insight into neurovascular development. CLINICAL PRESENTATION: The patient presented with severe recurring headaches and an otherwise nonfocal neurological examination. He maintained a stable neurological course throughout evaluation and therapy. INTERVENTION: The patient underwent endovascular embolization of the arteriovenous malformations without consequence. He was then scheduled for radiosurgical treatment planning. CONCLUSION: This case demonstrates an unusual neurovascular anomaly with associated arteriovenous malformations. To the best of our knowledge, this is the first reported case of such an association. An understanding of anomalous angioarchitecture and neurovascular development is essential for prudent endov ascular and surgical planning.

Adult↗
PubMed1997

Impaired cerebrovascular autoregulation after hypoxic-ischemic injury in extremely low-birth-weight neonates: detection with power and pulsed wave Doppler US.

PURPOSE: To evaluate regional cerebral blood flow with power and pulsed wave Doppler ultrasound (US) in extremely low-birth-weight neonates with periventricular leukomalacia (PVL), germinal matrix hemorrhage (GMH), or both. MATERIALS AND METHODS: The lenticulostriate arteries of 17 preterm neonates (birth weight < or = 1,100 g) were assessed daily with Doppler US during the first 5-6 days of life. The mean arterial pressure and bilateral peak velocity, resistive index, coronal vascular cross-sectional area, and product of the peak velocity and vascular cross-sectional area were measured. RESULTS: Five neonates developed PVL, GMH, or both; results of follow-up examinations in 11 patients were normal. One neonate with severe intrauterine growth retardation and renal tubular acidosis was excluded. Neonates with PVL, GMH, or both showed significantly greater mean values and more variable values of vascular cross-sectional area and product of peak velocity and cross-sectional area than neonates without PVL or GMH (P < .025). Mean resistive index was significantly lower in neonates with PVL, GMH, or both than in neonates without (P < .01). There were no significant differences between mean arterial pressure in neonates with and those without PVL, GMH, or both. CONCLUSION: By enabling the detection of autoregulatory fluctuations in cerebral blood flow associated with hypoxic-ischemic injury, power and pulsed wave Doppler US may enable identification of preterm neonates who are at risk of developing PVL, GMH, or both during the 1st week of life.

Blood Flow Velocity↗
PubMed1997

Diffusion-weighted MRI in transient global amnesia precipitated by cerebral angiography.

BACKGROUND: Transient global amnesia is a well-described complication of cerebral angiography. Speculation about the pathophysiology exists but is as yet unsubstantiated. Diffusion-weighted MRI is a new imaging technique that is very sensitive in detecting acute ischemia. Its use in the evaluation of transient amnesia precipitated by cerebral angiography has not previously been reported. CASE DESCRIPTION: A 44-year-old man underwent posterior circulation cerebral angiography for the investigation of episodic vertigo. Shortly after completion of the procedure, he was noted to have symptoms of transient global amnesia. Diffusion-weighted MRI at 6 and 44 hours after the procedure demonstrated increased signal in the right hippocampus and other areas within the posterior circulation bilaterally consistent with ischemia from emboli. Abnormalities on conventional MRI images performed at the same time points were noted only in retrospect. A follow-up MRI at 2 months was normal. CONCLUSIONS: Ischemia from cerebral emboli may cause transient global amnesia precipitated by cerebral angiography. Diffusion-weighted MRI may be useful in defining the pathophysiology.

Adult↗
PubMed1996

Characterization of postoperative edema following laser-assisted uvulopalatoplasty using MRI and polysomnography: implications for the outpatient treatment of obstructive sleep apnea syndrome.

Laser-assisted uvulopalatoplasty (LAUP) has been introduced as an alternative to uvuloplatopharyngoplasty for the treatment of snoring. Despite limited study, the use of this procedure has been expanded to include patients with obstructive sleep apnea syndrome. Although the potential cost-savings of performing sleep apnea surgery on an outpatient basis are self-evident, concern exists regarding the safety of this practice. In an effort to characterize the risk of performing LAUP on an outpatient basis, eight patients with mild or no sleep apnea were identified and intensively studied before and after the first stage of LAUP to cure snoring. Assessment included preoperative magnetic resonance imaging (MRI) scans, polysomnography, and videoendoscopy. Each of these diagnostic studies was then repeated between 48 and 72 hours after LAUP. Complete polysomnographic data were available for seven of the eight patients. The mean ( +/- SD) preoperative respiratory disturbance index (RDI) was 11.3 +/- 10.9, and the mean oxygen saturation nadir (LSAT) was 87.7 +/- 6.2% (n = 7). The mean airway cross-sectional area at the palate (by MRI) was 49.8 +/- 22.8 mm2 (n = 8). After LAUP, the mean RDI nearly doubled to 21.7 +/- 9.9 (P > .1). The apnea index increased fourfold from 3.3 +/- 3.5 to 14.8 +/- 10.9 (P < .03). The mean LSAT remained stable at 87.4 +/- 4.1% (P > .5). The cross-sectional area of the airway decreased to a mean of 47.9 +/- 22.4 mm2 (P > .5). These data suggest that LAUP may temporarily worsen obstructive sleep apnea. Although the clinical significance of this degree of worsening is uncertain, it would be prudent to consider perioperative use of nasal continuous positive airway pressure in patients with more than mild obstructive sleep apnea who undergo ambulatory LAUP.

Adult↗
PubMed1996

Neonatal intracranial ischemia and hemorrhage: diagnosis with US, CT, and MR imaging.

PURPOSE: To assess the usefulness of ultrasound (US), computed tomography (CT), and magnetic resonance (MR) imaging in the detection of intracranial hemorrhage and ischemia in newborns. MATERIALS AND METHODS: Seventy-six neonates who underwent US within 72 hours of CT or MR examination were studied. Four observers rated images for the presence of germinal matrix hemorrhage (GMH), intraventricular hemorrhage (IPH), extraaxial hemorrhage, and hypoxic-ischemic encephalopathy. RESULTS: In 39% of neonates, CT and MR imaging provided greater confidence than US for the diagnosis or exlusion of neonatal ischemia or hemorrhage. Kappa analysis revealed significantly better interobserver agreement with CT than with US for the detection of GMH, IVH, IPH, and cortical infarction or ischemia (P <.005). Interobserver agreement was significantly better with MR imaging than with US for the detection of GMH, IVH, and cortical infarction or ischemia (P < .005). CONCLUSION: Sensitivity and interobserver agreement are better with MR imaging and CT than with US for the detection of neonatal cortical ischemia or infarction.

Apgar Score↗
PubMed1996

Perspective volume rendering of CT and MR images: applications for endoscopic imaging.

PURPOSE: To use perspective volume rendering (PVR) of computed tomographic (CT) and magnetic resonance (MR) imaging data sets to simulate endoscopic views of human organ systems. MATERIALS AND METHODS: Perspective views of helical CT and MR images were reconstructed from the data, and tissues were classified by assigning color and opacity based on their CT attenuation or MR signal intensity. "Flight paths" were constructed through anatomic regions by defining key views along a spline path. Twelve movies of the thoracic aorta (n=3), tracheobronchial tree (n=4), colon (n=3), paranasal sinuses (n=1), and shoulder joint (n=1) were generated to display images along the flight path. All abnormal results were confirmed at surgery. RESULTS: PVR fly-through enabled evaluation of the full range of tissue densities, signal intensities, and their three-dimensional spatial relationships. CONCLUSION: PVR is a novel way to present volumetric data and may enable noninvasive diagnostic endoscopy and provide an alternate method to analyze volumetric imaging data for primary diagnosis.

Aorta, Thoracic↗
PubMed1996

Vertebral artery stenting following percutaneous transluminal angioplasty. Technical note.

The authors report initial results and follow up using stent placement to treat atherosclerotic stenosis in vertebral arteries. Three patients with severe atherosclerotic vascular disease underwent vertebral artery stent placement using a balloon expandable stent. Medical therapy (aspirin and warfarin) and conventional percutaneous angioplasty failed to resolve the disease and the patients developed symptomatic restenosis within 3 months of angioplasty. Two patients had symptoms of anterior circulation ischemia with carotid artery occlusions and reduced supply to the anterior circulation from the stenosed vertebral arteries. One patient had recurrent posterior circulation symptoms. Stents were successfully placed in all three, resulting in immediate reversal of stenosis and resolution of symptoms. Clinical follow-up study (mean 9 months) has shown no recurrent symptoms in the patient with posterior circulation symptoms, but the two patients with anterior circulation ischemia did develop recurrent symptoms. Angiographic follow up in these two patients at 3 months and 1 year, however, demonstrated continued patency of vertebral artery lumina. They underwent extracranial-intracranial bypass surgery to relieve their symptoms. This experience suggests stents can be placed without complication in the proximal vertebral arteries and may have an adjunctive role in the treatment of atherosclerotic cerebrovascular disease following unsuccessful angioplasty.

Aged↗
PubMed1996

Techniques for reducing interventional neuroradiologic skin dose: tube position rotation and supplemental beam filtration.

PURPOSE: To limit the side effects of interventional neuroradiologic radiation, such as epilation, by applying a technique involving tube position rotation and by adding a supplemental inexpensive primary beam filter; and to show the dose effect of modifying technical factors. METHODS: Combined skin dose from fluoroscopy and digital subtraction angiography was measured with an array of 16 thermoluminescent dosimeters during interventional neuroradiologic procedures in 12 control subjects, in 18 patients whose procedures included addition of an inexpensive primary beam filter (0.5 mm aluminum/0.076 mm copper), and in 10 patients in whom the tube position was rotated, additional primary beam filtration was used, and close attention was paid to technique. RESULTS: Maximum thermoluminescent dosimetric measurements obtained with existing machine filtration ranged from 0.31 to 2.70 Gy in the control group (mean, 1.51 +/- 0.88); 0.25 to 2.42 Gy in the group with additional filtration alone (mean 0.96 + 0.64; average dose reduction, 36%); and 0.13 to 1.23 Gy in the group with additional filtration, tube position rotation, and close attention to technique (mean, 0.58 +/- 0.34; average dose reduction, 63%). Differences were statistically significant. CONCLUSIONS: Greater than 50% skin dose reductions were documented during interventional neuroradiologic procedures by combining tube position rotation, supplemental primary beam filtration, and technical modifications.

Adolescent↗
PubMed1995

Correction of scaphocephaly secondary to ventricular shunting procedures.

Craniosynostosis following ventricular shunting procedures for hydrocephalus has become a recognized complication of shunting procedures. Secondary synostosis results from a decrease in intracranial volume leading to collapse of the cranial vault. Since this represents a distinct etiopathogenesis different from that typically involved, the surgical approach should be altered. Eight patients with secondary scaphocephaly underwent surgical reconstruction. The clinical data and radiographic studies were reviewed for these patients. The surgical approach consisted of sagittal or parasagittal strip craniectomies, lateral osteotomies with bone-flap expansion, occipital and frontal remodeling as needed, and the application of rigid fixation to maintain contour and prevent recurrent collapse of the cranial vault. Patient follow-up ranged from 3 to 37 months. Five of these patients were premature infants, an association not previously recognized in the literature. Satisfactory results were obtained in all patients. Keeping the craniectomy sites parent and achieving a more normal cranial contour through cranial remodeling have provided good results in this population.

Cerebrospinal Fluid Shunts↗
PubMed1994

Shunt flow measurement and evaluation of valve oscillation with a spin-echo phase-contrast MR sequence.

PURPOSE: To present a spin-echo phase-contrast (SEPC) magnetic resonance pulse sequence designed to measure the very slow flow in ventricular shunt tubing. MATERIALS AND METHODS: A flow phantom constructed of shunt tubing and incorporating no valve or a high-, medium-, or low-pressure valve was connected to a flow pump. Flow rates were 0.05-1.00 mL/min (72-1,440 mL/d). Flow measurement was performed with the thin-section SEPC sequence. RESULTS: The flow rates measured with SEPC imaging correlated closely with the pump flow rate for the entire physiologic spectrum of shunt flow rates. This was true for all valves, resulting in overall R2s of .974 at 4 cm/sec and .980 at 2 cm/sec. Shunt flow was pulsatile with valves in place. There was a linear relationship between flow rate and the frequency of valve opening and closing. CONCLUSION: The SEPC technique is an accurate and noninvasive method of measuring shunt flow.

Cerebrospinal Fluid Shunts↗
PubMed1994

Stent placement for arterial and venous cerebrovascular disease: preliminary experience.

PURPOSE: To report initial clinical experience with stent placement in the cerebrovascular circulation. MATERIALS AND METHODS: Four patients underwent arterial or venous stent placement. Two patients had cervical internal carotid artery dissections, with aneurysms and stenoses of the distal cervical carotid artery. Two patients had venous occlusive disease involving the major dural sinuses, with substantial pressure gradients across the stenoses. RESULTS: Immediately after stent placement, the true arterial lumina returned to normal diameter and both carotid aneurysms were more than 90% occluded. Follow-up angiography demonstrated continued improvement in the arterial aneurysms. Both patients with dural sinus venous occlusive disease showed substantial improvement of the sinus stenoses and substantial reversal of the pressure gradients after venous stent placement. At follow-up, these patients have done well. CONCLUSION: This preliminary experience suggests there may be a role for stents in the management of arterial and venous cerebrovascular disease, including carotid artery dissection and venous occlusive disease.

Adult↗
PubMed1994

Correlation of pressure measurements with angiographic characteristics predisposing to hemorrhage and steal in cerebral arteriovenous malformations.

PURPOSE: To determine whether there is a physiologic explanation for the predisposition of patients with certain angiographic characteristics to symptoms of hemorrhage and steal. METHODS: Superselective transcatheter feeding arterial pressure and mean arterial pressure measurements were obtained before embolotherapy in 32 patients with cerebral arteriovenous malformations. Pressures were correlated with previously described angioarchitectural characteristics predisposing to hemorrhage and steal. These included size of the arteriovenous malformation, feeding artery length, venous drainage pattern, and angiomatous change. RESULTS: The feeding arterial pressure and feeding arterial pressure/mean arterial pressure ratios were significantly decreased in patients with angiomatous change. Feeding arterial pressure and feeding arterial pressure/mean arterial pressure ratios progressively decreased as lesions went from peripheral, to mixed, to central venous drainage. A trend for lower feeding arterial pressure was also demonstrated with greater feeding pedicle length. A statistically significant correlation could not be demonstrated between feeding arterial pressure or feeding arterial pressure/mean arterial pressure ratios and size of the arteriovenous malformation, hemorrhage, or symptoms of steal. CONCLUSIONS: Feeding arterial pressure measurements help provide a physiologic basis for the relationship between certain angiographic characteristics and hemorrhage and steal symptoms in patients with arteriovenous malformation.

Adolescent↗
PubMed1994

Magnetic resonance imaging and measurement of blood flow.

Blood flow can be shown as a negative image with magnetic resonance spin-echo techniques or as a positive image with gradient-echo techniques. Phase contrast refers to techniques where structures can be seen because of flow-induced phase shifts. These techniques can show the presence (slow flow) and also the direction of flow. Gradient-echo techniques--including phase-contrast versions--can be used with cardiac synchronization to obtain multiple images during the cardiac cycle. These images can be viewed in a movie or cine format to provide dynamic information about blood flow. Blood flow can be measured by using contrast media in boluses or even more elegantly with phase-contrast methods. Clinical applications of flow measurements are growing rapidly. Phase-contrast or gradient-echo techniques can be used to create magnetic resonance angiography, which was first used to study the carotid bifurcation and intracranial circulation and is now being used throughout the body.

Angiography↗
PubMed1992

Intracerebral lesion contrast with spin-echo and fast spin-echo pulse sequences.

Fast spin-echo (FSE) magnetic resonance (MR) imaging was compared with conventional, peripherally gated T2-weighted spin-echo (SE) imaging in the detection of high- and low-signal-intensity lesions in the central nervous system. Lesion detectability was determined with percentage of contrast measurements and contrast-to-noise ratios with two different measurements for noise. All three measures of lesion detectability were similar. FSE and SE sequences were quantitatively equivalent in the detection of high-signal-intensity lesions. The SE sequence, however, was superior to the FSE sequence in the detection of small, low-signal-intensity lesions in the central nervous system caused by magnetic susceptibility effects.

Adolescent↗