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Biomedical subjects

L M Ramos

Publications and source records attributed to L M Ramos.

At least 19 recordsLinked to original sources
PubMed2001

MRI of the brachial plexus in polyneuropathy associated with monoclonal gammopathy.

On magnetic resonance (MR) imaging of the brachial plexus increased signal intensity and swelling of the brachial plexus has been found in chronic inflammatory demyelinating polyneuropathy (CIDP). Whether these proximal abnormalities are also present in the distal polyneuropathy associated with monoclonal gammopathy is unknown. Therefore, we performed MR imaging of the brachial plexus in 21 patients with polyneuropathy associated with IgM monoclonal gammopathy (11 IgM with anti-MAG antibodies, 10 IgM without anti-MAG antibodies). For comparison we studied 9 patients with polyneuropathy associated with IgG monoclonal gammopathy and 8 patients with CIDP. Among the 30 patients with monoclonal gammopathy, 24 patients had demyelinating polyneuropathy. Among these 24 patients, there was increased signal intensity of the brachial plexus on the T2-weighted images regardless of whether clinical deficits were generalized or purely distal in location. No association was found with the isotype of the monoclonal gammopathy. Of the 8 patients with CIDP, 5 had brachial plexus abnormalities. None of the 6 patients with axonal polyneuropathy associated with monoclonal gammopathy had such abnormalities. Thus, MR imaging of the brachial plexus shows that the distal demyelinating polyneuropathy associated with monoclonal gammopathy is more generalized than presumed.

Adult↗
PubMed2001

Prevalence of cerebral white matter lesions in elderly people: a population based magnetic resonance imaging study. The Rotterdam Scan Study.

OBJECTIVE: White matter lesions are often seen on MR scans of elderly non-demented and demented people. They are attributed to degenerative changes of small vessels and are implicated in the pathogenesis of cognitive decline and dementia. There is evidence that especially periventricular white matter lesions are related to cognitive decline, whereas subcortical white matter lesions may be related to late onset depression. The frequency distribution of subcortical and periventricular white matter lesions according to age and sex reported. METHODS: A total of 1077 subjects aged between 60-90 years were randomly sampled from the general population. All subjects underwent 1.5T MR scanning; white matter lesions were rated separately for the subcortical region and the periventricular region. RESULTS: Of all subjects 8% were completely free of subcortical white matter lesions, 20% had no periventricular white matter lesions, and 5% had no white matter lesions in either of these locations. The proportion with white matter lesions increased with age, similarly for men and women. Women tended to have more subcortical white matter lesions than men (total volume 1.45 ml v 1. 29 ml; p=0.33), mainly caused by marked differences in the frontal white matter lesion volume (0.89 ml v 0.70 ml; p=0.08). Periventricular white matter lesions were also more frequent among women than men (mean grade 2.5 v 2.3; p=0.07). Also severe degrees of subcortical white matter lesions were more common in women than in men (OR 1.1; 95% confidence interval (95% CI) 0.8-1.5) and periventricular white matter lesions (OR 1.2; 95% CI 0.9-1.7), albeit that none of these findings were statistically significant. CONCLUSIONS: The prevalence and the degree of cerebral white matter lesions increased with age. Women tended to have a higher degree of white matter lesions than men. This may underlie the finding of a higher incidence of dementia in women than in men, particularly at later age.

Aged↗
PubMed2001

Reproducibility of measurements of cerebral infarct volume on CT scans.

BACKGROUND AND PURPOSE: Infarct volume is increasingly used as an outcome measure in clinical trials of therapies for acute ischemic stroke. We tested which of 5 different methods to measure infarct size or volume on CT scans has the highest reproducibility. METHODS: Infarct volume and total intracranial volume were measured with Leica Q500 MCP image analysis software, or with a caliper, on 38 CT scans of patients who participated in the Tirilazad Efficacy Stroke Study II (TESS II). The scans were performed 8 days (+/-2 days) after the onset of symptoms. The 5 methods tested were based on (1) semiautomated pixel thresholding, (2) manual tracing of the perimeter, (3) a stereological counting grid, (4) measurement of the 3 largest diameters, and (5) the single largest diameter. The measurements were performed independently by 2 observers; the first observer performed all measurements twice. RESULTS: The single largest diameter did not correlate well with infarct volume. Of the other methods, manual tracing of the perimeter of the infarct had the lowest intraobserver and interobserver variability: coefficients of variation were 8.6% and 14.1%, respectively. For total intracranial volume, manual tracing also provided the highest reproducibility: intraobserver and interobserver coefficients of variation were 3.3% and 4.9%, respectively. CONCLUSIONS: Manual tracing of the perimeter is the most reproducible method for measuring the volumes of the infarct and the total intracranial space in multicenter trials of therapies for acute ischemic stroke.

Adult↗
PubMed2001

Surgical anatomy of the cerebral arteries in patients with subarachnoid hemorrhage: comparison of computerized tomography angiography and digital subtraction angiography.

OBJECT: The purpose of this study was to compare computerized tomography (CT) angiography and digital subtraction (DS) angiography studies in patients with subarachnoid hemorrhage (SAH) to assess their vascular anatomy relevant to cerebral aneurysm surgery. METHODS: From a prospective series of 100 patients with SAH, the authors selected 73 patients whose CT angiography studies were of adequate quality and in whom DS angiography of both carotid arteries had been performed. Eleven patients with no DS angiographic studies of the vertebrobasilar artery were only evaluated for the anterior half of the circle of Willis. Anterior communicating arteries (ACoAs), both precommunicating anterior cerebral arteries (A1 segments), both posterior communicating arteries (PCoAs), and both precommunicating posterior cerebral arteries (P1 segments) were assessed on CT angiography and DS angiography by two independent observers. CONCLUSIONS: Computerized tomography angiography compares well with DS angiography for visualizing normal-sized arteries, and is superior for visualizing ACoAs and hypoplastic A1 and P, segments. Important preoperative aspects such as dominant A1 segments and PCoAs are equally well seen using either modality. Neither method enabled the authors to visualize more than 50% of PCoAs. Use of CT angiography can provide the required preoperative anatomical information for aneurysm surgery in most patients with SAH.

Adult↗
PubMed2000

Frontal lobe damage and thalamic volume changes.

The aim of this study was to investigate whether frontal lobe damage affects thalamic volume in humans. Ipsilateral and contralateral thalamic areas were measured in 0.5T T1-weighted sagittal magnetic resonance images in 12 patients, first at the time of their surgery for relief of a unilateral frontal lobe brain tumor and at follow-up approximately 2 years later. A 5% decrease in ipsilateral and 4.5% increase in contralateral thalamic area was found over time (F(1,11) = 6.15, p < 0.05). We conclude that unilateral frontal lobe damage results in a decrease in the ipsilateral thalamus and an increase in the contralateral thalamus in humans in vivo. The findings may have implications for the interpretation of the reported changes in thalamic volume in neuropsychiatric diseases.

Adolescent↗
PubMed2000

Prognostic value of perfusion- and diffusion-weighted MR imaging in first 3 days of stroke.

The aim of this study was to evaluate the differences in cerebral perfusion seen on mean transit time (MTT) and cerebral blood volume (CBV) maps and to assess the subsequent prognostic value of the MTT-DWI (diffusion-weighted MRI) and CBV-DWI mismatch in the first three days of stroke on lesion enlargement and clinical outcome. In 38 patients, imaged 1-46 h after onset of symptoms, lesion volumes on proton-density (PD)-weighted MRI, DWI and PWI (both MTT and CBV maps) were compared with lesion volumes on follow-up PD-weighted scans, and to clinical outcome (National Institutes of Health Stroke Scale, Barthel index, and Rankin scale). The MTT-CBV, MTT-DWI and CBV-DWI mismatches were compared with change in lesion volume between initial and follow-up PD-weighted scans. Lesion volume on both DWI and PWI correlated significantly with clinical outcome parameters (p < 0.001) with strongest correlation for lesion volume on CBV. Perfusion-diffusion mismatches were found for both CBV and MTT and correlated significantly with lesion enlargement on PDweighted imaging with strongest correlation for the CBV-DWI mismatch. The CBV-DWI mismatch has the highest accuracy in predicting lesion size on follow-up imaging and in predicting clinical outcome. Lesion volume measurements on CBV maps have a higher specificity than on PD-weighted, MTT or DWI images in predicting clinical follow-up imaging and in predicting clinical outcome.

Adult↗
PubMed1999

Correlation of MR images of disc injuries with anatomic sections in experimental thoracolumbar spine fractures.

This cadaver study evaluated the value of MR images for detection of acute intervertebral disc damage associated with fractures of the thoracolumbar spine. Damage to the intervertebral disc may be a major contributor to chronic instability in non-operative treatment or failure of fixation and recurrence of deformity in posterior fixation methods. MR imaging can help us to understand the injury patterns and their prognostic significance. However, before we can justify the use of MRI in clinical cases, determination of MRI's ability to detect acute injury to the disc is necessary. Ten fresh cadaver specimens were used for this study. After obtaining radiograms and MR images, injuries were created with a weight-dropping apparatus using a variety of weights and compression angles. Post-injury radiograms and MR images were taken and the specimens were frozen at -20 degrees C. Slides of these specimens obtained with cryosection techniques were compared with MR images for evaluation of the damage to different parts of the discs. A total of 20 fractures were observed on cryosections. In 12 of the discs adjacent to fractured vertebral bodies, macroscopic damage was seen on the sections. These were all detected on the corresponding MR images. The study showed that MRI is able to detect acute, macroscopic injury to the intervertebral disc. It is therefore justified to use MR for the study of acute disc damage associated with thoracolumbar fractures.

Aged↗
PubMed1999

Venous malformation of the glans penis: efficacy of treatment with neodymium:yttruim-aluminum-garnet laser.

OBJECTIVES: Vascular anomalies in the urogenital tract are very rare and those located in glans penis are the most uncommon. There is some controversy concerning their nomenclature, diagnosis and treatment. We present an analysis of our experience and a critical review of the literature. METHODS: Three cases of vascular lesions in the glans penis concordant with venous malformations were diagnosed at our center in 1996. The patients were 22, 20, and 12 years old, and attended our center for aesthetic reasons only. Even though two of the lesions were large, treatment with neodymium:yttrium-aluminium-garnet (Nd:YAG) laser irradiation was used. RESULTS: The outcome of treatment was satisfactory and no signs of recurrence were observed at follow-up examinations after a minimum of 18 months. CONCLUSIONS: Until recently, surgery has been the classical therapeutic approach, and only a few cases treated with the Nd:YAG laser have been reported. However, in our opinion, this should be the first choice treatment for this anomaly, given its efficacy, cosmetic results, and low morbidity.

Adult↗
PubMed1999

Perimesencephalic hemorrhage. Exclusion of vertebrobasilar aneurysms with CT angiography.

BACKGROUND AND PURPOSE: It is important to recognize a perimesencephalic pattern of hemorrhage in patients with subarachnoid hemorrhage (SAH), because in 95% of these patients the cause is nonaneurysmal and the prognosis is excellent. The purpose of this study was to investigate whether CT angiography can accurately exclude vertebrobasilar aneurysms in patients with perimesencephalic patterns of hemorrhage and therefore replace digital subtraction angiography (DSA) in this setting. METHODS: In 40 patients with posterior fossa SAH as shown on unenhanced CT, 2 radiologists independently evaluated unenhanced CT for distinguishing between perimesencephalic and nonperimesencephalic pattern of hemorrhage and assessed CT angiography for detection of aneurysms. All patients subsequently underwent DSA or autopsy. RESULTS: Observers agreed in 38 of 40 patients (95%) in differentiating perimesencephalic and nonperimesencephalic patterns of hemorrhage on unenhanced CT. On the CT angiograms, both observers detected a vertebrobasilar aneurysm in 16 patients and no aneurysm in 24 patients. These findings were confirmed by DSA or autopsy. No patients with a perimesencephalic pattern of hemorrhage were found to have an aneurysm on either CT angiography or DSA. CONCLUSIONS: Good recognition of a perimesencephalic pattern of hemorrhage is possible on unenhanced CT, and CT angiography accurately excludes and detects vertebrobasilar aneurysms. DSA can be withheld in patients with a perimesencephalic pattern of hemorrhage and negative CT angiography.

Adult↗
PubMed1999

MR angiography as a screening tool for intracranial aneurysms: feasibility, test characteristics, and interobserver agreement.

OBJECTIVE: MR angiography may be an appropriate tool to screen for unruptured intracranial aneurysms. Feasibility, test characteristics, and interobserver agreement in evaluation of MR angiograms were assessed by members of the MARS (Magnetic resonance Angiography in Relatives of patients with Subarachnoid hemorrhage) Study Group. SUBJECTS AND METHODS: We screened 626 first-degree relatives of a consecutive series of 193 patients with subarachnoid hemorrhage examined at two institutions. We used MR imaging and MR angiography (three-dimensional time-of-flight imaging at both institutions and additional three-dimensional phase-contrast imaging at one institution). Three observers independently assessed the MR angiograms. Conventional angiography was performed in relatives with possible or definite aneurysms on MR angiography and was considered the standard of reference. RESULTS: Thirty-three aneurysms were found in 25 (4%; 95% confidence interval [CI], 3-6%) of 626 relatives. Thirteen (8%) of 169 relatives who refused screening had MR-related reasons; an additional six persons could not be screened because of contraindications for MR imaging (pregnancy, n = 1; claustrophobia, n = 5). The positive predictive value of MR angiography was 100% (95% CI, 79-100%) for "definite" aneurysms and 58% (95% CI, 28-85%) for "possible" aneurysms. Sensitivity of MR angiography was estimated at 83% (95% CI, 65-94%) and specificity at 97% (95% CI, 94-98%). Interobserver agreement in the evaluation of MR angiograms was poor (kappa < .30), probably because different diagnostic strategies used by individual observers resulted in different use of the assessment category "possible aneurysm." CONCLUSION: MR angiography is a feasible screening tool for detection of intracranial aneurysms. Positive predictive value, sensitivity, and specificity are acceptable when at least two neuroradiologists independently assess MR angiograms.

Adult↗
PubMed1999

Computerized tomography angiography in patients with subarachnoid hemorrhage: from aneurysm detection to treatment without conventional angiography.

OBJECT: The purpose of this study was to determine prospectively whether and to what extent computerized tomography (CT) angiography can serve as the sole imaging method for a preoperative workup in patients with ruptured intracranial aneurysms. METHODS: During a 1-year period, all patients who presented to the authors' hospital with subarachnoid hemorrhage demonstrated by unenhanced CT scanning or lumbar puncture underwent CT angiography. Two radiologists evaluated the CT angiography source images and maximum intensity projection slabs and arrived at a consensus. They categorized the quality of the CT angiography as adequate or inadequate and classified aneurysms that were detected as definitely or possibly present. The parent artery of anterior communicating artery aneurysms was identified by asymmetrical anterior cerebral artery size and asymmetrical aneurysm location. The parent artery was indicated by the larger A1 segment in cases of asymmetrical A1 size. Only CT angiograms of adequate quality that revealed aneurysms classified as definitely present and with an unequivocal parent artery were presented to the neurosurgeons, who decided whether preoperative digital subtraction (DS) angiography should still be performed. Forty-nine of the 100 studied patients did not undergo surgery because of poor clinical condition, nonaneurysmal cause of the hemorrhage, or endovascular treatment of the ruptured aneurysm. Of the 51 patients who underwent surgery, radiologists required DS angiography in 17 patients; the imaging technique provided greater certainty in 13 instances. The neurosurgeons required DS angiography 11 times; this provided additional information in two instances. Twenty-three (45%) of the 51 patients were surgically treated successfully on the basis of CT angiography findings alone. CONCLUSIONS: Computerized tomography angiography can replace DS angiography as the preoperative neuroimaging technique in a substantial proportion of patients with ruptured intracranial aneurysms.

Adolescent↗
PubMed1998

Treatment planning of brain implants using vascular information and a new template technique.

A new template technique has been developed for implanting hyperthermia catheters in the treatment of brain tumors. The technique utilizes an imaging template and a drill template which can be rigidly secured to the head with three skull screws. The anatomic and vascular information needed for hyperthermia treatment planning may be assessed with three-dimensional magnetic resonance (MR) imaging and angiography acquisitions which use a surface coil. In the companioning treatment planning system the catheter positions and lengths and the electrodes in the catheter can be interactively manipulated relative to the anatomy and vasculature. The visualization of the blood vessels relative to the template allows the minimization of the risk on intracranial hemorrhages. This template technique is useful for any brain tumor implants, especially when a large number of catheters are involved. A phantom test has shown that this procedure has an accuracy in the order of 1 mm provided that the MR-related geometry distortions are minimized.

Brain Neoplasms↗
PubMed1998

Subarachnoid hemorrhage: aneurysm detection and preoperative evaluation with CT angiography.

PURPOSE: To evaluate if computed tomographic (CT) angiography can replace digital subtraction angiography (DSA) for aneurysm detection and as preoperative work-up in patients with subarachnoid hemorrhage (SAH). MATERIALS AND METHODS: Prospectively, 100 patients with SAH underwent CT angiography; 80 also underwent DSA. Two observers independently evaluated CT angiographic source images and maximum intensity projection slabs. Neurosurgeons compared CT angiograms and DSA images for presurgical evaluation. RESULTS: On CT angiograms, the observers detected 73 and 70 of 75 symptomatic aneurysms; 96% of the detected aneurysms were classified as definitely present. Of 16 incidental aneurysms, 12 and 10 were detected by the observers. With adequate CT angiographic quality, parent artery side of anterior communicating aneurysms was correctly predicted in 100% (95% confidence interval [CI]: 87%, 100%). Neurosurgeons assessed CT angiography as equal or superior to DSA in 83% (95% CI: 73%, 90%) of 87 aneurysms, and in 74% (95% CI: 63%, 82%) operation might have been based on CT angiographic findings alone. CONCLUSION: CT angiography depicted 90% of all aneurysms, and 90% were classified as definitely present. CT angiography must be of high quality with adequate depiction of the aneurysm and the parent artery for surgery to be performed on the basis of CT angiographic findings alone.

Adult↗
PubMed1998

Effect of age on cerebral blood flow: measurement with ungated two-dimensional phase-contrast MR angiography in 250 adults.

PURPOSE: To determine the normal values and effects of age and sex on total cerebral blood flow (CBF) as measured with ungated two-dimensional phase-contrast magnetic resonance (MR) angiography. MATERIALS AND METHODS: Volume flow rates in the basilar artery and both internal carotid arteries were measured on two-dimensional phase-contrast MR angiograms obtained in 250 subjects (age range, 19-88 years; mean age, 50 years) undergoing MR imaging because of indications other than cerebrovascular disease. Volume flow rates for the three arteries were summed to obtain the total CBF, and the values were analyzed in terms of age and sex. RESULTS: Mean total CBF was 616 mL/min +/- 143. There was a significant yearly decrease with age in total CBF of 4.8 mL/min (P < .001). Mean total CBF ranged from 748 mL/min +/- 121 to 474 mL/min +/- 105 in subjects aged 19-29 and 80-89 years, respectively. No sex differences were found. Mean relative contributions of the right and left internal carotid arteries and the basilar artery to total CBF were 41%, 40%, and 19%, respectively, with no substantial change due to age. CONCLUSION: Ungated two-dimensional phase-contrast MR angiography is a useful, noninvasive technique for assessing total CBF. By using this technique, a significant decrease in total CBF with age was demonstrated.

Adult↗
PubMed1998

Diffusion-weighted magnetic resonance imaging in acute stroke.

BACKGROUND AND PURPOSE: Diffusion-weighted MRI (DWI) is highly sensitive in detecting early cerebral ischemic changes in acute stroke patients. In this study we compared the sensitivity of DWI with that of conventional MRI techniques. Furthermore, we investigated the prognostic value of the volume of ischemic lesions on DWI scans and of the apparent diffusion coefficient (ADC). METHODS: We performed DWI, fluid-attenuated inversion recovery, spin-echo T2-weighted MRI, and spin-echo proton density-weighted MRI in 42 patients with acute stroke and 15 control subjects. The volume of ischemic lesions was measured on early (<60 hours after onset) and follow-up MRI scans. Clinical outcome was measured 4 months after onset of symptoms with the National Institutes of Health Stroke Scale, the Barthel Index, and the Rankin Scale. RESULTS: With DWI, 98% of the ischemic lesions were detected, and with fluid-attenuated inversion recovery, 91% were detected, whereas with early T2-weighted or proton density-weighted scans, only 71% (P=0.002, chi2) and 80% (P=0.02, chi2) of lesions, respectively, were found. Lesion volume on early DWI scans correlated significantly with clinical outcome ratings (P<0.01). In patients with a first-ever stroke, a lesion volume of < or =22 mL on DWI predicted good outcome with a 75% sensitivity and a 100% specificity. The mean ADC of ischemic lesions was 29% lower than the ADC of normal-appearing parts of the brain (P<0.001). The ADC ratio correlated significantly with clinical outcome (P<0.05). CONCLUSIONS: DWI is a better imaging method than conventional MRI in detecting early ischemic lesions in stroke patients. Lesion size as measured on DWI scans and, to a lesser extent, ADC values are potential parameters for predicting clinical outcome in acute stroke patients.

Acute Disease↗
PubMed1998

Initial and follow-up screening for aneurysms in families with familial subarachnoid hemorrhage.

BACKGROUND AND OBJECTIVE: In families with two or more relatives with subarachnoid hemorrhage (SAH), other first-degree relatives have an increased risk of SAH. We studied the presence of unruptured intracranial aneurysms in 125 members of 23 families with familial SAH, defined as two or more affected first-degree relatives, in a cross-sectional design. METHODS: MR angiography was performed in 116 relatives; CT angiography was performed in the remaining 9 relatives because they had been treated for intracranial aneurysms in the past. RESULTS: Overall, we found 16 aneurysms in 10 of 125 relatives (8%; 95% CI, 4 to 14%). Of the nine patients with previous surgery for ruptured or unruptured intracranial aneurysms, three had new aneurysms. Two factors were associated with a significantly higher risk of intracranial aneurysms: 1) a history of treatment for ruptured or unruptured intracranial aneurysms (relative risk 5.5; 95% CI, 1.7 to 17.8) and 2) having three or more affected relatives (relative risk 3.3; 95% CI, 1.0 to 10.6). Siblings tended to have a higher risk of intracranial aneurysms than did children of SAH patients, although the difference was not significant. CONCLUSIONS: Because the yield is high, screening is recommended in first-degree members of families with familial SAH. Repeated screening should be considered in relatives who have been treated for familial intracranial aneurysms.

Adolescent↗