Biomedical subjects

N Patronas

Publications and source records attributed to N Patronas.

13 recordsLinked to original sources

PubMed1992

Using gadolinium-enhanced magnetic resonance imaging lesions to monitor disease activity in multiple sclerosis.

The highly variable clinical course and the lack of a direct measurement of disease activity have made evaluation of experimental therapies in multiple sclerosis (MS) difficult. Recent studies indicate that clinically silent lesions can be demonstrated by magnetic resonance imaging (MRI) in patients with mild relapsing-remitting MS. Thus, MRI may provide a means for monitoring therapeutic trials in the early phase of MS. We studied 12 patients longitudinally for 12 to 21 months with monthly gadolinium (Gd)-enhanced MRIs. The data have been used to identify the most effective design of a clinical trial using Gd-enhanced lesions as the outcome measure. Frequent ( > 1/mo) Gd-enhancing lesions were observed in 9 of the 12 patients, indicating that the disease is active even during the early phase of the illness. The frequency of the lesions was not constant; there was marked fluctuation in lesion number from month to month. However, the magnitude of the peak number of lesions and the frequency of the peaks varied among patients. Because of this variability, the most effective use of Gd-enhancing lesions as an outcome measure in a clinical trial was a crossover design with study arms of sufficient duration to allow accurate estimation of lesion frequency. Monitoring Gd-enhancing lesions may be an effective tool to assist in the assessment of experimental therapies in early MS.

Adult↗

PubMed1992

Cerebral artery aneurysms in children infected with human immunodeficiency virus.

More than 250 children treated at our institution on antiretroviral treatment protocols have been monitored with brain imaging studies. We documented the occurrence and progression of aneurysms of major cerebral arteries in two children with advanced human immunodeficiency virus infection. In both cases these lesions remained clinically silent initially, despite progression to marked dilation.

Brain↗

PubMed1992

Diffusion MR imaging: clinical applications.

Water self-diffusion, a recently discovered source of contrast on MR images, has already shown promise for some clinical applications. Most studies have been of the brain, essentially for technical reasons. Diffusion is useful in distinguishing the different components of brain tumors (cystic regions, edema, necrosis) from the tumor core itself. Recent studies have shown that diffusion is anisotropic in brain white matter (i.e., dependent on the fiber tract's orientation in space), offering new insights into myelin disorders. Diffusion is also dramatically altered in the minutes following ischemic injury in the cat brain, which may have tremendous impact for the diagnosis and management of hyperacute stroke. With ultrafast acquisition schemes, diffusion imaging has also been used outside the CNS, for instance, in the eye and kidney. Future applications include diffusion-localized spectroscopy and temperature imaging. This article reviews recent progress in this field and suggests potential applications.

Body Water↗

PubMed1991

Serial gadolinium-enhanced magnetic resonance imaging scans in patients with early, relapsing-remitting multiple sclerosis: implications for clinical trials and natural history.

Six patients with early, mild, relapsing-remitting multiple sclerosis were studied with monthly gadolinium-enhanced magnetic resonance imaging scans for 8 to 11 months. Numerous enhancing lesions were observed irrespective of clinical activity. Four of the 6 patients had one or more enhancing lesions present on each examination. The other 2 patients had enhancing lesions noted in 7 and 9 of 11 months. In contrast, only two clinical exacerbations were observed during the study period. Neither the exacerbations nor other changes in symptoms or signs correlated with occurrence of the enhancing lesions. Enhancement generally persisted for less than 1 month. The opening of the blood-brain barrier as reflected by gadolinium enhancement on magnetic resonance imaging may represent ongoing disease activity in patients with mild, relapsing-remitting multiple sclerosis who are clinically stable. The frequency of these lesions appears to be sufficient to use as an outcome measure in clinical trials testing clinical efficacy in patients with early, relapsing-remitting multiple sclerosis.

Adult↗

PubMed1990

Neurologic, computed cranial tomographic, and magnetic resonance imaging abnormalities in patients with small-cell lung cancer: further follow-up of 6- to 13-year survivors.

To determine the subsequent evolution of neurologic, neuropsychologic, and intracranial anatomic findings in long-term survivors of small-cell cancer, we repeated an evaluation done 4 years previously in patients 6 to 13 years after treatment. Fifteen patients were reevaluated with a history and physical examination, mental status examination, neuropsychologic testing, computed cranial tomographic (CCT) scans, and magnetic resonance imaging (MRI). All but one was ambulatory and none were institutionalized. Thirteen of 15 had neurologic complaints, 10 of 15 had an abnormal neurologic examination, seven of 14 had an abnormal mental status examination, 12 of 14 had abnormal neuropsychologic testing, 12 of 15 had abnormal CCT scans, and seven of 15 had white-matter abnormalities on MRI scans. No dramatic decline in performance status, functional status, neurologic symptoms, or neurologic examination occurred in these patients with 4 years of additional follow-up. More patients showed a decline in mental status examinations and neuropsychologic testing than demonstrated improvement. Anatomic studies showed no dramatic changes in the CCT scans and MRI confirmed these findings. From these data we conclude that there is a slow decline in neuropsychologic function in some of the patients surviving more than 6 years from a diagnosis of small-cell lung cancer. The anatomic abnormalities documented by CCT scans and MRI are more frequent in patients with abnormal neuropsychologic function.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1990

Pathology of temporal lobe foci: correlation with CT, MRI, and PET.

Twenty-six patients with medically refractory complex partial seizures had temporal lobectomy after evaluation, which included prolonged scalp EEG recordings, positron emission tomography (PET), MRI, and x-ray CT. PET showed a region of focal interictal temporal hypometabolism corresponding to electrographic localization of seizure onset in 21. Five patients had a region of increased MRI signal intensity on the spin echo image in the region of the EEG focus, 2 had an abnormality ipsilateral to but distinct from the EEG focus, and 1 had bilateral findings. CT was abnormal in 3 cases; 2 had tumors. Three patients had low grade tumors (1 with a normal PET). PET can detect metabolic dysfunction associated with mild pathologic changes in epileptic foci, but increased signal intensity on MRI does not necessarily correlate with the degree of pathologic abnormality. Tumors may be less likely when both CT and MRI are normal.

Adolescent↗

PubMed1989

Divided attention, as measured by dichotic speech performance, in dementia of the Alzheimer type.

To determine if impaired dichotic performance in patients with dementia of the Alzheimer type is due to the inability to divide attention or the inability to perceive degraded auditory stimuli, we measured performance on tasks of both dichotic and degraded monotic speech materials. We also examined whether perception of degraded speech stimuli presented monaurally is related to abnormalities of temporal lobe anatomy and physiology, as we have shown for dichotic performance. Although the patients were impaired on both dichotic and monotic tests, significantly greater impairment was seen on the dichotic test. Our earlier finding of a significant relation between dichotic performance and measures of anterior temporal lobe atrophy and reduced glucose metabolism was replicated, but no significant relation was found between monotic tests and measures to temporal lobe integrity. We conclude that the inability to divide attention, rather than abnormal processing of degraded stimuli per se, is reflected in poor dichotic performance in patients with dementia of the Alzheimer type, and that dichotic performance, unlike degraded monotic perception, depends directly on the integrity of temporal cortex in these patients.

Aged↗

PubMed1988

Computed tomography and magnetic resonance imaging in adult-onset leukodystrophy.

Five clinically affected and nine at-risk members of a kindred with an autosomal dominant adult-onset leukodystrophy simulating chronic progressive multiple sclerosis were studied with computed tomography (CT) and magnetic resonance imaging (MRI). Computed tomographic scans showed white matter lucencies occurring earliest and most prominently in the frontoparietal region. The lesions were nondiscrete, diffuse, and bilaterally symmetric. These changes were more clearly visualized as areas of increased signal intensity with T2-weighted MRI. Magnetic resonance imaging also showed increased signal intensity in the brain stem, cerebellar white matter, or both of four patients. Both MRI and CT differentiated this entity from multiple sclerosis, but MRI was superior to CT in detailing the extent of white matter involvement.

Adult↗

PubMed1988

Hemispheric asymmetries, fourth ventricular size, and cerebellar morphology in autism.

Hemispheric asymmetries, fourth ventricular size, and cerebellar morphology were examined in 15 healthy men, aged 18 to 39 years, with documented childhood diagnoses of infantile autism, and in 20 healthy age- and sex-matched controls using computerized transverse axial tomography (CT). Nine patients were of approximately average intelligence, 3 showed specific language impairments, and 3 were mentally retarded. No significant group differences were seen in the distributions of frontal or posterior asymmetries of width or petalia. No subject showed evidence of cerebellar atrophy or an enlarged fourth ventricle. These results fail to support a hypothesis of unusual hemispheric asymmetry or macroscopic abnormalities of the posterior fossa in autism.

Adolescent↗

PubMed1988

Magnetic resonance imaging of cerebral lesions in patients with the Sjögren syndrome.

Thirty-eight patients with the primary Sjögren syndrome, 16 with active neuropsychiatric manifestations and 22 without clinical evidence of central nervous system involvement had magnetic resonance (MR) imaging. Eight patients had focal neurologic deficits (6 of these also had psychiatric, or cognitive dysfunction), and 8 had psychiatric or cognitive abnormalities alone. Magnetic resonance imaging showed abnormal results in 12 of 16 (75%; 95% CI, 48 to 93) patients with active central nervous system disease (67 focal lesions predominantly within the subcortical and periventricular white matter), and in 2 of 22 (9%; 95% CI, 1 to 29) patients without clinical evidence of central nervous system disease (P less than 0.0001). Seven of eight patients with focal neurologic deficits and 5 of 8 patients with psychiatric or cognitive dysfunction alone had abnormal results on MR imaging. Magnetic resonance imaging was more sensitive in the subgroup with focal deficits, (sensitivity, 88%; 95% CI, 44 to 97) than computerized axial tomography or cerebral angiography. Magnetic resonance imaging detects focal cerebral lesions in patients with the Sjögren syndrome and central nervous system involvement, including patients with psychiatric and cognitive dysfunction alone.

Adult↗

PubMed1987

Cerebral glucose metabolism in the Lennox-Gastaut syndrome.

We used positron emission tomography with fluorine 18-labeled 2-deoxyglucose to study cerebral glucose metabolism in 10 patients with Lennox-Gastaut syndrome who had normal neuroradiological studies. The scans showed decreased metabolic rates relative both to those in the caudate nucleus and to normal control values in 3 patients whose seizures began before the age of 1, as well as in a patient with hyperprolinemia. No patient had a region of persistent focal hypometabolism. Metabolic rates increased in parallel with increased electroencephalographic discharges in 1 patient; 3 patients had lower metabolic rates when the electroencephalogram showed epileptiform discharges and while the patients were taking barbiturates.

Adolescent↗

PubMedDate not supplied

MR imaging of cerebral hematomas at different field strengths: theory and applications.

Existing theory on relaxation effects in blood and their field dependence is related to magnetic resonance (MR) imaging of hematomas. These effects include (a) relaxation caused by protein and other macromolecules; (b) inhomogeneous susceptibility created by paramagnetic forms of hemoglobin (Hb) (deoxy and met) within the red blood cells; and (c) direct interaction of water protons with paramagnetic metHb. The effect of proton density is also discussed. These effects combine in a complex way to create hypo- or hyper-intensity on MR images of hematomas. Further, the effects change as the hematoma evolves both physically and chemically. In particular, there are five stages that are associated with typical image appearance: (a) oxygenated blood; (b) deoxygenated blood; (c) conversion to metHb; (d) hemolysis; and (e) protein resorption.

Cerebral Hemorrhage↗

PubMedDate not supplied

MR color mapping of myelin fiber orientation.

Diffusion of water in brain white matter has been shown to be anisotropic: Water mobility is lower when measured perpendicular to the fiber direction rather than parallel to it. This feature was used to produce images of the myelin fiber orientation. Coronal and sagittal MR diffusion images were obtained in volunteers using an echo-planar imaging sequence sensitized to molecular diffusion in perpendicular directions. Color-coded images of myelin orientation were then generated by combining these images together. The orientation of the white matter tracts was found to be in excellent agreement with known anatomy. Myelin fiber orientation mapping may offer a new perspective to evaluate white matter disorders.

Algorithms↗