Characterization of white matter damage in ischemic leukoaraiosis with diffusion tensor MRI

BACKGROUND AND PURPOSE: Information on the neuropathological changes underlying ischemic leukoaraiosis is only available postmortem, and there are limited data on histological appearances early in the disease. Diffusion tensor imaging allows determination of the directionality of diffusion, which is greater in the direction of white matter bundles. Therefore, the technique might be expected to show loss of anisotropy (directional diffusion) in leukoaraiosis. METHODS: Nine patients with ischemic leukoaraiosis (radiological leukoaraiosis and clinical lacunar stroke) and 10 age-matched controls were studied. Diffusion tensor imaging was performed, and maps of diffusion trace and fractional anisotropy were constructed. Mean values of trace and fractional anisotropy were determined in standard regions of the anterior and posterior white matter in both hemispheres. RESULTS: In all patients with ischemic leukoaraiosis, a characteristic abnormal pattern was found, with loss of anisotropy and increased trace in the white matter. For example, in the right anterior white matter mean (SD) trace/3 was 1.12 (0.33) x10(-3) mm2 s-1 in patients and 0.75 (0.11) in controls (P=0.001). In the same region, fractional anisotropy was 0.53 (0.11) in patients and 0.78 (0.09) in controls (P<0.001). Within the white matter regions, there was a strong negative correlation between mean diffusivity and anisotropy (r=-0.92, P<0.0001). CONCLUSIONS: The characteristic pattern found on diffusion tensor imaging in this patient group is consistent with axonal loss and gliosis leading to impairment to and loss of directional diffusion. The "in vivo histological" information obtained may be useful in monitoring disease progression and in investigating the pathogenesis of the cognitive impairment that may be present.     

Solubility Limit of MgO in Al2O3 at 1600°C

The solubility of Mg in alumina was measured using wavelength-dispersive spectroscopy mounted on a scanning electron microscope. Careful calibration of the microscope's working conditions was performed in order to optimize the detection limit and accuracy. Measurements were conducted on water-quenched and furnace-cooled samples, without any thermal or chemical etching to avoid alteration of the bulk concentration. The results indicate the solubility limit of Mg in alumina to be 132±11 ppm at 1600°C.     

Air Pollution Emission Inventory Survey for Israel

High ozone levels are regularly measured during summer months over the inland and mountainous regions of Israel. Studies analyzing the back trajectories of air masses responsible for the high ozone levels showed that the precursors originated from the densely populated Israeli coastline. In order to better understand the contribution of those emission sources to ozone production, it is essential to have an accurate emission inventory that can be inputted into a photochemical model. The present paper describes the methods used in preparing an emission inventory for Israel based on information available and published until 1998. The source and accuracy of the data available are described. The calculations performed and the assumptions taken in order to obtain data not directly available are clarified. The sources reported in the inventory were the major polluters (power plants, oil refineries, and cement industries); industry; transportation; and biogenic sources. The pollutants studied were SO₂, NO_x, CO, saturated and unsaturated hydrocarbons, ethylene, isoprene, toluene, xylene, formaldehyde, and aldehydes. The inventory showed that transportation is responsible for almost the entire CO and 30% of the volatile organic compounds emitted, although transportation itself accounts for only a fifth of total fuel consumption. About 75% of the NO_x emitted can be attributed to industrial sources and the remaining 25% to transportation. Model simulations using the emission inventory were performed and compared to data available from a monitoring station situated 30 km east of Tel Aviv. The results showed good agreement, validating the accuracy of the emission inventory. The present emission inventory provides an important database as input to photochemical models used in forecasting ozone levels over Israel.     

Germ-line mutations in the neurofibromatosis 2 gene: correlations with disease severity and retinal abnormalities

Neurofibromatosis 2 (NF2) features bilateral vestibular schwannomas, other benign neural tumors, and cataracts. Patients in some families develop many tumors at an early age and have rapid clinical progression, whereas in other families, patients may not have symptoms until much later and vestibular schwannomas may be the only tumors. The NF2 gene has been cloned from chromosome 22q; most identified germ-line mutations result in a truncated protein and severe NF2. To look for additional mutations and clinical correlations, we used SSCP analysis to screen DNA from 32 unrelated patients. We identified 20 different mutations in 21 patients (66%): 10 nonsense mutations, 2 frameshifts, 7 splice-site mutations, and 1 large in-frame deletion. Clinical information on 47 patients from the 21 families included ages at onset and at diagnosis, numbers of meningiomas, spinal and skin tumors, and presence of cataracts and retinal abnormalities. We compared clinical findings in patients with nonsense or frameshift mutations to those with splice-site mutations. When each patient was considered as an independent random event, the two groups differed (P < or = .05) for nearly every variable. Patients with nonsense or frameshift mutations were younger at onset and at diagnosis and had a higher frequency and mean number of tumors, supporting the correlation between nonsense and frameshift mutations and severe NF2. When each family was considered as an independent random event, statistically significant differences between the two groups were observed only for mean ages at onset and at diagnosis. A larger data set is needed to resolve these discrepancies. We observed retinal hamartomas and/or epiretinal membranes in nine patients from five families with four different nonsense mutations. This finding, which may represent a new genotype-phenotype correlation, merits further study.     

Periodic limb movement in sleep in children with Williams syndrome

Difficulty differentiating physiologic genu varum from early Blount's disease persists. Drennan's metaphyseal-diaphyseal (MD) angle remains the most consistently valuable radiographic parameter despite measurement error. Clinical risk factors also should be considered. All patients receiving orthoses for genu varum since 1985 were reviewed. The focus of the study was those patients with an MD angle of >16 degrees or between 9 and 16 degrees with a clinical risk factor for progression. Risk factors considered were ligamentous instability, obesity, asymmetry, and being female, black, or Hispanic. Thirty-eight patients with 60 tibiae were included. The success rate was 90%. Risk factors for failure (six cases) were instability, obesity, and delayed bracing. In cases with MD angles >16 degrees, the success rate was 86%. The results of orthotic treatment, restricted to patients meeting the stated parameters, represent improvement on the reported natural history.