MTT and Blood-Brain Barrier Disruption within Asymptomatic Vascular WM Lesions.

BACKGROUND AND PURPOSE: White matter lesions of presumed ischemic origin are associated with progressive cognitive impairment and impaired BBB function. Studying the longitudinal effects of white matter lesion biomarkers that measure changes in perfusion and BBB patency within white matter lesions is required for long-term studies of lesion progression. We studied perfusion and BBB disruption within white matter lesions in asymptomatic subjects. MATERIALS AND METHODS: Anatomic imaging was followed by consecutive dynamic contrast-enhanced and DSC imaging. White matter lesions in 21 asymptomatic individuals were determined using a Subject-Specific Sparse Dictionary Learning algorithm with manual correction. Perfusion-related parameters including CBF, MTT, the BBB leakage parameter, and volume transfer constant were determined. RESULTS: MTT was significantly prolonged (7.88 [SD, 1.03] seconds) within white matter lesions compared with normal-appearing white (7.29 [SD, 1.14] seconds) and gray matter (6.67 [SD, 1.35] seconds). The volume transfer constant, measured by dynamic contrast-enhanced imaging, was significantly elevated (0.013 [SD, 0.017] minutes-1) in white matter lesions compared with normal-appearing white matter (0.007 [SD, 0.011] minutes-1). BBB disruption within white matter lesions was detected relative to normal white and gray matter using the DSC-BBB leakage parameter method so that increasing BBB disruption correlated with increasing white matter lesion volume (Spearman correlation coefficient = 0.44; P < .046). CONCLUSIONS: A dual-contrast-injection MR imaging protocol combined with a 3D automated segmentation analysis pipeline was used to assess BBB disruption in white matter lesions on the basis of quantitative perfusion measures including the volume transfer constant (dynamic contrast-enhanced imaging), the BBB leakage parameter (DSC), and MTT (DSC). This protocol was able to detect early pathologic changes in otherwise healthy individuals.

Diagnostic role of stool culture & toxin detection in antibiotic associated diarrhoea due to Clostridium difficile in children.

BACKGROUND & OBJECTIVE: Mere diagnosis of Clostridium difficile by culture does not help in the diagnosis of antibiotic associated diarrhoeae (AAD) due to C. difficile. Detection of toxins A and B form the mainstay in the diagnosis of AAD due to C. difficile. This study was undertaken to find out the role of stool culture and toxin detection in the diagnosis of AAD due to C. difficile. As there are very few documented reports from India about AAD due to C. difficile in children in the age group of 5-12 yr, this age group was selected. METHODS: Faecal samples were collected from 250 hospitalized children in the age group of 5-12 yr who developed diarrhoea on receiving antibiotics for different medical problems for more than five days duration. Also faecal samples of 250 age and sex matched controls were collected. Culture for C. difficile was done on cycloserine cefoxitin fructose egg yolk agar (CCFA) and colonies were identified by standard laboratory techniques. ELISA for toxins A and B detection and tissue culture on HeLa cells for toxin B detection were also done. RESULTS: Overall positivity was 18 per cent in this study group compared to the controls (P<0.001). Maximum positive cases were in 5-8 yr age group (84.4%). Severe diarrhoea, liquid stool with mucus and blood, faecal leucocytes >5/high power field, altered flora and presence of Gram-positive bacilli with oval subterminal spores on Gram stain were sensitive predictors for diagnosis of AAD due to C. difficile. Amongst positive cases, 68.9 per cent responded to discontinuation of antibiotics and 31.1 per cent to metronidazole therapy. INTERPRETATION & CONCLUSION: C. difficile was an important pathogen responsible for antibiotic associated diarrhoea (AAD) in children of 5-12 yr age group. Conservative use of antibiotics would be beneficial to decrease the incidence of AAD.