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BACKGROUND AND AIM: The apparent diffusion coefficient (ADC) and anisotropy (eg, fractional anisotropy (FA)) of ischaemic tissue evolve over time. A reduction in diffusivity (ie, λ2and λ3) is an important marker for characterising hyperacute-stage infarction, as these parameters may reflect axonal membrane status. The study examines whether transverse diffusivity could be useful in assessing white matter infarcts of various ages. METHODS: Diffusion tensor imaging data from 44 adult patients (34 men, 10 women, aged 46 to 89 years, mean = 70.3) with acute white matter infarction (1–168 h) of the internal capsule were analysed. Relative eigenvalues were calculated as: (λipsi–λcontra)/λcontra. Lesions were classified based on theoretically expected evolution of diffusivity over time as follows: stage I, FA higher than the contralesional region of interest (ROI); stage II, diffusivity lower than the contralesional side for all eigenvalues; stage III, one of two transverse eigenvalues (λ2or λ3) higher than the contralesional ROI. RESULTS: Stage I infarcts (n = 5) were found primarily within 24 h of the onset of symptoms, with one case found on the third day. Stage II infarcts were found most commonly within 24 h (n = 18), and fewer after 24 h. After the first day, the ratio of stage III infarcts increased significantly. Thus, diffusivity-based classification of white matter infarcts seems to show a chronological trend. CONCLUSIONS: Diffusion anisotropy may be useful for defining the biological tissue clock of white matter infarctions. [ABSTRACT FROM AUTHOR]

In patients with severe hypertension, chronic heart failure or a history of stroke, the lower limit of autoregulation of cerebral blood flow (CBF) is shifted to higher levels of blood pressure (BP) than those observed in healthy subjects. The aim of pharmacotherapy for hypertensive patients with an impaired autoregulation of CBF should be to reduce BP while preserving an appropriate CBF. In the present study, 16 hypertensive patients who had had an episode of stroke more than 4 weeks previously were administered the angiotensin II (AT1) receptor antagonist losartan at daily doses of 25-100?mg for 4 weeks. Systolic and diastolic blood pressures were recorded for 24?h using an ambulatory BP monitoring system. CBF in both hemispheres of the cerebrum and cerebellum was quantified using single photon emission tomography with N-isopropyl-p-[123I]iodoamphetamine. At baseline, CBF was 29.7±6.7?ml/min/100?g in the cerebrum and 31.5±7.5?ml/min/100?g in the cerebellum. At the end of treatment, BP was lower, while CBF increased by 7.7%in the cerebrum, and remained at the baseline level in the cerebellum. Thus, CBF was preserved despite the reduction in BP. We consider the use of losartan is advantageous for hypertensive patients with a history of stroke in whom autoregulation of CBF is potentially impaired.Journal of Human Hypertension (2004) 18, 693-699. doi:10.1038/sj.jhh.1001735 Published online 6 May 2004 [ABSTRACT FROM AUTHOR]