PURPOSE:To investigate the intersubject and intrasubject variability of the activated area in the visual cortex with functional MR imaging. METHODS: Double-section gradient-echo MR images were acquired at 1.5 T in 28 healthy volunteers using the fast low-angle shot (FLASH) technique. Visual stimulation was obtained with light-emitting diode (LED) goggles. Eighteen volunteers were studied twice. The size of the activated areas in the visual cortex and the increase in signal were measured. A reproducibility ratio for size (R size ) and for location (R overlap ) was calculated on a scale of 0.0 to 1.0. RESULTS: Activation was seen in 89% of the subjects. The size of the activated area was widely variable among subjects: mean, 460 Ϯ 284 mm 2 ; range, 0 to 1029 mm 2 in the first study in all volunteers. Signal increases ranged from 3.2% to 10.9%, with a mean of 6.6 Ϯ 1.7%. The mean values of intrasubject variability testing were R size ϭ 0.83 Ϯ 0.16 and R overlap ϭ 0.31 Ϯ 0.11. CONCLUSION: Functional MR imaging with the FLASH technique is useful in identifying certain cortical areas that have quite variable locations among subjects. This study provides reference data for the intrasubject and intersubject variability of the activation pattern of the visual cortex.

It has recently been suggested that most small (<15 mm) subcortical infarcts (SSI) of the centrum ovale (CO) are of lacunar type. We investigated this hypothesis in 255 consecutive patients with a first-ever ischemic stroke who were examined within 24 h after stroke onset and survived on day 10. Fifty-seven patients had CO-SSI: they were older and more likely to have a silent infarct, a lacunar syndrome, arterial hypertension, leuko-araiosis and SSI localized in the basal ganglia or internal capsule and less likely to have a nonlacunar syndrome. On multiple linear regression analysis, independent factors correlated with CO-SSI were the leuko-araiosis score and the presence of a silent infarct, diabetes mellitus and arterial hypertension. However, the presumed cause of the index stroke was large-vessel disease in 7 patients and heart disease in 16. Though we confirm that patients with CO-SSI are more likely to have risk factors for small-vessel disease, a complete diagnostic workup remains necessary in patients with such infarcts because other mechanisms account for one third of them.

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MC's are an increasing part of standard care for people with early dementia and other cognitive disorders.

Functional MRI (fMRI) of the visual cortex was evaluated in 42 sedated 18-month-old infants (mean corrected age; 31 males, 11 females) with or without periventricular leukomalacia (PVL). Data from 14 infants could not be evaluated because of movement artefacts. Ten of the remaining 28 infants showed no significant fMRI response upon visual stimulation. In 18 infants, a significant signal change upon stimulation was found in the visual cortex: in 17 a signal decrease and in one a signal increase. Functional changes were located mainly in the anterior part of the visual cortex. Seven of the 28 infants had normal MRI and 21 showed variable occipital PVL. An fMRI response was equally frequent in infants without PVL (4 of 7 infants) and with PVL (14 of 21 infants). In conclusion, fMRI was shown to be feasible in sedated infants. No correlation was found between functional activation and the presence or absence of occipital PVL. Type of fMRI response (signal decrease) and localization (anterior part of the visual cortex) are different from those seen in adults, probably reflecting a combination of sedation effects and immaturity of the visual system. At present, fMRI is a highly promising research tool; its clinical relevance still has to be established.

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