Fractional anisotropy correlates with auditory simple reaction time performance.

During the last two decades, modern imaging studies focused intensively on the broad field of reaction time paradigms and significantly enhanced the understanding of behavioral performance. However, interindividual variations of simple reaction time (SRT) have been barely investigated. In this study, we intended to identify neural correlates of interindividual variation in auditory SRT (aSRT) employing the Poffenberger paradigm with auditory stimuli, in order to investigate neural processing speed performance.

Iomazenil-single-photon emission computed tomography reveals selective neuronal loss in magnetic resonance-defined mismatch areas.

Background And Purpose: The mismatch of hypoperfused tissue on perfusion imaging and ischemic tissue on diffusion-weighted imaging is used as a surrogate marker for thrombolytic therapy in the extended time window. Mismatch tissue may recover completely, progress toward infarction, or proceed toward incomplete infarction with selective loss of cortical neurons. We used [(123)I]iomazenil-single-photon emission computed tomography (IMZ-SPECT) to characterize the neuronal integrity of reperfused "tissue at risk of infarction" that appeared morphologically intact on follow-up magnetic resonance imaging (MRI).

Magnetic resonance imaging and clinical patterns of patients with 'spectacular shrinking deficit' after acute middle cerebral artery stroke.

Background: Rapid resolution of neurological deficits after severe middle cerebral artery (MCA) stroke has been coined spectacular shrinking deficit (SSD). We studied clinical and MRI patterns in patients with SSD.

Methods: Patients with acute MCA stroke <6 h were examined by stroke MRI (perfusion- and diffusion-weighted imaging (PWI, DWI), MR angiography (MRA)) at admission, day 1 and day 7.

Tissue at risk is overestimated in perfusion-weighted imaging: MR imaging in acute stroke patients without vessel recanalization.

Background And Purpose: The volume of decreased cerebral blood flow (CBF) in acute stroke perfusion-weighted imaging frequently overestimates final infarct volume. We hypothesized that surviving tissue exists even in patients without recanalization and tried to determine perfusion thresholds from initial MR imaging.

Methods: Stroke MR imaging including MR angiography was carried out at days 0, 1, and 7 after stroke onset in 19 patients without recanalization at least until day 1.

Cerebral perfusion impairment correlates with the decrease of CT density in acute ischaemic stroke.

Within the first 6 h of ischaemic stroke, changes on computed tomography (CT) scans are known as early ischaemic signs. We tested the hypothesis that the severity of perfusion impairment correlates with the degree of CT density decrease. Water uptake in ischaemic brain tissue results in a subtle decrease of CT density, and was quantified by delineation of the corresponding decrease of the apparent diffusion coefficient (ADC).

Transient ischemic attacks before ischemic stroke: preconditioning the human brain? A multicenter magnetic resonance imaging study.

Background And Purpose: We investigated whether transient ischemic attacks (TIAs) before stroke can induce tolerance by raising the threshold of tissue vulnerability in the human brain.

Methods: Sixty-five patients with first-ever ischemic territorial stroke received diffusion- and perfusion-weighted MRI within 12 hours of symptom onset. Epidemiological and clinical data, lesion volumes in T2, apparent diffusion coefficient (ADC) maps and perfusion maps, and cerebral blood flow and cerebral blood volume values were compared between patients with and without a prodromal TIA.

The influence of extra- and intracranial artery disease on the BOLD signal in FMRI.

Functional MRI is based on the vascular response due to neuronal activation. The underlying mechanism of fMRI is the blood oxygenation level-dependent (BOLD) effect-a complex interplay between changes in the cerebral metabolisation rate of oxygen (CMRO2), neurovascular coupling, and the resulting hemodynamic response. An intact neurovascular coupling is essential for the detection of the BOLD signal and it seems likely that a disturbed cerebrovascular reserve capacity (CVRC) alters the BOLD response.

Prediction of malignant middle cerebral artery infarction by early perfusion- and diffusion-weighted magnetic resonance imaging.

Background And Purpose: We tested the hypothesis that early diffusion- and perfusion-weighted MRI (DWI and PWI, respectively) allows the prediction of malignant middle cerebral artery (MCA) infarction (MMI).

Methods: Thirty-seven patients with acute MCA infarction and proximal vessel occlusion (carotid-T, MCA main stem) were studied by DWI, PWI, and MR angiography within 6 hours of symptom onset. Eleven patients developed MMI, defined by decline of consciousness and radiological signs of space-occupying brain edema.

Cerebral blood flow predicts lesion growth in acute stroke patients.

Background And Purpose: We sought to study the role of MRI-derived cerebral blood flow (CBF) measurements for the prediction of lesion development in acute stroke patients.

Methods: Thirty-two patients were treated with tissue plasminogen activator. Diffusion-weighted (DWI) and perfusion-weighted MRI, T2-weighted imaging, and MR angiography were performed before treatment (2.

Negative dip in BOLD fMRI is caused by blood flow--oxygen consumption uncoupling in humans.

The sensitivity of MRI for local changes in the deoxyhemoglobin concentration is the basis of the blood oxygen level dependent (BOLD) effect. Time-resolved fMRI studies during visual activation show an early signal intensity (SI) decrease indicating a short lasting uncoupling of oxygen consumption and cerebral blood flow (CBF) before a SI increase due to the overcompensating hemodynamic response occurs. Normal neuronal activity may be preserved despite absent vascular responsiveness.