Diffusion-weighted imaging predicts cognitive impairment in multiple sclerosis

Following a previous study with diffusion tensor imaging, we investigated the correlation between diffusion-weighted imaging (DWI) and cognitive dysfunction in multiple sclerosis (MS). We studied 60 MS patients (mean age 45.8+/-9.0 years) using 1.5-T MRI. Disease course was RR=40 and SP = 20. Mean disease duration was 12.8+/-8.7 years. Mean EDSS was 3.4+/-1.7. Whole brain, gray and white matter normalized volumes were calculated on 3D SPGR T1-WI using a fully automated Hybrid SIENAX method. Parenchymal mean diffusivity (PMD) maps were created after automated segmentation of the brain parenchyma and cerebrospinal fluid using T2-WI and DW images. Histogram analysis was performed and DWI indices of peak position (PP), peak height (PH), mean parenchymal diffusivity (MPD) and entropy were obtained. Neuropsychological (NP) evaluation emphasized auditory/verbal and visual/spatial memory, as well as processing speed and executive function. We found significant correlations between DWI and performance in all cognitive domains. Overall, stronger correlations emerged for MPD and entropy than other DWI measures, although all correlations were in the expected direction. The strongest association was between DWI entropy and performance on the Symbol Digit Modalities Test, which assesses processing speed and working memory (r = -0.54). Fisher r to z transformations revealed that DWI, gray matter (GMF) and whole brain (BPF) atrophy, T1-lesion volume (LV) and T2-LV all accounted for similar amounts of variance in NP testing. Stepwise regression models determined whether multiple MRI measures predicted unique additive variance in test performance. GMF (R2 = 0.35, F =30.82, P <0.01) and entropy (DeltaR2 =0.06, DeltaF=5.47, P <0.05) both accounted for unique variance in processing speed. Our data make a stronger case for the clinical validity of DWI in MS than heretofore reported. DWI has very short acquisition times, and the segmentation method applied in the present study is reliable and fully automated. Given its overall simplicity and moderate correlation with cognition, DWI may offer several logistic advantages over more traditional MRI measures when predicting the presence of NP impairment.     

Abnormal brain activation on functional MRI in cognitively asymptomatic HIV patients

BACKGROUND/OBJECTIVES: A previous fMRI study demonstrated increased brain activation during working memory tasks in patients with HIV with mild dementia. The current study aims to determine whether patients who are HIV-1 positive and have normal cognitive function also show increased brain activation on fMRI. METHODS: Blood oxygenation level-dependent (BOLD) fMRI was performed in 10 patients with HIV (CD <500) and 10 age-, sex-, education-, and handedness-matched seronegative subjects. Each subject performed a battery of neuropsychological tests and fMRI with three tasks (0-back, 1-back, and 2-back) that required different levels of attention for working memory. RESULTS: Compared with control subjects, patients with HIV showed greater magnitude of brain activation (BOLD signal intensity changes, p 相似文献   

The joint effect of aging and HIV infection on microstructure of white matter bundles

Recent evidence suggests the aging process is accelerated by HIV. Degradation of white matter (WM) has been independently associated with HIV and healthy aging. Thus, WM may be vulnerable to joint effects of HIV and aging. Diffusion‐weighted imaging (DWI) was conducted with HIV‐seropositive (n = 72) and HIV‐seronegative (n = 34) adults. DWI data underwent tractography, which was parcellated into 18 WM tracts of interest (TOIs). Functional Analysis of Diffusion Tensor Tract Statistics (FADTTS) regression was conducted assessing the joint effect of advanced age and HIV on fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) along TOI fibers. In addition to main effects of age and HIV on WM microstructure, the interactive effect of age and HIV was significantly related to lower FA and higher MD, AD, and RD across all TOIs. The location of findings was consistent with the clinical presentation of HIV‐associated neurocognitive disorders. While older age is related to poorer WM microstructure, its detrimental effect on WM is stronger among HIV+ relative to HIV? individuals. Loss of WM integrity in the context of advancing age may place HIV+ individuals at increased risk for brain and cognitive compromise.     

Combined diffusion and perfusion MRI with correlation to single-photon emission CT in acute ischemic stroke. Ischemic penumbra predicts infarct growth.

BACKGROUND AND PURPOSE: More effective imaging methods are needed to overcome the limitations of CT in the investigation of treatments for acute ischemic stroke. Diffusion-weighted MRI (DWI) is sensitive in detecting infarcted brain tissue, whereas perfusion-weighted MRI (PWI) can detect brain perfusion in the same imaging session. Combining these methods may help in identifying the ischemic penumbra, which is an important concept in the hemodynamics of acute stroke. The purpose of this study was to determine whether combined DWI and PWI in acute (<24 hours) ischemic stroke can predict infarct growth and final size. METHODS: Forty-six patients with acute ischemic stroke underwent DWI and PWI on days 1, 2, and 8. No patient received thrombolysis. Twenty-three patients underwent single-photon emission CT in the acute phase. Lesion volumes were measured from DWI, SPECT, and maps of relative cerebral blood flow calculated from PWI. RESULTS: The mean volume of infarcted tissue detected by DWI increased from 46.1 to 75.6 cm(3) between days 1 and 2 (P<0.001; n=46) and to 78.5 cm(3) after 1 week (P<0.001; n=42). The perfusion-diffusion mismatch correlated with infarct growth (r=0. 699, P<0.001). The volume of hypoperfusion on the initial PWI correlated with final infarct size (r=0.827, P<0.001). The hypoperfusion volumes detected by PWI and SPECT correlated significantly (r=0.824, P<0.001). CONCLUSIONS: Combined DWI and PWI can predict infarct enlargement in acute stroke. PWI can detect hypoperfused brain tissue in good agreement with SPECT in acute stroke.     

Infarct volume on apparent diffusion coefficient maps correlates with length of stay and outcome after middle cerebral artery stroke

BACKGROUND: Diffusion-weighted MRI (DWI) can depict acute ischemia based on decreased apparent diffusion coefficient (ADC) values. ADC maps, unlike DWI (which have contributions from T2 properties), solely reflect diffusion properties. Recent studies indicate that severity of neurological deficit corresponds with degree of ADC alteration. PURPOSE: To determine whether infarct volume on ADC maps correlates with length of hospitalization and clinical outcome in patients with acute ischemic middle cerebral artery (MCA) stroke. STUDY POPULATION: Forty-five consecutive patients with acute (3 SDs below the average ADC value of a contralateral control region. Infarct volume was correlated with length of hospitalization and 6-month outcome assessed with Glasgow Outcome Scale (GOS), Modified Rankin Score (mRS), Barthel Index (BI) and a dichotomized outcome status with favorable outcome defined as GOS 1, mRS or=95. RESULTS: Infarct volume on ADC maps ranged from 0.2 to 187 cm(3) and was significantly correlated with length of hospitalization (p < 0.001, r = 0.67). Furthermore, ADC infarct volume was significantly correlated with GOS (r = 0.73), mRS (r = 0.68), BI (r = 0.67) and outcome status (r = 0.65) (each p < 0.001). Multiple logistic regression revealed a statistically significant correlation between ADC infarct volume and outcome status (p < 0.05), but none for Canadian Neurological Scale score, age and gender (p >0.05 each). CONCLUSION: Infarct volume measured by using a quantitative definition for infarcted tissue on ADC maps correlated significantly with length of hospitalization (as a possible surrogate marker for short-term outcome) and functional outcome after 6 months. ADC infarct volume may provide prognostic information for patients with acute ischemic MCA stroke.     

MR perfusion imaging reveals regions of hypoperfusion associated with aphasia and neglect

OBJECTIVE: To evaluate diffusion-weighted imaging (DWI) and MR perfusion imaging (MRPI) as tools for identifying regions of infarct and hypoperfusion associated with aphasia and neglect in hyperacute stroke. Secondary goal: to establish a functional correlate of a radiologically defined "ischemic penumbra." METHODS: Forty subjects underwent DWI, MRPI, and standardized tests for lexical deficits or hemispatial neglect within 24 hours of stroke onset or progression. Ten patients had repeat DWI, MRPI, and cognitive testing after 3 days (in some cases after reperfusion therapy). Pearson correlations between error rate on cognitive testing and volume of abnormality on DWI versus MRPI were determined at each time period, and regions of hypoperfusion corresponding to specific cognitive deficits were identified. RESULTS: Error rate was more strongly correlated with volume of hypoperfused tissue on MRPI (r = 0.65 to 0.93; p < 0.01 to p < 0.0003) than with volume of lesion on DWI (r = 0.54 to 0.75; p = 0.14 to p < 0.01) for dominant and nondominant hemisphere stroke, at each time point. Forty-eight percent of aphasic patients and 67% of those with hemispatial neglect had either no infarct or only small subcortical infarct on DWI, but had focal cortical hypoperfusion. Patients who had successful reperfusion therapy showed resolution of the hypoperfused territory beyond the infarction on repeat MRPI and showed resolution of corresponding deficits. CONCLUSIONS: MRPI shows regions of hypoperfused cortex associated with lexical deficits or hemispatial neglect, even when DWI shows no infarct or only small subcortical infarct. MRPI-DWI mismatch indicates regions of functionally salvageable tissue.     

Highly active antiretroviral therapy reverses brain metabolite abnormalities in mild HIV dementia.

OBJECTIVE: To determine whether cerebral metabolite abnormalities normalize with highly active antiretroviral therapy (HAART). BACKGROUND: Patients with HIV-cognitive motor complex (HIV-CMC) show cerebral metabolite abnormalities in the early stages of dementia. METHODS: Sixteen patients with HIV-CMC were evaluated before and after HAART, and compared with 15 HIV-negative healthy volunteers. Cerebral metabolite ratios and concentrations in the frontal lobe and basal ganglia were measured using proton MRS (1H MRS). RESULTS: In 14 of 16 patients who tolerated HAART, CD4 count increased by 133+/-101 cells/mm3 (p = 0.0003), HIV Dementia Scale score increased by 1.8+/-2.4 points (p = 0.02), and AIDS dementia complex (ADC) stage decreased by 0.54+/-0.54 points (p = 0.003). The initially increased choline/creatine (CHO/CR) reversed in the midfrontal cortex (-8.0%; p = 0.02) and in the basal ganglia (-14.7%; p = 0.01). The initially elevated myoinositol (MI)/CR and myoinositol concentration [MI] in the basal ganglia also decreased (MI/CR: -14.1%; p = 0.005; [MI]: 11.8%; p = 0.02), along with normalization of [MI] in the frontal white matter (11.4%; p = 0.05). Furthermore, the change in [MI] in the frontal white matter correlated with the change in CD4 count (r = -0.67, p = 0.03) and with the change in ADC stage (p = 0.04). CONCLUSIONS: HAART improves HIV-CMC in addition to systemic measures of HIV infection. 1H MRS detects improvement of brain injury measured by cerebral metabolites, particularly the glial marker [MI], in patients with early HIV-CMC after HAART. In addition, the degree of improvement in clinical severity of HIV-CMC is related to the degree of recovery with [MI].     

Cognitive correlates of cerebral white matter lesions and water diffusion tensor parameters in community-dwelling older people

BACKGROUND: The biological basis of cognitive ageing is unknown. One underlying process might be disruption of white matter tracts connecting cortical regions. White matter lesions (WML) seen on structural MRI may disrupt cortical connections, but diffusion tensor MRI (DT-MRI) parameters - mean diffusivity () and fractional anisotropy (FA) - may reflect more subtle changes in white matter integrity. Here the relationships between WML load, DT-MRI parameters and cognition in a large cohort of elderly subjects with a very narrow age range were investigated. METHODS: 105 community-dwelling volunteers underwent MRI and neuropsychological assessment. Seventy-two (68.6%) were female, and their mean age was 78.4 (SD 1.5) years. Scans were rated for WML load. and FA were measured from regions of interest in normal-appearing frontal and occipital white matter, and centrum semiovale. RESULTS: and FA differed significantly among the three brain regions studied (p < 0.01). increased with age (r = 0.22 to 0.35, p < 0.03), and was negatively correlated with FA (r = -0.20 to -0.51, p < 0.05) in all three regions. There was a trend towards increased WML load correlating with poorer cognitive function, and this was statistically significant for the Mini-Mental State Examination (rho = -0.23, p = 0.02). was generally negatively correlated with cognitive test score, and FA was positively correlated. This pattern was more consistent for than for FA, and particularly for verbal fluency (: r = -0.22 to -0.27, p < 0.03), which measures executive function. CONCLUSIONS: DT-MRI parameters, in particular , are sensitive to early ultrastructural changes underlying cognitive ageing. Executive function may be the cognitive domain most sensitive to age-related decline in white matter tract integrity.     

'Importance sampling' in MS: use of diffusion tensor tractography to quantify pathology related to specific impairment

Specific neurological impairments in multiple sclerosis (MS) are dependent on the pathology in clinically eloquent areas of the central nervous system. We aimed to use diffusion tensor fiber tracking to identify the pyramidal tracts and corpus callosum in MS patients, measure the apparent diffusivity within the tracts, and evaluate whether this would correlate with relevant disability scores. Dual-echo and diffusion tensor magnetic resonance imaging (DT-MRI) brain scans were obtained from 29 patients with relapsing remitting MS, and 13 age and gender matched normal controls. Voxels from pyramidal tracts and corpus callosum were automatically identified using a tractography based algorithm. Mean apparent diffusion coefficient (ADC(av)) was measured for these tracts. Scores of Expanded Disability Status Scale (EDSS) and Paced Auditory Serial Addition Test (PASAT) were obtained. The median EDSS score was 2.5 (inter-quartile range 2-3.25). The ADC(av) in the pyramidal tracts (p=0.02) and corpus callosum (p=0.0004) in patients was significantly higher than in controls. Pyramidal tracts ADC(av) was correlated with pyramidal FSS (r=0.5, p=0.008). Corpus callosum ADC(av) was correlated with PASAT (r=-0.58, p=0.001). Global T2 lesion volume did not correlate with the EDSS, but correlated with ADC(av) of the pyramidal tracts (r=0.6, p=0.0007) and corpus callosum (r=0.8, p<0.0001). T2 lesion volume within the pyramidal tracts and corpus callosum correlated with ADC(av) in the pyramidal tracts (r=0.6, p=0.0009) and corpus callosum (r=0.65, p=0.0002) respectively, but not with pyramidal FSS or PASAT score. DT-MRI quantifies pathology in specific white matter tracts and may increase the specificity of MRI in monitoring progression of motor and cognitive deficits in MS.     

A Progressive Neurologic Disorder with Multiple CNS Lesions: A Neuroimaging Clinicopathologic Correlation

A 51‐year‐old man with a diagnosis of myelodysplasia and non‐Hodgkin's lymphoma underwent an unmatched allogenic bone marrow transplantation and was treated posttransplant with chronic immunosuppressive medication. Eight months following transplantation, he presented with progressive dysarthria, cognitive and visual decline. Evaluation included brain magnetic resonance (MR) imaging demonstrating multifocal areas of increased T2 and FLAIR (fluid attenuated inversion recovery) signals involving the left frontal, parietal, and occipital lobes. The MR lesions demonstrated diffuse increased signal on DWI (diffusion‐weighted images) and normal to low signal on ADC (apparent diffusion coefficients). Contrast‐enhanced T1 images were unremarkable. Lumbar puncture revealed a mild elevation in cerebrospinal fluid (CSF) protein. CSF PCR assay for viral DNA fragments were negative on two occasions. Serum serology for HIV was negative as well. A brain biopsy was subsequently performed. The clinical and neuroimaging differential diagnoses as well as neuropathologic correlation are presented.     

Neuroimaging of infections of the central nervous system

Neuroimaging plays a crucial role in the diagnosis and therapeutic management of neurologic infections. This article summarizes imaging findings in brain abscesses, ventriculitis, viral diseases, and opportunistic infections. In cases of uncomplicated meningitis, cranial computed tomography is sufficient to exclude brain edema, hydrocephalus, and skull base pathology. Magnetic resonance imaging (MRI) is superior in depicting complications (e.g., empyema, vasculitis). Diffusion-weighted imaging (DWI) shows parenchymal complications of meningitis earlier and is of help in differentiation of pyogenic abscess from other ring-enhancing lesions. Proton magnetic resonance spectroscopy can produce specific peak-patterns in cases of abscess, such as the presence of lactate and cytosolic amino acids. In toxoplasmosis, DWI may help to differentiate from lymphoma, showing no restriction of water diffusion. In patients with viral encephalitis, DWI allows earlier lesion detection. MRI has revolutionized the rapid diagnosis of spinal abscess.     

Can diffusion‐weighted imaging be used as a tool to predict seizures in patients with PLEDS?

It is unclear which patients with PLEDs will have associated seizures and therefore will need to be treated aggressively with antiepileptic medications. We present a prospective observational study of ten consecutive non‐anoxic patients with PLEDs based on continuous 24‐hour EEG monitoring. According to the EEG, five of the patients had seizures associated with PLEDs and five had PLEDs but no seizures. The aetiology included: neoplasm (n=1), cortical dysplasia (n=1), acute head trauma (n=1), encephalomalacia related to healed abscess (n=1), intra‐parenchymal haemorrhage (n=1), and no structural lesion (n=5). All patients underwent brain MRI using diffusion‐weighted imaging (DWI). We found that the five patients who had seizures with PLEDs on continuous EEG had restricted diffusion on DWI. In contrast, the five patients who had PLEDs but no seizures on continuous EEG did not show a restricted diffusion pattern on DWI. We will continue to prospectively assess DWI findings in this group of patients and encourage other centres to also review similar data. If our observation is replicated, this would indicate that restricted diffusion on brain MRI may be a useful marker to identify patients with PLEDs on their EEG who are likely to have associated seizures.     

Diffusion-weighted magnetic resonance imaging of white matter in bipolar disorder: a pilot study

OBJECTIVE: Diffusion-weighted magnetic resonance imaging (MRI) has shown increased sensitivity in detecting brain white matter disease compared to traditional T2-weighted MRI. Diffusion-weighted imaging (DWI) can quantitatively assess the microstructural integrity of white matter using the average apparent diffusion coefficient (ADC(av)), a measure of the extent to which water molecules move freely within tissue. On the basis of numerous studies suggesting white matter disease in bipolar patients, particularly patients with more severe illness, this study aimed to test the utility of DWI in assessing the white matter integrity of bipolar patients with severe illness. METHODS: The existing MRI scans of eight bipolar patients and eight age-matched controls with neurological illness were examined retrospectively. ADC(av) values for pixels within white matter regions of interest (ROIs) were calculated and used to plot ADC(av) frequency histograms for each ROI. Mean ADC(av) values for the two groups were then compared by ANCOVA. RESULTS: The bipolar mean ADC(av) (0.855 +/- 0.051 x 10(-3) mm2/s) for combined white matter ROIs significantly exceeded that of controls (0.799 +/- 0.046 x 10(-3) mm2/s), while covarying for age (F = 4.47, df = 3, p = 0.025). CONCLUSIONS: This is the first report of an elevated ADC(av) in the white matter of a group of patients with bipolar disorder. In this group of patients with severe illness, increased white matter ADC(av) suggests microstructural changes consistent with decreased white matter integrity. DWI may be an additional, useful tool to assess white matter abnormalities in bipolar disorder.     

Diffusion tensor magnetic resonance imaging at 3.0 tesla shows subtle cerebral grey matter abnormalities in patients with migraine

BACKGROUND AND OBJECTIVE: Diffusion tensor (DT) magnetic resonance imaging (MRI) has the potential to disclose subtle abnormalities in the brain of migraine patients. This ability may be increased by the use of high field magnets. A DT MRI on a 3.0 tesla scanner was used to measure the extent of tissue damage of the brain normal appearing white (NAWM) and grey matter in migraine patients with T2 visible abnormalities. METHODS: Dual echo, T1 weighted and DT MRI with diffusion gradients applied in 32 non-collinear directions were acquired from 16 patients with migraine and 15 sex and age matched controls. Lesion load on T2 weighted images was measured using a local thresholding segmentation technique, and brain atrophy assessed on T1 weighted images using SIENAx. Mean diffusivity and fractional anisotropy histograms of the NAWM and mean diffusivity histograms of the grey matter were also derived. RESULTS: Brain atrophy did not differ between controls and patients. Compared with healthy subjects, migraine patients had significantly reduced mean diffusivity histogram peak height of the grey matter (p=0.04). No diffusion changes were detected in patients' NAWM. In migraine patients, no correlation was found between T2 weighted lesion load and brain DT histogram derived metrics, whereas age was significantly correlated with grey matter mean diffusivity histogram peak height (p=0.05, r=-0.52). CONCLUSIONS: DT MRI at high field strength discloses subtle grey matter damage in migraine patients, which might be associated with cognitive changes in these patients.     

Decreased homovanilic acid in cerebrospinal fluid correlates with impaired neuropsychologic function in HIV-1-infected patients

To determine whether dopamine metabolism is abnormal in HIV infected patients and whether dopamine metabolism abnormalities are related to specific neuropsychologic characteristics in HIV-infected patients, we measured cerebrospinal fluid (CSF) levels of homovanilic acid (HVA), the primary dopamine metabolite, in 10 HIV-infected patients and compared it to HVA levels in CSF in a group of 13 healthy control subjects. HIV-infected patients were also assessed with a battery of neuropsychologic tests and HVA levels were then correlated with performance on specific neuropsychologic tests. The mean (+/-SD) HVA level in CSF was 100.9 +/- 29.3 nmol/L in the HIV-infected study group and 230.5 +/- 50.0 nmol/L in the non-HIV-infected control group (p < 0.0001). The decrease in concentrations of HVA in CSF correlated with impairment on performance on neuropsychologic testing (Spearman r = 0.67; p = 0.03). When the relationship between HVA levels and specific cognitive domains was evaluated, we observed trends for positive correlation between HVA levels and tests that measure motor speed (r = 0.59; p = 0.074) and those testing attention, concentration, and executive control (r = 0.54; p = 0.108). There was no relationship between performance on memory tests and CSF HVA levels (r = -0.0061; p = 0.987). These results further support the hypothesis that dopaminergic dysfunction plays an important role in the pathogenesis of AIDS dementia complex (ADC) and suggest that specific motor and cognitive abnormalities may be related to depressed dopaminergic activity. This may have important implications for the development of treatments or preventive strategies for ADC.     

Principles of diffusion-weighted MR imaging and application to clinical neurology]

Diffusion-weighted Imaging (DWI) is a advantageous method for early detection of cerebral ischemia. DWI with echo-planar sequence (EP-DWI) offers multisectional images sensitive to cytotoxic edema in a very short aquisition time and is almost free from motion artifact. However, the susceptibility artifacts and low spatial resolution of EP-DWI must be improved. In estimation of DWI, influence of T2 must be considered, because DWI is almost always based on T2-weighted imaging. DWI is applied to other cerebral disorders such as degenerative and demyelinating disease, infectious disease, tumors or so. In order to demonstrate water diffusion precisely, diffusion tensor imaging (DTI) must be introduced and applied to anisotropy indices such as fractional anisotropy (FA) and depiction of neurofiber direction, tractography. Measurements of FA in various degenerative diseases may contribute to differentiation in normal appearing white matter. Diffusion tensor tractography may provide more information about relationship of major white matter tract such as corticospinal tract with brain lesion. Furthermore, DWI and DTI are expected to demonstrate diffusion of protons of aminoacids such as choline, creatine, NAA and provide more pertinent information of regional pathologic state of the brain in future.     

Acute and chronic changes of the apparent diffusion coefficient in neurological disorders--biophysical mechanisms and possible underlying histopathology

Diffusion-weighted imaging (DWI) of the brain has become a valuable tool for the reliable detection and diagnosis of several neurological disorders. Although DWI is in wide use in daily practice, the underlying biophysical mechanisms that contribute to changes in the apparent diffusion coefficient (ADC) are still under discussion. Alterations in the apparent water diffusion rate reflect pathological changes in the brain tissue state, via changes in the diffusion characteristics of the intra- and extra-cellular water compartments including restricted diffusion, water exchange across permeable boundaries, the concept of the extra-cellular tortuosity and the intra- and extra-cellular volume fraction. A reduction of the ADC has been detected in acute neurological diseases, while disease states associated with dominant acute vasogenic edema formation or chronic tissue destruction usually show elevations of the ADC. Compromise of energy metabolism is likely to contribute to a reduction of the ADC while already minor structural disintegration may contribute to elevations of the ADC.     

Decreased CXCL12 (SDF-1) plasma levels in early Alzheimer's disease: a contribution to a deficient hematopoietic brain support?

The chemokine CXCL12 (also known as stromal cell-derived factor 1, SDF-1) controls many aspects of bone marrow-derived stem cell functions and has been associated with neurogenesis as well with recruitment of brain resident and non-resident circulating cells towards sites of lesion in the central nervous system (CNS). Disrupting this line of chemokine-mediated intercellular communication may contribute to the pathogenesis of Alzheimer's disease (AD). In this study, decreased CXCL12 plasma levels in patients with early AD (p = 0.003) were found, which significantly inversely correlated with CSF tau protein levels (r = -0.373; p = 0.042) and positively with CXCL12 CSF levels (r = 0.429; p = 0.018) and with changes of cognitive functions over the time period of 15 months (r = 0.583; p = 0.009). Our findings indicate a lack of chemotactic activity in early AD and support the view of a deficient regenerative hematopoietic brain support in early AD with putative pathogenic and therapeutic relevance.     

Brain diffusion after single seizures

PURPOSE: Diffusion-weighted magnetic resonance imaging (DWI) after focal status epilepticus has demonstrated focal alterations of the apparent diffusion coefficient (ADC) in the epileptogenic zone. We hypothesized that localized dynamic alterations of brain diffusion during the immediate postictal state will be detectable by serial DWI and correlate with the epileptogenic zone. METHODS: Nine adult patients (four men, five women) with medically intractable epilepsy were prospectively examined with a total of 25 DWI scans taken 2-210 min after a seizure. RESULTS: The interictal ADC was significantly (p < 0.05) elevated in the ictogenic hippocampus in all patients with temporal lobe epilepsy. The following postictal changes of the ADC were seen: (a) decreases by maximally 25-31%, which were most pronounced in the epileptogenic zone (n = 2); (b) generalized ADC changes after generalized seizures (n = 1) or prolonged complex partial seizures (n = 2); (c) no major changes after short-lived seizures or if the time to first DWI scan was >15 min or both (n = 3); and (d) widespread bilateral ADC increases after a flumazenil-induced seizure (n = 1). CONCLUSIONS: ADC changes seen during serial postictal DWI are complex and appear to reflect origin and spread of the preceding seizure. A delineation of the epileptogenic zone appears to be possible only in complex-partial seizures of >60 s duration that do not secondarily generalize.     

Diagnostic Value of Apparent Diffusion Coefficient Hyperintensity in Selected Patients With Acute Neurologic Deficits

BACKGROUND AND PURPOSE: A pattern of decreased intensity on apparent diffusion coefficient (ADC) maps is useful in the early detection of ischemic brain injury. Less information exists with regard to patients with acute neurologic deficits in whom there is abnormal conventional magnetic resonance imaging (MRI) and increased ADC intensity. METHODS: The authors identified 13 patients with acute neurologic deficits who underwent diffusion MRI and had calculated ADC maps demonstrating hyper-intensity in regions characterized by computed tomography hypodensity and MRI T2 hyperintensity. The initial and follow-up imaging characteristics and clinical syndromes were recorded. RESULTS: Clinical syndromes included hypertensive encephalopathy, posterior leukoencephalopathy, hyperperfusion following carotid endarterectomy, venous sinus thrombosis, HIV encephalopathy, and brain tumor. Diffusion-weighted imaging (DWI) was hyperintense in 3 of 13 patients, isointense in 4 of 13 patients, heterogeneous in 3 of 13 patients, and hypointense in 3 of 13 patients. The ADC values in these regions were significantly higher than those in control regions (P < .0001). At early follow-up, MRI abnormalities resolved completely in 3 of 13 patients and partially in 9 of 13 patients. MRI abnormalities were unchanged in 1 patient. CONCLUSIONS: In the evaluation of patients with acute neurologic deficits, ADC hyperintensity may identify a subset of patients with vasogenic edema of nonischemic etiology. Frequently, these conditions are potentially reversible if appropriately managed. DWI and conventional images alone are not sufficient to identify these neurologic conditions.