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At least 865 records · Page 48Linked to original sources
PubMed2003

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.

Aged↗
PubMed1999

[A case of spontaneous intracranial hypotension with a remarkable leakage and collection of CSF].

We reported a case of spontaneous intracranial hypotension (SIH) who exhibited a remarkable leakage and collection of CSF in the spinal vertebral column. A 28-year old woman suddenly developed a severe occipital headache and vomiting. She had no headache while lying, but the headache was severe while sitting and standing. She had no recent history of trauma, but she fell down and hit her neck while skiing 6 months before the onset of headache. Neurological examination, urine and blood tests failed to reveal abnormal findings. Lumbar puncture showed a very low CSF pressure of 10 mmHg. Brain MRI demonstrated diffuse thickening and contrast enhancement of the meninges and spinal MRI displayed a CSF collection in the epidural spaces. RI cisternography showed a CSF leakage and an early accumulation of isotope in the kidneys and urinary bladder. Myelography revealed a CSF leakage at the C2 level from the spinal sac out to the extravertebral tissue and a CSF collection in the epidural spaces in the cervical to lumbar spinal canal. The root sleeves were also visualized by the CSF leakage. Thus, we demonstrated in this patient with SIH the location of CSF leakage at C2 dural sac and an extensive collection of leaked CSF in the epidural spaces, which apparently played a role in the occurrence of SIH.

Adult↗
PubMed2002

Medial medullary infarction: a role of diffusion-weighted magnetic resonance imaging for stroke rehabilitation.

We report a patient with medial medullary infarction who could be diagnosed in an early stage, and we discuss the role of diffusion-weighted magnetic resonance imaging (MRI) for stroke rehabilitation. In the case of our patient, the infarction was difficult to diagnose because the patient had atypical features and a past history of head injury. Nonetheless, we could diagnose the medial medullary infarction easily using diffusion MRI within several hours of onset. Then, a rehabilitation program was started the day after onset. We believe that diffusion MRI can be used as a useful method for very early stage diagnosis and to execute rehabilitation for early stroke patients.

Activities of Daily Living↗
PubMed2003

Gliomatosis cerebri evaluated by 18Falpha-methyl tyrosine positron-emission tomography.

Gliomatosis cerebri is a rare condition in which an infiltrative glial neoplasm spreads through the brain with preservation of the underlying structure. CT and MRI show diffuse abnormal density or signal, without mass effect, and because these findings are nonspecific, it is difficult to make a definitive diagnosis. Our purpose was to assess the usefulness of a new tumour-detecting amino acid tracer for positron-emission tomography (PET), L-[3-(18)F] alpha-methyl tyrosine (FMT), in patients with gliomatosis cerebri. We performed FMT PET, fluorodeoxyglucose FDG PET and MRI eight patients with gliomatosis cerebri and six with non-neoplastic disease, whose MRI also showed diffuse high signal on T2-weighted images. Standardised uptake (SUV) of FMT and FDG in the area of gliomatosis was obtained and the tumour-to-normal cortex (T/N) ratio of this was compared. The tumours were shown on FMT PET as areas of increased uptake, except in one patient with severe intracranial hypertension. There were significant differences between the SUV of FMT and the T/N ratio of FMT in patients and in controls (both P<0.01), and between the T/N ratio of FMT and FDG in patients ( P<0.01). Increased uptake of FMT PET strongly suggests neoplasia. FMT PET is valuable for differentiating gliomatosis cerebri from non-neoplastic diseases showing similar diffuse high signal on T2-weighted images and little contrast enhancement.

Adult↗
PubMed2004

Quantitative analysis of diffusion tensor orientation: theoretical framework.

Diffusion-tensor MRI (DT-MRI) yields information about the magnitude, anisotropy, and orientation of water diffusion of brain tissues. Although white matter tractography and eigenvector color maps provide visually appealing displays of white matter tract organization, they do not easily lend themselves to quantitative and statistical analysis. In this study, a set of visual and quantitative tools for the investigation of tensor orientations in the human brain was developed. Visual tools included rose diagrams, which are spherical coordinate histograms of the major eigenvector directions, and 3D scatterplots of the major eigenvector angles. A scatter matrix of major eigenvector directions was used to describe the distribution of major eigenvectors in a defined anatomic region. A measure of eigenvector dispersion was developed to describe the degree of eigenvector coherence in the selected region. These tools were used to evaluate directional organization and the interhemispheric symmetry of DT-MRI data in five healthy human brains and two patients with infiltrative diseases of the white matter tracts. In normal anatomical white matter tracts, a high degree of directional coherence and interhemispheric symmetry was observed. The infiltrative diseases appeared to alter the eigenvector properties of affected white matter tracts, showing decreased eigenvector coherence and interhemispheric symmetry. This novel approach distills the rich, 3D information available from the diffusion tensor into a form that lends itself to quantitative analysis and statistical hypothesis testing.

Adolescent↗
PubMed2006

Human growth hormone-related iatrogenic Creutzfeldt-Jakob disease with abnormal imaging.

BACKGROUND: Although more than 160 cases of iatrogenic Creutzfeldt-Jakob disease (iCJD) from human growth hormone (hGH) treatment have been documented, to our knowledge abnormal cerebellar findings on magnetic resonance imaging (MRI) have not been reported. OBJECTIVE: To report a case of hGH-related iCJD with abnormal cerebellar MRI findings on fluid-attenuated inversion recovery (FLAIR) and diffusion-weighted MRI (DWI). DESIGN: Case report. SETTING: Outpatient neurology clinic at a university medical center. PATIENT: A 33-year old man who had subacute gait ataxia and blurred vision. RESULTS: Beginning 19 years prior, this patient had received cadaveric pituitary-derived hGH treatment for at least 5 years. Magnetic resonance imaging revealed FLAIR and DWI abnormalities, particularly in the cerebellum. He died 7 months after disease onset of autopsy-confirmed iCJD. Pathological changes corresponded largely to MRI findings. CONCLUSIONS: To our knowledge, this is the first case of hGH-related iCJD with FLAIR and DWI abnormalities within the cerebellum. As symptoms referable to the cerebellum occur early in iCJD, it suggests that these MRI sequences may allow earlier diagnosis of this form of prion disease.

Adult↗
PubMed2003

Application of diffusion tensor imaging to magnetic-resonance-guided brain tumor resection.

Interventional magnetic resonance imaging (MRI) continues to make a profound impact on the practice of neurosurgery. We describe a new MRI modality, diffusion tensor imaging (DTI), which uses the diffusion energy of water to map white matter fibers. DTI has been established in other disorders such as metabolic, demyelinating and ischemic diseases. We describe the use of DTI in identifying white matter tracts such as optic radiations and avoiding them intraoperatively in 2 children with low-grade glial tumors.

Adolescent↗
PubMed2001

[Creutzfeldt-Jakob disease: value of MRI].

PURPOSE: To define the role of MRI in the diagnosis of Creutzfeldt-Jakob disease (CJD). METHODS: 14 patients with suspected CJD were studied within 3 years. MRI findings were correlated with WHO established diagnostic criteria (clinical findings, EEG, CSF with 14-3-3 protein assay). RESULTS: 12 patients had CJD. One patient each suffered from Hashimoto's encephalitis and ALS dementia complex, respectively. Nine of 12 CJD patients had increased signal intensity of the striatum (n = 8), pulvinar thalami (n = 5) and/or cerebellar and cerebral cortex (n = 3), respectively. Signal intensity was most pronounced on FLAIR sequences; six patients were studied with diffusion-weighted MRI and showed impaired diffusion in these areas. Both patients without CJD did not show the abovementioned signal changes (sensitivity 75%, specificity and positive predictive value 100%, respectively). CONCLUSION: If patients with suspected CJD are studied with FLAIR and diffusion-weighted sequences, this disorder can reliably be proven or ruled out. Typical MRI findings narrow down the differential diagnosis and should be included in the WHO diagnostic criteria.

Adult↗
PubMed2002

[Reversible posterior leukoencephalopathy syndrome in two patients with microscopic polyarteritis nodosa].

We report here two cases (72-year-old woman, 77-year-old-woman) with perinuclear anti-neutrophil antibody (P-ANCA) positive microscopic polyarteritis nodosa (mPN). Both patients presented with generalized convulsion, consciousness disturbance and severe hypertension several days after the administration of high dose methylpredonisolone followed by oral predonisolone. CT brain scan showed hypodensity area on bilateral posterior lobes. MRI T2 weighted image and FLAIR image showed increased signal intensity on the occipital gray and white matter. Although diffusion weighted MRI disclosed slightly high signal intensity, apparent diffusion coefficient (ADC) value at the occipital gray and white matter remained normal or even elevated. These findings, which were consistent with vasogenic edema, lead us to diagnose them as suffering from reversible posterior leukoencephalopathy syndrome (RPLS). After the second administration of high dose methylpredonisolone, their symptoms and signs, together with the MRI findings, gradually improved. To our knowledge, this is the first report concerning RPLS in a patient with mPN.

Aged↗
PubMed2005

Dysmorphology and microstructural degradation of the corpus callosum: Interaction of age and alcoholism.

Chronic alcohol abuse is a ubiquitous health and societal problem, with a growing prevalence in the older population. Alcoholism is a source of substantial deterioration in brain tissue and has been consistently observed in vivo and postmortem in white matter. To quantify the potential compounded effect of age and alcoholism, we used conventional structural MRI and diffusion tensor imaging (DTI) to examine the macrostructural and microstructural integrity of the corpus callosum, one of the most prominent white matter structures of the brain, in 131 adults, age 27-75 years. Compared with the 74 controls, the 40 alcoholic men and 17 alcoholic women, who were abstinent from alcohol for an average of 3 months, showed similar patterns and extents of callosal shrinkage, which was greatest in the genu and body and less prominent in the splenium. Microstructural integrity was measured with DTI as fractional anisotropy, an index of intravoxel orientational coherence of white matter fibers, and bulk mean diffusivity, an index of the amount of intravoxel water motility. The macrostructural shrinkage was accompanied by abnormalities in anisotropy and diffusivity of the microstructural environment of these callosal regions, indicative of disruption of structural constituents of local brain white matter. Correlational analyses revealed an age-alcohol interaction, where older alcoholics had smaller genu and splenium and higher diffusivity in these regions than younger alcoholics. Significant correlations between regional MRI and DTI measures and performance on working memory, visuospatial ability, and gait and balance provided evidence for the functional ramifications of the callosal abnormalities in the alcoholics. Thus, despite abstinence from alcohol, the interaction of age and recent alcoholism history exerted a compounded untoward effect on callosal macrostructure and microstructure.

Adult↗
PubMed1999

Correction for eddy current induced Bo shifts in diffusion-weighted echo-planar imaging.

The importance of diffusion-weighted MRI in the assessment of acute stroke is well-recognized, and quantitative maps of the apparent diffusion coefficient (ADC) are now widely used. Echoplanar imaging provides a robust method of acquiring diffusion-weighted images free of motion artifact. However, initial experience with clinical MRI systems indicates that calculation of artifact-free ADC maps from a series of echo-planar diffusion-weighted images is not necessarily straight-forward. One of the problems is that frequency shifts resulting from eddy currents can cause misregistration of base diffusion-weighted images. In this study, an on-line correction method that overcomes this problem is described, and phantom and human images that demonstrate the validity of the technique are presented. The method uses a non-phase-encoded reference scan to correct the phase of each echo in the echo train, and can provide ADC maps that are free of misregistration artifacts, without the need for off-line postprocessing.

Anisotropy↗
PubMed1999

Increased extracellular brain water after coronary artery bypass grafting is avoided by off-pump surgery.

OBJECTIVE: To determine if coronary artery bypass graft (CABG) surgery without cardiopulmonary bypass (CPB) avoids the brain swelling known to occur after CPB, to quantify these brain water compartment changes, and to identify the water shifts as due to intracellular or extracellular water. DESIGN: Prospective, controlled, and blinded. SETTING: Cardiac surgical unit in a university teaching hospital. SUBJECTS: Patients scheduled for CABG who were assigned to conventional (n = 10) or off-pump (n = 7) surgery according to their coronary anatomy. INTERVENTIONS: Magnetic resonance imaging (MRI) examinations were performed 1 day before surgery and 1 hour and 1 week after CABG surgery. MAIN OUTCOME MEASURES: Extracellular and intracellular water homeostasis was described quantitatively by calculating the averaged apparent diffusion coefficient of brain water using diffusion-weighted MRI. Blinded visual ordering of the images from the three examinations was performed according to brain size using conventional MRI. RESULTS: The average diffusion coefficient of brain water increased 4.7%+/-1.5% immediately after CABG with CPB and normalized after 1 week but did not change after CABG without CPB. No focal ischemic changes were seen in either group, and no gross neurologic deficits were observed. Visual analysis showed consistent brain swelling after CPB and variable changes in those operated without CPB. CONCLUSION: Changes consistent with increased extracellular brain water seen after CABG with CPB were not observed in patients undergoing CABG without CPB. The clinical significance of brain water changes and increased brain water content after surgery with CPB remains undefined.

Brain↗
PubMed2004

Applications of diffusion/perfusion magnetic resonance imaging in experimental and clinical aspects of stroke.

The acute evaluation of stroke patients has undergone dramatic advances in the recent past. The increasing availability of novel magnetic resonance imaging (MRI) techniques, such as diffusion and perfusion MRI, provides a plethora of information to clinicians evaluating patients suspected of having an acute stroke. This review focuses on recent advances with experimental and clinical applications of perfusion and diffusion imaging and their utility in identifying potentially salvageable ischemic tissue in rat stroke model and stroke patients.

Animals↗
PubMed2002

Apparent diffusion of water, ions, and small molecules in the Xenopus oocyte is consistent with Brownian displacement.

The incoherent displacement of water in living tissues is of considerable interest because of the widespread use of diffusion-weighted MRI, for which image contrast is based on the water apparent diffusion coefficient (ADC). It has been hypothesized that the decrease in water ADC associated with brain injury is primarily due to a reduction in the ADC of water in the intracellular space. Xenopus oocytes permit direct measurement of ADC values for intracellular molecules, thereby providing insight into the nature of intracellular motion. In this study, the measured ADC values of small molecules and ions are shown to be primarily size-dependent, indicating that intracellular water motion in the oocyte is mainly Brownian displacement with little or no role for cytoplasmic streaming. Further, intracellular water ADC values show no dependence on diffusion time over a broad range (3.4-100 ms), suggesting that barriers to displacement are finely spaced (< or = 2-3 microm). The water diffusion shows some small anisotropy, suggesting that the cell has structure, giving water displacement a directional preference. The calculated intracellular apparent viscosity, which reflects the combined effects of barriers to motion, intermolecular binding, and fluid phase viscosity was 2.07 +/- 0.09 cP.

Animals↗
PubMedDate not supplied

Canavan disease: diffusion magnetic resonance imaging findings.

A 15-month-old boy with Canavan disease is reported in whom a restricted diffusion pattern on diffusion magnetic resonance imaging (MRI) (high signal on b = 1,000 mm2/s images and low apparent diffusion coefficient [ADC] values) was evident in the affected regions of the brain, including the peripheral white matter, globi pallidi, thalami, brainstem, dorsal pons, and dentate nuclei. The ADC values at these regions ranged from 0.42 to 0.56 x 10(-3) mm2/s compared with the normal ADC values from the uninvolved deep frontal white matter (0.68-0.92 x 10(-3) mm2/s). The known histopathologic features in Canavan disease include edematous and gelatinous brain tissue associated with diffuse vacuolization. Considering these and the diffusion MRI findings in this patient, it is likely that existence of a gel (gelatinous) state rather than the usual sol state of water molecules in the affected brain regions accounted for the restricted diffusion pattern in Canavan disease.

Brain↗
PubMed2003

CSF hypovolemia vs intracranial hypotension in "spontaneous intracranial hypotension syndrome".

OBJECTIVES: To investigate the role of CSF hypovolemia in spontaneous intracranial hypotension (SIH) syndrome because so-called SIH syndrome sometimes lacks intracranial hypotension. METHODS: Ten women (aged from 28 to 49 years) with characteristic orthostatic headache without a previous history of dural tear were investigated. In addition to gadolinium (Gd)-enhanced brain MRI, spinal MRI with and without Gd enhancement was performed. RESULTS: Gd-enhanced brain MRI demonstrated diffuse pachymeningeal enhancement in all patients. Sagittal T2-weighted spinal MRI revealed a variable amount of CSF in the extradural space in all patients. Sagittal T2-weighted MRI or axial Gd-enhanced T1-weighted MRI showed dilated epidural veins located in the high cervical portion in each patient. The intensity of dilatation of the epidural veins correlated significantly with the amount of CSF in the epidural space. This suggested that the Monro-Kellie doctrine was applicable in this circumstance. CONCLUSIONS: Since some patients with SIH syndrome have normal CSF pressure and since a downward displacement of the brain due to a reduction of the buoyant action of CSF may induce symptoms, CSF hypovolemia, not intracranial hypotension, may be the cause. Based on the Monro-Kellie doctrine, detecting leaked CSF and venous engorgement (epidural vein dilatation and pachymeningeal enhancement) is an important clue to diagnose so-called SIH syndrome. Dilatation of epidural veins suggests CSF hypovolemia in appropriate conditions.

Adult↗
PubMed1996

Clinical outcome in ischemic stroke predicted by early diffusion-weighted and perfusion magnetic resonance imaging: a preliminary analysis.

Perfusion and diffusion-weighted magnetic resonance imaging (MRI) can demonstrate, respectively, cerebral ischemia and ischemic brain injury in the first several hours after onset of symptoms, when proton density and T2-weighted MRI may appear normal. It is hypothesized that these techniques could distinguish regions destined for infarction from those that will not progress to infarction. We provide preliminary evidence from an analysis of 19 patients with severely disabling clinical deficits attributable to ischemia in at least an entire division of the middle cerebral artery, that initial perfusion and diffusion MRI were more accurate than conventional MRI in predicting no, partial or complete improvement--17 of 19 cases (p < 0.0001) versus 10 of 19 cases, respectively. In the subset of patients studied within 6 h of onset, diffusion/perfusion MRI was an even better predictor than conventional MRI--11 of 12 versus four of 12, respectively. In this small sample of patients with severe clinical deficits, perfusion and diffusion MRI were highly accurate in distinguishing those who would improve from those who would not. These results need to be confirmed in a larger prospective study, which may support a future role in the initial screening, selection, and evaluation of patients with stroke for acute pharmacologic interventions.

Brain Ischemia↗
PubMed2006

The effects of SNR on ADC measurements in diffusion-weighted hyperpolarized He-3 MRI.

The theoretical dependence of the mean and standard deviation of ADC values on signal-to-noise ratio (SNR) was derived and compared to measured values in porous phantoms and the lungs of human subjects using diffusion-weighted hyperpolarized helium-3 MRI. For SNR values below 15, mean ADC values were highly SNR-dependent due to a combination of noise and choice of noise thresholding. Above SNR values of 15 and for mean ADC values within ranges relevant for evaluating lung disease (<0.6 cm2/s), the mean ADC was largely independent of SNR. The standard deviation, by contrast, was highly dependent on SNR over a much larger range, but this dependence was well predicted by theory, suggesting the histogram of ADC values might be corrected for these stochastic processes to more accurately evaluate disease using restricted diffusion measures in the lungs.

Artifacts↗