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Results for “Diffusion MRI”

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At least 1,063 records · Page 59Linked to original sources
PubMed1992

Temporal evolution of focal cerebral ischemia in the rat assessed by T2-weighted and diffusion-weighted magnetic resonance imaging.

The present study was undertaken to characterize the formation of ischemic brain edema using diffusion-weighted and T2-weighted magnetic resonance imaging in a rat model of focal ischemia. The extent of edema formation was measured from multislice diffusion-weighted and T2-weighted spin-echo images acquired at various times after ischemia. The spin-spin relaxation time (T2) and the apparent diffusion coefficient in normal and ischemic tissue were also determined. The results show that on the diffusion-weighted images the lesion was clearly visible at 30 minutes after ischemia, while on the T2-weighted images it became increasingly evident after 2-3 hours. On both types of images the hyperintense area increased in size over the first 48 hours. After 1 week the hyperintensity on the diffusion-weighted images rapidly disappeared and evolved as a hypointense lesion in the chronic phase. These results confirm the high sensitivity of diffusion-weighted MRI for the detection of early ischemia. The temporal course of the edema observed on T2W-images is in agreement with the reported increase of total water content occurring in this model. The increase of the lesion observed on the diffusion-weighted images during the first 2 days points to an aggravation of cytotoxic edema that parallels the changes in free water shown by the T2-weighted images. It is shown that the highly elevated T2's of the infarcted area several days after ischemia can substantially contaminate the diffusion-weighted images.

Animals↗
PubMed1996

Extensive brain calcifications, leukodystrophy, and formation of parenchymal cysts: a new progressive disorder due to diffuse cerebral microangiopathy.

A new cerebral disorder, described in three unrelated children, has recognizable clinical, radiologic, and neuropathologic findings. The onset occurs from early infancy to adolescence with slowing of cognitive performance, rare convulsive seizures, and a mixture of extrapyramidal, cerebellar, and pyramidal signs. CT shows progressive calcifications in the basal and cerebellar gray nuclei and the central white matter. MRI reveals diffuse abnormal signals of the white matter on T2-weighted sequences. A special feature is the development of parenchymal cysts in the cerebellum and the supratentorial compartment, leading to compressive complications and surgical considerations. Neuropathologic examination of surgically removed pericystic samples reveals angiomatous-like rearrangements of the microvessels, together with degenerative secondary changes of other cellular elements. Both the anatomic findings and the course of the disease suggest a constitutional, diffuse cerebral microangiopathy resulting in microcystic, then macrocystic, parenchymal degeneration.

Brain Diseases↗
PubMed2002

Apparent diffusion coefficient mapping of infarcted tissue and the ischaemic penumbra in acute stroke.

MRI assessment of diffusion changes in acute cerebral ischaemia necessitates analysis of the apparent diffusion coefficient (ADC). We used the concept of relative weighted mean ADC (rwmADC) to obtain an accurate estimate of the extent of infarcted tissue. We studied ten patient with of acute ischaemic stroke, using diffusion- and perfusion- weighted MRI. The rwmADC was used to calculate a corrected ADC-lesion volume (DLVR), which was compared with the diffusion-lesion volume (DLV), initial perfusion lesion volumes and the follow-up infarct volume on T2-weighted images. We looked at correlations between the MRI and clinical findings. DLVR was closest to the final infarct size and had the best clinicoradiological correlation (r=0.77). Weighting the mean ADC within the ischaemic and normal parenchyma can give a more correct estimate of the volume of infarcted brain parenchyma, thus improving the definition of the penumbra.

Brain↗
PubMed1994

Symptomatic cataplexy in pontomedullary lesions.

Cataplexy is a cardinal manifestation of the narcolepsy syndrome. Although symptomatic narcolepsy is well described, isolated cataplexy is extremely rare. We reviewed clinical and radiologic data in two patients with isolated symptomatic cataplexy and associated CNS disease. In an HLA-DR2-positive patient with chronic progressive MS, we confirmed cataplexy by observation of reported spells. MRI revealed diffuse white-matter lesions involving the medial medulla, pons, and subcortical white matter; protriptyline provided symptomatic relief. A second patient with a pontomedullary pilocytic astrocytoma developed infrequent but recurrent cataplectic attacks in association with sleep fragmentation due to nocturnal cough and nausea. MRI revealed an enhancing lesion involving the dorsal pons and medulla. Genetic predisposition and sleep fragmentation may precipitate symptomatic cataplexy in patients with structural pontomedullary lesions.

Adult↗
PubMed1998

Detection of MRI brain contour using isotropic and anisotropic diffusion filter. A comparative study.

Reconstructed brain surface from MRI are still based on either interactive or manual edge detection methods which are time consuming and subjective. In order to overcome such inadequate result, the scale-space technique was applied using isotropic and anisotropic diffusion filter. Isotropic diffusion was not adequate because it did not allow locally adaptive blurring. On the contrary, stopping the anisotropic diffusion process at the best time of diffusion, edge detector provided the true location and morphology of the sulci and gyri. Although some sulci appeared open curves this one didn't have to be considered as failure of anisotropic diffusion because it was related to the resolution of the original MR image. Nevertheless the human vision subjectively made explicit their closure.

Anisotropy↗
PubMed2006

White matter damage on diffusion tensor imaging correlates with age-related cognitive decline.

BACKGROUND: Damage to white matter tracts, resulting in "cerebral disconnection," may underlie age-related cognitive decline. METHODS: Using diffusion tensor MRI (DTI) to investigate white matter damage, and magnetic resonance spectroscopy (MRS) to look at its underlying pathologic basis, the authors investigated the relationship between white matter structure and cognition in 106 healthy middle-aged and elderly adults. Fractional anisotropy (FA) and mean diffusivity (MD) values, whole brain white matter histograms, and regions of interest placed in the white matter of the centrum semiovale were analyzed. Correlations with executive function, working memory, and information-processing speed were performed. RESULTS: There was a progressive reduction in FA and increase in diffusivity with age in both region of interest (r = 0.551, p < 0.001), and whole brain histograms (r = 0.625, p < 0.001). DTI values correlated with performance in all three cognitive domains. After controlling for age, DTI parameters correlated with working memory but not with the other two cognitive domains. MRS studies found a correlation of N-acetyl aspartate, a neuronal marker, with DTI parameters (r = 0.253, p < 0.05). CONCLUSION: The results are consistent with white matter damage due to axonal loss, causing age- related cognitive decline. Working memory may be particularly dependent on complex networks dependent on white matter connections.

Aged↗
PubMedDate not supplied

Magnetic resonance imaging in the diagnosis of PMR.

The cause of musculoskeletal symptoms in polymyalgia rheumatica (PMR) is not clearly defined because joint synovitis may only partially explain the diffuse discomfort. MRI imaging of the shoulders, hip and extremities of patients with PMR has been analyzed. MRI showed that subacromial and subdeltoid bursitis of the shoulders and iliopectineal bursitis and hip synovitis are the predominant and most frequently observed lesions in active PMR. The inflammation of the bursae associated with glenohumeral synovitis, bicipital tenosynovitis and hip synovitis may explain the diffuse discomfort and morning stiffness.

Bursitis↗
PubMed2001

[A case of sarcoidosis with simultaneous involvement of the lower brainstem and the whole cervical cord and the extraocular muscles].

We report a 63-year-old woman with sarcoidosis which involved the spinal cord, lower brainstem and extraocular muscules simultaneously. In this patient, uveitis developed in 1991 and the skin lesion in 1992. A biopsy of the skin lesion showed changes consistent with sarcoidosis. The ocular and dermal symptoms improved with oral corticosteroid. In October 1997, she noted the left blepharoptosis and numbness of the hands. The MRI showed diffuse swelling of the lower brainstem and the cervical and upper thoracic cord. These lesions showed high intensity signal on T2WI and low intensity signal on T1WI. T1WI with contrast enhancement revealed localized enhancement within the spinal lesion at the C4/5 level. The ocular MRI showed swelling of the left superior rectus muscle and upper levator palpebral muscle. The steroid pulse therapy and subsequent oral administration of prednisolone markedly improved the clinical symptoms. MRI after treatment showed marked improvement of both the spinal cord and ocular muscle lesions. To our knowledge, the simultaneous occurrence of myelopathy and symptomatic extraocular musculopathy in the condition has not been reported previously.

Brain Diseases↗
PubMed2003

[An autopsy case of cryptococcal meningoencephalitis: correlation of MRI and pathologic findings].

A comparative study of MRI and pathology was performed on a case of cryptococcal meningoencephalitis. An 11-year-old female presented with confusion and vomiting. On admission, CSF examination revealed spherical fungal cells with mild pleocytosis, decreased glucose and elevated protein level. MRI showed multiple punctate lesions in the basal ganglia with high intensity on T2-weighted image, while enhanced MRI revealed diffuse meningeal involvement. Post-mortem examination disclosed that the T2-weighted lesions found in the basal ganglia were aggregated small cystic lesions consisting of a cryptococcal invasion of Virchow-Robin spaces, termed "soap bubble lesions", characteristic findings of cryptococcal meningoencephalitis. Thus MRI findings of the basal ganglia and meninges may help to diagnose cryptococcal meningoencephalitis.

Brain↗
PubMed2003

FK506-associated limbic injury following umbilical cord blood transplantation.

A 5-year-old girl with Ph-positive chronic myelogenous leukemia, who underwent umbilical cord blood transplantation, developed two episodes of electrical status epilepticus while receiving tacrolimus (FK506) then cyclosporin A (CsA), as treatment against graft-versus-host disease. MRI including diffusion weighted MR imaging of the brain revealed abnormalities in the hippocampus and posterior white matter following FK506 and CsA treatment, respectively. While posterior white matter injury has been described with both FK506 and CsA, no previous report describes hippocampal injury from either drug. The MRI changes in the hippocampus in our case suggest possible increased susceptibility to hippocampal injury with FK506.

Child, Preschool↗
PubMed2005

Fronto-thalamo-striatal gray and white matter volumes and anisotropy of their connections in bipolar spectrum illnesses.

BACKGROUND: Neurons in the basal ganglia are connected to areas of prefrontal cerebral cortex involved in higher cognitive functions, and these connections occur primarily via the thalamus. In patients with bipolar disorder, regardless of age, neuroimaging studies have consistently reported an increased number of white matter hyperintensities, indicating possible alterations in striatum-thalamus and thalamus-prefrontal cortex connections. METHODS: In the current study, we acquired high-resolution magnetic resonance imaging (MRI) and diffusion tensor (DT) scans of 40 patients with bipolar spectrum (BPS) illnesses (bipolar type I = 17, bipolar type II = 7, cyclothymia = 16) and 36 sex- and age-matched control subjects. Two researchers, without knowledge of diagnosis, outlined the caudate, putamen, and thalamus on contiguous axial MRI slices. We measured the volumes of the basal ganglia, thalamus, and gray/white matter of the frontal cortex. RESULTS: Bipolar spectrum patients as a single group did not differ from control subjects in thalamus and the basal ganglia volumes, but the cyclothymia patients had reductions in the volumes of putamen and the thalamus compared with control subjects. The BPS patients had significantly reduced volume of the white and the gray matter of the frontal cortex. Furthermore, compared with control subjects, BPS patients as a group showed alterations in anisotropy of the internal capsule adjacent to the striatum and thalamus and the frontal white matter. CONCLUSIONS: Our findings indicate that BPS patients may have distinct anatomical alterations in brain structures involved in the regulation of mood and cognition, as well as alterations in these structures' connection to related brain areas.

Adult↗
PubMed2002

Seizure at stroke onset: should it be an absolute contraindication to thrombolysis?

BACKGROUND: Current guidelines for the treatment of acute ischemic stroke exclude patients with seizure at stroke onset from consideration for thrombolytic therapy. It may be difficult to differentiate an ischemic stroke from postictal Todd's paralysis by clinical examination and noncontrast CT scan. Magnetic resonance imaging (MRI) with diffusion- (DWI) and perfusion-weighted images (PWI) and angiography (MRA) can be used to confirm the diagnosis of an acute ischemic process in the presence of concurrent seizures. METHODS: A case report of a patient who presented with seizures, in whom the combination of DWI/PWI MRI and MRA confirmed the diagnosis of an embolic ischemic stroke. The patient was treated with intravenous recombinant tissue plasminogen activator with clinical and radiological improvement. CONCLUSIONS: Treatment decisions with regard to thrombolysis in acute stroke patients should be based on parameters of cerebral perfusion, assessment of collateral blood flow and presence of potentially salvageable tissue. Modern neuroimaging techniques that can rapidly assess these variables, such as DWI/PWI MRI and MRA, can improve the current selection of patients who are likely to benefit from thrombolysis and extend its benefit to patients who would otherwise be excluded, such as those with seizures at stroke onset.

Aged↗
PubMedDate not supplied

Hydrocephalus as the initial presentation of a spinal cord astrocytoma associated with leptomeningeal spread.

A 3-year-old boy presented with headaches, vomiting, lethargy and papilledema. Communicating hydrocephalus along with transependymal fluid absorption and meningeal contrast enhancement was identified on CT. The enhancement was initially thought to be the result of a partially treated meningitis (child was previously on oral antibiotics for a presumed mycoplasma pneumonia). A right ventricular-peritoneal shunt was placed. CSF studies procured during the procedure were all normal. In contrast, CSF from a lumbar puncture contained a high protein, and cytology was highly suspicious for malignancy. Spine MRI showed diffuse leptomeningeal enhancement and a 1.5-cm intramedullary lesion at T12-L1 associated with minimal edema. The lesion was subtotally resected (70%) and diagnosed as an astrocytoma (mostly Kernohan grade 2 but with areas of grade 3). Chemotherapy was administered and follow-up spine MRI at 2 months did not reveal any residual tumor, however, the leptomeningeal enhancement persisted. Sixteen months later, at the completion of the chemotherapy and radiation therapy, the spine MRI remained unchanged. Neurological examination has always been normal. This case illustrates how a spinal cord astrocytoma can metastasize via spinocranial dispersion and present early with hydrocephalus rather than myelopathy.

Astrocytoma↗
PubMed2006

Assessment with magnetic resonance imaging and spectroscopy in Lhermitte-Duclos disease.

Lhermitte-Duclos disease (LDD) is a rare benign lesion of uncertain pathogenesis characterized by distortion of the normal cerebellar laminar cytoarchitecture. We report a 22-year-old man admitted for injury sustained in a traffic accident with the incidental finding of a cerebellar mass. Magnetic resonance imaging (MRI) revealed a mass lesion within the right cerebellar hemisphere. The final diagnosis of LDD was made by obtaining a surgical specimen and identifying the characteristic appearance of the lesion by MRI study. The images showed the typical striated pattern of hyperintensity on T2-weighted images and corresponding hypointensity on T1-weighted images, as well as the typical absence of enhancement following gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA) administration. In addition, no disturbance of water diffusion on diffusion-weighted MRI, and associations of decreases in the N-acetylaspartate/creatine (NAA/Cr) and NAA/Choline (Cho) ratios with near normal values of Cho/Cr, as well as an obvious lactate peak gave supplemental information for diagnosis.

Adult↗
PubMed2002

Severe ADC decreases do not predict irreversible tissue damage in humans.

BACKGROUND AND PURPOSE: A mismatch between diffusion- and perfusion-weighted MRI is thought to define tissue at risk of infarction. This concept is based on the assumption that diffusion slowing of and decreases in the apparent diffusion coefficient (ADC) serve as indicator of tissue proceeding to infarction. We tested this hypothesis. METHODS: MRI (diffusion weighted, perfusion weighted, MRA, T2 weighted) was performed in 15 patients with acute stroke within 2.9+/-0.8 hours (mean+/-SD) of onset and on days 1 and 7. After intraindividual realignment of the ADC maps, the development of ADC range volumes and ADC values was determined. RESULTS: An increase (354%, group A1) in the total ADC-based lesion volume below a threshold of < 80% occurred in 4 patients on day 1, persisting on day 7 with a pronounced increase of ADC range volumes with low ADC values. An increase in total ADC-based lesion volume (201%, group A2) followed by a secondary drop to day 7 was found in 7 patients. A significant reduction in total ADC-based lesion volume (14%, group B) was found in 4 patients. ADC-based lesion volume increase was associated with persistent vessel occlusion in group A, whereas recanalization in group B resulted in ADC volume decrease. ADC normalization was observed independently from the degree of the initial ADC decrease on days 1 and 7 in group B. CONCLUSIONS: In line with results from animal experiments, ADC decreases do not reliably indicate tissue infarction Even severely decreased ADC values may normalize in human stroke, and it seems likely that ADC normalization depends on the duration and severity of ischemia rather than the absolute value.

Aged↗
PubMed2004

3 Tesla magnetic resonance imaging of the brain in newborns.

While it has been hypothesized that brain development is abnormal in schizophrenia and other neurodevelopmental disorders, there have been few attempts to study very early brain development in children. Twenty unsedated healthy newborns underwent 3 Tesla magnetic resonance imaging (MRI), including diffusion tensor imaging (DTI). The left ventricle was significantly larger than the right; females had significantly larger ventricles than males. Fractional anisotropy (FA) increased significantly with gestational age in the genu and splenium of the corpus callosum. It is feasible to study brain development in unsedated newborns using 3 T MRI.

Brain↗
PubMedDate not supplied

[Leukoencephalopathy with vanishing white matter: A case report].

INTRODUCTION: Leukoencephalopathy with vanishing white matter is an autosomal recessive hereditary disease that was first reported in 1997. Some time later the genetic anomalies responsible for the disease were identified, these being different mutations in any of the five genes that code for the five subunits of the translation initiation factor, eIF2B. Since then, the clinical spectrum of this condition has proved to be much broader and far more frequent than was initially believed. We report on a case of the classical clinical form, which is to our knowledge the first to be published in Spain to date. CASE REPORT: A 5-year-old female who presented gait instability that recently got worse following a mild traumatic head injury. The examination revealed overall cerebellar ataxia and generalised spasticity. Magnetic resonance imaging (MRI) showed diffuse and symmetrical involvement of the white matter of the brain with the presence of cavities in which the signal intensity and the proton spectrum were similar to those of cerebrospinal fluid. The genetic study revealed a mutation of the gene that codes for eIF2B-epsilon. CONCLUSIONS: A suggestive MRI scan, even in an atypical presentation, would be enough to rule out a mutation of the genes that code for eIF2B. This would make it possible to reach an early diagnosis of this disease, which is probably more prevalent than is currently thought. This would allow genetic counselling to be conducted and would help to establish a genotype-phenotype correlate that would also make it possible to offer an estimated prognosis.

Brain Diseases↗