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PubMed1991

Ultrafast magnetic resonance imaging: diffusion and perfusion.

Echo-planar magnetic resonance imaging (MRI) can be used to measure apparent diffusion coefficients noninvasively in vivo, with scan times of 150 milliseconds or less, and to assess early ischemic effects in the feline experimental model, which has an occluded middle cerebral artery (MCA). The apparent diffusion coefficient in ischemic regions, which are identified later from vital staining, is significantly decreased from normal values within 1 hour after the MCA becomes occluded. A series of 10 echo-planar images that are progressively diffusion-weighted can be collected in 1 minute (effective TR of 6 seconds). Semilogarithmic plots of image intensity versus gradient strength factors (b values) were linear. Collecting sequential gradient echo-planar images during the passage of a bolus of contrast medium is also useful when assessing perfusion or vascular integrity before and during ischemic episodes. After intravenous injection of dysprosium-diethylene triamine penta-acetic acid-bis(methylamide), typical signal losses of 40% to 80% were observed and were dose-dependent. Areas of possible ischemia identified from diffusion-weighted images did not lose signal intensity with the use of contrast medium and were seen as regions of relative hyperintensity, clearly discernible from normally perfused tissues.

Animals↗
PubMed1989

[Significance of magnetic resonance imaging in diffuse axonal injury].

Advantages of magnetic resonance imaging (MRI) to computed tomography (CT) on a diagnosis of diffuse axonal injury (DAI) were discussed. Sixteen patients diagnosed as DAI defined by the criteria of Gennarelli were studied with CT and MRI. Lesions were demonstrated as high intensity areas on MRI of T2 weighted imaging (SE 2000/111) in all of the patients. These lesions were located only in a cerebral white matter in the cases of mild DAI, whereas in the cases of severe DAI located in a basal ganglia, corpus callosum, dorsal part of the brain stem as well as in the cerebral white matter. As for the findings of CT, these parenchymal lesions were not visualized in nine cases including six cases without any pathological findings. Our series suggest that MRI is superior to CT on the diagnosis of DAI and provides some information to evaluate the severity of DAI.

Adolescent↗
PubMed2005

Magnetic resonance imaging in multiple sclerosis.

Magnetic resonance imaging (MRI) has played a central role in the clinical management and scientific investigation of multiple sclerosis (MS) and has become the most important ancillary tool for diagnosing and monitoring the disease. Conventional MRI techniques are used to assess overt lesions and atrophy in the central nervous system and include spin-echo T2-weighted, pre- and post-gadolinium-enhanced spin-echo T1-weighted, and fluid-attenuated inversion-recovery images. Advanced MRI techniques such as diffusion-weighted imaging, magnetization transfer imaging, magnetic resonance spectroscopy, and functional MRI have increased our understanding of the pathogenesis of MS. The role of these newer techniques in clinical practice remains under investigation. In this review, we will focus on the role of MRI in the diagnosis and management of MS. We will also review how advanced MRI techniques contribute to our understanding of MS.

Atrophy↗
PubMed2006

Intra- and interrater reliability of ischemic lesion volume measurements on diffusion-weighted, mean transit time and fluid-attenuated inversion recovery MRI.

BACKGROUND AND PURPOSE: We investigated the intra- and interrater reliability of ischemic lesion volumes measurements assessed by different MRI sequences at various times from onset. METHODS: Ischemic lesion volumes were measured for intrarater reliability using diffusion-weighted (DWI), mean transit time (MTT) perfusion and fluid-attenuated inversion recovery (FLAIR) MRI at chronic (>3 days from stroke onset) time points. A single intrarater reader, blind to clinical information and time point, repeated the volume measurements on two occasions separated by at least 1 week. Interrater reliability was also obtained in the second set of patients using acute DWI, MTT and chronic FLAIR MRI. Four blinded readers performed these volume measurements. Average deviations across repeat measurements per lesion and differences between sample means between the two measurements were calculated globally, ie, across all sequences and time points, and per reader type for each sequence at each time point. RESULTS: There was good concordance of the mean sample volumes of the 2 intrarater readings (deviations were <4% and 2 mL globally, <2% and 2 mL for DWI, <6% and 7 mL for MTT, and <2% and 1 mL for FLAIR). There was also good concordance of the interrater readings (<5% and 2 mL globally). CONCLUSIONS: Repeat measurements of stroke lesion volumes show excellent intra- and interrater concordance for DWI, MTT and FLAIR at acute through chronic time points.

Brain Ischemia↗
PubMed2000

In vivo fiber tractography using DT-MRI data.

Fiber tract trajectories in coherently organized brain white matter pathways were computed from in vivo diffusion tensor magnetic resonance imaging (DT-MRI) data. First, a continuous diffusion tensor field is constructed from this discrete, noisy, measured DT-MRI data. Then a Frenet equation, describing the evolution of a fiber tract, was solved. This approach was validated using synthesized, noisy DT-MRI data. Corpus callosum and pyramidal tract trajectories were constructed and found to be consistent with known anatomy. The method's reliability, however, degrades where the distribution of fiber tract directions is nonuniform. Moreover, background noise in diffusion-weighted MRIs can cause a computed trajectory to hop from tract to tract. Still, this method can provide quantitative information with which to visualize and study connectivity and continuity of neural pathways in the central and peripheral nervous systems in vivo, and holds promise for elucidating architectural features in other fibrous tissues and ordered media.

Artifacts↗
PubMedDate not supplied

MRI appearance of AIDS subacute encephalopathy.

A case of biopsy documented subacute encephalopathy of AIDS was evaluated by CT and MRI. CT scanning revealed ventriculomegaly and ill-defined nonspecific periventricular white matter hypodensities. MRI, however, demonstrated extensive unequivocal diffuse white matter disease as the cause of the ventriculomegaly. MRI findings in this patient support the preliminary suggestion that MRI is more useful than computed tomography (CT) in demonstrating AIDS subacute encephalopathy.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Ischaemic and haemorrhagic brain lesions in newborns with seizures and normal Apgar scores.

Serial ultrasound scans and conventional and diffusion weighted magnetic resonance imaging (MRI) were performed on 16 neonates who presented with seizures. The Apgar scores were normal and subsequently no metabolic or infective cause could be found. The aim of the study was to evaluate the extent to which early sequential imaging can elucidate the cause of seizures in apparently neurologically normal infants. Fourteen of the infants had haemorrhagic or ischaemic lesions on MRI and these were detected by ultrasound scanning in 11. Early ultrasound scanning detected the haemorrhagic lesions but the ischaemic lesions were often not seen until the end of the first week of life. Early MRI, however, was able to detect all the ischaemic lesions. The evolution of the insult could be timed by using serial ultrasound scans and a combination of diffusion weighted and conventional MRI during the first week of life, confirming a perinatal insult even in the absence of fetal distress. Although the aetiology of these lesions remains obscure, serial ultrasound scans will detect the presence of cerebral lesions in neonates presenting with isolated seizures but additional MRI sequences will give better definition on type, site, and extent of the pathology.

Apgar Score↗
PubMed2004

Familial leptomeningeal amyloidosis with a transthyretin variant Asp18Gly representing repeated subarachnoid haemorrhages with superficial siderosis.

OBJECTIVES: To report the clinical features of two Japanese brothers with familial leptomeningeal amyloidosis, showing a causative gene abnormality of a transthyretin (TTR) variant Asp18Gly, previously reported only in a Hungarian family. METHODS: The authors reported on a 42 year old man (patient 1) and his 45 year old brother (patient 2), both suffering from subarachnoid haemorrhage (SAH) without and with hydrocephalus, respectively. DNA sequences of the TTR gene were determined in both patients and the patients' clinical features described. A surgical biopsy of the leptomeninges was performed on patient 1. RESULTS: DNA sequence analyses demonstrated the glycine-for-aspartate substitution at position 18 of the TTR variant. Both patients revealed pyramidal tract signs and cerebellar ataxia. Audiometric studies showed bilateral, mild sensorineural hearing loss in the patients whose cerebrospinal fluid (CSF) protein levels increased. T1 weighted MRI after contrast administration showed diffuse leptomeningeal enhancement along the Sylvian fissures and over the surface of the brainstem, cerebellum, and spinal cord. Gradient echo T2* weighted MRI showed superficial siderosis mainly in the cerebellum. A biopsy of the leptomeninges was obtained from the spinal cord of patient 1. While performing the biopsy, the authors observed the varicose, elongating, and fragile veins on the dorsal surface of the spinal cord. Immunohistochemical study revealed marked deposits of TTR derived amyloid on his leptomeninges. CONCLUSIONS: This is the second report of familial leptomeningeal amyloidosis with an Asp18Gly TTR gene mutation, clinically causing only CNS symptoms. Repeated SAH from fragile veins on the dorsal surface of the spinal cord seemed to induce superficial siderosis of the CNS. So far, there have been two reliable hallmarks leading to the diagnosis of leptomeningeal amyloidosis: diffuse leptomeningeal enhancement on contrast MRI and greatly increased CSF protein content. This study has contributed a third hallmark: the presence of superficial siderosis is useful in diagnosing leptomeningeal amyloidosis.

Adult↗
PubMed2006

Diffusion-weighted magnetic resonance imaging and its application to cancer.

Diffusion-weighted magnetic resonance imaging (DW-MRI) provides image contrast through measurement of the diffusion properties of water within tissues. Application of diffusion sensitising gradients to the MR pulse sequence allows water molecular displacement over distances of 1-20 microm to be recognised. Diffusion can be predominantly unidirectional (anisotropic) or not (isotropic). Combining images obtained with different amounts of diffusion weighting provides an apparent diffusion coefficient (ADC) map. In cancer imaging DW-MRI has been used to distinguish brain tumours from peritumoural oedema. It is also increasingly exploited to differentiate benign and malignant lesions in liver, breast and prostate where increased cellularity of malignant lesions restricts water motion in a reduced extracellular space. It is proving valuable in monitoring treatment where changes due to cell swelling and apoptosis are measurable as changes in ADC at an earlier stage than subsequent conventional radiological response indicators.

Brain Neoplasms↗
PubMed2004

MRI for the management of neonatal cerebral infarctions: importance of timing.

PURPOSE: Focal ischemic stroke in neonates is a rare occurrence. Diagnosis with most imaging modalities is difficult, but necessary for initiating an anticoagulatory treatment. The purpose of this study was to evaluate the sensitivity of MRI sequences within the first 14 days of birth. PATIENTS AND METHODS: Four patients with neonatal stroke presenting as seizures were examined using a standard MRI protocol including diffusion-weighted images (DWI) and magnetic resonance angiography (MRA) within 72 h of birth. The time between the onset of symptoms and MRI ranged from 6 h to 48 h. Follow-up examinations were performed on days 5 ( n=1), 7 ( n=2), and 14 ( n=1) for the control of a treatment with low-molecular heparin. RESULTS: Eight infarctions were detected in the four patients, 5 in the middle cerebral artery (MCA), three in the posterior cerebral artery (PCA) territory. All lesions were visible using DWI, four on T2-weighted images. Whereas in two patients small lesions contralateral to a large stroke were missed on T2-weighted images, the diagnosis would have been missed altogether without DWI in one patient. On follow-up, the visibility of the infarctions had declined using DWI after 5 days and the lesions were invisible after 1 week. Fourteen days after the stroke, an increased diffusion was detected in the infarcted brain tissue. By this time, all lesions were visible on T2-weighted images. CONCLUSION: In neonates, infarcted brain tissue can be detected using DWI with high sensitivity during the first 2 days after stroke and before other sequences are diagnostic. However, the diffusion restriction does not persist beyond 1 week. After 5 days, diagnosis has to rest mainly on T2-weighted images.

Brain Mapping↗
PubMed2001

Perfusion and diffusion magnetic resonance imaging in human cerebral venous thrombosis.

BACKGROUND: Diagnosis of cerebral venous thrombosis (CVT) is usually achieved by digital subtraction angiography or magnetic resonance angiography, while structural brain tissue damage can be assessed by computed tomography or magnetic resonance imaging (MRI). Using perfusion and diffusion weighted imaging (PWI, DWI) we aimed in this study to identify pathophysiological patterns corresponding to only functional and hence reversible tissue involvement. METHODS: PWI, DWI, and conventional MRI were performed in six CVT patients acutely and after 16-26 days when their clinical condition had improved. All patients were treated with partial thromboplastin time-effective intravenous heparin. After intravenous administration of a paramagnetic contrast agent, bolus track PWI allows pixel based determination of mean transit time (MTT) and cerebral blood volume (CBV). DWI was performed with two different b values (0, 1000 s/mm2) for calculation of apparent diffusion coefficient (ADC) maps. RESULTS: In five of six cases increased MTT values were observed initially, whereas the CBV was normal, indicating a reduction of cerebral blood flow. ADC values were normal. On follow up after clinical recovery MTT prolongations had resolved. Areas with prolonged MTT did not evolve into structural lesions. CONCLUSION: In patients with CVT, prolongations of MTT in the absence of changes in CBV and ADC seem to indicate reversible involvement of brain tissue, a situation corresponding to the ischaemic penumbra.

Adult↗
PubMedDate not supplied

Recanalization and reversal of diffusion abnormalities and markedly reduced cerebral blood volume in a patient with transient ischemic attack.

Resolution of diffusion abnormalities is a finding that is rarely seen in hyperacute cerebral ischemia. We report a serial study of diffusion and perfusion magnetic resonance imaging (MRI) in a case of transient ischemic attack (TIA). In the current case, marked decrease of cerebral blood volume (CBV) as well as reduced diffusion in the affected middle cerebral arterial territory was shown by the initial diffusion and perfusion MRI at 1.5 h after onset. The initial MRI findings as well as neurological symptoms recovered probably due to prompt and spontaneous recanalization of thrombosed vessel.

Aged↗
PubMed2006

Surgical treatment of polymicrogyria with advanced radiologic and neurophysiologic techniques.

INTRODUCTION: Coexistence of multiple seizure types, inclusion of the motor cortex in the epileptogenic zone, and poor delimitation of the abnormal cortex make most patients with polymicrogyria (PMG) unlikely candidates for epilepsy surgery (Guerrini R et al., Epilepsy and malformations of the cerebral cortex in Epileptic syndromes in infancy, childhood and adolescence, 2005). CASE REPORT: We present here a child with frontal PMG and intractable epilepsy evaluated with advanced magnetic resonance imaging (MRI) and neurophysiologic techniques. Diffusion tensor imaging and fiber tractography showed severe involvement of neighboring white matter tracts besides the cortex. The evaluation also included functional MRI, chronic subdural electroencephalogram monitoring, and intra-operative motor mapping. The patient had a decrease in seizure frequency and an increase in his developmental skills after the surgery. CONCLUSION: Advanced neuroradiologic and neurophysiologic techniques are required to provide an effective and safe resection of the epileptogenic cortex in cortical dysplasias.

Brain Diseases↗
PubMed2001

Time course of lesion development in patients with acute brain stem infarction and correlation with NIHSS score.

BACKGROUND AND PURPOSE: diffusion weighted magnetic resonance imaging (MRI) is highly sensitive in detecting acute supratentorial cerebral ischemia and Diffusion Weighted Imaging (DWI) lesion size has been shown to correlate strongly with the neurologic deficit in middle cerebral artery territory stroke. However, data concerning infratentorial strokes are rare. We examined the size and evolution of acute brain stem ischemic lesions and their relationship to neurological outcome. METHODS: brain stem infarctions of 11 patients were analyzed. We performed DWI in all patients and in 7/11 patients within 24 h, T2W sequences within the first 2 weeks (10/11 patients) and follow-up MRI (MR2) within 3-9 months (median 4.8 months) later (12/12 patients). Lesion volumes were compared with early and follow-up neurologic deficit as determined by National Institutes of Health Stroke Scale (NIHSS) score. RESULTS: the relative infarct volumes--with MR2 lesion size set to 100%--decreased over the time (P<0.02) with a mean shrinking factor of 3.3 between DWI (MR0) and the follow-up MRT (P<0.02), and 1.6 between early T2W (MR1) and MR2 (P<0.04). The mean DWI volume size (MR0) was larger than the early T2W (P<0.02). Although neurological outcome was good in all patients (mean NIHSS score of 1.3 at follow-up), early NIHSS and follow-up NIHSS scores were strongly correlated (r=0.9, P<0.00). NIHSS score at follow-up was highly correlated with lesion size of DWI (MR0; r=0.71, P<0.04) and T2W of MR1 (r=0.86, P<0.001). CONCLUSIONS: in this study, we saw a shrinking of the brain stem infarct volume according to clinical improvement of patients. Great extension of restricted diffusion in the acute stage does not necessarily implicate a large resulting infarction or a bad clinical outcome.

Brain Stem Infarctions↗
PubMed2000

AR-R15896AR reduces cerebral infarction volumes after focal ischemia in cats.

OBJECTIVE: The use of competitive and noncompetitive N-methyl-D-aspartate receptor antagonists to prevent neuronal death during ischemia has been comprehensively studied. This study was performed to examine the neuroprotective effects and pharmacokinetics of the noncompetitive N-methyl-D-aspartate receptor channel blocker (S)-alpha-phenylpyridine-ethanamine dihydrochloride, AR-R15896AR (formerly designated ARL 15896AR), using a gyrencephalic cat middle cerebral artery occlusion model. METHODS: In a separate experiment, three cats were used for pharmacokinetic analysis, thus establishing the optimal dose of AR-R15896AR. Focal cerebral ischemia was induced in 21 cats. After 30 minutes of a 90-min ischemic insult, the cats received an intravenous infusion (total volume, 3 ml), in a 15-minute period, of either AR-R15896AR or normal saline solution (control). Physiological data were obtained after 40 and 80 minutes of ischemia and at 2, 4, and 6 hours after ischemia. At 6 hours after ischemia, each cat was positioned for both T2- and diffusion-weighted scans (eight slices, 5-mm thick). At 8 hours after ischemia, the animals were perfusion-fixed for histopathological analysis. RESULTS: Pharmacokinetic studies indicated that AR-R15896AR remained in the blood at elevated levels for the 6 hours studied, with a calculated half-life of approximately 6 hours. AR-R15896AR rapidly entered the brain and exhibited a brain/plasma ratio of approximately 8:1. The infarction volumes for the AR-R15896AR-treated group were 1138.5+/-363.1, 651.3+/-428.9, and 118.6+/-50.1 mm3, as calculated using diffusion- and T2-weighted MRI and histopathological data, respectively. The infarction volumes for the control group were 3866.3+/-921, 3536+/-995.7, and 359.9+/-80.2 mm3, as calculated using diffusion- and T2-weighted MRI and histopathological data, respectively. No significant changes were observed in the physiological parameters measured (mean arterial blood pressure, pH, arterial carbon dioxide pressure, arterial oxygen pressure, sodium, potassium, chloride, and glucose levels, hematocrit, and temperature) for either the control or AR-R15896AR-treated group. Postischemic calcium levels returned to normal in the AR-R15896AR-treated cats, whereas they decreased in the control cats. CONCLUSION: When administered after ischemia, AR-R15896AR was effective in significantly reducing infarction volumes, as measured using diffusion- or T2-weighted magnetic resonance imaging data or quantitative histopathological data. This study also demonstrated that infarction volumes were greater in the diffusion- and T2-weighted magnetic resonance imaging scans than in the qualitative histopathological analyses, with the diffusion-weighted scans exibiting the largest infarction volumes.

Animals↗
PubMedDate not supplied

[A case of postural and kinetic tremor caused by diffuse axonal injury].

We reported a 25-year-old woman with postural and kinetic tremor caused by diffuse axonal injury. The patient demonstrated consciousness disturbance, left oculomotor palsy and tetraparesis because of an automobile accident. T2-weighted and FLAIR MRI showed features of diffuse axonal injury. Hyperintense lesions appeared in the corpus callosum, fornix, dorsal portion of midbrain, right cerebral peduncle, and bilateral internal capsules. About 3 weeks later, head tremor and left hemiparesis appeared with improvement of consciousness. Administration of trihexyphenidyl decreased the tremor. Ten weeks after the accident, a coarse tremor in the head and right upper extremity developed after withdrawal of trihexyphenidyl. Tremor in the right upper limb predominantly occurred while maintaining an upright posture and with intended movements. Re-administration of trihexyphenidyl decreased the tremors. The dentatothalamic pathway is one of the lesions responsible for posttraumatic tremor. Our patient demonstrated lesions of diffuse axonal injury involving the dentatothalamic pathway. We considered that these lesions were associated with postural and kinetic tremor in our case. The tremor occurred at least 3 weeks after the accident. This finding suggested that the tremor was caused by transsynaptic alternations of thalamus or the extrapyramidal system secondary to involvement of the dentatothalamic pathway.

Accidents, Traffic↗
PubMed1996

Adult schizophrenic-like variant of adrenoleukodystrophy.

A 35-year-old man died after 30 months following the onset of the disease. There was a history of changes in his mental condition, including disturbances of behavior as well as the evidence of progressing dementia. The patient revealed gait disturbances and finally became bed ridden. Bizarre behavior and changes of mood with concurrent growing irritability which predominated during the course of disease, may explain the initial diagnosis of schizophrenia. Then cerebellar and spastic movement disorders leading to paraparesis and sphincters disturbances developed. Clinical symptoms of adrenal failure were not found apart from episodes of arterial pressure fall. After two years a magnetic resonance imaging (MRI) revealed an extensive diffuse demyelinative process in white matter of cerebral and cerebellar hemispheres. Activity of lysosomal enzymes was normal. A general autopsy revealed atrophy of adrenal cortex and the presence of ballooned cells with striated cytoplasm in the reticular and fasciculate zones. Neuropathological examination revealed an extensive demyelination of white matter in cerebral and cerebellar hemispheres and of the long paths of the brain stem, corresponding to changes in MRI examination. Within demyelination areas damage of axons and diffuse cellular and fibrous gliosis were found as well as perivascular lymphocytic infiltrations with the presence of strong PAS (+) and Sudan (+) macrophages. Immunocytochemical reactions with HAM-56 and RCA1 in macrophages were positive. Electron microscopy examination revealed lamellar inclusions in cytoplasm of macrophages. Similar structures were present in the lysosomes of astrocytes. Morphological examination of adrenal glands as well as morphological and ultrastructural study of the brain allowed us to diagnose the cerebral form of adrenoleukodystrophy (ALD). Topography and character of the brain changes seems to be in keeping with a rare schizophrenic-like variant of ALD with progressive dementia. Abnormal plasma profile and increased VLCFA concentration in the patient's 13-year-old daughter confirm the ALD diagnosis.

Adrenoleukodystrophy↗
PubMed1995

MRI changes in the central nervous system in a child with lupus erythematosus.

We report on a 10-year-old girl with systemic lupus erythematosus who presented in status epilepticus as the only manifestation of central nervous system involvement. MRI of the brain showed diffuse gray and white matter lesions which almost completely resolved after treatment with methylprednisolone. MRI findings in this child are similar to those in adults with diffuse clinical manifestations. The study is essential in the initial evaluation of patients suspected of central nervous system lupus.

Brain↗