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PubMed2000

Developmental neuroimaging of children using magnetic resonance techniques.

Cognitive and motor development in children remain fascinating processes that are uniquely human. Progress has been made in recent years in elucidating the prenatal process of human brain development. In addition, much information exists regarding the behavioral aspects of postnatal human development. However, little is known about the relationship between anatomic postnatal central nervous system development and the accretion of functional milestones observed in children from the neonatal period through adolescence. Recently, powerful qualitative and quantitative magnetic resonance techniques have been developed that will permit detailed inquiry into the connection between the developing brain and the developing mind. In this review, first, the steps of prenatal and postnatal brain development are reviewed briefly. Subsequently, recent magnetic resonance imaging data related to human brain development during the fetal, neonatal, and later childhood periods are presented. Finally, functional magnetic resonance imaging (fMRI) is discussed. Specific examples of its usefulness are provided. Magnetic resonance imaging techniques such as quantitative MRI, volumetric MRI, diffusion tensor imaging, and functional magnetic resonance imaging (fMRI) when combined with neurologic and neuropsychologic evaluation, will provide new insights into the cognitive development of children. MRDD Research Reviews 6:68-80, 2000.

Brain↗
PubMed2001

Use of spin echo T(2) BOLD in assessment of cerebral misery perfusion at 1.5 T.

Inadequate blood supply relative to metabolic demand, a haemodynamic condition termed as misery perfusion, often occurs in conjunction with acute ischaemic stroke. Misery perfusion results in adaptive changes in cerebral physiology including increased cerebral blood volume (CBV) and oxygen extraction ratio (OER) to secure substrate supply for the brain. It has been suggested that the presence of misery perfusion may be an indication of reversible ischaemia, thus detection of this condition may have clinical impact in acute stroke imaging. The ability of single spin echo T(2) to detect misery perfusion in the rat brain at 1.5 T owing to its sensitivity to blood oxygenation level dependent (BOLD) contrast was studied both theoretically and experimentally. Based on the known physiology of misery perfusion, tissue morphometry and blood relaxation data, T(2) behaviour in misery perfusion was simulated. The interpretation of these computations was experimentally assessed by quantifying T(2) in a rat model for cerebral misery perfusion. CBF was quantified with the H(2) clearance method. A drop of CBF from 58+/-8 to 17+/-3 ml/100 g/min in the parieto-frontal cortex caused shortening of T(2) from 66.9+/-0.4 to 64.6+/-0.5 ms. Under these conditions, no change in diffusion MRI was detected. In contrast, the cortex with CBF of 42+/-7 ml/100 g/min showed no change in T(2). Computer simulations accurately predicted these T(2) responses. The present study shows that the acute drop of CBF by 70% causes a negative BOLD that is readily detectable by T(2) MRI at 1.5 T. Thus BOLD may serve as an index of misery perfusion thus revealing viable tissue with increased OER.

Animals↗
PubMed2003

MR evidence of structural and metabolic changes in brains of patients with Werner's syndrome.

OBJECTIVE: To assess CNS abnormalities in patients with Werner's syndrome (WS) using MR metrics specific for tissue damage. BACKGROUND: WS is a rare autosomal recessive disorder that causes premature aging. The CNS involvement in this disease is still debated. METHODS: Two siblings who showed signs of neurological involvement underwent MR spectroscopic imaging (MRSI) and magnetization transfer (MT) imaging. Also, on conventional T1-weighted MR images, measurements of total brain volume were performed. RESULTS: Conventional MR images of both WS patients did not show abnormalities on visual inspection. However, both WS patients showed significantly lower values of normalized total brain volume and MT ratio in the white matter than age-matched normal controls. Also, proton MRSI showed significantly lower values of central brain NAA/Cr in WS patients than in normal controls. CONCLUSIONS: Our findings suggest that, despite normal appearance on conventional MRI, diffuse structural and metabolic tissue damage can be demonstrated in WS brains by means of sensitive MR methods even in patients with moderate or subclinical CNS involvement.

Adult↗
PubMed2003

MRI aspects of the "inflammatory phase" of multiple sclerosis.

In early relapsing-remitting (RR) multiple sclerosis (MS), conventional magnetic resonance imaging (MRI) has proved to be a valuable tool to assess disease activity over time. However, conventional MRI can only provide gross estimates of irreversible tissue damage within and outside such lesions. Other MR-based techniques, including magnetization transfer MRI, diffusion-weighted MRI, proton MR spectroscopy and functional MRI, have the potential to provide additional pieces of information about the nature and the extent of MS tissue damage since the early "inflammatory phase" of the disease. The application of these MR techniques to the study of early RRMS is likely to improve our understanding of the pathophysiology of MS and our ability to assess the efficacy of experimental treatments.

Brain↗
PubMed2006

MRI markers of destructive pathology in multiple sclerosis-related cognitive dysfunction.

Studies with conventional magnetic resonance imaging (MRI) indicate that cognitive impairment in multiple sclerosis (MS) patients is not fully explained by the burden of T2-visible lesions in the brain. Other non-conventional MRI techniques with increased specificity to the more destructive aspects of MS pathology, such as magnetization transfer MRI, diffusion-weighted MRI and proton magnetic resonance spectroscopy, have recently been applied to MS cognitive studies. The results suggest that the presence and extent of "occult" MS pathological features in the normal-appearing brain tissue and the location of lesions in eloquent sites play a central role in the pathogenesis of MS neuropsychological impairment.

Atrophy↗
PubMed1999

Cerebral neoplasms in adults.

MRI plays a critical role in the diagnosis, management, and follow-up of adult supratentorial neoplasms. However, there is considerable overlap in the imaging findings of these lesions. New imaging methods, such as functional MRI, diffusion imaging, and spectroscopy may further improve diagnostic specificity and surgical management. Knowledge of the pathogenesis of these tumors, imaging characteristics, and available novel imaging tools will aid the radiologist in making meaningful contributions in the evaluation and treatment of these lesions.

Adult↗
PubMed2003

Consciousness disturbances in megalencephalic leukoencephalopathy with subcortical cysts.

Megalencephalic leukoencephalopathy with subcortical cysts (MLC) is a genetic disorder featuring diffuse MRI white matter abnormalities and a discrepantly mild clinical picture. It is related to different mutations in MLC1 gene encoding a putative membrane protein of still unknown function. We report on a genetically proven MLC patient who presented with a peculiar clinical course characterized by a prolonged comatose state following a minor head trauma at 12 years of age. The disturbance of consciousness lasted for over four months and then gradually improved. Proton MR spectroscopic imaging studies showed a moderately severe depletion of N-acetylaspartate restricted to the white matter with sparing of the cortical grey matter. The full recovery from coma suggests a transitory functional impairment of the structures implicated in the maintenance of consciousness.

Brain Diseases↗
PubMed2004

Brainstem neurodegeneration correlates with clinical dysfunction in SCA1 but not in SCA2. A quantitative volumetric, diffusion and proton spectroscopy MR study.

Magnetic resonance (MR) techniques enable in vivo measurement of the atrophy of the brainstem and cerebellum in spinocerebellar ataxia type 1 (SCA1) and 2 (SCA2) patients, which is accompanied by a decrease in the concentration of N-acetyl aspartate (NAA) or of the NAA/creatine ratio in the pons and cerebellum. Mean diffusivity (D) is emerging as an additional sensitive and quantitative MR parameter to investigate brain diseases. In order to explore differences between the MR features of SCA1 and SCA2 and correlate the MR and clinical findings in the two conditions, we examined 16 SCA1 patients, 12 SCA2 patients and 20 healthy control subjects. The MR protocol included T1-weighted 3D gradient echo sequences, single-voxel proton spectroscopy of the right cerebellar hemisphere (dentate and peridentate region) and of the pons with a PRESS sequence and an external reference quantitation method, and (in nine patients with SCA1 and nine patients with SCA2) diffusion-weighted echo-planar images with reconstruction of the D maps. The patients were evaluated with the Inherited Ataxia Clinical Rating Scale (IACRS). Compared with control subjects, the SCA1 and SCA2 patients showed a decrease (P < 0.01) in the volume of the brainstem and cerebellum and in the concentration of NAA in the pons and cerebellar hemisphere, whereas D of the brainstem and cerebellum was increased. No significant difference was observed between the SCA1 and SCA2 patient groups. No correlation between cerebellar volume and dentate and peridentate NAA concentration was found in SCA1 or SCA2 patients. The volume of the brainstem, D of the brainstem and cerebellum and the concentration of NAA in the pons were correlated (P < 0.05) with the IACRS score in SCA1 but not in SCA2. This discrepancy is in line with the clinical observation that the clinical deficit has a later onset and faster progression in SCA1 and an earlier onset and slower progression in SCA2, and suggests that neurodegeneration of the brainstem is a comparatively more rapid process in SCA1. In conclusion, our study indicates that SCA1 and SCA2 substantially exhibit the same MR features. The correlation in SCA1 between clinical severity and quantitative volumetric, diffusion MRI and proton MR spectroscopy findings in the brainstem indicates that these measurements might be employed for longitudinal studies and hopefully as surrogate markers in future pharmacological trials of this condition.

Adult↗
PubMed2002

Diffusion tensor in posterior cingulate gyrus: correlation with cognitive decline in Alzheimer's disease.

To determine whether the diffusion abnormalities in brains with Alzheimer's disease (AD) correlate with disease severity, we studied 34 AD patients using diffusion tensor MRI. Mean diffusivity and fractional anisotropy (FA) as well as three eigenvalues (lambda1, lambda2, and lambda3) of the diffusion tensor of the posterior cingulate white matter correlated with the Mini-Mental State Examination (MMSE) score. The mean diffusivity and the three eigenvalues showed significant correlation with the MMSE score. On the other hand, no significant correlation was seen between the FA and MMSE score. Our results suggested that mean diffusivity and the eigen-values, but not FA, reflect progression of AD-related histopathlogical changes in the posterior cingulate white matter and may be useful biological indices to monitor AD.

Aged↗
PubMed2003

Anesthesia during high-field intraoperative magnetic resonance imaging experience with 80 consecutive cases.

Intraoperative magnetic resonance imaging (MRI) has been used for years to update neuronavigation and for intraoperative resection control. For this purpose, low-field (0.1-0.2 T) MR scanners have been installed in the operating room, which, in contrast to machines using higher magnetic field strength, allowed the use of standard anesthetic and surgical equipment. However, these low-field MR systems provided only minor image quality and a limited battery of MR sequences, excluding functional MRI, diffusion-weighted MRI, or MR angiography and spectroscopy. Based on these advantages, a concept using high-field MRI (1.5 T) with intraoperative functional neuronavigational guidance has been developed that required adaptation of the anesthetic regimen to working in the close vicinity to the strong magnetic field. In this paper the authors present their experience with the first 80 consecutive patients who received anesthesia in a specially designed radio frequency-shielded operating room equipped with a high-field (1.5 T) MR scanner. We describe the MR-compatible anesthesia equipment used including ventilator, monitoring, and syringe pumps, which allow standard neuroanesthesia in this new and challenging environment. This equipment provides the use of total intravenous anesthesia with propofol and remifentanil allowing rapid extubation and neurologic examination following surgery. In addition, extended intraoperative monitoring including EEG monitoring required for intracranial surgery is possible. Moreover, problems and dangers related to the effects of the strong magnetic field are discussed.

Adolescent↗
PubMed2004

No evidence of cerebral oedema in severe acute mountain sickness.

In a randomized, double-blind cross-over study 10 subjects were exposed to a simulated altitude of 4500 m for 10 h after administration of placebo, acetozolamide (250 mg bid) or theophylline (250 mg bid). T2-weighted magnetic resonances images (MRI) and diffusion weighted MRI were obtained directly after exposure to altitude under hypoxic conditions. Although eight of 10 subjects had moderate to severe acute mountain sickness (AMS), we found no evidence of cerebral oedema, irrespective of the medication taken. Almost all subjects showed a decrease in inner cerebrospinal fluid (iCSF) volumes (placebo - 10.3%, P= 0.02; acetazolamide - 13.2%, P= 0.008, theophylline -12.2%, n.s.). There was no correlation between AMS symptoms and fluid shift. However, we found a significantly positive correlation of large (>10 ml) iCSF volume and more severe AMS after administration of placebo (r = 0.76, P= 0.01). Moderate to severe AMS after high altitude exposure for 10 h is associated with a decreased iCSF-volume independent of AMS severity or medication without signs of cerebral oedema.

Acetazolamide↗
PubMedDate not supplied

Cerebral venous congestion following closed head injury in a child.

In pediatric patients with head injury, progressive hemispheric low density (HLD) on CT is a specific phenomenon although the underlying mechanism remains controversial. We used CT, MRI, diffusion weighted imaging (DWI), and perfusion weighted imaging (PWI) studies to identify pathophysiological patterns in a child. A 6-year-old boy sustained a left temporal head injury in a car accident. Although the initial CT was normal, serial CT demonstrated progressive left HLD; an extensive heterogeneous high-intensity lesion was noted on fluid-attenuated imaging recovery (FLAIR) and DWI studies. On PWI, the regional cerebral blood volume was increased and the mean transit time was markedly prolonged. After the conservative treatment, despite the widespread abnormal imaging on CT and DWI, the final brain damage located in isolated left temporal cortical brain damage. The lesion coincided with the area on PWI where increased rCBV and MTT prolongation were noted. Based on these findings, we posit that the extensive but reversible brain changes seen on neuroimaging studies were the result of venous congestion. Our result stresses the importance of functional neuroimaging such as DWI and PWI in order to elucidate the pathophysiology of HLD.

Accidents, Traffic↗
PubMed2002

Diazepam does not reduce infarct size in rats subjected to transient occlusion of the middle cerebral artery when normothermia is maintained.

Activation of the gamma-amino butyric acid (GABA)-ergic system might protect against the damage that occurs after cerebral ischaemia. We examined this hypothesis by administering diazepam to rats subjected to transient middle cerebral artery occlusion (MCAO) using the intraluminal thread method. Diffusion MRI (DWI) and perfusion imaging (PI) were acquired during MCAO to assess brain tissue status and haemodynamics, respectively. Rats were intraperitoneally injected with either 10 mg kg(-1) diazepam (n = 5) or vehicle (n = 5) both 30 min and 90 min after the onset of MCAO. To exclude the possibility that neuroprotection was due to the hypothermic action of the drug, body temperature was maintained at 37-38 degrees C for up to 7 h postischaemia with a feed-back controlled thermoregulatory unit. Infarct volumes quantified 2 days after MCAO from T(2)-weighted images were similar in ischaemic control rats and in ischaemic rats treated with diazepam. We conclude that diazepam-induced enhancement of GABA(A) activity does not effectively protect against neuronal damage that occurs after transient MCAO in normothermic rats.

Animals↗
PubMed2002

MRI techniques to monitor MS evolution: the present and the future.

Conventional MRI (cMRI) is limited in its ability to provide specific information about pathology in MS. Measures commonly derived from cMRI include T2 lesions, T1-enhanced lesions, atrophy, and possibly T1-hypointense lesions, which have been extensively investigated in many clinical trials. Better MRI measures are needed to advance our understanding of MS and design ideal clinical trials. This article reviews the strengths and weaknesses of the major MRI-based methods used to monitor MS evolution and submits that 1) metrics derived from magnetization transfer MRI, diffusion-weighted MRI, and proton MRS should be implemented to achieve reliable specific in vivo quantification of MS pathology; 2) targeted multiparametric MRI protocols rather than generic application of cMRI should be used in all possible clinical circumstances and trials; and 3) reproducible quantitative MR measures should ideally be used for the assessment of patients but are essential for clinical trials.

Brain↗
PubMed1999

Echoplanar MRI in patients with an acute stroke syndrome.

An increasing number of patients with an acute stroke syndrome are being admitted to hospitals with on-site echoplanar MRI scanners. In this pictorial review, we describe our experience of an MRI protocol in the first 150 such patients scanned in our hospital. We illustrate some of the advantages of using echoplanar MRI. Diffusion and susceptibility weighted acquisitions may supplement conventional MR sequences by providing useful additional information about the age and location of the lesion, together with a high sensitivity to the presence of blood breakdown products.

Acute Disease↗
PubMed1998

[Brain water diffusion coefficients and diffusion anisotropy in non-demented patients with diffuse leuko-araiosis].

PURPOSE: To investigate changes in both water diffusion coefficients and diffusion anisotropy in white matter of non-demented patients with leuko-araiosis using diffusion-weighted MRI. METHODS: Diffusion mapping was performed on 8 non-demented patients with leuko-araiosis, 6 patients with chronic cerebral infarction and 6 healthy volunteers, using a spin-echo sequence with motion probing gradient applied sequentially at two gradient strength settings in three orthogonal directions. The apparent diffusion coefficients (ADC) were calculated from 4 regions of interest located within the frontal and parietal subcortical white matter. The index of diffusion anisotropy (IDA) was calculated from the ADC in three orthogonal directions. (IDA = ADCmax-min/ADCmean x 100). RESULTS: Significantly larger ADC were found within the frontal and parietal subcortical white matter in the non-demented patients with leuko-araiosis (mean = 1.51 +/- 0.36 x 10(-3) mm2/s) and the were also significantly larger in patients with cerebral infarction (mean = 2.12 +/- 0.46 x 10(-3) mm2/s) than in the control group (mean = 1.01 +/- 0.33 x 10(-3) mm2/s). But no significant differences were found in the IDA between the non-demented patients with leuko-araiosis (mean = 43.1 +/- 29.2) and the control group (mean = 46.5 +/- 32.5). CONCLUSION: An increase in extracellular space caused by the loss of axonal fibers and myelin is probably the cause of the higher ADC in periventricular hyperintensity lesions. However, the remaining nerve fibers maintain the anisotropy in the lesions in non-demented patients with leuko-araiosis.

Aged↗
PubMed1998

[Spontaneous intracranial hypotension: case report].

Spontaneous intracranial hypotension is a rare syndrome associated with postural cephalalgia and low pressure of the cerebrospinal fluid. We report the case of a 45 years-old man with spontaneous intracranial hypotension with MRI diffuse meningeal enhancement.

Humans↗
PubMed2000

Diagnostic imaging for stroke.

With the advent of therapy for acute stroke via in intraarterial or intravenous pathway, early diagnosis with physician education is extremely important. A common theme in all studies is the continued stress on patient and physician education, rapid triage and diagnosis with the use of CT scanning, xenon blood flow or diffusion MRI, cerebral protection, and revascularization with either carotid surgery or percutaneous angioplasty for an offending lesion, if such is identified. Although the current studies are cautiously optimistic, prospective randomized trials are needed for the evaluation of intraarterial thrombolytics as well as percutaneous transluminal angioplasty. It is important that the neurosurgical community be identified as physicians who can diagnose and treat the patient with an acute stroke.

Cerebral Angiography↗