MRI in neurofibromatosis type I: Using fluid-attenuated inversion recovery pulse sequences

Cranial magnetic resonance imaging results of 14 patients with neurofibromatosis type I were examined with T₂-weighted fluid-attenuated inversion recovery pulse sequences, as well as conventional T₂-weighted spin-echo sequences. Definition was better in 62 of 79 lesions or groups of lesions on fluid-attenuated inversion recovery images than on T₂-weighted spin-echo images. The lesions were demonstrated not only in the brainstem, cerebellum, globus pallidus, and cerebral white matter, but also in the hippocampus, pulvinar thalami, and splenium of the corpus callosum. The latter 3 lesions have not been demonstrated or emphasized in previous studies. It is concluded that fluid-attenuated inversion recovery imaging is more effective in detecting multiple lesions in patients with neurofibromatosis type I than conventional T₂-weighted spin-echo imaging.     

Magnetic Resonance Imaging and Diffusion-Weighted Imaging Changes After Hypoglycemic Coma

The authors report a case of severe hypoglycemic encephalopathy in an elderly patient. The magnetic resonance images showed bilateral cortical signal changes and basal ganglia lesions, which spared the thalami. The lesions were bright on fluid-attenuated inversion recovery and diffusion-weighted images and dark on the apparent diffusion coefficient map, being more conspicuous on the diffusion-weighted images than on the fluid-attenuated inversion recovery images. A literature review of the imaging features and pathophysiological mechanism in comparison with those of hypoxic ischemic injury is discussed.     

Correlation between blink reflex abnormalities and magnetic resonance imaging findings in patients with multiple sclerosis

This study investigates the correlation between brain magnetic resonance imaging findings and blink reflex abnormalities in patients with relapsing remitting multiple sclerosis. Twenty-six patients and 17 healthy subjects were included in this study. Blink reflex test (BRT) results were obtained using right and left stimulations; thus, 52 BRT results were recorded for the patient group, and 34 BRT results were recorded for the control group. The magnetic resonance imaging (MRI) findings were classified based on the existence of brainstem lesions (hyperintense lesion on T2 weighted (W) and fast fluid-attenuated inversion recovery MRI or contrast-enhancing lesion on T1W MRI). Correlation analysis was performed for the BRT and MRI findings. The percentage of individuals with abnormal BRT results (including R1 latency, ipsilateral R2 latency, and contralateral R2 latency) was significantly higher in the patient group as compared to the control group (p values: 0.015, 0.001, and 0.002, respectively). Correlation analysis revealed significant correlations between contralateral R2 latency abnormalities and brainstem lesions (p value: 0.011). Our results showed significant correlation correlations between contralateral R2 latency abnormalities and brainstem lesions and these results may be explained the effects of multiple demyelinating lesions of the brain stem of patients with relapsing remitting multiple sclerosis.     

The place of conventional MRI and newly emerging MRI techniques in monitoring different aspects of treatment outcome

Magnetic resonance imaging (MRI) is the most important paraclinical measure for assessing and monitoring the pathologic changes implicated in the onset and progression of multiple sclerosis (MS). Conventional MRI sequences, such as T1-weighted gadolinium (Gd) enhanced and spin-echo T2-weighted imaging, only provide an incomplete picture of the degree of inflammation and underlying neurodegenerative changes in this disease. Two- and three-dimensional fluid-attenuated inversion recovery and double inversion recovery sequences allow better identification of cortical, periventricular and infratentorial lesions. Ultra-high field strength MRI has the potential to detect subpial cortical and deep gray matter lesions. Unenhanced T1-weighted imaging can reveal hypointense black holes, a measure of chronic neurodegeneration. Magnetization transfer imaging (MTI) is increasingly used to characterize the evolution of MS lesions and normal-appearing brain tissue. Evidence suggests that the dynamics of magnetization transfer changes correlate with the extent of demyelination and remyelination. Magnetic resonance spectroscopy, which provides details on tissue biochemistry, metabolism, and function, also has the capacity to reveal neuroprotective mechanisms. By measuring the motion of water, diffusion imaging can provide information about the orientation, size, and geometry of tissue damage in white and gray matter. These advanced non-conventional MRI techniques relate better to clinical impairment, disease progression, accumulation of disability, and have the potential to detect neuroprotective effects of treatment. Although detecting the status of neuronal integrity using MRI techniques continues to improve, a "gold standard" model remains to be established.     

Continuing optic nerve atrophy following optic neuritis: a serial MRI study

To investigate optic neuritis as a model for atrophy in multiple sclerosis (MS) lesions we performed serial magnetic resonance imaging (MRI) on 10 patients with a history of optic neuritis using a fat saturated short-echo fast fluid-attenuated inversion recovery (sTE fFLAIR) sequence. The first study was performed a median of 19.5 months after the onset of optic neuritis and the second 1 year later. Using a computer-assisted contouring technique, a blinded observer calculated the mean area of the intro-orbital optic nerves. The mean area of affected optic nerves decreased over 1 year by 0.9 mm2 from 11.1 to 10.2 mm2 (p = 0.01). Poor visual acuity and decreased visual-evoked potential (VEP) amplitude were associated with atrophy. These findings suggest that atrophy is a feature of focal demyelinating lesions, it may evolve over several years, and may have functional significance. Optic neuritis provides a model to study the effect of inflammatory demyelination through the ability to accurately measure visual function and to visualize and measure the optic nerves using magnetic resonance imaging.     

Long spinal cord lesions in a patient with pathologically proven multiple sclerosis

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system. We report the case of a 50-year-old man who presented with progressive gait ataxia. Brain magnetic resonance imaging (MRI) on fluid-attenuated inversion recovery revealed a hyperintense lesion in the right temporal white matter. The spinal cord showed a long hyperintense lesion between the vertebral levels C6 and L1 on T2-weighted MRI. Biopsied tissues from the brain lesion demonstrated features of inflammatory demyelination with preservation of astrocytes, consistent with typical MS. This is the first reported case of pathologically proven MS with longitudinally extensive spinal cord lesions.     

Neuronal damage in T1-hypointense multiple sclerosis lesions demonstrated in vivo using proton magnetic resonance spectroscopy.

Hypointense T1 lesions in multiple sclerosis patients correlate with axonal loss at autopsy and biopsy. We evaluated the chemical substrate of hypointense T1 lesions by using in vivo proton magnetic resonance spectroscopy, and analyzed the spectroscopic correlate of increased T1-relaxation time measurements. Localized proton magnetic resonance spectroscopy and T1-relaxation time measurements were performed in lesions, selected on T1-weighted spin-echo magnetic resonance images according to degree of hypointensity, in normal appearing white matter (NAWM) and in normal white matter of controls. In NAWM, prolongation of T1-relaxation time and a decrease in N-acetylaspartate (NAA) were present, compared with normal white matter. Severely hypointense lesions showed a lower concentration of NAA and creatine compared with NAWM and a lower concentration of NAA compared with isointense to mildly hypointense lesions. NAA concentration correlated with degree of hypointensity of lesions and with T1-relaxation time within the spectroscopic voxel. Our results provide the first in vivo evidence of axonal damage in severely hypointense T1 lesions in multiple sclerosis patients. T1-relaxation time correlates with the concentration of NAA in both multiple sclerosis lesions and NAWM, indicating that this parameter deserves further evaluation to monitor disease progression.     

Infratentorial lesions predict long-term disability in patients with initial findings suggestive of multiple sclerosis

BACKGROUND: The number and volume of abnormalities on baseline brain magnetic resonance images in patients with initial findings suggestive of multiple sclerosis are known to predict outcome in terms of disability. However, no long-term data exist on specific locations or types of lesions. OBJECTIVE: To assess the long-term predictive value of baseline magnetic resonance imaging parameters, including location of lesions and gadolinium-enhancing and hypointense lesions in patients with initial findings suggestive of multiple sclerosis for the occurrence of clinically relevant disability as defined by an Expanded Disability Status Scale score of 3. PATIENTS: After a median follow-up period of 8.7 years, the medical records of 42 patients were reviewed and assessed for time until patients received an Expanded Disability Status Scale score of 3. Magnetic resonance imaging parameters were dichotomized according to maximum accuracy and then used to calculate hazard ratios using the Cox model for proportional hazard ratios. RESULTS: Conversion to clinically definite multiple sclerosis was observed in 26 patients (62%), of whom 14 (54%) progressed to an Expanded Disability Status Scale score of 3. Two or more infratentorial lesions best predicted long-term disability (hazard ratio, 6.3). Gadolinium-enhancing and hypointense T1-weighted lesions did not show prognostic value. CONCLUSION: Infratentorial lesions are related to long-term prognosis for patients with initial findings suggestive of multiple sclerosis and thus may help to identify patients at high risk for earlier occurrence of clinically relevant disability.     

Reversible posterior encephalopathy syndrome as the presentation of late postpartum eclampsia: a case report

We presented a case of previous healthy postpartum woman suffering from seizure of sudden onset with conscious change and anisocoric pupils. Head magnetic resonance imaging (MRI) revealed multiple high signal-intensity lesions on fluid-attenuated inversion recovery (FLAIR) / T2 weighted image (T2WI) in bilateral subcortical white matters (especially the parieto-occipital areas), brain stem, and bilateral cerebellum, and mild high signal-intensity lesions on diffusion weighted MRI (DWI). These neurological and radiological anomalies recovered completely later. The final diagnosis was the rare presentation of late postpartum eclampsia as reversible posterior encephalopathy syndrome (RPES).     

Diffusion-weighted magnetic resonance imaging and identification of the epileptogenic tuber in patients with tuberous sclerosis

BACKGROUND: Patients with tuberous sclerosis complex and drug-resistant epilepsy may be considered candidates for epilepsy surgery. This demands the unambiguous demonstration of the epileptogenicity of one of the tubers. OBJECTIVE: To test whether diffusion-weighted magnetic resonance imaging enables differentiation of epileptogenic tubers from inert ones. METHODS: In 4 patients with clear unifocal interictal spike activity, fluid-attenuated inversion recovery and diffusion-weighted magnetic resonance imaging were performed. Apparent diffusion coefficient maps were calculated in the identified epileptogenic tuber and compared withthose in nonepileptogenic tubers and regions of normal-appearing cortex. RESULTS: A significant increase in the apparent diffusion coefficient was found in the epileptogenic tubers. Furthermore, the apparent diffusion coefficient of the nonepileptogenic tubers was significantly higher than the trace apparent diffusion coefficient of regions of normal-appearing cortex. CONCLUSION: Diffusion-weighted magnetic resonance imaging may be of clinical importance for the identification of epileptogenic tubers in patients with tuberous sclerosis and intractable epilepsy.     

Clinical and radiologic manifestations of H1N1 virus infection associated with neurological complications: a case report

Encephalitis complicating novel influenza A (H1N1) viral infection is rare and has only been reported in children. We present cerebral magnetic resonance imaging findings from a confirmed adult case with H1N1 infection who presented with acute encephalitis and subsequent respiratory failure. Cerebral magnetic resonance imaging showed hyperintense abnormalities in the bilateral globus pallidus in T1-weighted images, and multiple hyperintense abnormalities in the right insular cortex, right parahippocampus, and the pontine tegmentum in fluid-attenuated inversion recovery images.     

Magnetic resonance techniques in multiple sclerosis: the present and the future

Magnetic resonance imaging (MRI) is sensitive to focal multiple sclerosis (MS) lesions. For this reason, conventional MRI measures of the burden of disease derived from dual-echo, fluid-attenuated inversion recovery and postcontrast T1-weighted sequences are regularly used to monitor disease course in patients with confirmed MS and have been included in the diagnostic workup of patients in whom MS is suspected. Other quantitative magnetic resonance (MR)-based techniques with a higher pathological specificity (including magnetization transfer-MRI, diffusion tensor-MRI, and proton MR spectroscopy) have been extensively applied to measure disease burden within focal visible lesions and in the normal-appearing white matter and gray matter of MS patients at different stages of the disease. These methods, combined with functional imaging techniques, are progressively improving our understanding of the factors associated with MS evolution. More recently, the application of new imaging modalities capable of measuring pathological processes related to the disease that have been neglected in the past (eg, iron deposition and perfusion abnormalities) and the advent of high- and ultrahigh-field magnets have provided further insight into the pathobiological features of MS. After a brief summary of the main results obtained from the established and emerging MR methods, this review discusses the steps needed before the latter become suitable for widespread use in the MS research community.     

Prediction of neuropsychological impairment in multiple sclerosis: comparison of conventional magnetic resonance imaging measures of atrophy and lesion burden

BACKGROUND: Cognition and magnetic resonance imaging correlations are well established in patients with multiple sclerosis (MS), but it is unclear whether lesion burden or atrophy accounts for most of the predictive variance. These indices have been directly compared in only a few studies. No such study included measurement of the third ventricle, which was strongly predictive of neuropsychological competence in the early literature. Furthermore, few studies accounted for the influence of age, premorbid intelligence, or depression. OBJECTIVE: To determine if conventional measures of lesion burden or atrophy predict cognitive dysfunction in MS while accounting for age, premorbid intelligence, and depression. METHODS: We studied 37 patients with MS and 27 controls matched according to demographic variables. Correlations between neuropsychological tests and the following magnetic resonance imaging indices were considered: T1 hypointense lesion volume, fluid-attenuated inversion recovery hyperintense lesion volume, third ventricle width, bicaudate ratio, and brain parenchymal fraction. Regression models predicting neuropsychological performance controlled for the effects of age, premorbid intelligence, and depression. We included only those tests discriminating patients with MS from controls. RESULTS: In each regression model, third ventricle width was the sole magnetic resonance imaging measure retained. When this variable was removed from consideration, brain parenchymal fraction was retained in all analyses. CONCLUSIONS: Brain atrophy accounts for more variance than lesion burden in predicting cognitive impairment in MS, and central atrophy in particular is strongly associated with neuropsychological morbidity. This finding may be explained in part by atrophy of the thalamus, a deep gray matter structure that mediates cognitive function via cortical and subcortical pathways. Enthusiasm for the clinical utility of third ventricle width is tempered by modest intraobserver and interobserver reliability.     

The effect of the neuroprotective agent riluzole on MRI parameters in primary progressive multiple sclerosis: a pilot study

Progressive axonal loss is the most likely pathologic correlate of irreversible neurologic impairment in primary progressive multiple sclerosis. In a run-in versus treatment trial, we show that the neuroprotective agent riluzole seems to reduce the rate of cervical cord atrophy and the development of hypointense T1 brain lesions on magnetic resonance imaging.     

Nuclear magnetic resonance imaging in multiple sclerosis

Ten patients with definite multiple sclerosis underwent hydrogen nuclear magnetic resonance imaging with a 3.5 kilogauss superconducting magnet, using the inversion recovery and spin-echo techniques of signal acquisition. Results were compared with high-resolution x-ray computed tomography. Spin-echo images demonstrated abnormal regions as areas of variably increased signal intensity. The contrast between abnormal and normal white matter improved as the intervals between sequential radiofrequency pulses and between pulse administration and signal sampling were increased. Inversion recovery images demonstrated abnormal areas as regions of decreased signal intensity but did not visualize lesions as well as spin-echo imaging. Spin-echo and inversion recovery imaging each demonstrated more extensive abnormalities than did computed tomography.     

Evaluation of T2-FLAIR combined with ASL on the collateral circulation of acute ischemic stroke

Neurological Sciences - Using magnetic resonance fluid-attenuated inversion recovery sequence (FLAIR) combined with three-dimensional arterial spin labeling (3D-ASL) cerebral perfusion imaging to...     

Diagnostic usefulness of diffusion-weighted magnetic resonance imaging in influenza-associated acute encephalopathy or encephalitis

A magnetic resonance imaging (MRI) study was performed for a 20-month-old girl with an influenza type A infection who presented acute encephalopathy. Conventional MRI performed 8 days after the onset of encephalopathy, including T1-weighted, T2-weighted, and fluid-attenuated inversion recovery imaging, revealed only vague lesions in the right frontal, temporal, and parietal lobes. In contrast, diffusion-weighted imaging (DWI) then demonstrated the lesions much more intensively. On the 26th day, the lesions previously observed on DWI had become less discernible. The hyperintensity observed on DWI might reflect cytotoxic edema. Thus, DWI may be useful for evaluation of acute influenzal encephalopathy/encephalitis.     

Chronological changes of lacunar infarctions on fluid-attenuated inversion recovery magnetic resonance images]

In 26 patients with lacunar syndromes, emergence of new lacunar infarctions were identified within 13 days from onset by diffusion-weighted magnetic resonance images. The identified lacunar infarctions were repeatedly imaged using fluid-attenuated inversion recovery (FLAIR) sequence up to 600 days from onset. On FLAIR images taken by 23 days from onset, lacunar infarctions showed homogeneous hyperintensity. On the later FLAIR images beyond 25 days from onset they were observed as heterogeneously hyperintense lesions in half of the patients. In the other patients, lacunar infarctions were observed as hypointense areas with a hyperintense rim beyond 41 days from onset, which indicates cystic transformation with surrounding gliosis. These FLAIR images of lacunar infarction differ from those of dilated perivascular space which is observed as an area of simple hypointensity.     

Rasmussen syndrome: multifocal spread of inflammation suggested from MRI and PET findings

BACKGROUND: A 6-year-old girl with Rasmussen syndrome (RS) showed multiple small high-signal-intensity areas independently in the right hemisphere by fluid-attenuated inversion recovery (FLAIR) imaging on magnetic resonance imaging (MRI) 1 year after the onset of epilepsy. METHODS: MRI performed 4 months later demonstrated a further increase in the number of these foci and enlargement in the size of the previous FLAIR lesions. RESULTS: An [18F]-fluorodeoxyglucose-positron emission tomography (FDG-PET) study showed a strong, spotty uptake in the right temporooccipital regions, corresponding to the sites of continuous EEG seizure discharges. In contrast, [11C]methionine PET demonstrated multifocal uptake regions, which corresponded anatomically to the FLAIR lesions, suggesting sites of underlying chronic inflammation. CONCLUSIONS: These neuroimaging findings suggested that the inflammatory process in RS spreads either multifocally at the same time, as seen in this case, or from one discrete area to the adjacent region, as reported previously.     

Hypertensive encephalopathy involving the brainstem and deep structures: a case report

Hypertensive encephalopathy rarely presented with widespread edema in the cerebral white matters, deep structures and whole brainstem. A 80-year-old woman manifested as high arterial blood pressure, visual disturbance, severe headache, nausea, and vomiting. T2-weighted and fluid-attenuated inversion recovery magnetic resonance imaging showed high signal-intensity lesions in the cerebral white matter, cerebellum, basal ganglia, thalamus, and brainstem. Diffusion-weighted brain MRI did not show hyperintense signals in these lesions. These findings suggested the pathological basis of vasogenic edema. After control of hypertension, clinical symptoms and these edematous lesions on MRI gradually reduced.