Diffusion-weighted MR findings in a reversible case of acute Wernicke encephalopathy

We report a case of acute Wernicke encephalopathy (WE) in which apparent diffusion coefficient maps showed areas of increased diffusion in the bilateral medial thalami that corresponded to the hyperintense lesions on T2-weighted imaging. The hyperintense lesions on T2-weighted imaging disappeared with full recovery from symptoms. These findings suggest that the hyperintense lesions of the acute changes of WE include reversible vasogenic edema and are not caused by acute ischemia.     

Diffusion-weighted magnetic resonance imaging in Wernicke's encephalopathy

OBJECTIVE: To report diffusion-weighted imaging (DWI) findings and postulate the pathogenic mechanism of Wernicke's encephalopathy (WE). PATIENT: A 47-year-old-woman presented with altered consciousness, ophthalmoplegia, and ataxia. DWI revealed the abnormal signal changes in periaqueductal gray matter, mamillary bodies and bilateral medial thalami. Apparent diffusion coefficient (ADC) map revealed the high signal intensity lesions in bilateral medial thalami, suggestive of vasogenic edema. The abnormal signal intensity lesions disappeared on follow-up imaging with clinical improvement. CONCLUSIONS: Vasogenic edema plays an important role in the pathogenesis of WE and can be reversed by proper management. DWI findings in the early stage of WE may provide useful information about the prognosis.     

Diffusion-weighted magnetic resonance imaging in early stage of 5-fluorouracil-induced leukoencephalopathy

We report a case of 5-fluorouracil (5-FU)-induced leukoencephalopathy in which magnetic resonance imaging (MRI) of the brain, including diffusion-weighted imaging (DWI), was performed serially. The initial T2-weighted and FLAIR images showed diffuse mild hyperintensity in bilateral deep cerebral white matter and corpus callosum, which on T1WI appeared as non-enhanced faint hypointensity. Isotropic DWI disclosed the abnormality as well-conspicuous diffuse hyperintensity with decreased ADC. Serial studies revealed that majority of the abnormal signal intensity on these sequences resolved, and the decreased ADC values approached normal. Some hyperintensity remained in the deep cerebral white matter and the splenium, but no further significant ADC change after normalization was noted. Measurement of ADC along the three orthogonal directions showed the presence of directional dependence of diffusion throughout the length of study. These findings suggest that early stage of 5-FU-induced leukoencephalopathy is associated with reversible restricted diffusion and preservation of anisotropy. Diffusion-weighted imaging may be useful for the diagnosis.     

Sequential magnetic resonance imaging findings in hypereosinophilia-induced encephalopathy

Hypereosiophilia-induced encephalopathy (HE) is a rare but well-described clinical syndrome. However, serial magnetic resonance imaging (MRI) findings of HE have rarely been reported. We describe serial MRI findings of three patients with HE. The patients presented with acute confusion, focal neurological deficits and/or seizures. Eosinophils in repeated blood tests were more than 3000/mm³ in all the patients. Echocardiography in two patients showed findings consistent with eosinophilic endomyocardial fibrosis or global hypokinesia. The initial MRI revealed multiple high-signal lesions on T2-weighted images with gadolinium-DTPA enhancement on T1-weighted images, which were predominantly distributed in the border zone of the middle-anterior cerebral arteries and the middle-posterior cerebral arteries. The second MRIs taken prior to the initiation of steroid therapy showed that the lesions increased in size and number in the same area. The third MRIs performed long after the therapy showed that the lesions were shrunken. A brain biopsy specimen in one patient showed reactive gliosis following infarction with abundant intravascular eosinophils. The MRI-identified lesions in the patients with HE thus develop mainly in the border zone. The lesions occasionally increase in size and number and shrink if the eosinophilia is adequately treated. Although the nature of the MRI-identified lesions remains unclear, their pathogenesis may be related to multiple embolisms associated with concomitant cardiac abnormality and hypercoagulable state. Received: 18 July 2000, Received in revised form: 26 September 2000, Accepted: 24 October 2000     

Diffusion-weighted magnetic resonance imaging (MRI) in acute brain stem infarction]

Diffusion-weighted magnetic resonance imaging (DWI) provides one of the earliest demonstrations of ischemic lesions. However, some lesions may be missed in the acute stage due to technical limitation of DWI. We therefore conducted the study to clarify the sensitivity of DWI to acute brain stem infarctions. Twenty-eight patients with the final diagnosis of brain stem infarction(midbrain 2, pons 9, medulla oblongata 17) who had been examined by DWI within 24 hours of onset were retrospectively analyzed for how sensitively the initial DWI demonstrated the final ischemic lesion. Only obvious(distinguishable with DWI alone without referring clinical symptoms and other informations) hyperintensity on DWI was regarded to show an ischemic lesion. Sixteen(57.1%) out of 28 patients had brain stem infarctions demonstrated by initial DWI. In the remaining 12 cases, no obvious ischemic lesion was evident on initial DWI. Subsequent MRI studies obtained 127 hours, on average after the onset showed infarction in the medulla oblongata in 11 cases and in the pons in one case. Negative findings of DWI in the acute stage does not exclude possibility of the brain stem infarction, in particulary medulla oblongata infarction.     

Diffusion-weighted magnetic resonance imaging.

Diffusion-weighted magnetic resonance imaging is a specialized technique that measures the degree of diffusion of water molecules within extracellular space and between intracellular and extracellular space. Diffusion-weighted imaging signal is high (bright) when diffusion is restricted, as occurs in cytotoxic damage from ischemia, inflammation, trauma, or tumor. This technique, now available on most magnetic resonance imaging units, is especially helpful in detecting early ischemic stroke and multiple sclerosis and in differentiating arachnoid cyst from epidermoid tumor and brain abscess from neoplasm.     

Diffusion-weighted magnetic resonance imaging at 3.0 Tesla in alcohol intoxication

Acute alcohol intake has pronounced effects on brain function. However, the exact mechanism of action is unclear. Diffusion Magnetic Resonance Imaging (dwMRI) can detect subtle changes in microstructural neural states. Here we tested if dwMRI can detect such changes during alcohol intoxication. We used high-field dwMRI in four healthy subjects at different blood alcohol concentration (0.0 g/L, 0.3 g/L, 0.6 g/L and 1.0 g/L). Although neuropsychological performances declined markedly, no changes in diffusion parameters emerged. First, this finding argues against alcohol-induced diffuse changes of microstructural state and in favour of more specific, possibly receptor-mediated actions of alcohol on brain function. Second, processes involving neurotransmitters that are primarily linked to cognitive function might not be viewable with high-field diffusion MRI.     

Diffusion-weighted magnetic resonance imaging at 3.0 Tesla in alcohol intoxication

Acute alcohol intake has pronounced effects on brain function. However, the exact mechanism of action is unclear. Diffusion Magnetic Resonance Imaging (dwMRI) can detect subtle changes in microstructural neural states. Here we tested if dwMRI can detect such changes during alcohol intoxication. We used high-field dwMRI in four healthy subjects at different blood alcohol concentration (0.0 g/L, 0.3 g/L, 0.6 g/L and 1.0 g/L). Although neuropsychological performances declined markedly, no changes in diffusion parameters emerged. First, this finding argues against alcohol-induced diffuse changes of microstructural state and in favour of more specific, possibly receptor-mediated actions of alcohol on brain function. Second, processes involving neurotransmitters that are primarily linked to cognitive function might not be viewable with high-field diffusion MRI.     

Unusual MR findings of Wernicke encephalopathy with cortical involvement]

We report a 48-year-old chronic alcoholic man, who developed consciousness disturbance, oculomotor paresis, and flaccid tetraplegia. His dietary habit was very poor since one month prior to the present admission and he was drinking alcoholic beverage. On admission on April 19, 1999, he showed disturbance of consciousness, tetraparesis without sensory disturbance, gaze paresis, and vertical nystagmus on downward gaze. His blood thiamine level was 12 ng/ml (normal range: 23.8-45.9). MRI demonstrated symmetric hyperintense lesions in the motor and premotor cortices bilaterally, in addition to other changes indicating Wernicke's encephalopathy. His motor weakness and oculomotor disturbance improved after treatment with intravenous thiamine. His cortical MRI also normalized. We believe that his cortical abnormality was responsible for his motor paresis and this is an unusual and unique finding for Wernicke's encephalopathy.     

Diffusion-weighted and perfusion-weighted magnetic resonance imaging to monitor acute intra-arterial thrombolysis

Diffusion-weighted and perfusion-weighted magnetic resonance imaging (DWI, PWI) are useful in detecting early cerebral ischemic lesions. Intra-arterial thrombolysis is an effective treatment for some patients with acute thromboembolic occlusion. We evaluated the efficacy of acute thrombolytic therapy by using DWI and PWI in 3 patients who presented with internal carotid artery or middle cerebral artery occlusion. On the initial magnetic resonance imaging scans, the abnormal areas shown by PWI were bigger than those shown by DWI. All patients received thrombolytic therapy within 6 hours after stroke onset. In 1 patient, the hyperintensity area detected by initial DWI scanning diminished after thrombolysis. DWI and PWI may be useful to monitor the effectiveness of intra-arterial thrombolysis.     

Diffusion-weighted magnetic resonance imaging of cerebral ischemia

Functional magnetic resonance imaging is providing new insight into neurologic imaging that was not possible with conventional techniques. Diffusion magnetic resonance imaging is one aspect of functional imaging and it allows detection of acute cerebral ischemia that would not have been identified with standard T2-weighted sequences while also differentiating acute from chronic stroke. These unique characteristics suggest tremendous potential of diffusion imaging to help direct therapy of acute ischemic stroke. An understanding of the principles of diffusion imaging is necessary for optimal application of this technique.     

Diffusion-weighted magnetic resonance imagings at the acute stage in two patients with spectacular shrinking deficit due to cardioembolic stroke]

We report diffusion-weighted magnetic resonance imagings (DWI) at the acute stage of two patients with spectacular shrinking deficit (SSD) due to cardioembolic stroke. Patient 1 was a 74-year-old woman with atrial fibrillation (Af) who had been admitted for acute cholecystitis. She abruptly developed consciousness disturbance, global aphasia and right hemiparesis. Her neurological symptoms rapidly improved 30 minutes after onset, and completely disappeared in four hours. Patient 2 was a 84-year-old woman with Af who had been on medication of warfarin potassium for three years. She abruptly developed consciousness disturbance and left hemiplegia. Her neurological symptoms rapidly improved 90 minutes after onset, and almost completely disappeared in ten hours. Their conditions were consistent with SSD in acute cardioembolic stroke. DWI of Patient 1 taken 27 hours after onset showed hyperintense signal areas in the insular and temporal cortices of the left middle cerebral artery territory, and in the parietal cortex corresponding to the border zone between the territories of the left middle cerebral artery and posterior cerebral artery. DWI of Patient 2 taken 39 hours after onset showed hyperintense signal areas in the insular and frontal cortices of the right middle cerebral artery territory, and in the parietal cortex corresponding to the border zone between the territories of the right middle cerebral artery and posterior cerebral artery. They indicated multifocal ischemic injuries at the acute stage. The T2-weighted MRI of Patient 2 showed a slight hyperintense signal area only in the right parietal cortex, but the fluid-attenuated inversion recovery (FLAIR) in both patients showed no abnormal signals in the corresponding areas. To our knowledge, ischemic lesions in DWI of SSD at the acute stage after rapid recovery have not been reported previously. DWI is useful in SSD for detecting ischemic injuries of cardioembolic origin at the early stage.     

Diffusion-weighted magnetic resonance imaging in Alzheimer's disease

Diffusion-weighted imaging (DWI) is a powerful new magnetic resonance imaging technique for evaluating tissue pathophysiology in vivo. We performed DWI in three orthogonal spatial directions in 10 patients with mild to moderate Alzheimer's disease (AD) and 11 control subjects. Average apparent diffusion coefficients (ADCavg) were calculated for gray matter regions, and anisotropy indexes were calculated for white matter regions. Global measures of atrophy and white matter hyperintensities (WMH) were obtained on T2-weighted images to control for their potential confounding effects on ADCavg and anisotropy. The measures of atrophy and WMH differed between the groups and were used as covariates in the subsequent statistical analyses. Patients with AD demonstrated diminished anisotropy in the posterior white matter (p < 0.0001) and increased ADCavg in the hippocampus (p < 0.05) when compared to the control group. Diffusion measures did not correlate with the severity of dementia. DWI provides a unique, quantitative parameter that may be sensitive to the pathophysiological and/or microstructural abnormalities that occur in AD.     

Diffusion-weighted magnetic resonance imaging in brain death

BACKGROUND; Traditionally the diagnosis of brain death is established on the basis of a combination of clinical signs and paraclinical methods. Diffusion-weighted MRI is a new method sensitive to cerebral ischemia. Its value in brain death has not been demonstrated until now. CASE DESCRIPTION: A patient was referred to MRI with suspicion of a brain stem stroke. Echo-planar whole-brain, multislice, diffusion-weighted MRI was performed in addition to conventional sequences and MR angiography sequences. In addition to the extensive bilateral hyperintensities observed on T2-weighted images, diffusion-weighted MRI showed diffuse hyperintensities involving both hemispheres as well as a severe drop in the apparent diffusion coefficient in both affected hemispheres. There was also transtentorial herniation with compression of the brain stem as well as absence of flow voids on the T2-weighted images and absence of intracranial vessels on MR angiography. On the basis of the clinical and imaging findings, it was concluded that the patient was in a state of brain death. The patient died the same day. CONCLUSIONS: With the use of new fast techniques such as diffusion-weighted imaging, now MRI can not only display anatomic changes associated with severe brain suffering but can also demonstrate ultrastructural changes secondary to brain death and differentiate them from edematous changes seen on T2-weighted images.     

Functional magnetic resonance imaging and cognition at the very early stage of MS

Dysfunction of high controlled information processing is present in patients with multiple sclerosis (MS) right at the beginning of the disease. One hypothesis is that disruption of communication inside large-scale cortical networks, occurring as a consequence of white matter damage, may constitute the anatomical substrate of cognitive impairment at the very early stage of MS. Disturbance of interregional synchronization might be the main pathogenic factor in controlled information processing deficiency in early MS. Preliminary functional MRI studies (fMRI) have provided important clues to corroborate the connectivity hypotheses. First, brain connectivity assessed by fMRI has brought new data about the influence of diffuse white matter damage on connectivity efficiency inside large-scale networks. These studies have suggested that connectivity disturbances occur inside the working memory network in patients at the very early stage of MS and appear related to the extent of structural white matter damage. Also, fMRI studies have suggested that patients may partially compensate for connectivity impairment by a greater cognitive control. Such a compensatory mechanism could limit the determinant functional impact of diffuse white matter damage on high controlled information processing.