Diffusion MR imaging: an important tool in the assessment of brain tumors

For over 20 years, conventional MR imaging has been used for assessing brain tumors. However, conventional MR imaging tends to underestimate the extent of the tumor, perhaps leading to suboptimal treatment. New MR imaging tools have been widely used to determine the grade, heterogeneity, and extent of brain tumors. Diffusion-weighted imaging has been studied extensively, helping in tumor grading, differential diagnosis, and postoperative evaluation. Diffusion tensor imaging can apparently delineate more accurately the tumor versus the infiltrating tumor between the peritumoral edema and the normal brain parenchyma. This article shows the main clinical applications of these sequences.     

Diffusion- and perfusion-weighted magnetic resonance imaging in deep cerebral venous thrombosis

BACKGROUND: Diffusion-weighted (DWI) and perfusion-weighted (PI) MRI are highly sensitive techniques for early diagnosis of arterial infarction, but little data on venous cerebral ischemia are available. We describe a case in which DWI, PI, and fast T2-weighted sequences were performed in the acute phase of deep cerebral venous thrombosis (CVT). CASE DESCRIPTION: An 11-year-old girl with Crohn's disease developed deep CVT in which extensive edema was shown in the deep gray matter on T2-weighted sequence images. Isotropic echo-planar DWI demonstrated a local augmentation of the apparent diffusion coefficient (1.1 to 1.6x10(-3) mm2/s), consistent with vasogenic edema. In dynamic contrast-enhanced PI, the regional cerebral blood volume was increased and the passage time of the contrast bolus was markedly prolonged. Clinically, the patient recovered totally after intravenous full-dose heparinization. T2 abnormalities, apparent diffusion coefficient values (0.8 to 0.92x10(-3) mm2/s), and brain perfusion alterations resolved without damage to brain tissue. CONCLUSIONS: Unlike arterial infarction, DWI demonstrated vasogenic edema in a patient with deep CVT, which proved to be reversible in follow-up magnetic resonance imaging. PI showed areas with extensive venous congestion, but perfusion deficits were missing. Therefore, we believe that DWI and PI may play a role in detecting venous congestion in CVT and in prospective differentiation of vasogenic edema and venous infarction.     

Diffusion-weighted magnetic resonance imaging is useful for assessing inflammatory myopathies

Introduction: Short tau inversion recovery (STIR) sequences in whole-body MRI are usually used for detecting muscle edema (ME) in inflammatory myopathies. We evaluated b-value 800 diffusion-weighted imaging (b800 DWI).Methods: Two radiologists independently and a consensus reader retrospectively reexamined 60 patients with inflammatory myopathies and 15 controls. For each participant, 78 muscles were analyzed with 3 sets of imaging acquisitions: T1-weighted (T1) turbo spin echo and STIR; T1 and DWI; and T1, STIR and DWI. Mean edema per patient was compared between sequences. Agreement was evaluated. Results: Diffusion-weighted imaging detected more ME compared with STIR (P < 0.001). Agreement between readers was better with both sequences (k = 0.94) than with b800 DWI (k = 0.89) or STIR (k = 0.84) alone. Discussion: Diffusion-weighted imaging is a valuable add-on for the study of inflammatory myopathies. Muscle Nerve 59:555–555, 2019     

Diffusion-weighted mr in cerebral venous thrombosis

The diagnosis of cerebral venous thrombosis is often difficult both clinically and radiologically and until now there is no method available to predict if brain lesions, detected clinically and using conventional brain imaging methods, may lead to full recovery, as expected in vasogenic edema or ischemic infarcts and even a hematoma. New fast neuroimaging techniques such as diffusion-weighted imaging (DWI) are sensitive to different reasons of changes in local tissular water concentration thus giving further insight into the pathophysiological mechanism as well as prognosis of cerebral venous thrombosis. We report the cases of 18 consecutive patients with a diagnosis of cerebral venous thrombosis based on clinical and imaging criteria. All patients underwent magnetic resonance imaging (MRI) of the brain, which comprised isotropic diffusion-weighted MR. Diffusion-weighted MRI showed positive findings in 17/18 cases. In 7 cases the clot could be directly visualized as an area of hyperintensity in the affected vein on DWI. In 7 cases DWI showed areas of signal loss corresponding to hematomas. In 6 cases DWI showed changes in signal intensity that were more subtle. In 4 cases of superficial venous thrombosis, there were areas of decreased ADC values (0.65-0.79 x 10(-3) mm(2)/s) whereas in 2 cases of deep venous thrombosis, increased DWI intensities could be found that corresponded to both an increase and a decrease in ADC, corresponding to a coexistence of cytotoxic and vasogenic edemas. Diffusion-weighted MRI can demonstrate directly the presence of an intravenous clot in a select number of patients. It can also demonstrate early ischemic changes, and can differentiate conventional T2-weighted MR areas of cytotoxic from vasogenic edema.     

Neuroimaging of Cerebral Venous Thrombosis

Early and accurate diagnosis of cerebral venous thrombosis (CVT) is possible with the help of computed tomography (CT) scan and magnetic resonance imaging (MRI). Empty delta sign on postcontrast CT is present in only up to 30% of the cases. The role of CT venography is not yet established, but it is emerging as an effective modality for diagnosis of CVT. T2* MRI sequence is superior to spin echo in detecting CVT and small hemor rhages. MR venography is considered the technique of choice for diagnosis and follow-up of CVT, but in certain cases, MRI could be superior as it shows the thrombus itself and not just the absence of signal as seen on MR venography. Diffusion-weighted imaging is a relatively new MRI technique that is extremely sensitive in detecting acute arterial strokes and can distinguish cytotoxic and vasogenic edema. The presence of hyperintense signal on diffusion-weighted imaging in the occluded veins or sinuses at the time of diagnosis may predict a low rate of vessel recanalization. Contrast angiography should be strongly considered if isolated cortical vein thrombosis is suspected.     

Neuroimaging of infections of the central nervous system

Neuroimaging plays a crucial role in the diagnosis and therapeutic management of neurologic infections. This article summarizes imaging findings in brain abscesses, ventriculitis, viral diseases, and opportunistic infections. In cases of uncomplicated meningitis, cranial computed tomography is sufficient to exclude brain edema, hydrocephalus, and skull base pathology. Magnetic resonance imaging (MRI) is superior in depicting complications (e.g., empyema, vasculitis). Diffusion-weighted imaging (DWI) shows parenchymal complications of meningitis earlier and is of help in differentiation of pyogenic abscess from other ring-enhancing lesions. Proton magnetic resonance spectroscopy can produce specific peak-patterns in cases of abscess, such as the presence of lactate and cytosolic amino acids. In toxoplasmosis, DWI may help to differentiate from lymphoma, showing no restriction of water diffusion. In patients with viral encephalitis, DWI allows earlier lesion detection. MRI has revolutionized the rapid diagnosis of spinal abscess.     

Diffusion-weighted magnetic resonance imaging in the syndrome of acute bilateral basal ganglia lesions in diabetic uremia.

In this report, we have presented a diabetic patient with uremia, in which acute Parkinsonism occurred, coupled with acute mental confusion, after a sudden increase in blood urea nitrogen and serum creatinin levels. Diffusion-weighted magnetic resonance imaging revealed a unique cytotoxic-type edema in the bilateral basal ganglia during the acute phase. Signal alterations were shown to regress in accordance with the normalized apparent diffusion coefficient (ADC) values, but irreversible cystic degeneration developed in the globus pallidus, with the very low preceding ADC values.     

Progressive collapse of PMMA-augmented vertebra: a report of three cases

Vertebroplasty using polymethylmethacrylate (PMMA) for augmentation is accepted as a safe and effective treatment for vertebral compression fracture. However, various complications related to PMMA vertebroplasty have recently been reported. We experienced three cases with progressive collapse of PMMA-augmented vertebra. Collapse progressed after augmentation in cases where PMMA conglomerated without contiguous bone interdigitation. A high viscosity of the PMMA preparation and vertebral body cavitory lesion may play a role in progressive vertebral collapse. To avoid this complication, bone cement should be injected sufficiently and permeate to contiguous bone to create strong support and anchorage.     

Transient abnormalities associated with status epilepticus on diffusion-weighted MR imaging]

We report on two patients with transient abnormalities on MRI during status epilepticus(SE). Diffusion-weighted MR imaging(DWI) and T2-weighted and fluid-attenuated inversion recovery (FLAIR) MR images showed cortical and thalamic hyperintensity with swelling of the cortex. The lesions did not respect vascular territories. We also observed an increased signal in the ipsilateral middle cerebral artery on magnetic resonance angiography(MRA), and leptomeningeal enhancement on postcontrast MRI. Follow-up imaging revealed that the abnormal findings resolved within a few weeks, although a residual area of increased T2 signal intensity persisted. These findings suggest the presence of reversible cytotoxic and vasogenic edema induced by seizure. We conclude that this disorder should be taken into consideration in the differential diagnosis of other conditions, including ischemic stroke.     

Acute intermittent porphyria presenting as a diffuse encephalopathy

Although acute intermittent porphyria presents with dramatic neurological findings, the diagnosis is difficult. An 18-year-old woman had a clinical picture of porphyric encephalopathy. Magnetic resonance (MR) imaging demonstrated multiple large contrast-enhancing subcortical white matter lesions, which regressed with glucose and hematin infusions. Diffusion-weighted MR imaging was normal, and MR spectroscopy excluded acute demyelination or tissue necrosis. MR findings of acute intermittent porphyria can differ from those in posterior reversible encephalopathy syndrome by virtue of intense contrast enhancement. Because diffusion-weighted MR imaging and spectroscopy were normal, the lesions are likely caused by reversible vasogenic edema and transient breakdown of the blood-brain barrier.     

Diffusion-weighted imaging and fluid-attenuated inversion recovery sequence in sporadic Creutzfeldt-Jakob disease One-case report

The diagnosis of sporadic Creutzfeldt-Jakob disease (sCJD) is extremely difficult.Diffusion-weighted imaging has been shown to be the most sensitive technique for the detection of signal alterations in sCJD patients.The present study analyzed the diagnostic value of diffusion-weighted imaging and fluid-attenuated inversion recovery sequence in the early stage of sCJD in one female patient and correlated the clinical symptoms during disease course and magnetic resonance manifestations.Thalamic and basal ganglia hyperintensities were observed on magnetic resonance images in a very early stage,i.e.,when the clinical typical manifestations of the disease were not present.With the progression of the disease,cortical and basal ganglia hyperintensities were observed on magnetic resonance images,showing an obvious cerebral atrophy.These findings suggest that diffusion-weighted imaging and fluid-attenuated inversion recovery sequence are helpful in diagnosing sCJD.     

Comparison of spontaneous intracranial vertebral artery dissection with large artery disease

OBJECTIVE: To compare clinical and angiographic characteristics and stroke patterns between spontaneous intracranial vertebral artery dissection (VAD) and vertebral large artery disease (LAD) (atherosclerosis). DESIGN: Retrospective study. SETTING: Tertiary referral center for cerebrovascular diseases. Patients Twenty-two patients with spontaneous VAD and 25 with LAD in the intracranial portion of the vertebral artery. MAIN OUTCOME MEASURES: We compared (1) clinical characteristics, including epidemiologic data, vascular risk factors including inflammatory markers, the presence of headache, and stroke syndromes and severity; (2) stroke pattern on diffusion-weighted imaging, which was classified as vertebral perforator infarct, basilar perforator infarct, small scattered infarct, large scattered infarct, and territorial infarct; and (3) angiographic findings, ie, the distribution of involved arteries, degree of stenosis, and the involvement on the anterior circulation and calcification of vertebral artery. RESULTS: Although patients with VAD were younger, and more often had headaches and fewer vascular risk factors than those with LAD (P<.01 in all cases), these clinical features were also observed in some LAD patients. Diffusion-weighted imaging data showed that vertebral perforator infarct and small scattered infarct were most common in the VAD group, while territorial infarct and large scattered infarct were most common in the LAD group (P = .02). On angiography, LAD more frequently had anterior circulation arterial involvement (P = .002), higher degree of stenosis (P = .002), and calcifications (P = .008). CONCLUSION: Our findings indicate that results of diffusion-weighted imaging and noninvasive vascular studies might provide clues to the clinical characteristics in differential diagnosis between VAD and LAD.     

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.     

Ischemic stroke revealed by a thunderclap headache: contribution of diffusion-weighted mri sequences

INTRODUCTION: Sub-arachnoid hemorrhage, cerebral venous thrombosis and cerebral reversible angiopathies are the main causes of secondary thunderclap headache. Ischemic stroke is rarely revealed by thunderclap headache. CASE REPORT: A 80-year-old woman developed for the first time a thunderclap headache associated with transient distal motor deficit of the right hand. Diffusion-weighted sequences revealed a recent left infarct in a vascular border zone. CONCLUSION: Ischemic stroke is a rare cause of thunderclap headache but practitioners should bear in mind this etiology when the diagnostic work-up is negative. Diffusion-weighted sequences of the brain MRI can provide the diagnosis.     

Thoracic radiculopathy related to collapsed thoracic vertebral bodies.

Three cases are presented of thoracic radiculopathy related to collapsed thoracic vertebral bodies. In all cases proximal weakness of the legs was present, leading to the diagnosis of myopathy in two cases. Sensory symptoms were present in two cases. In one, anterior thigh paresthesias lead to a diagnosis of meralgia paresthetica. This diagnostic entity must be remembered if appropriate corroborative tests are to be performed. In cases of trauma this diagnosis should be considered if thoracic vertebral collapse is present. Conversely, an evaluation of proximal weakness should include a review of thoracic radiographs for vertebral collapse, especially in the presence of sensory findings in the lower abdominal or proximal thigh region.     

Delayed signal detection by diffusion-weighted imaging in brainstem infarction

Diffusion-weighted magnetic resonance imaging (DW MRI) is a sensitive and specific technique for imaging acute hemispheric infarction. Its utility in the diagnosis of acute brainstem infarction has not been well studied. We present 3 cases of brainstem infarction in which DW MRI performed 5 to 15 hours after symptom onset failed to reveal any abnormality. Repeat diffusion-weighted imaging (DWI) 2 to 5 days later did demonstrate an abnormality in the clinically appropriate region in each instance. This suggests that the time course to the development of abnormalities detectable by DWI may be longer in brainstem than in hemispheric infarctions. Therefore, repeat studies after initially negative DWI might be useful in the diagnosis of brainstem infarctions.     

Diffusion-weighted MR findings of central pontine and extrapontine myelinolysis

Diffusion-weighted MR (DWI) can detect changes in water diffusion associated with cellular dysfunction, which enables the differentiation of cytotoxic edema from vasogenic edema. In this study on DWI findings in central pontine (CPM) and extrapontine myelinolysis (EPM), DWI showed high signal intensities in the bilateral pons, midbrain, and genu of the corpus callosum. The corresponding apparent diffusion coefficient values were rather low. This suggests that cytotoxic edema does in fact exist in CPM and EPM and that DWI can be useful in the rapid diagnosis and prediction of the various types of edema occurring in active demyelinating diseases.     

Acute and chronic changes of the apparent diffusion coefficient in neurological disorders--biophysical mechanisms and possible underlying histopathology

Diffusion-weighted imaging (DWI) of the brain has become a valuable tool for the reliable detection and diagnosis of several neurological disorders. Although DWI is in wide use in daily practice, the underlying biophysical mechanisms that contribute to changes in the apparent diffusion coefficient (ADC) are still under discussion. Alterations in the apparent water diffusion rate reflect pathological changes in the brain tissue state, via changes in the diffusion characteristics of the intra- and extra-cellular water compartments including restricted diffusion, water exchange across permeable boundaries, the concept of the extra-cellular tortuosity and the intra- and extra-cellular volume fraction. A reduction of the ADC has been detected in acute neurological diseases, while disease states associated with dominant acute vasogenic edema formation or chronic tissue destruction usually show elevations of the ADC. Compromise of energy metabolism is likely to contribute to a reduction of the ADC while already minor structural disintegration may contribute to elevations of the ADC.     

Spinal cord infarction demonstrated by diffusion-weighted magnetic resonance imaging.

Spinal cord infarction is a rare entity of varying etiology although most often associated with atherosclerotic aortic disease. Definitive diagnosis of (idiopathic) spinal cord infarction in the acute stage and in the absence of demonstrable predisposing factors is not always possible even with MRI. Diffusion-weighted MRI (dwMRI) may provide valuable information in the evaluation of spinal cord ischemia. A 45-year-old woman presented with idiopathic spinal cord infarction manifesting as sudden onset of paraparesis and sphincter dysfunction. Both T2-weighted and line-scan dwMRI revealed hyperintense signals in the dorsal part of the spinal conus. Apparent diffusion coefficient values were significantly low in the lesion, suggesting cytotoxic edema compatible with acute ischemia. The clinical course and other radiographic findings were also compatible with idiopathic spinal cord infarction. Diffusion-weighted MRI is an important diagnostic tool for examining patients with suspected spinal cord ischemia.