Diffusion-weighted echo-planar MR imaging: clinical applications and pitfalls -- a pictorial essay

Quantification of Diffusion Magnetic Resonance Imaging for Prognostic Prediction of Neonatal Hypoxic-Ischemic Encephalopathy

Neonatal hypoxic-ischemic encephalopathy (HIE) is the leading cause of acquired neonatal brain injury with the risk of developing serious neurological sequelae and death. An accurate and robust prediction of short- and long-term outcomes may provide clinicians and families with fundamental evidence for their decision-making, the design of treatment strategies, and the discussion of developmental intervention plans after discharge. Diffusion tensor imaging (DTI) is one of the most powerful neuroimaging tools with which to predict the prognosis of neonatal HIE by providing microscopic features that cannot be assessed by conventional magnetic resonance imaging (MRI). DTI provides various scalar measures that represent the properties of the tissue, such as fractional anisotropy (FA) and mean diffusivity (MD). Since the characteristics of the diffusion of water molecules represented by these measures are affected by the microscopic cellular and extracellular environment, such as the orientation of structural components and cell density, they are often used to study the normal developmental trajectory of the brain and as indicators of various tissue damage, including HIE-related pathologies, such as cytotoxic edema, vascular edema, inflammation, cell death, and Wallerian degeneration. Previous studies have demonstrated widespread alteration in DTI measurements in severe cases of HIE and more localized changes in neonates with mild-to-moderate HIE. In an attempt to establish cutoff values to predict the occurrence of neurological sequelae, MD and FA measurements in the corpus callosum, thalamus, basal ganglia, corticospinal tract, and frontal white matter have proven to have an excellent ability to predict severe neurological outcomes. In addition, a recent study has suggested that a data-driven, unbiased approach using machine learning techniques on features obtained from whole-brain image quantification may accurately predict the prognosis of HIE, including for mild-to-moderate cases. Further efforts are needed to overcome current challenges, such as MRI infrastructure, diffusion modeling methods, and data harmonization for clinical application. In addition, external validation of predictive models is essential for clinical application of DTI to prognostication.

The Significance of Hypothalamic Inflammation and Gliosis for the Pathogenesis of Obesity in Humans

Accumulated preclinical literature demonstrates that hypothalamic inflammation and gliosis are underlying causal components of diet-induced obesity in rodent models. This review summarizes and synthesizes available translational data to better understand the applicability of preclinical findings to human obesity and its comorbidities. The published literature in humans includes histopathologic analyses performed postmortem and in vivo neuroimaging studies measuring indirect markers of hypothalamic tissue microstructure. Both support the presence of hypothalamic inflammation and gliosis in children and adults with obesity. Findings predominantly point to tissue changes in the region of the arcuate nucleus of the hypothalamus, although findings of altered tissue characteristics in whole hypothalamus or other hypothalamic regions also emerged. Moreover, the severity of hypothalamic inflammation and gliosis has been related to comorbid conditions, including glucose intolerance, insulin resistance, type 2 diabetes, and low testosterone levels in men, independent of elevated body adiposity. Cross-sectional findings are augmented by a small number of prospective studies suggesting that a greater degree of hypothalamic inflammation and gliosis may predict adiposity gain and worsening insulin sensitivity in susceptible individuals. In conclusion, existing human studies corroborate a large preclinical literature demonstrating that hypothalamic neuroinflammatory responses play a role in obesity pathogenesis. Extensive or permanent hypothalamic tissue remodeling may negatively affect the function of neuroendocrine regulatory circuits and promote the development and maintenance of elevated body weight in obesity and/or comorbid endocrine disorders.

ADC Restriction is Not Associated with Clinical Response to Plasma Exchange Following a Cerebral Attack of Multiple Sclerosis

BACKGROUND

MS is the most common CNS inflammatory demyelinating disease. Plasma exchange (PLEX) has well-demonstrated efficacy in acute corticosteroid-refractory attacks of demyelination but identifying the factors that predict favorable PLEX response remains elusive. We aimed to determine if apparent diffusion coefficient (ADC) restriction on brain MRI predicts clinical response to PLEX in individuals with an acute cerebral attack of MS.

METHODS

Retrospective chart review of individuals with a cerebral attack of MS who underwent PLEX at Mayo Clinic.

RESULTS

We identified 34 individuals who fulfilled the inclusion criteria. Twenty-seven (79%) responded to plasma exchange, with 16/34 (47%) having moderate and 11/34 (32%) marked improvement. Twenty-three (68%) people had ADC restriction on brain MRI prior to PLEX.  ADC restriction did not predict response (p = 0.51). Several other pre-PLEX factors, including sex, Expanded Disability Status Scale (EDSS) at initial attack, time to PLEX, and concurrent spinal cord attack, also failed to predict response. Plasma-exchange responders had less disability at 6-month follow-up compared to non-responders (median EDSS 2.5 (range 1.0-10.0) vs. 7.5 (5.5-10.0), p<0.001).

CONCLUSION

Acute cerebral attacks of MS have a high rate of plasma exchange response resulting in a lower EDSS at 6-months. ADC restriction does not predict response to plasma exchange.

Development of a composite diffusion tensor imaging score correlating with short-term neurological status in neonatal hypoxic-ischemic encephalopathy

Hypoxic-ischemic encephalopathy (HIE) is the most common cause of neonatal acquired brain injury. Although conventional MRI may predict neurodevelopmental outcomes, accurate prognostication remains difficult. As diffusion tensor imaging (DTI) may provide an additional diagnostic and prognostic value over conventional MRI, we aimed to develop a composite DTI (cDTI) score to relate to short-term neurological function. Sixty prospective neonates treated with therapeutic hypothermia (TH) for HIE were evaluated with DTI, with a voxel size of 1 × 1 × 2 mm. Fractional anisotropy (FA) and mean diffusivity (MD) from 100 neuroanatomical regions (FA/MD *100 = 200 DTI parameters in total) were quantified using an atlas-based image parcellation technique. A least absolute shrinkage and selection operator (LASSO) regression was applied to the DTI parameters to generate the cDTI score. Time to full oral nutrition [short-term oral feeding (STO) score] was used as a measure of short-term neurological function and was correlated with extracted DTI features. Seventeen DTI parameters were selected with LASSO and built into the final unbiased regression model. The selected factors included FA or MD values of the limbic structures, the corticospinal tract, and the frontotemporal cortices. While the cDTI score strongly correlated with the STO score (rho = 0.83, p = 2.8 × 10-16), it only weakly correlated with the Sarnat score (rho = 0.27, p = 0.035) and moderately with the NICHD-NRN neuroimaging score (rho = 0.43, p = 6.6 × 10-04). In contrast to the cDTI score, the NICHD-NRN score only moderately correlated with the STO score (rho = 0.37, p = 0.0037). Using a mixed-model analysis, interleukin-10 at admission to the NICU (p = 1.5 × 10-13) and tau protein at the end of TH/rewarming (p = 0.036) and after rewarming (p = 0.0015) were significantly associated with higher cDTI scores, suggesting that high cDTI scores were related to the intensity of the early inflammatory response and the severity of neuronal impairment after TH. In conclusion, a data-driven unbiased approach was applied to identify anatomical structures associated with some aspects of neurological function of HIE neonates after cooling and to build a cDTI score, which was correlated with the severity of short-term neurological functions.

Diffusion-Weighted MRI Findings of Caudate Nucleus and Putamen in Patients With Obsessive-Compulsive Disorder

Objective The purpose of this study was to establish the diffusion-weighted magnetic resonance imaging (DW-MRI) findings of the caudate nucleus and putamen in patients with obsessive-compulsive disorder (OCD) and to obtain new information on the etiopathogenesis of OCD, which is still unclear. Methods The study comprised 20 patients with OCDs and 20 healthy volunteers. In these cases, DW-MRI and diffusion-weighted echo-planar images (DW-EPI) at b600 and b1000 gradient values were taken and the measurements were made using the apparent diffusion coefficient (ADC) maps of each group at b600 and b1000 values from the caudate nucleus and putamen. Results When the DW-MRI examination in patients with OCD was compared with the control group, the mean ADC values in the caudate nucleus and putamen were not found to have statistically significantly changed. In addition, there were no significant differences regarding the right and left caudate nuclei and putamen ADC values at the b600 and b1000 in the patients with OCD or the control group. Conclusion There are still many unknowns about the neurobiology of OCD. When the DW-MRI examination of the patients with OCD was compared with the control group in our study, no significant difference was found between the ADC values of the caudate nucleus and putamen. Further studies are required for this present study on DW-MRI in patients with OCD to be meaningful.

Cerebral Metastases of Lung Cancer Mimicking Multiple Ischaemic Lesions - A Case Report and Review of Literature

Background

Restricted diffusion that is found on magnetic resonance diffusion-weighted imaging (DWI) typically indicates acute ischaemic stroke. However, restricted diffusion can also occur in other diseases, like metastatic brain tumours, which we describe in this case report.

Case Report

A 57-year-old male, with a diagnosis of small-cell cancer of the right lung (microcellular anaplastic carcinoma), was admitted with focal neurological symptoms. Initial brain MRI revealed multiple, disseminated lesions that were hyperintense on T2-weighted images and did not enhance after contrast administration; notably, some lesions manifested restricted diffusion on DWI images. Based on these findings, disseminated ischaemic lesions were diagnosed. On follow-up MRI that was performed after 2 weeks, we observed enlargement of the lesions; there were multiple, disseminated, sharply outlined, contrast-enhancing, oval foci with persistent restriction of diffusion. We diagnosed the lesions as disseminated brain metastases due to lung cancer. To our knowledge, this is the first description of a patient with brain metastases that were characterised by restricted diffusion and no contrast enhancement.

Conclusions

Multiple, disseminated brain lesions, that are characterised by restricted diffusion on DWI, typically indicate acute or hyperacute ischemic infarcts; however, they can also be due to hypercellular metastases, even if no contrast enhancement is observed. This latter possibility should be considered particularly in patients with cancer.

Brain diffusion changes in Eisenmenger syndrome

OBJECTIVE

This preliminary study aimed to evaluate whether there are changes in the apparent diffusion coefficient (ADC) values of the brain in patients presenting with Eisenmenger syndrome (ES).

METHODS

This cross-sectional study included 10 consecutively recruited patients with ES and 10 healthy control subjects. In the patients and controls, eight distinct neuroanatomical locations were selected for analysis. Quantitative measurements of ADC values of the frontal white matter (FWM), occipital white matter, lentiform nucleus (LN), thalamus, frontal cortex, anterior and posterior limbs of the internal capsule and caudate nucleus were measured. Statistical analysis was performed using SPSS^® (IBM Corp., New York, NY; formerly SPSS Inc., Chicago, IL) for Windows v. 20. Data were presented as mean ± standard deviation values. The Kruskal-Wallis test was used to assess differences in the ADC values of each brain location between the ES group and the control group. Statistical significance was accepted at the level of p < 0.05.

RESULTS

The ADC values of the FWM and LN were significantly higher in the ES group than that in the control group. The mean ADC levels of other brain regions were not significantly different between the groups.

CONCLUSION

Chronic hypoxia in patients with ES may lead to diffusion changes in the brain tissue. There is a need for further studies to assess the clinical significance of cerebral ADC values in patients with ES. Advances in knowledge: The ratio of extracellular volume to intracellular volume in the FWM and LN can be considered to be increased in patients with ES.

Diffusion-weighted magnetic resonance imaging of femoral head osteonecrosis in two groups of patients: Legg-Perthes-Calve and Avascular necrosis

INTRODUCTION

The aim of this prospective study was to evaluate the value of diffusion-weighted magnetic resonance imaging (DW-MRI) in patients with osteonecrosis. Patients were divided into two subgroups as avascular necrosis (AVN) of femoral head for adult group and Legg-Calvé-Perthes (LCP) patients for children.

PATIENTS AND METHODS

Seventeen patients with femoral head AVN (mean age 42.3 years) and 17 patients with LCP (mean age 8.2 years) were included in this study. Diagnosis confirmed with clinical and other imaging procedures among the patients complaining hip pain. DW images were obtained using the single-shot echo planar sequence and had b values of 0, 500, 1000 s/mm(2). The apparent diffusion coefficient (ADC) values were measured from ADC maps in epiphysis of patients with AVN, both from metaphysis and epiphysis in patients with LCP, respectively. Mann-Whitney U test was used to compare ADC values.

RESULTS

The mean ADC value of femoral heads (1.285 ± 0.204 × 10(-3) mm(2)/s) was increased in patients with AVN when compared to normal bone tissue (0.209 ± 0.214 × 10(-3) mm(2)/s) (p < 0.01). The mean ADC values (×10(-3) mm(2)/s) of both metaphysis (0.852 ± 0.293) and epiphysis (0.843 ± 0.332) were also increased in patients with LCP and differences were statistically significant (p < 0.01).

CONCLUSIONS

As a result, osteonecrosis shows increased ADC values. But it is a controversial concept that DWI offers a valuable data to conventional MRI or not. However, as there are report states, there is a correlation between the stage of the disease with ADC values in the LCP disease. DWI is a fast, without-contrast administration technique and provides quantitative values additional to conventional MR techniques; we believe DWI may play an additional assistance to the diagnosis and treatment for LCP patients. Multicentric larger group studies may provide additional data to this issue.

Brain diffusion changes in unilateral carotid artery stenosis with non-shunt endarterectomy: Correlation with white matter lesions

OBJECTIVE

Carotid stenosis is associated with hemodynamic cerebral ischemia. Diffusion-weighted MR imaging allows for the assessment of changes related to alterations in tissue integrity. The aim of this study was to investigate (a) whether white matter lesions (WML) and apparent diffusion coefficient (ADC) values differ between ipsilateral and contralateral hemispheres, (b) whether ADC values are related to WMLs and common vascular risk factors, and (c) whether ADC values differ after carotid endarterectomy (CEA) without a shunt in patients with unilateral internal carotid artery stenosis (ICAS).

METHODS

Twenty-five patients (16 men, 9 women; mean age of 68 years) with unilateral ICAS (≥ 70% carotid stenosis) were assessed with brain MRI before and after CEA, prospectively. Two experienced radiologists scored the WMLs. Bilateral ADC values in anterior and posterior periventricular WM, occipital WM, and thalamus were evaluated on preoperative and postoperative MRI. Differences in ADC values and WML scores between the two hemispheres were assessed and associations between ADC values, WML scores, and explanatory variables (e.g., age, sex, vascular risk factors) were analyzed.

RESULTS

WMLs were significantly greater and ADC values were elevated in the ipsilateral cerebral WM. After CEA, ADC values rapidly decreased but remained higher than within the contralateral hemisphere. Ipsilateral hemispheric ADC values were associated with basal ganglia WMLs. No association between ADC values and vascular risk factors was found.

CONCLUSION

ICAS is associated with increased diffusion in normal-appearing WM in comparison to more prominent chronic ischemic lesions. CEA has a partial effect on diffusion. These cerebral changes may be related to chronic low-grade ischemic damage that is induced by ICAS.

Assessment of neural alterations in obstructive sleep apnoea syndrome: can apparent diffusion coefficient measurements be useful?

BACKGROUND AND AIMS

Our aim was to investigate whether neurological alteration in patients with obstructive sleep apnoea syndrome (OSAS) with apparently normal cerebral and cerebellar structures can be assessed by means of apparent diffusion coefficient (ADC) measurement and to investigate the association between OSAS severity and ADC values.

METHODS

Following the acquisition of diffusion-weighted cranial magnetic resonance imaging, ADC measurements were performed in 24 different apparently normal cerebral and cerebellar structures, including the bilateral frontal and parietal cortices, insulae, cingulate gyri, hippocampi, frontal and parieto-occipital periventricular white matter (PWM), caudate nuclei, putamen, thalami, cerebellar hemispheres, pons and mesencephalon in 47 OSAS patients and 20 control subjects. The ADC values of the patients and the control group were compared. The association between the apnoea-hypopnoea index (AHI) and the ADC values of the patients were investigated.

RESULTS

The ADC values in the bilateral frontal PWM were lower in the patient group than those in the control subjects (P < 0.05). The measurements in the right cingulate gyri of the OSAS patients exhibited significantly higher ADC values than those of the control group (P = 0.002). Bilateral thalamic ADC values in severe OSAS patients were significantly higher than those in mild and moderate OSAS patients (P < 0.05).

CONCLUSION

The ADC measurement is a simple and effective technique to evaluate neural alteration of the brain in patients with OSAS. ADC measurements can also be useful in the evaluation of the association between the AHI and the degree of neural alteration in the central nervous system.

The effect of obesity on brain diffusion alteration in patients with obstructive sleep apnea

Purpose. We investigated diffusion alterations in specific regions of the brain in morbid obese, obese, and nonobese OSA patients and searched whether there is a correlation between BMI and ADC values. Materials and Methods. DWIs of 65 patients with OSA were evaluated. The patients were classified according to BMI as morbid obese (n = 16), obese (n = 27), and nonobese (control, n = 22) groups. ADC measurements were performed from 24 different regions of the brain in each patient. The relationship of BMI with ADC values was searched. Results. The ADC values in hypothalamus, insular cortex, parietal cortex, caudate nucleus, frontal white matter, and posterior limb of internal capsule were all increased in obese patients (n = 43) compared to control group. The ADC values of midbrain, hypothalamus, orbitofrontal cortex, and parietal cortex were significantly increased in morbid obese compared to obese patients. In obese patients, the degree of BMI was positively correlated with ADC values of orbitofrontal cortex, parietal cortex, and hypothalamus. Conclusion. We observed increasing brain vasogenic edema with increasing BMI, suggesting that the main reason of brain diffusion alteration in patients with OSA could be obesity related.

Brain diffusion changes in obstructive sleep apnoea syndrome

BACKGROUND

Obstructive sleep apnoea syndrome (OSAS) is a disorder characterized by repeated apnoeic episodes during sleep. Neurocognitive changes secondary to OSAS are likely to occur due to hypoxia in certain brain locations. Advances in magnetic resonance imaging technology, such as diffusion-weighted imaging (DWI), enable non-invasive and accurate identification of OSAS-induced changes.

OBJECTIVE

We aimed to use DWI to investigate changes in the brain secondary to hypoxia in OSAS.

METHODS

Eighty-eight patients underwent polysomnography and were classified as non-OSAS, mild-moderate OSAS and severe OSAS sufferers. DWI was used to evaluate 14 areas of the brain, and apparent diffusion coefficients (ADCs) were calculated. We investigated whether there were differences in the ADC values in specific areas of the brain between the non-OSAS and OSAS patients.

RESULTS

We measured the ADC values of the 68 newly diagnosed OSAS patients (21 mild, 15 moderate and 32 severe) and of 20 healthy controls. There were significant increases in the ADC values in the hippocampus, amygdala and putamen in OSAS patients. Compared to the non-OSAS subjects, the ADC values of the putamen in severe OSAS patients, those of the hippocampus in moderate or severe OSAS patients and those of the amygdala in moderate OSAS patients were significantly increased. A negative correlation between the lowest oxygen saturation during sleep and the ADC values of the hippocampus and amygdala was found.

CONCLUSIONS

Increased ADC levels in the hippocampus, amygdala and putamen in OSAS patients indicate hypoxia and likely cause vasogenic oedema in specific regions of the brain.

Diffusion-weighted imaging characteristics of biopsy-proven demyelinating brain lesions

OBJECTIVES

To describe lesional diffusion-weighted imaging characteristics in a cohort of patients with biopsy-proven CNS inflammatory demyelinating disease (IDD) and compare diffusion characteristics of ring-enhancing CNS IDD lesions vs abscesses and tumors.

METHODS

Forty prebiopsy apparent diffusion coefficient (ADC) maps were reviewed from 30 patients with CNS IDD. Lesions were analyzed for size, T2-weighted (T2W) hypointense rim, enhancement, and ADC pattern. ADC patterns of CNS IDD ring-enhancing lesions were compared with a published cohort of 35 patients with ring-enhancing tumors and abscesses.

RESULTS

IDD lesions displayed a spectrum of peripheral ADC patterns at the lesion edge: restricted diffusion (low ADC), 33%; increased diffusion (high ADC), 60%; and normal diffusion (homogeneously isointense), 7%. Of biopsied lesions, 93% enhanced (ring, 52%; heterogeneous, 34%; homogeneous, 7%). A hypointense T2W rim was observed in 53%. A ring pattern on ADC (isointense or dark) was associated with T2W hypointense rims (p = 0.02) but not with ring enhancement. On serial imaging, 4 of 7 (57%) patients demonstrated changes in ADC patterns. Peripheral restriction was more common in IDD (p = 0.006) than in tumors or abscesses, whereas central restriction was only observed in abscesses. Restricted lesions in the same stage were more common in the non-IDD cohort (42% vs 20%), with a uniform restricted pattern seen only in abscesses.

CONCLUSIONS

In ring-enhancing lesions, peripheral diffusion restriction is more common in IDD than in tumors/abscesses, whereas central restriction is more common among abscesses. Rapid ADC pattern changes in IDD probably reflect dynamic lesion evolution and may distinguish IDD from tumors.

Diffusion MRI abnormalities in pediatric neurological disorders

Diffusion-weighted imaging (DWI) makes it possible to measure early changes in cellular function in the central nervous system. The purpose of this article is to discuss the diagnostic value of diffusion-weighted and diffusion tensor imaging (DTI) in different pediatric cerebral disorders. First, the principles of DWI and DTI are briefly reviewed. The clinical usefulness of these imaging techniques is then discussed using cases with pediatric neurological disorders, such as hypoxic-ischemic encephalopathy in neonates, trauma (shaken baby syndrome), encephalopathy or encephalitis in infants, posterior reversible encephalopathy syndrome and congenital brain anomaly (callosal dysgenesis). In addition, using DTI, we evaluate normal brain development, particularly in the corpus callosum and cortico-spinal tract, and discuss the application of DTI to the study of white matter in the developing brain.

Cytotoxic edema in neuro-Behcet's disease ?

We report a case of a 52-year-old woman with Behcet's disease who presented with dysarthria and right-sided hemiparesis. T2-weighted and diffusion-weighted images (DWI) showed a hyperintense lesion in the left pons with a relatively decreased apparent diffusion coefficient (ADC). Imaging showed almost complete resolution of the lesion after treatment with prednisolone. The atypical DWI and ADC findings in this case may reflect cytotoxic edema due to excitotoxic brain injury. This case thus illustrates the radiological diversity of neuro-Behcet's lesions.

Diffusion-weighted imaging features of brain in obesity

PURPOSE

Obesity is characterized by an altered distribution of body fluid. However, distribution of fluid (extracellular/intracellular) in brain tissues has not been studied in obese subjects yet. The purpose of this study was to detect possible brain diffusion changes especially in satiety and hunger related centers in obese subjects by diffusion weighted imaging (DWI).

METHODS

Conventional MRI and DWI of the brain was obtained from 81 obese patients (obese=68, morbid obese=13) and 29 age-matched, nonobese. The apparent diffusion coefficient (ADC) values were calculated in hypothalamus; amygdala; hippocampal gyrus; thalamus; insula; cingulate gyrus; orbitofrontal, dorsomedial and dorsolateral frontal, middle temporal and occipital cortex; cerebellum; midbrain and corpus striatum.

RESULTS

The ADC values of hypothalamus, hippocampal gyrus, amygdala, insula, cerebellum and midbrain were significantly increased in patients (n:81) when compared to nonobese subjects. The ADC values of thalamus, hippocampal gyrus, amygdala, orbitofrontal, occipital, dorsolateral and middle temporal cortex, insula and midbrain were significantly increased in morbid obese when compared to nonobese subjects. The ADC values of orbitofrontal and occipital cortex were significantly higher in morbid obese than the values in the obese. The body mass index positively correlated with ADC values of amygdala, insula, orbitofrontal and middle temporal cortex.

CONCLUSION

We observed increased ADC values of distinct locations related to satiety and hunger that suggest altered fluid distribution and/or vasogenic edema in obese subjects. Awareness of this abnormalities in brain tissue composition/function in obesity may contribute to better understanding of the underlying mechanisms.

Diffusion weighted MR imaging in non-infarct lesions of the brain

Diffusion weighted imaging (DWI) is a relatively new method in which the images are formed by the contrast produced by the random microscopic motion of water molecules in different tissues. Although DWI has been tried for different organ systems, it has been found its primary use in the central nervous system. The most widely used clinical application is in the detection of hyperacute infarcts and the differentiation of acute or subacute infarction from chronic infarction. Recently DWI has been applied to various other cerebral diseases. In this pictorial paper the authors demonstrated different DWI patterns of non-infarct lesions of the brain which are hyperintense in the diffusion trace image, such as infectious, neoplastic and demyelinating diseases, encephalopathies - including hypoxic-ischemic, hypertensive, eclamptic, toxic, metabolic and mitochondrial encephalopathies - leukodystrophies, vasculitis and vasculopathies, hemorrhage and trauma.

Subacute sclerosing panencephalitis: Relationship between clinical stage and diffusion-weighted imaging findings

PURPOSE

To investigate the relationship between clinical stages and apparent diffusion coefficient (ADC) changes in the brain of patients with subacute sclerosing panencephalitis (SSPE).

MATERIALS AND METHODS

A total of 18 patients with stage II (N = 11) and III (N = 7) SSPE and 11 age-matched controls underwent routine MRI and diffusion-weighted imaging (DWI). The ADC values were automatically calculated. Seven distinct neuroanatomic structures (frontal, parieto-occipital, and cerebellar white matter; deep white matter; thalamus; basal ganglia; and brainstem) were selected for analysis in the patient and control groups.

RESULTS

Hyperintensities in the periventricular and subcortical white matters on T2-weighted images and ADC maps were detected in 63.6% of patients with stage II and in all patients with stage III. There were significant differences between stage II and III patients and also between patients and control group in ADC values that obtained from all locations. The highest mean ADC values were calculated in stage III patients. Although MRI and DWI findings were normal in four patients with stage II disease, ADC values were significantly increased when compared with controls.

CONCLUSION

The stage of disorder may be independent of DWI appearance during the early stage (stages I and II), even though the brain is affected. Therefore, DWI and ADC values supplemental to routine MRI should also be utilized for lesion detection and definition to enhance diagnostic accuracy in patients with SSPE.

Diffusion-weighted imaging in chronic Behçet patients with and without neurological findings

Our aim was to investigate whether neurological impairment in chronic Behçet's disease (BD) patients with normal appearing brain can be assessed by means of diffusion-weighted imaging (DWI). The averaged apparent diffusion coefficient (ADC) values were calculated in 22 different radiologically normal appearing brain regions in 32 patients with and without neurological findings and 20 control subjects. The ADC values in bilateral frontal, temporal and occipital normal appearing white matter were significantly higher in the patient groups compared with the control subjects (p < 0.05). In these brain regions, DWI revealed differences in the ADC values between patients with neurological findings (including symptomatic and neuro-Behçet patients) and the asymptomatic patient group. The similarity of the ADC values of patients without symptoms to those of the control group allowed clear discrimination between patients with and without neurological findings. DWI may serve to assess subclinical neurological involvement in BD, even when structural changes are absent.

Intravascular lymphoma: magnetic resonance imaging correlates of disease dynamics within the central nervous system

BACKGROUND

Intravascular lymphoma (IVL) is a rare non-Hodgkin's lymphoma with relative predilection for the central nervous system. In the absence of extraneural manifestations, the disease is not recognised until autopsy in the majority of cases underlining the need for new clinical markers.

METHODS

This is a retrospective series of five patients with IVL seen at a single institution over three years. An advanced magnetic resonance imaging (MRI) protocol was performed at various time points prior to diagnosis and during treatment.

RESULTS

MRI revealed multiple lesions scattered throughout the cerebral hemispheres; the brainstem, cerebellum, and spinal cord were less frequently involved. On initial presentation, hyperintense lesions were seen on diffusion weighted images suggestive of ischaemia in three of four patients in whom the images were obtained at that time point. In four patients lesions were also identifiable as hyperintense areas on fluid attenuated inversion recovery (FLAIR) sequences. Initial contrast enhancement was encountered in three cases. Diffusion weighted imaging lesions either vanished or followed the typical pattern of an ischaemic small vessel stroke with evolution of abnormal FLAIR signal followed by enhancement with gadolinium in the subacute stage and tissue loss in the chronic stage. Diffusion weighted imaging and FLAIR abnormalities proved to be partially reversible, correlating with the response to chemotherapy.

CONCLUSION

We provide the first detailed description of the dynamic pattern of diffusion weighted MRI in IVL. These patterns in combination with systemic findings may facilitate early diagnosis and serve as a new tool to monitor treatment response.

Diffusion-weighted MR imaging of pleural fluid: differentiation of transudative vs exudative pleural effusions

The aim of this study was to evaluate the ability of diffusion-weighted MRI in differentiating transudative from exudative pleural effusions. Fifty-seven patients with pleural effusion were studied. Diffusion-weighted imaging (DWI) was performed with an echo-planar imaging (EPI) sequence (b values 0, 1000 s/mm(2)) in 52 patients. The apparent diffusion coefficient (ADC) values were reconstructed from three different regions. Subsequently, thoracentesis was performed and the pleural fluid was analyzed. Laboratory results revealed 20 transudative and 32 exudative effusions. Transudates had a mean ADC value of 3.42+/-0.76 x 10(-3) mm(2)/s. Exudates had a mean ADC value of 3.18+/-1.82 x 10(-3) mm(2)/s. The optimum cutoff point for ADC values was 3.38 x 10(-3) mm(2)/s with a sensitivity of 90.6% and specificity of 85%. A significant negative correlation was seen between ADC values and pleural fluid protein, albumin concentrations and lactate dehydrogenase (LDH) measurements ( r=-0.69, -0.66, and -0.46, respectively; p<0.01). The positive predictive value, negative predictive value, and diagnostic accuracy of ADC values were determined to be 90.6, 85, and 88.5%, respectively. The application of diffusion gradients to analyze pleural fluid may be an alternative to the thoracentesis. Non-invasive characterization of a pleural effusion by means of DWI with single-shot EPI technique may obviate the need for thoracentesis with its associated patient morbidity.

Diffusion-weighted MR imaging of neuro-Behçet's disease: a case report

We present a serial study of diffusion-weighted imaging (DWI) in a patient with neuro-Behçet's disease. Initial T2-weighted magnetic resonance images showed a hyperintense lesion in the brain stem. The lesion was slightly hyperintense on DWI and the apparent diffusion coefficient (ADC) was slightly increased. Ten months later, DWI showed an improvement in the abnormal signal intensity and the region of increased ADC had increased in size, especially on the left side. DWI is useful for differentiating an acute exacerbation of neuro-Behçet's disease from acute infarction.