Decrease in the volume of white matter lesions with improvement of hepatic encephalopathy

High field brain proton magnetic resonance spectroscopy and volumetry in children with chronic, compensated liver disease - A pilot study

BACKGROUND

and rationale: There is increasing evidence that children or young adults having acquired liver disease in childhood display neurocognitive impairment which may become more apparent as they grow older. The molecular, cellular and morphological underpinnings of this clinical problem are incompletely understood.

AIM

Therefore, we used the advantages of highly-resolved proton magnetic resonance spectroscopy at ultra-high magnetic field to analyze the neurometabolic profile and brain morphometry of children with chronic, compensated liver disease, hypothesizing that with high field spectroscopy we would identify early evidence of rising brain glutamine and decreased myoinositol, such as has been described both in animals and humans with more significant liver disease.

METHODS

Patients (n = 5) and age-matched controls (n = 19) underwent 7T MR scans and short echo time ¹H MR spectra were acquired using the semi-adiabatic SPECIAL sequence in two voxels located in gray and white matter dominated prefrontal cortex, respectively. A 3D MP2RAGE sequence was also acquired for brain volumetry and T₁ mapping. Liver disease had to have developed at least 6 months before entering the study. Subjects underwent routine blood analysis and neurocognitive testing using validated methods within 3 months of MRI and MRS.

RESULTS

Five children currently aged 8-16 years with liver disease acquired in childhood were included. Baseline biological characteristics were similar among patients. There were no statistically significant differences between subjects and controls in brain metabolite levels or brain volumetry. Finally, there were minor neurocognitive fluctuations including attention deficit in one child, but none fell in the statistically significant range.

CONCLUSION

Children with chronic, compensated liver disease did not display an abnormal neurometabolic profile, neurocognitive abnormalities, or signal intensity changes in the globus pallidus. Despite the absence of neurometabolic changes, it is an opportunity to emphasize that it is only by developing the use of ¹H MRS at high field in the clinical arena that we will understand the significance and generalizability of these findings in children with CLD. Attention deficit was observed in one child. Healthy children displayed neurometabolic regional differences as previously reported in adult subjects.

Spectrum of Neuroimaging Abnormalities in Brain in Patients of Acute-on-Chronic Liver Failure

Background and aims

Acute-on-chronic liver failure (ACLF) is associated with high short-term mortality. There is a paucity of data about the spectrum of neuroimaging abnormalities in the brain in ACLF patients. The present study was aimed to study the prevalence of cerebral edema and other parenchymal changes in MR imaging of the brain in patients with ACLF.

Methods

In this prospective observational study, MR imaging was done in patients with ACLF (n = 41), and findings were compared with age and sex-matched patients with acute decompensation (AD) (n = 13) and those with cirrhosis but without any decompensation at recruitment (n = 21).

Results

Forty-one patients with ACLF (24.4% Grade 1 and Grade 2, 51.2% Grade 3) with 14 (34.1%) having cerebral failure were included in the study. T2-weighted (T2W) diffuse white matter hyperintensities (WMHs) and focal WMHs were seen in 17 (41.4%) and 7 (17%) patients, respectively. T1W basal ganglia hyperintensities in 20 (48.7%), cerebral microbleeds (CMBs) in 6 (14.6%), and 2 (4.8%) patients had cerebral edema. In patients with AD, T2W diffuse WMHs were seen in 3 (23%), T2W focal WMHs in 3 (23%) patients. None of the patients with AD had cerebral edema or CMBs. In compensated cirrhosis patients, T2W diffuse WMHs were present in 7 (33.3%), T2W focal WMHs in 5 (23.8%), while 3 (14.2%) patients had CMBs. T1 weighted hyperintensities in basal ganglia were more common in AD [9 (69.2%)] and compensated cirrhosis [15 (71.4%)] as compared to ACLF patients [20 (48.7%)], P = 0.174. The survival time of 30 and 90 days for patients with diffuse T2W WMHs was significantly lesser than patients without T2W WMHs (P = 0.007).

Conclusion

Cerebral edema is uncommon in ACLF patients, and T2-weighted diffuse white matter hyperintensities may be associated with worse outcomes. However, due to the limited scope of the present study, the same needs to be explored further in larger cohorts.

Automatic spatial estimation of white matter hyperintensities evolution in brain MRI using disease evolution predictor deep neural networks

Previous studies have indicated that white matter hyperintensities (WMH), the main radiological feature of small vessel disease, may evolve (i.e., shrink, grow) or stay stable over a period of time. Predicting these changes are challenging because it involves some unknown clinical risk factors that leads to a non-deterministic prediction task. In this study, we propose a deep learning model to predict the evolution of WMH from baseline to follow-up (i.e., 1-year later), namely "Disease Evolution Predictor" (DEP) model, which can be adjusted to become a non-deterministic model. The DEP model receives a baseline image as input and produces a map called "Disease Evolution Map" (DEM), which represents the evolution of WMH from baseline to follow-up. Two DEP models are proposed, namely DEP-UResNet and DEP-GAN, which are representatives of the supervised (i.e., need expert-generated manual labels to generate the output) and unsupervised (i.e., do not require manual labels produced by experts) deep learning algorithms respectively. To simulate the non-deterministic and unknown parameters involved in WMH evolution, we modulate a Gaussian noise array to the DEP model as auxiliary input. This forces the DEP model to imitate a wider spectrum of alternatives in the prediction results. The alternatives of using other types of auxiliary input instead, such as baseline WMH and stroke lesion loads are also proposed and tested. Based on our experiments, the fully supervised machine learning scheme DEP-UResNet regularly performed better than the DEP-GAN which works in principle without using any expert-generated label (i.e., unsupervised). However, a semi-supervised DEP-GAN model, which uses probability maps produced by a supervised segmentation method in the learning process, yielded similar performances to the DEP-UResNet and performed best in the clinical evaluation. Furthermore, an ablation study showed that an auxiliary input, especially the Gaussian noise, improved the performance of DEP models compared to DEP models that lacked the auxiliary input regardless of the model's architecture. To the best of our knowledge, this is the first extensive study on modelling WMH evolution using deep learning algorithms, which deals with the non-deterministic nature of WMH evolution.

Brain Edema in Chronic Hepatic Encephalopathy

Brain edema is a common feature associated with hepatic encephalopathy (HE). In patients with acute HE, brain edema has been shown to play a crucial role in the associated neurological deterioration. In chronic HE, advanced magnetic resonance imaging (MRI) techniques have demonstrated that low-grade brain edema appears also to be an important pathological feature. This review explores the different methods used to measure brain edema ex vivo and in vivo in animal models and in humans with chronic HE. In addition, an in-depth description of the main studies performed to date is provided. The role of brain edema in the neurological alterations linked to HE and whether HE and brain edema are the manifestations of the same pathophysiological mechanism or two different cerebral manifestations of brain dysfunction in liver disease are still under debate. In vivo MRI/magnetic resonance spectroscopy studies have allowed insight into the development of brain edema in chronic HE. However, additional in vivo longitudinal and multiparametric/multimodal studies are required (in humans and animal models) to elucidate the relationship between liver function, brain metabolic changes, cellular changes, cell swelling, and neurological manifestations in chronic HE.

Enzyme replacement therapy and white matter hyperintensity progression in Fabry disease

Objective

To explore the association between enzyme replacement therapy (ERT), clinical characteristics, and the rate of progression of white matter hyperintensities (WMH) in patients with Fabry disease (FD).

Methods

Patients with a confirmed diagnosis of FD, aged 18 years or older, participating in an existing FD observational study (NCT00196742), with at least 2 serial MRI brain scans at least 2 years apart for the period between December 2006 and August 2016 were included in this cohort study. Total WMH volume was estimated for each image using a semiautomated procedure. We performed linear regression to calculate the primary outcome measure of WMH change rate for each participant. Associations between ERT, clinical characteristics, and the primary outcome were explored using multiple linear regression.

Results

Eight hundred sixty-three MRI time points were analyzed for the 149 included participants. Age (p < 0.0005; increasing age associated with faster WMH progression), total cholesterol (p = 0.03; increasing total cholesterol associated with slower WMH progression), and a history of peripheral pain (p = 0.02; peripheral pain associated with faster WMH progression) were independently associated with WMH change rate in the primary analysis. We did not find an association between “ERT at any point between baseline and final MRI” and WMH change rate (p = 0.22).

Conclusion

In a large cohort of patients with FD, we did not find an association between ERT and WMH progression, while higher total cholesterol was associated with slower WMH progression. Further research is needed into the pathogenesis and treatment of cerebrovascular disease in this rare condition.

Relationship Between Successful Extracranial-Intracranial Bypass Surgeries and Ischemic White Matter Hyperintensities

BACKGROUND AND PURPOSE

Few studies have described regression of white matter hyperintensities (WMHs); however, no studies have described their recurrence or fluctuation. Thus, we aimed to study the course of WMHs on fluid-attenuated inversion recovery (FLAIR) magnetic resonance image (MRI) after extracranial-intracranial (EC-IC) bypass surgery and its correlation with the clinical outcome.

METHODS

We enrolled perioperative FLAIR MRIs of 12 patients with WMHs who underwent EC-IC bypass surgeries because of ischemic-vascular stenosis with postoperative improvement of the cerebral blood flow confirmed by (123)I-iodoamphetamine single-photon emission computed tomography. Correlation between WMHs and cerebral blood flow was confirmed by perioperative single-photon emission computed tomography and diffusion-weighted imaging MRI. The WMHs were assessed visually with meticulous volumetric grading. Depending on postoperative changes among different grades, the WMHs course was determined to be improved, fluctuating, worsened, or unchanged. A statistical analysis was performed on the course of WMHs over time.

RESULTS

Imaging analysis was done with FLAIR MRI in 12 patients. The course of WMHs over time was 41.7% improvement, 33.3% fluctuation, 16.7% unchanged, and 8.3% worsening of the deep WMHs. After unilateral bypass surgery, 80% of the improved WMHs occurred bilaterally. Among patients with improved clinical outcomes, 16.7% showed improvement and 33.3% showed fluctuation, whereas in patients with unchanged clinical outcomes, 25% showed improvement of their WMHs on follow-up FLAIR MRIs.

CONCLUSIONS

This study might be considered the first step to find a relationship between successful EC-IC bypass surgeries and the course of ischemic WMHs. It could also open the door for further studies to make more solid conclusions.

Dynamic Progression of White Matter Hyperintensities in Alzheimer's Disease and Normal Aging: Results from the Sunnybrook Dementia Study

Although white matter hyperintensities (WMH), markers of cerebral small vessel disease (SVD), are believed to generally increase over time, some studies have shown sharp decreases after therapeutic intervention, suggesting that WMH progression may be more dynamic than previously thought. Our primary goal was to examine dynamic progression of WMH in a real-world sample of Alzheimer’s disease (AD) patients and normal elderly (NC), with varying degrees of SVD. WMH volumes from serial magnetic resonance imaging (MRI; mean = 1.8 years) were measured from NC (n = 44) and AD patients (n = 113) with high and low SVD burden. Dynamic progression for each individual was measured using spatial overlap images to assess shrinkage, growth, and stable WMH volumes. Significant group differences were found for shrinkage (p < 0.001), growth (p < 0.001) and stable (p < 0.001) WMH, where the AD high SVD group showed the largest changes relative to low SVD and NC. Our results suggest spatial progression measured at the individual patient level may be more sensitive to the dynamic nature of WMH.

Cerebral white matter lesions in patients with cirrhosis - causative for hepatic encephalopathy or bystanders?

BACKGROUND & AIMS

Focal white matter lesions mimicking microvascular lesions were connected to the development of hepatic encephalopathy (HE) in patients with cirrhosis. This study aims to assess the relationship between cerebrovascular risk factors and the prevalence and extent of these lesions in patients with cirrhosis, as well as their impact upon cognitive function.

METHODS

55 cirrhotic patients underwent neurological examination, psychometric testing and magnetic resonance imaging. T2-weighted images were reviewed for white matter lesions by a neuroradiologist and a neurologist, independently. Patients were allocated into three groups: (i) no or <5, (ii) 6-15 and (iii) more than 15 lesions. Allocation was confirmed by a senior neuroradiologist blinded for the clinical data. The patient groups were compared concerning age, underlying liver disease, mortality, MELD Score, history of HE, treatment for HE, cerebrovascular risk factors and psychometric test results. Regression analysis was performed to identify risk factors for the presence and extent of white matter lesions.

RESULTS

Patient groups 2 and 3 were older and showed worse results in the psychometric tests than group 1 (P < 0.05). Correlation analyses showed a significant relationship between the number of white matter lesions and the grade of HE (P < 0.001) and cognitive function (P < 0.05), but no interrelationship between the lesions and cerebrovascular risk factors or other factors tested.

CONCLUSIONS

Focal white matter lesions in patients with cirrhosis do not represent cerebrovascular small-vessel disease but are related to the pathology of HE. Further studies are needed to clarify the mechanisms behind in detail.

Postoperative cognitive dysfunction after liver transplantation

OBJECTIVE

Postoperative cognitive dysfunction (POCD) in liver transplant (LT) recipients is defined as a "more than expected" postoperative deterioration in cognitive domains, including short-term and long-term memory, mood, consciousness and circadian rhythm. It is diagnosed, after exclusion of other neurological complications, by using specific neuropsychological tests that need preoperative baseline. The aim of this systematic review was to assess the prevalence of POCD after LT and to analyze patients' symptoms, type and timing of assessment used.

METHODS

PubMed, MEDLINE and The Cochrane Li-brary were searched up from January 1986 to August 2014. Study eligibility criteria are as follows: prospective and retrospective studies on human adult subjects describing prevalence of POCD and/or its sequelae after LT episodes were included.

RESULTS

Eighteen studies were identified. The timing of testing for POCD may vary between different studies and within the single study, ranging from 0.5 to 32 weeks. POCD occurs in up to 50% of LT recipient.

CONCLUSION

Future studies should be focused on detecting preoperative and intraoperative factors associated to POCD in order to carry out appropriate strategies aimed at reducing this disabling health condition. Relationship between POCD and long-term outcome needs to be investigated.

White matter hyperintensity in ischemic stroke patients: it may regress over time

Background and Purpose

White matter hyperintensities (WMH) are frequently observed on MRI in ischemic stroke patients as well as in normal elderly individuals. Besides the progression of WMH, the regression of WMH has been rarely reported. Thus, we aimed to investigate how WMH change over time in patients with ischemic stroke, particularly focusing on regression.

Methods

We enrolled ischemic stroke patients who underwent brain MRI more than twice with at least a 6 month time-interval. Based on T2-weighted or FLAIR MRI, WMH were visually assessed, followed by semiautomatic volume measurement. Progression or regression of WMH change was defined when 0.25 cc increase or decrease was observed and it was also combined with visible change. A statistical analysis was performed on the pattern of WMH change over time and factors associated with change.

Results

A total of 100 patients were enrolled. Their age (mean±SD) was 67.5±11.8 years and 63 were male. The imaging time-interval (mean) was 28.0 months. WMH progressed in 27, regressed in 9 and progressed in distinctive regions and regressed in others in 5 patients. A multiple logistic regression model showed that age (odds ratio[OR] 2.51, 90% confidence interval[CI] 1.056-5.958), male gender (OR 2.957, 95% CI 1.051-9.037), large vessel disease (OR 1.955, 95% CI 1.171-3.366), and renal dysfunction (OR 2.900, 90% CI 1.045-8.046) were associated with progression. Regarding regression, no significant factor was found in the multivariate analysis.

Conclusions

In 21.5% of ischemic stroke patients, regression of WMH was observed. WMH progression was observed in a third of ischemic stroke patients.

Brain magnetic resonance in hepatic encephalopathy

The term hepatic encephalopathy (HE) covers a wide spectrum of neuropsychiatric abnormalities caused by portal-systemic shunting. The diagnosis requires demonstration of liver dysfunction or portal-systemic shunts and exclusion of other neurologic disorders. Most patients with this condition have liver dysfunction caused by cirrhosis, but it also occurs in patients with acute liver failure and less commonly, in patients with portal-systemic shunts that are not associated with hepatocellular disease. Various magnetic resonance (MR) techniques have improved our knowledge about the pathophysiology of HE. Proton MR spectroscopy and T1-weighted imaging can detect and quantify accumulations of brain products that are normally metabolized or eliminated such as glutamine and manganese. Other MR techniques such as T2-weighted and diffusion-weighted imaging can identify white matter abnormalities resulting from disturbances in cell volume homeostasis secondary to brain hyperammonemia. Partial or complete recovery of these abnormalities has been observed with normalization of liver function or after successful liver transplantation. MR studies have undoubtedly improved our understanding of the mechanisms involved in the pathogenesis of HE, and some findings can be considered biomarkers for monitoring the effects of therapeutic measures focused on correcting this condition.

Brain magnetic resonance spectroscopy in episodic hepatic encephalopathy

Brain magnetic resonance (MR) study has shown metabolic abnormalities and changes in water distribution of the brain tissue that may relate to the pathogenesis of hepatic encephalopathy (HE). We designed a study to investigate the disturbances in brain water and metabolites during episodic HE using a 3-T MR scanner. Cirrhotic patients with different grades of HE underwent MR during hospitalization (n=18). The MR was repeated at 6 weeks' follow-up (n=14). The results were compared with those of a group of healthy volunteers (n=8). During episodic HE, brain diffusion-weighted imaging showed a high apparent diffusion coefficient (ADC) (12% to 14%) that decreased during follow-up (-1% to -4%). These disturbances were accompanied by high glutamine (581%), low choline (-31%), and low myo-inositol (-86%) peaks on MR spectroscopy. In overt HE, patients showed high glutamine that decreased during follow-up (-22%). In addition, these patients exhibited a rise in plasma S100 beta and enlargement of brain white-matter lesions. In conclusion, several disturbances detected by MR support the presence of impaired brain water homeostasis during episodic HE. Although astrocytes have a major role in this condition, brain edema during episodic HE may be extracellular and does not appear to be directly responsible for the development of neurologic manifestations.

White matter abnormalities correlate with neurocognitive performance in patients with HBV-related cirrhosis

BACKGROUND

White matter (WM) abnormalities are common in cirrhotic patients and possibly contribute to hepatic encephalopathy (HE), a frequent neuropsychiatric complication of cirrhosis. However, little is known about these WM abnormalities and their relationship to neurocognitive deficits in patients with HBV-related cirrhosis.

METHODS

Three-dimensional T1-weighted magnetic resonance imaging and diffusion tensor imaging (DTI) scans were obtained from 67 patients with HBV-related cirrhosis and 40 controls. Voxel-based morphometry and voxel-based DTI were performed to detect macroscopic atrophy and damage to the microstructural integrity of the WM, respectively. Correlation analyses were performed to investigate the relationships between WM abnormalities and neurocognitive performances.

RESULTS

Patients with cirrhosis exhibited significantly decreased WM volume and fractional anisotropy (FA) values, especially in the corpus callosum, thalamus, extra-nuclear area, sensorimotor area, fusiform gyrus, lingual gyrus, and frontal lobes. These abnormalities were more severe with increasing Child-Pugh stage, minimal HE, and previous overt HE. Changes in the corpus callosum, frontal lobe, sensorimotor area, internal capsule, and temporal-occipital lobes were correlated with poor neurocognitive performance. Also, the significantly decreased global WM volume and mean FA value were correlated with poor neurocognitive performances.

CONCLUSIONS

Diffuse WM abnormalities are common in patients with HBV-related cirrhosis. Advanced liver disease and episodes of HE are two factors associated with WM abnormalities. The correlation between poor neurocognitive performance and WM abnormalities suggests that WM abnormalities may be one of mechanisms underlying neurocognitive deficits in patients with HBV-related cirrhosis.

Brain imaging and hepatic encephalopathy

Novel imaging techniques allow the investigation of structural and functional neuropathology of hepatic encephalopathy in greater detail, but limited techniques are applicable to the clinic. Computed tomography and magnetic resonance imaging (MRI) can rule out other diagnoses and, in MRI, give diagnostic features in widely available sequences. An internationally accepted diagnostic framework that includes an objective imaging test to replace or augment psychometry remains elusive. Quantitative MRI is likely to be the best candidate to become this test. The utility of MR and nuclear medical techniques to the clinic and results from recent research are described in this article.

Neuroimaging findings in alcohol-related encephalopathies

OBJECTIVE

Our aim was to review the emergent neuroimaging findings of alcohol-related CNS nontraumatic disorders. Alcohol (ethanol) promotes inflammatory processes, increases DNA damage, and creates oxidative stress. In addition, the accompanying thiamine deficiency may lead to Wernicke encephalopathy. Associated changes in serum osmolarity may lead to acute demyelination.

CONCLUSION

Alcohol-related encephalopathies can be life-threatening conditions but can be prevented or treated, if recognized.

Hyponatremic and hepatic encephalopathies: similarities, differences and coexistence

Hyponatremic and hepatic encephalopathy are common causes of metabolic encephalopathy that may coexist in patients with cirrhosis. The clinical picture is common to any metabolic encephalopathy and is characterized by a confusional syndrome that may evolve into coma. Chronic mild or minimal manifestations can be seen in both, but motor symptoms are more common in hepatic encephalopathy. Recent advances show that in addition to clinical manifestations both encephalopathies share some pathogenetic mechanisms. Dysfunction of astrocytes, osmotic changes in the brain and brain edema are present in both situations. Recognition of these abnormalities is important to plan therapy. New drugs that affect brain hydration may be useful for both encephalopathies.

Neurocognitive-neurological complications of liver transplantation: a review

Neurological complications are common after liver transplantation (LT) and they are associated with a significant morbidity. Long-term effects of LT on cognitive and psychological outcomes are not clear. The objective of this study was to summarize the present knowledge on the neurological and cognitive complications of LT, resulting from a systematic review of the literature in the last 10 years. Several studies have investigated the incidence and the pathophysiology of neurological complications; in contrast, the knowledge of cognitive and psychological status after LT is poor. Currently, the effect of LT on mental performance is debated. Some studies have shown an improvement of cognitive function after OLTX and, at the same time, a persistence of different cognitive deficits. In addition, the quality of life (QoL) and the psychological status after LT seem to improve but LT recipients have significant deficiencies in most QoL domains. Consequently, future studies are necessary in order to investigate cognitive alterations and QoL in LT recipients.

Reversible hyperglycemic homonymous hemianopia

We report a 67-year-old female diabetic with homonymous hemianopia as the presenting sign of nonketotic hyperglycemia. Magnetic resonance imaging (MRI) was abnormal with diffuse bilateral hyperintense white matter changes. A follow-up MRI scan 15 years later showed persisting abnormality. Her hemianopic visual field loss was reversed after correction of her hyperglycemia. Diabetes mellitus should be considered with the sudden onset of a homonymous hemianopia.

Relationship between aquaporin-4 expression and brain edema in cirrhotic rats with hepatic encephalopathy

AIM: To investigate the mechanism of brain edema in cirrhotic rats with hepatic encephalopathy, and to provide the theoretical basis for management of brain edema.

METHODS: Rats were divided into 4 groups randomly: normal group (n = 10), normal ammonia burden group (n = 10), cirrhosis group (n = 20), cirrhosis ammonia burden group (n = 20). After models were generated successfully, the arterial plasma ammonia was measured by dry biochemical method, and the evans blue (EB) content was examined by colorimetric method; the brain water content (BWC) was measured by means of dry-wet method and the aquaporin-4 (APQ-4) in the brain tissue was assessed by immunohistochemistry.

RESULTS: In comparison with that in the normal group and nomal ammonia burden group, the arterial plasma ammonia was significantly increased in the cirrhosis group and cirrhosis ammonia burden group (420.18 ± 75.91, 97.20 ± 29.66 μmol/L vs 42.62 ± 10.11, 59.33 ± 15.06 μmol/L; P < 0.05 or P < 0.01). The EB content (1.96 ± 0.55 μg/g) and brain water content (75.14 ± 5.68) in the cirrhosis ammonia burden group were higher than those in the nomal group, nomal ammonia burden group, and cirrhosis group (1.96 ± 0.55 μg/g vs 1.05 ± 0.18, 1.19 ± 0.38, 1.41 ± 0.46 μg/g; 75.14 ± 5.68 vs 62.14 ± 2.29, 66.27 ± 4.57 65.58 ± 4.14; all P < 0.05). The location of APQ-4 expression in cirrhotic rats was consistent with that in normal rats, but both the intensity and area of APQ-4 expression were increased as compared with those in normal controls (P < 0.05).

CONCLUSION: APQ-4 expression is up-regulated in cirrhotic rats with hepatic encephalopathy, suggesting that APQ-4 may play a role in the occurrence of hepatic encephalopathy.

MR imaging findings in hepatic encephalopathy

The term hepatic encephalopathy (HE) includes a spectrum of neuropsychiatric abnormalities occurring in patients with liver dysfunction. Most cases are associated with cirrhosis and portal hypertension or portal-systemic shunts, but the condition can also be seen in patients with acute liver failure and, rarely, with portal-systemic bypass and no associated intrinsic hepatocellular disease. Although HE is a clinical condition, several neuroimaging techniques, particularly MR imaging, may eventually be useful for the diagnosis because they can identify and measure the consequences of central nervous system (CNS) increase in substances that under normal circumstances, are efficiently metabolized by the liver. Classic MR imaging abnormalities include high signal intensity in the globus pallidum on T1-weighted images, likely a reflection of increased tissue concentrations of manganese, and an elevated glutamine/glutamate peak coupled with decreased myo-inositol and choline signals on proton MR spectroscopy, representing disturbances in cell-volume homeostasis secondary to brain hyperammonemia. Recent data have shown that white matter abnormalities, also related to increased CNS ammonia concentration, can also be detected with several MR imaging techniques such as magnetization transfer ratio measurements, fast fluid-attenuated inversion recovery sequences, and diffusion-weighted images. All these MR imaging abnormalities, which return to normal with restoration of liver function, probably reflect the presence of mild diffuse brain edema, which seems to play an essential role in the pathogenesis of HE. It is likely that MR imaging will be increasingly used to evaluate the mechanisms involved in the pathogenesis of HE and to assess the effects of therapeutic measures focused on correcting brain edema in these patients.

Portal-systemic shunt encephalopathy presenting with diffuse cerebral white matter lesion: an autopsy case

We report herein an autopsy case of portal-systemic encephalopathy (PSE) presenting with diffuse tissue rarefaction in the cerebral deep white matter. Clinically, the patient showed recurrent episodes of unconsciousness, abnormal behavior and urinary incontinence, as well as flapping tremor. Cognitive impairment and peripheral neuropathy developed following recurrent episodes. Although conventional arterial portography revealed a small portal-systemic collateral vessel of a left gastro-renal venous shunt, abdominal CT and liver biopsy showed no evidence of liver cirrhosis and serum ammonia level showed a mild increase. T2-weighted MRI demonstrated symmetrical signal hyperintensities in the deep white matter. Neuropathological findings showed Alzheimer type II astrocytes in the deep layers of the cerebral cortices and severe tissue rarefaction with no or slight reactive astrocytosis in the subcortical and deep white matter. These white matter changes have been reported infrequently in patients with PSE. The present case suggests that chronic PSE without liver cirrhosis may develop diffuse white matter lesions.

Decreased white matter lesion volume and improved cognitive function after liver transplantation

Focal T2-weighted white matter lesions (WML) on brain magnetic resonance imaging (MRI), mimicking those seen in cerebrovascular small-vessel disease described in patients with persistent hepatic encephalopathy, decreased in volume with the improvement of hepatic encephalopathy. This outcome has been interpreted as a decrease in the edema that it is proposed to be involved in the pathogenesis of hepatic encephalopathy. We designed a study to further investigate potential changes in focal WML in the brains of patients with cirrhosis following liver transplantation and to study the relationship between these changes and overall cognitive function. We used MRI to measure the volume of supratentorial focal WML and a neuropsychological examination to assess cognitive function before and after liver transplantation in 27 patients with cirrhosis without signs of overt hepatic encephalopathy. Baseline MRI identified focal T2-weighted lesions in 19 patients (70.3%). The presence of WML was associated with older age but not with vascular risk factors, severity of liver function, or psychometric tests. A significant reduction in lesion volume was observed after liver transplantation (from a median of 1.306 cm(3) to 0.671 cm(3), P = 0.001). This decrease correlated with an improvement in an index of global cognitive function (r = -0.663; P < 0.001). This evolution indicates that lesion volume is partially related to a reversible type of tissue damage, which is compatible with brain edema.

CONCLUSION

Focal WML probably induced by age-related microvascular injury can decrease their volume with liver transplantation. The associated improvement of cognitive function supports a relationship between brain edema and minimal hepatic encephalopathy.