MR imaging of the basal ganglia in chronic liver disease: correlation of T1-weighted and magnetisation transfer contrast measurements with liver dysfunction and neuropsychiatric status

[WITHDRAWN] Serum biomarkers of liver fibrosis identify changes in striatal metabolite levels

The full text of this preprint has been withdrawn by the authors due to author disagreement with the posting of the preprint. Therefore, the authors do not wish this work to be cited as a reference. Questions should be directed to the corresponding author.

Regulation of mild cognitive impairment associated with liver disease by humoral factors derived from the gastrointestinal tract and MRI research progress: a literature review

Patients with liver disease are prone to various cognitive impairments. It is undeniable that cognitive impairment is often regulated by both the nervous system and the immune system. In this review our research focused on the regulation of mild cognitive impairment associated with liver disease by humoral factors derived from the gastrointestinal tract, and revealed that its mechanisms may be involved with hyperammonemia, neuroinflammation, brain energy and neurotransmitter metabolic disorders, and liver-derived factors. In addition, we share the emerging research progress in magnetic resonance imaging techniques of the brain during mild cognitive impairment associated with liver disease, in order to provide ideas for the prevention and treatment of mild cognitive impairment in liver disease.

Serum biomarkers of liver fibrosis identify globus pallidus vulnerability

The CNS manifestation of chronic liver disease can include magnetic resonance (MR) signal hyperintensities in basal ganglia structures. Here, relations between liver (serum-derived fibrosis scores) and brain (regional T1-weighted signal intensities and volumes) integrity were evaluated in a sample of 457 individuals including those with alcohol use disorders (AUD), people living with human immunodeficiency virus (HIV), those comorbid for AUD and HIV, and healthy controls. Liver fibrosis was identified from cutoff scores as follows: aspartate aminotransferase to platelet ratio index (APRI) > 0.7 in 9.4% (n = 43) of the cohort; fibrosis score (FIB4) > 1.5 in 28.0% (n = 128) of the cohort; and non-alcoholic fatty liver disease fibrosis score (NFS) > -1.4 in 30.2% (n = 138) of the cohort. Presence of serum-derived liver fibrosis was associated with high signal intensities selective to basal ganglia (i.e., caudate, putamen, and pallidum) structures. High signal intensities in the pallidum, however, explained a significant portion of the variance in APRI (25.0%) and FIB4 (23.6%) cutoff scores. Further, among the regions evaluated, only the globus pallidus showed a correlation between greater signal intensity and smaller volume (r = -0.44, p <.0001). Finally, higher pallidal signal intensity correlated worse ataxia (eyes open ρ = -0.23, p =.0002; eyes closed ρ = -0.21, p =.0005). This study suggests that clinically relevant serum biomarkers of liver fibrosis such as the APRI may identify individuals vulnerable to globus pallidus pathology and contribute to problems with postural balance.

Hepatic encephalopathy

Hepatic encephalopathy (HE) is a prognostically relevant neuropsychiatric syndrome that occurs in the course of acute or chronic liver disease. Besides ascites and variceal bleeding, it is the most serious complication of decompensated liver cirrhosis. Ammonia and inflammation are major triggers for the appearance of HE, which in patients with liver cirrhosis involves pathophysiologically low-grade cerebral oedema with oxidative/nitrosative stress, inflammation and disturbances of oscillatory networks in the brain. Severity classification and diagnostic approaches regarding mild forms of HE are still a matter of debate. Current medical treatment predominantly involves lactulose and rifaximin following rigorous treatment of so-called known HE precipitating factors. New treatments based on an improved pathophysiological understanding are emerging.

Severe Acute Hepatic Dysfunction Induced by Ammonium Acetate Treatment Results in Choroid Plexus Swelling and Ventricle Enlargement in the Brain

Hepatic encephalopathy is a major cause of liver failure. However, the pathophysiological role of ventricle enlargement in brain edema remains unclear. Here, we used an acute hepatic encephalopathy mouse model to examine the sequential pathological changes in the brain associated with this condition. We collected tissue samples from experimental animals treated with ammonium acetate at 3 and 24 h post-injection. Despite the normalization of the animal’s ammonia levels, samples taken at 24 h after injection exhibited distinct enlargement of lateral ventricles. The choroid plexus samples obtained at 3 h post-ammonium acetate treatment indicated enlargement; however, this swelling was reduced at the later timepoint. The aquaporin-1 proteins that regulate the choroid plexus were localized both in the apical membrane and the cytoplasm of the epithelia in the control; however, they translocated to the apical membranes of the epithelia in response to ammonia treatment. Therefore, severe acute hepatic encephalopathy induced by ammonium acetate administration caused enlargement of the ventricles, through swelling of the choroid plexus and aquaporin-1 transport and aggregation within the apical membranes.

Hepatic encephalopathy: Novel insights into classification, pathophysiology and therapy

Hepatic encephalopathy (HE) is a frequent and serious complication of both chronic liver disease and acute liver failure. HE manifests as a wide spectrum of neuropsychiatric abnormalities, from subclinical changes (mild cognitive impairment) to marked disorientation, confusion and coma. The clinical and economic burden of HE is considerable, and it contributes greatly to impaired quality of life, morbidity and mortality. This review will critically discuss the latest classification of HE, as well as the pathogenesis and pathophysiological pathways underlying the neurological decline in patients with end-stage liver disease. In addition, management strategies, diagnostic approaches, currently available therapeutic options and novel treatment strategies are discussed.

Laboratory Abnormalities of Hepatic Encephalopathy

Currently, there is no gold standard serologic or imaging modality to detect hepatic encephalopathy (HE). It is a clinical diagnosis gathered from the history and physical. Imaging is nonspecific; however, PET and MRI have shown areas of utility, but are not widely available, cost-efficient, or necessary for diagnosis. Electroencephalogram has shown promise as it can be used in conjunction with the Portal Systemic Hepatic Encephalopathy Score test to diagnose minimal HE. Further research on these techniques would need to be performed to identify strict criteria and cutoffs for diagnosing HE as well as associated sensitivities and specificities.

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.

Multimodal MR imaging in hepatic encephalopathy: state of the art

Hepatic encephalopathy (HE) is a neurological or neuropsychological complication due to liver failure or portosystemic shunting. The clinical manifestation is highly variable, which can exhibit mild cognitive or motor impairment initially, or gradually progress to a coma, even death, without treatment. Neuroimaging plays a critical role in uncovering the neural mechanism of HE. In particular, multimodality MR imaging is able to assess both structural and functional derangements of the brain with HE in focal or neural network perspectives. In recent years, there has been rapid development in novel MR technologies and applications to investigate the pathophysiological mechanism of HE. Therefore, it is necessary to update the latest MR findings regarding HE by use of multimodality MRI to refine and deepen our understanding of the neural traits in HE. Herein, this review highlights the latest MR imaging findings in HE to refresh our understanding of MRI application in HE.

A longitudinal study of patients with cirrhosis treated with L-ornithine L-aspartate, examined with magnetization transfer, diffusion-weighted imaging and magnetic resonance spectroscopy

The presence of overt hepatic encephalopathy (HE) is associated with structural, metabolic and functional changes in the brain discernible by use of a variety of magnetic resonance (MR) techniques. The changes in patients with minimal HE are less well documented. Twenty-two patients with well-compensated cirrhosis, seven of whom had minimal HE, were examined with cerebral 3 Tesla MR techniques, including T₁- and T₂-weighted, magnetization transfer and diffusion-weighted imaging and proton magnetic resonance spectroscopy sequences. Studies were repeated after a 4-week course of oral L-ornithine L-aspartate (LOLA). Results were compared with data obtained from 22 aged-matched healthy controls. There was no difference in mean total brain volume between patients and controls at baseline. Mean cerebral magnetization transfer ratios were significantly reduced in the globus pallidus and thalamus in the patients with cirrhosis irrespective of neuropsychiatric status; the mean ratio was significantly reduced in the frontal white matter in patients with minimal HE compared with healthy controls but not when compared with their unimpaired counterparts. There were no significant differences in either the median apparent diffusion coefficients or the mean fractional anisotropy, calculated from the diffusion-weighted imaging, or in the mean basal ganglia metabolite ratios between patients and controls. Psychometric performance improved in 50 % of patients with minimal HE following LOLA, but no significant changes were observed in brain volumes, cerebral magnetization transfer ratios, the diffusion weighted imaging variables or the cerebral metabolite ratios. MR variables, as applied in this study, do not identify patients with minimal HE, nor do they reflect changes in psychometric performance following LOLA.

Quantitative magnetic resonance imaging in patients with cirrhosis: a cross-sectional study

Cerebral magnetic resonance imaging was undertaken, at 3 Tesla field strength, employing magnetization transfer (MT) and diffusion-weighted imaging (DWI) sequences, in 26 patients with well-compensated cirrhosis, free of overt hepatic encephalopathy. Results were compared to those from 18 aged-matched healthy volunteers. Cerebral magnetization transfer ratios (MTR) were reduced in the frontal white matter, caudate, putamen and globus pallidus in patients with cirrhosis, compared to healthy controls, while the apparent diffusion coefficients (ADC) on DWI were significantly increased in the genu and body of the corpus callosum. An association between previous excessive alcohol consumption and both MTR and ADCs was noted, but this association was lost when controls were exercised for the severity of liver disease and psychometric impairment on multivariate analysis. Eight (31 %) of the 26 patients had impaired psychometric performance consistent with a diagnosis of minimal hepatic encephalopathy. No statistically significant difference in regional cerebral MTRs or ADCs was found in relation to neuropsychiatric status, although there was a trend towards lower MTRs in patients with impaired psychometric performance. The alterations in MTR and ADC in the patients with functionally compensated cirrhosis are compatible with theories governing the genesis of hepatic encephalopathy, including changes in astrocyte membrane permeability, with subsequent redistribution of macromolecules.

Early primary biliary cholangitis is characterised by brain abnormalities on cerebral magnetic resonance imaging

BACKGROUND

Brain change can occur in primary biliary cholangitis (PBC), potentially as a result of cholestatic and/or inflammatory processes. This change is linked to systemic symptoms of fatigue and cognitive impairment.

AIM

To identify whether brain change occurs early in PBC. If the change develops early and is progressive, it may explain the difficulty in treating these symptoms.

METHODS

Early disease brain change was explored in 13 patients with newly diagnosed biopsy-proven precirrhotic PBC using magnetisation transfer, diffusion-weighted imaging and ¹ H magnetic resonance spectroscopy. Results were compared to 17 healthy volunteers.

RESULTS

Cerebral magnetisation transfer ratios were reduced in early PBC, compared to healthy volunteers, in the thalamus, putamen and head of caudate with no greater reduction in patients with greater symptom severity. Mean apparent diffusion coefficients were increased in the thalamus only. No ¹ H magnetic resonance spectroscopy abnormalities were seen. Serum manganese levels were elevated in all PBC patients, but no relationship was seen with imaging or symptom parameters. There were no correlations between neuroimaging data, laboratory data, symptom severity scores or age.

CONCLUSIONS

This is the first study to be performed in this precirrhotic patient population, and we have highlighted that neuroimaging changes are present at a much earlier stage than previously demonstrated. The neuroimaging abnormalities suggest that the brain changes seen in PBC occur early in the pathological process, even before significant liver damage has occurred. If such changes are linked to symptom pathogenesis, this could have important implications for the timing of second-line-therapy use.

Delineation of microhemorrhage in acute hepatic encephalopathy using susceptibility-weighted imaging

INTRODUCTION

Microhemorrhages (MH's) in patients with acute hepatic encephalopathy (AHE) have scarcely been described. This study set out to assess if MH's occur in characteristic locations and frequency in patients with AHE superimposed on chronic liver failure, and to determine if such findings correlate with the clinical and MRI severity.

MATERIALS AND METHODS

Over a 4.5-year period, AHE patients with SWI MRI were included. The maximum plasma ammonia level (PAL), number and location of "frank" hemorrhages (>5mm size) or MH's (<5mm) on SWI, and severity of DWI and FLAIR were recorded. Susceptibility foci in the basal ganglia were disregarded, as those changes might represent common mineralization. The presence of MH's was correlated with the MRI and clinical severity.

RESULTS

Punctate MH foci were found in 18/38 (47.4%) patients. The most common locations were periventricular white matter (6/38 patients, 15.8%) and cerebral cortex (5/38, 13.2%). Of 47 MH's, only a tiny minority (8.5%) occurred in regions of abnormality on FLAIR or DWI. Both the MRI severity on FLAIR (r=0.420, p=0.013) and DWI (r=0.320, p=0.045) mildly correlated with clinical outcome, but the correlation was not significant after Bonferroni correction. No significant correlation was found between the number of MH's and the clinical score, clinical outcome, FLAIR severity, or DWI severity (range r=-0.083-0.152, p=0.363-0.618). The number of MH's was not significantly different among various vasculopathies. Foci on SWI improved in two patients following liver transplantation.

CONCLUSION

SWI-positive foci outside of the basal ganglia (presumed MH's) are present in nearly half of AHE patients, but do not portend outcome. Regions with the most observed MH's were the periventricular white matter, cortical gray matter, and subcortical white matter.

Magnetic resonance imaging of the lentiform nuclei in dogs with portosystemic shunts

OBJECTIVES

To develop and evaluate a method to quantify the T1-weighted magnetic resonance imaging signal intensity of the lentiform nuclei in dogs, and to determine if there is any significant difference in this signal intensity between dogs with portosystemic shunts and a control group.

MATERIALS AND METHODS

A retrospective blinded study was performed to investigate the reliability and use of a quantitative method for assessing the T1-weighted magnetic resonance imaging signal intensity of the lentiform nuclei in dogs with and without portosystemic shunts. The lentiform nuclei index (mean lentiform nucleus signal intensity/mean white matter signal intensity) was calculated for nine dogs with portosystemic shunts and a control group of 14 dogs.

RESULTS

The intra- and inter-observer intraclass correlation coefficients were considered excellent (>0 · 75), suggesting that the lentiform nuclei index is a reliable method. The dogs with portosystemic shunts had a higher lentiform nuclei index than the control group (P = 0 · 0127).

CLINICAL SIGNIFICANCE

This method of quantifying the T1-weighted magnetic resonance imaging signal intensity of the lentiform nuclei was reliable and showed that dogs with portosystemic shunts tend to have increased signal intensity. Further prospective studies are necessary to investigate the clinical significance and applications of these findings.

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.

Serum endotoxin, inflammatory mediators, and magnetic resonance spectroscopy before and after treatment in patients with minimal hepatic encephalopathy

BACKGROUND

Minimal hepatic encephalopathy (MHE) represents the mildest form of hepatic encephalopathy (HE), with abnormal neuropsychologic findings. Inflammatory response may be important in the pathogenesis of MHE. On magnetic resonance spectroscopy (MRS), improvement of metabolic ratios after liver transplantation suggests an important role of myoinositol (mI) and choline (cho) in the development of MHE.

AIMS

To investigate arterial ammonia, tumor necrosis factor alpha (TNF-α), interleukin (IL)-6, IL-18, serum endotoxin, and MRS before and after treatment in MHE.

PATIENTS AND METHODS

Sixty patients of cirrhosis with MHE were randomized to two groups, Gr. MHE-L (n = 30), treated with lactulose for 3 months, and Gr. MHE-NL (n = 30), who did not received lactulose. Arterial ammonia, TNF-α, IL-6, IL-18, serum endotoxin, and MRS were performed in all patients at baseline and at 3 months and 20 patients of cirrhosis without MHE and 20 healthy controls.

RESULTS

After 3 months, median arterial ammonia (69.4 vs 52.7 mcg/dL), TNF-α (26.6 vs 22 pg/mL), IL-6 (17.6 vs 12.4 pg/mL), IL-18 (42.5 vs 29 pg/mL), and serum endotoxin (0.68 vs 0.43 EU/mL) significantly decreased in Gr. MHE-L compared with baseline (P < 0.0001), while no change was seen in Gr. MHE-NL patients. On MRS, compared with patients of cirrhosis without MHE, mI and cho were significantly lower (P < 0.001) and glutamine (Glx) was significantly higher in both MHE groups (P < 0.001). After 3 months, mI and cho increased and Glx decreased significantly in Gr. MHE-L (P < 0.001), without changes in Gr. MHE-NL patients. Psychometric hepatic encephalopathic score (PHES) correlated well with arterial ammonia, TNF-α, IL-6, IL-18, serum endotoxin, and metabolic parameters on MRS.

CONCLUSIONS

Arterial ammonia, inflammatory mediators (TNF-α, IL-6, IL-18), and serum endotoxin reduce and MRS abnormalities improve after treatment with lactulose in patients with MHE.

Modulation of neural activation following treatment of hepatic encephalopathy

OBJECTIVE

To measure changes in psychometric state, neural activation, brain volume (BV), and cerebral metabolite concentrations during treatment of minimal hepatic encephalopathy.

METHODS

As proof of principle, 22 patients with well-compensated, biopsy-proven cirrhosis of differing etiology and previous minimal hepatic encephalopathy were treated with oral l-ornithine l-aspartate for 4 weeks. Baseline and 4-week clinical review, blood chemistry, and psychometric evaluation (Psychometric Hepatic Encephalopathy Score and Cognitive Drug Research Score) were performed. Whole-brain volumetric and functional MRI was conducted using a highly simplistic visuomotor task, together with proton magnetic resonance spectroscopy of the basal ganglia. Treatment-related changes in regional BV and neural activation change (blood oxygenation level dependent) were assessed.

RESULTS

Although there was no change in clinical, biochemical state, basal ganglia magnetic resonance spectroscopy, or in regional BV, there were significant improvements in Cognitive Drug Research Score (+1.2, p = 0.003) and Psychometric Hepatic Encephalopathy Score (+1.5, p = 0.003) with treatment. This cognitive amelioration was accompanied by changes in blood oxygenation level-dependent activation in the posterior cingulate and ventral medial prefrontal cortex, 2 regions that form part of the brain's structural and metabolic core. In addition, there was evidence of greater visual cortex activation.

CONCLUSIONS

These structurally interconnected regions all showed increased function after successful encephalopathy treatment. Because no regional change in BV was observed, this implies that mechanisms unrelated to astrocyte volume regulation were involved in the significant improvement in cognitive performance.

T2* MRI of minimal hepatic encephalopathy and cognitive correlates in vivo

PURPOSE

To evaluate regional brain iron deposition in minimal hepatic encephalopathy (MHE) patients using T2*-weighted gradient-echo imaging and to explore the relationship between T2* MR changes and cognitive performance.

MATERIALS AND METHODS

Forty hepatitis-B virus (HBV)-related cirrhotic patients and 22 age-, sex-, and education-matched healthy controls were included in this study. Of the patients, twenty eight patients were diagnosed with MHE. All subjects were administered Number Connection Test-A (NCT-A), Letter Digit Substitution Test (LDST), Rey-Osterrieth Complex Figure Test (RCFT), and the Mini-Mental State Examination (MMSE). T2*-weighted gradient-echo images were acquired using 3 Tesla MRI. Phase values (putative iron levels) in the frontal-basal ganglia-thalamocortical circuits were measured. Spearman correlation and multiple linear regression analysis were performed.

RESULTS

MHE patients exhibited significantly prolonged NCT-A time and decreased LDST, RCFT immediate and delayed recall scores. Significant decreases of phase values in the bilateral putamen were detected in MHE patients compared to without MHE patients and controls. Multiple linear regression analysis confirmed significant correlations between the phase values in the putamen and right frontal white matter and cognitive performances by MHE patients.

CONCLUSION

Decreased phase values in the frontal cortical-basal ganglial circuits independently contribute to cognitive impairments in MHE patients.

Two patterns of cerebral metabolite abnormalities are detected on proton magnetic resonance spectroscopy in HIV-infected subjects commencing antiretroviral therapy

INTRODUCTION

Cerebral function impairment remains problematic in subjects with chronic human immunodeficiency virus (HIV) infection despite effective combination antiretroviral therapy (cART). Using cerebral proton magnetic resonance spectroscopy ((1)H MRS), we aimed to determine if abnormalities could be detected in neurologically asymptomatic HIV-infected subjects electively commencing cART.

METHODS

Therapy-naive, HIV-infected individuals and HIV-uninfected controls underwent (1)H MRS in several anatomical voxels including the mid-frontal grey matter (FGM) and right basal ganglia (RBG). Differences in cerebral metabolite ratios between groups and correlations between immune and virological status were assessed.

RESULTS

Forty-six subjects were recruited (26 HIV-infected and 20 control subjects). In the HIV-infected group, mean CD4+ count (SD, cells per microlitre) and plasma HIV RNA (SD, log10 copies per millilitre) were 192 (86) and 4.71 (0.64), respectively. Choline (Cho)/Creatine (Cr) and myoinositol (MI)/Cr ratios were significantly lower in the FGM in HIV-infected subjects compared to controls (0.67 (0.14) versus 0.88 (0.49), p = 0.036, and 0.94 (0.28) and 1.17 (0.26), p = 0.008, for Cho/Cr and MI/Cr, respectively) and Cho/Cr ratio associated with CD4+ lymphocyte count (p = 0.041). N-Acetyl-aspartate (NAA)/Cho ratio was significantly lower in the RBG in HIV-infected subjects compared to controls (2.27 (0.54) versus 2.63 (0.68), p = 0.002), and this was associated with greater plasma HIV RNA load (p = 0.014).

CONCLUSIONS

Two patterns of cerebral metabolite abnormalities were observed in HIV-infected subjects electively commencing cART. Greater inflammatory metabolite ratios (Cho/Cr and MI/Cr) associated with lower markers of peripheral immune markers (CD4+ lymphocyte count) in the FGM and lower neuronal metabolite ratios (NAA/Cho) associated with greater HIV viraemia in the RBG were present in HIV-infected subjects.

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.

Acquired hepatocerebral degeneration: clinical characteristics and MRI findings

OBJECTIVE

To determine the prevalence of acquired hepatocerebral degeneration (AHD), its clinical and neuroimaging characteristics and response to treatments.

BACKGROUND

Acquired hepatocerebral degeneration is a chronic encephalopathy with predominant motor signs in the context of severe liver disease. Its clinical picture is not well defined, and its prevalence and risk factors are not well known.

METHODS

Review of a database of 1000 patients with cirrhosis to identify cases of AHD. Clinical and neuroimaging data, follow-up and response to treatments, including liver transplantation, were recorded.

RESULTS

Eight patients with AHD were identified. Its prevalence was 0.8% of patients with cirrhosis. The main risk factor for AHD was the presence of portosystemic shunts. Movement disorders, especially a combination of parkinsonism and cerebellar signs were observed in all patients. All AHD cases showed on MRI T1-weighted images hyperintensities in the globus pallidus, and 75% had extrapallidal involvement as well. Antiparkisonian drugs and treatments to prevent acute encephalopathies were ineffective. Three patients who underwent liver transplantation did not experience neurological improvement. Persistence of portosystemic shunts was demonstrated in two cases.

CONCLUSIONS

Acquired hepatocerebral degeneration is a chronic encephalopathy which occurs in ∼1% of patients with liver cirrhosis and seems related to portosystemic shunts. Its is characterized by a combination of parkinsonism and cerebellar signs. MRI pallidal and extrapallidal lesions are seen in most patients, probably reflecting intracerebral deposits of manganese. Liver transplant did not improve the neurological signs in our patients, perhaps because of the persistence of portosystemic shunts.

Acquired hepatocerebral degeneration

Repeated episodes of liver failure or chronic liver cirrhosis may cause acquired (non-Wilsonian) hepatocerebral degeneration (AHCD). Patients with AHCD may show cognitive deficits, ataxia, dysarthria, movement disorders, including parkinsonism, and sometimes myelopathy. Various parenchymal and cholestatic hepatic disorders may result in AHCD. Most patients with AHCD have evidence of portosystemic shunting without necessarily having abnormal liver function. Recent evidence suggests manganese plays a crucial role in the pathogenesis of AHCD. Excess dietary manganese is rapidly cleared by the liver before reaching the systemic circulation. In patients with cirrhosis and portosystemic shunting, manganese bypasses the liver and accumulates in the internal pallidum, while serum manganese levels may be normal or increased. Magnetic resonance imaging abnormalities mainly consist of a signal hyperintensity on T1-weighted images in the internal pallidum. It may also be seen in the putamen, the caudate nucleus, the capsula interna, the mesencephalon, and the cerebellum, and is believed to reflect local manganese accumulation. No specific treatment of AHCD exists. Controlled studies are lacking, but case reports have stressed the usefulness of branched-chain amino acid therapy, trientine, and liver transplantation for the treatment of movement disorders. Levodopa may be efficacious in the treatment of AHCD parkinsonism.

Pathogenesis and diagnosis of hepatic encephalopathy

Hepatic encephalopathy (HE) is a common and potentially devastating neuropsychiatric complication of acute liver failure and cirrhosis. Even in its mildest form, minimal HE (MHE), the syndrome significantly impacts daily living and heralds progression to overt HE. There is maturity in the scientific understanding of the cellular processes that lead to functional and structural abnormalities in astrocytes. Hyperammonemia and subsequent cell swelling is a key pathophysiological abnormality, but this aspect alone is insufficient to fully explain the complex neurotransmitter abnormalities that may be observable using sophisticated imaging techniques. Inflammatory cytokines, reactive oxygen species activation and the role of neurosteroids on neurotransmitter binding sites are emerging pathological lines of inquiry that have yielded important new information on the processes underlying HE and offer promise of future therapeutic targets. Overt HE remains a clinical diagnosis and the neurophysiological and imaging modalities used in research studies have not transferred successfully to the clinical situation. MHE is best characterized by psychometric evaluation, but these tests can be lengthy to perform and require specific expertise to interpret. Simpler computer-based tests are now available and perhaps offer an opportunity to screen, diagnose and monitor MHE in a clinical scenario, although large-scale studies comparing the different techniques have not been undertaken. There is a discrepancy between the depth of understanding of the pathophysiology of HE and the translation of this understanding to a simple, easily understood diagnostic and longitudinal marker of disease. This is a present area of focus for the management of HE.

Brain MR imaging and 1H-MR spectroscopy changes in patients with extrahepatic portal vein obstruction from early childhood to adulthood

BACKGROUND AND PURPOSE

MR imaging and (1)H-MR spectroscopy changes are well reported in cirrhotic patients, whereas they are inadequately reported in EHPVO. The aim of this study was to investigate age-related changes in brain MR imaging and metabolite profile in EHPVO with and without MHE and to explore any correlation of imaging and (1)H-MR spectroscopy parameters with blood ammonia.

MATERIALS AND METHODS

Sixty-three patients with EHPVO (children, 7-12 years [n = 22], adolescents, 13-18 years [n = 15] and adults, 19-41 years [n = 26]) and 47 healthy age/sex-matched volunteers were studied. Neuropsychological tests, MR imaging, (1)H-MR spectroscopy, and blood ammonia estimation were performed in all subjects.

RESULTS

Of 63 EHPVO patients, 25 (40%) who had MHE showed significantly increased MD, Glx, and blood ammonia in all 3 age groups; however, myo-inositol was significantly lower only in adults when compared with controls. MD positively correlated with blood ammonia and Glx in all age groups. Brain choline levels were normal in all patients with different age groups.

CONCLUSIONS

Increases in brain MD, Glx, and blood ammonia were associated with MHE in all age groups. Normal brain choline in EHPVO signifies healthy liver and may serve as a diagnostic marker for its differentiation from cirrhosis-induced encephalopathy. Significant decrease of myo-inositol in adults is probably due to cellular osmoregulation secondary to long-standing hyperammonemia.

The role of magnetic resonance imaging and spectroscopy in hepatic encephalopathy

Hepatic encephalopathy (HE) is a diverse manifestation of acute and chronic liver failure, ranging from cognitive impairment, only detectable on psychometric evaluation through to confusion, coma and death from cerebral oedema. While there is widespread acceptance of its importance, there is little consensus on how best to diagnose and monitor HE. Clinical descriptions, psychometric testing, electroencephalography and magnetic resonance (MR) imaging (and lately, MR spectroscopy) have all been proposed. MR techniques, in contrast to other modalities, have the benefit of objectivity and of being able to interrogate the brain directly with respect to changes in brain size, function and the metabolic disturbances thought to underlie HE, particularly in the context of astrocyte swelling. Modern clinical MRI scanners with multinuclear MR spectroscopy capabilities and brain mapping software can demonstrate structural and functional cellular changes using volumetric MRI, magnetization transfer MRI, diffusion-weighting MRI, functional MRI with oxygenation measurements and in vivo and in vitro (1)H and (31)P MR spectroscopy. This review describes the relative merits of these techniques and provides guidance on the directions for future research and translation into clinical practice.

Voxel-based analyses of magnetization transfer imaging of the brain in hepatic encephalopathy

AIM: To evaluate the spatial distribution of cerebral abnormalities in cirrhotic subjects with and without hepatic encephalopathy (HE) found with magnetization transfer imaging (MTI).

METHODS: Nineteen cirrhotic patients graded from neurologically normal to HE grade 2 and 18 healthy control subjects underwent magnetic resonance imaging. They gave institutional-review-board-approved written consent. Magnetization transfer ratio (MTR) maps were generated from MTI. We tested for significant differences compared to the control group using statistical non-parametric mapping (SnPM) for a voxel-based evaluation.

RESULTS: The MTR of grey and white matter was lower in subjects with more severe HE. Changes were found in patients with cirrhosis without neurological deficits in the basal ganglia and bilateral white matter. The loss in magnetization transfer increased in severity and spatial extent in patients with overt HE. Patients with HE grade 2 showed an MTR decrease in white and grey matter: the maximum loss of magnetization transfer effect was located in the basal ganglia [SnPM (pseudo-)t = 17.98, P = 0.0001].

CONCLUSION: The distribution of MTR changes in HE points to an early involvement of basal ganglia and white matter in HE.

Neuropsychological assessment of hepatic encephalopathy: ISHEN practice guidelines

Low-grade or minimal hepatic encephalopathy (MHE) is characterised by relatively mild neurocognitive impairments, and occurs in a substantial percentage of patients with liver disease. The presence of MHE is associated with a significant compromise of quality of life, is predictive of the onset of overt hepatic encephalopathy and is associated with a poorer prognosis for outcome. Early identification and treatment of MHE can improve quality of life and may prevent the onset of overt encephalopathy, but to date, there has been little agreement regarding the optimum method for detecting MHE. The International Society on Hepatic Encephalopathy and Nitrogen Metabolism convened a group of experts for the purpose of reviewing available data and making recommendations for a standardised approach for neuropsychological assessment of patients with liver disease who are at risk of MHE. Specific recommendations are presented, along with a proposed methodology for further refining these assessment procedures through prospective research.

Acquired hepatocerebral degeneration

Cirrhosis and its co-morbidities may cause a variety of neurological complications, the most common being bouts of toxic metabolic encephalopathy. A proportion of patients with chronic liver disease develop acquired hepatocerebral degeneration (AHD), a chronic progressive neurological syndrome characterized by parkinsonism, ataxia and other movement disorders. This article reviews the clinical spectrum, pathophysiology, neuroimaging features and differential diagnosis of AHD along with emerging treatment options.

High pallidal T1 signal is rarely observed in obstructive jaundice, but is frequently observed in liver cirrhosis

Although high signal intensities in the globus pallidus are frequently observed in T1-weighted magnetic resonance images (MRI) of patients with liver cirrhosis, it is unclear whether these increases are due to portal-systemic shunt or obstruction of biliary excretion. We therefore studied pallidal signals in 18 cancer patients with bile duct obstruction and marked jaundice (>10 mg/dl). Patients who had fever, leukocytosis or liver cirrhosis were excluded to ensure that jaundice was due to bile duct obstruction. All patients showed a dilated intrahepatic duct on computed tomography (CT) scan. A high pallidal signal was observed in one of 18 biliary obstructive patients whereas high signals were highly prevalent in liver cirrhosis. A portal-systemic shunt rather than an obstruction of biliary excretion may be responsible for the increased blood manganese concentrations and pallidal T1 signals in chronic liver diseases.

Current and future applications of magnetic resonance imaging and spectroscopy of the brain in hepatic encephalopathy

Hepatic encephalopathy (HE) is a common neuro-psychiatric abnormality, which complicates the course of patients with liver disease and results from hepatocellular failure and/or portosystemic shunting. The manifestations of HE are widely variable and involve a spectrum from mild subclinical disturbance to deep coma. Research interest has focused on the role of circulating gut-derived toxins, particularly ammonia, the development of brain swelling and changes in cerebral neurotransmitter systems that lead to global CNS depression and disordered function. Until recently the direct investigation of cerebral function has been difficult in man. However, new magnetic resonance imaging (MRI) techniques provide a non-invasive means of assessment of changes in brain volume (coregistered MRI) and impaired brain function (fMRI), while proton magnetic resonance spectroscopy (¹H MRS) detects changes in brain biochemistry, including direct measurement of cerebral osmolytes, such as myoinositol, glutamate and glutamine which govern processes intrinsic to cellular homeostasis, including the accumulation of intracellular water. The concentrations of these intracellular osmolytes alter with hyperammonaemia. MRS-detected metabolite abnormalities correlate with the severity of neuropsychiatric impairment and since MR spectra return towards normal after treatment, the technique may be of use in objective patient monitoring and in assessing the effectiveness of various treatment regimens.

In vivo imaging of cerebral "peripheral benzodiazepine binding sites" in patients with hepatic encephalopathy

BACKGROUND AND AIMS

One proposed mechanism whereby hepatic encephalopathy (HE) leads to loss of brain function is dysregulated synthesis of neurosteroids. Mitochondrial synthesis of neurosteroids is regulated by "peripheral benzodiazepine binding sites" (PBBS). Expressed in the brain by activated glial cells, PBBS can be measured in vivo by the specific ligand [11C](R)-PK11195 and positron emission tomography (PET). Recently, it has been suggested that PBBS expressing glial cells may play a role in the general inflammatory responses seen in HE. Therefore, we measured PBBS in vivo in the brains of patients with minimal HE using [11C](R)-PK11195 PET.

METHODS

Five patients with minimal HE and biopsy proven cirrhosis of differing aetiology were assessed with a neuropsychometric battery. Regional expression of PBBS in the brain was detected by [11C](R)-PK11195 PET.

RESULTS

All patients showed brain regions with increased [11C](R)-PK11195 binding. Significant increases in glial [11C](R)-PK11195 binding were found bilaterally in the pallidum, right putamen, and right dorsolateral prefrontal region. The patient with the most severe cognitive impairment had the highest increases in regional [11C](R)-PK11195 binding.

CONCLUSION

HE is associated with increased cerebral binding of [11C](R)-PK11195 in vivo, reflecting increased expression of PBBS by glial cells. This supports earlier experimental evidence in rodent models of liver failure, suggesting that an altered glial cell state, as evidenced by the increase in cerebral PBBS, might be causally related to impaired brain functioning in HE.

Hepatic encephalopathy: a neurochemical, neuroanatomical, and neuropsychological study

Hepatic encephalopathy (HE) is normally diagnosed by neuropsychological (NP) tests, which are not very specific and do not reveal the underlying pathology. Magnetic resonance imaging (MRI) and spectroscopy (MRS) of the brain offer alternative and possibly more specific markers for HE. These methods were applied in conjunction with NP testing in order to determine their usefulness in the identification of HE and to understand the pathogenesis of HE more clearly. MR imaging and spectroscopy examinations, in addition to a battery of 15 NP tests, were administered to investigate 31 patients awaiting liver transplantation and 23 healthy controls. MR image intensities from the globus pallidus region were calculated and normalized to those of the thalamus. Absolute concentrations and ratios with respect to creatine (Cr) of several metabolites were computed from MR spectra. The MR data were correlated with the results of NP tests. The patients showed impairment in NP tests of attention and visuospatial and verbal fluency. In T1-weighted MRI, the relative intensity of the globus pallidus with respect to that of the thalamus region was significantly elevated in patients and correlated(negatively) with three NP tests (Hooper, FAS, and Trails B). The absolute concentrations of myo-inositol (mI) and choline (Ch) were significantly reduced in three brain regions. In addition, the absolute concentrations of glutamine (Gln) and combined glutamate and glutamine (Glx) were increased in all three locations, with Gln increase being significant in all areas while that of Glx only in the occipital white matter. In summary, this study partially confirms a hypothesized mechanism of HE pathogenesis, an increased synthesis of glutamine by brain glutamate in astrocytes due to excessive blood ammonia, followed by a compensatory loss of myo-inositol to maintain astrocyte volume homeostasis. It also indicates that the hyperintensity observed in globus pallidus could be used as complementary to the NP test scores in evaluating the mental health of HE patients.

Altered modulation of motor activity by group I metabotropic glutamate receptors in the nucleus accumbens in hyperammonemic rats

One of the neurological complications in hepatic encephalopathy is the impairment of motor coordination and function. Clinical signs of basal ganglia, cortico-spinal and cerebellar dysfunction have been commonly detected in these patients. We are studying the molecular bases of the alterations in motor coordination and function in hepatic encephalopathy. Hyperammonemia is considered the main factor responsible for the neurological alterations in patients with hepatic encephalopathy. Activation of metabotropic glutamate receptors (mGluRs) in the nucleus accumbens (NAcc) induces locomotion in rats. Asa first step in our studies on the alterations in motor co-ordination and function in hyperammonemia and hepatic encephalopathy we studied whether the control of motor function by mGluRs in the NAcc is altered in hyperammonemic rats. The locomotor activity induced by injection into the nucleus accumbens (NAcc) of DHPG, an agonist of group I mGluRs was significantly increased in hyperammonemic rats. Injection of DHPG increased extracellular dopamine but not glutamate in the NAcc of control rats. In hyperammonemic rats DHPG-induced increase in dopamine was significantly reduced, and extracellular glutamate increased 6-fold. The content of mGluR 1 but not mGluR 5, is increased in the NAcc of hyperammonemic rats. Blockade of mGluR 1 completely prevented motor and neurochemical effects induced by DHPG. These results show that modulation of both motor function and extracellular concentration of neurotransmitters by mGluRs in the NAcc is altered in hyperammonemia. This may contribute to the alterations in motor function in hepatic encephalopathy.

Cognitive Abilities in Children after Liver Transplantation

BACKGROUND

The authors investigated the cognitive status during the late postoperative phase in children who had undergone liver transplantation (LTx).

METHODS

The authors examined 44 children who had undergone liver transplantation at their center. The children were 8.9+/-2.3 (mean+/-SD) years of age and had received the transplant 6.1+/-2.6 years previously. In 24 of the 44 children, a living-related transplantation had been carried out. Cognitive abilities were assessed with the three subscales of the Kaufman Assessment Battery for Children (K-ABC): the sequential processing scale (SES), the simultaneous processing scale (SIS), and the achievement scale (AS).

RESULTS

The children scored below the population mean but within the normal range on all subscales of the K-ABC. In the SIS and the AS, age at transplantation influenced the cognitive outcome, as the children who were younger at transplantation scored significantly better than the older children and their results were within the normal range. However, for the SES, no such differences were found. A multiple regression analysis revealed that duration of illness and height at transplantation predicts the performance in the SIS and the AS. To a lesser degree, type of transplantation (cadaveric vs. living-related) predicts performance in the AS. Performance in the SES was not predicted by any of these variables. Time since LTx and type of immunosuppressive regimen were not associated with the cognitive status after transplantation.

CONCLUSIONS

Children who are younger, with a shorter duration of illness, and who are more physically developed before LTx have a better prognosis regarding their mental development. However, this result does not hold for sequential processing functions, which showed no relationship with any of these variables. This could indicate differential effects of liver disease and consecutive metabolic derangements on brain development during the preoperative phase.

Whole blood and red blood cell manganese reflected signal intensities of T1-weighted magnetic resonance images better than plasma manganese in liver cirrhotics

We examined whole blood (MnB), red blood cell (MnRBC), plasma (MnP) and urinary Mn (MnU) concentrations in 22 liver cirrhotics and 10 healthy controls to evaluate Mn concentration in which a fraction of biological samples best reflects pallidal signal intensities (pallidal index; PI) on T1-weighted magnetic resonance images (MRI) in liver cirrhotics. Increased signal intensity in the globus pallidus was observed in 18 (81.8%) of the 22 patients with liver cirrhosis. In a transplanted patient, increased pallidal signals also resolved as his liver function tests normalized after liver transplantation. There were significant correlations between MnB/MnRBC and PI (rho=0.529, rho=0.573, respectively) in liver cirrhotics, although no significant correlation was observed between MnP/MnU and PI. According to a multiple linear regression, MnB and MnRBC reflected the signal intensities of T1-weighted MRI better than MnP or MnU.

Changes in brain size in hepatic encephalopathy: a coregistered MRI study

Magnetic resonance imaging (MRI) coregistration techniques can be used to track changes in brain volume. We aimed to determine whether treatment in chronic liver disease altered brain size. The study group comprised nine patients with cirrhosis (7 Child's grade B and 2 Child's grade C). Six had minimal and three had overt hepatic encephalopathy on clinical, psychometric, and electrophysiological testing. Cerebral MRI was performed in seven patients before and 6 weeks after starting lactulose. A further two patients underwent transjugular intrahepatic portosystemic stent shunting with MRI performed before and 24 h afterwards. One patient had a further scan 3 months after TIPSS. Brain size was measured using a semiautomated contour/thresholding technique. Measurable changes were found after treatment intervention, but there was no correlation with severity of encephalopathy (West Haven criteria) or liver dysfunction (Child's score). Three patients improved on lactulose, the brain size decreased with an increase in ventricular volume. Two patients deteriorated; the brain size increased with a concomitant decrease in ventricular volume. Two stable patients had small changes, one with an increase in brain size and a decrease in ventricular volume and the other showing the converse. Following TIPSS, there was an increase in brain size in both patients, evident within 24 h in one patient and at 3 months in the other. Coregistered MRI demonstrates easily detectable changes in brain size following treatment intervention. Our results support the hypothesis that low-grade brain swelling is present, even in minimal hepatic encephalopathy.

Whole blood manganese correlates with high signal intensities on T1-weighted MRI in patients with liver cirrhosis

We examined whole blood (MnB), plasma (MnP) and urinary Mn (MnU) concentrations in 33 cirrhotics and 11 healthy controls to clarify: (1) whether, in chronic liver diseases, MnB or MnP reflects pallidal signal intensities in magnetic resonance imaging (MRI); and (2) which factors in chronic liver diseases correlate with pallidal signal intensities in T1-weighted MRI. Increased signal intensity in the pallidum was observed in 27 (81.8%) of 33 patients with liver cirrhosis in T1-weighted MRI. There was a significant correlation between MnB and pallidal index (PI) (gamma = 0.559, P < 0.01) in the patients. However, no significant correlation was observed between MnP and PI (gamma = 0.353, P > 0.05). According to a multiple linear regression, MnB reflected the signal intensities of T1-weighted MRI better than MnP or MnU. Child/Pugh score and total bilirubin level also correlated with PI. However, the hemoglobin level did not correlate with PI significantly.

Neurocognitive outcome in pediatric liver transplant recipients

Studies have shown that children with liver transplants demonstrate deficits on intellectual, academic, and language measures. However, limited information is known about the long-term cognitive development of these children. In this study, 15 children who were at least 2 yr post-liver transplantation (LT) were compared on cognitive measures to an equated group of 15 children with cystic fibrosis (CF). Children with CF were selected as a clinical control given similarities in disease onset and chronicity, as well as physical growth and development. Results indicated that children with LT tended to have lower verbal intelligence quotient scores and performed significantly lower than CF children on language measures, particularly on receptive language tasks. No significant differences were obtained on measures of academic achievement or visual-spatial performance. In the LT group, days in the intensive care unit, total number of days spent in the hospital during the first year following the transplant, and elevated pretransplant bilirubin levels significantly predicted the speech and language delays.

Orofacial dyskinesias in a patient with primary biliary cirrhosis: a clinicopathological case report and review

We describe the pathological and clinical aspects, including video and radiological magnetic resonance imaging, of a case of chronic acquired hepatocerebral degeneration with orofacial dyskinesias in relation to a primary biliary cirrhosis. We provide a review of the literature on this subject.

The development of low-grade cerebral edema in cirrhosis is supported by the evolution of (1)H-magnetic resonance abnormalities after liver transplantation

BACKGROUND/AIMS

Liver failure may cause brain edema through an increase in brain glutamine. However, usually standard neuroimaging techniques do not detect brain edema in cirrhosis. We assessed magnetization transfer ratio and (1)H-magnetic resonance (MR) spectroscopy before and after liver transplantation to investigate changes in brain water content in cirrhosis.

METHODS

Non-alcoholic cirrhotics without overt hepatic encephalopathy (n=24) underwent (1)H-MR of the brain and neuropsychological tests. (1)H-MR results were compared with those of healthy controls (n=10). In a subgroup of patients (n=11), the study was repeated after liver transplantation.

RESULTS

Cirrhotic patients showed a decrease in magnetization transfer ratio (31.5+/-3.1 vs. 37.1+/-1.1, P<0.01) and an increase in glutamine/glutamate signal (2.22+/-0.47 vs. 1.46+/-0.26, P<0.01). The increase in glutamine/glutamate signal was correlated to the decrease in magnetization transfer ratio and to neuropsychological function. Following liver transplantation, there was a progressive normalization of magnetization transfer ratio, glutamine/glutamate signal and neuropsychological function. Accordingly, correlations between these variables were lost after liver transplantation.

CONCLUSIONS

Cirrhotic patients show reversible changes in magnetization transfer ratio that are compatible with the development of low-grade cerebral edema. Minimal hepatic encephalopathy and low-grade cerebral edema appear to be the consequences of the metabolism of ammonia in the brain.

Movement dysfunction and hepatic encephalopathy

Hepatic encephalopathy is characterized by a variety of neurological symptoms. The occurrence of movement disorders is exceptional and is usually part of a clinical syndrome called acquired hepatocerebral degeneration, which is a subtype of chronic recurrent hepatic encephalopathy. The clinical picture is usually progressive and pathologic findings include regional astroglial and neuronal abnormalities found predominantly in cortex and basal ganglia. As for hepatic encephalopathy in general, the pathophysiology of this disorder is unknown but hyperammonemia and/or brain manganese overload may play a role. Medical treatment is often disappointing but in selected cases liver transplantation may be curative.

Hepatic encephalopathy

In the last decade, a significant amount of research has been devoted to the pathogenesis and treatment of hepatic encephalopathy (HE). Non-invasive neuroimaging techniques such as magnetic resonance imaging and spectroscopy have become important research tools. The search for a suitable animal model of HE associated with cirrhosis is still ongoing. Moreover, consensus terminology and diagnostic criteria for HE in humans are badly needed.

Intracellular pH measurements of the whole head and the basal ganglia in chronic liver disease: a phosphorus-31 MR spectroscopy study

The purpose of this study was to determine the intracellular pH of the whole head and in voxels localized to the basal ganglia in patients with chronic liver disease using phosphorus-31 magnetic resonance spectroscopy (31P MRS). The study group compromised 82 patients with biopsy-proven cirrhosis (43 Child's grade A, 25 Child's grade B and 14 Child's grade C). Eleven subjects showed no evidence of neuropsychiatric impairment on clinical, psychometric and electrophysiological testing, 37 showed evidence of minimal hepatic encephalopathy and 34 had overt hepatic encephalopathy. Unlocalized 31P MRS of the whole head was performed in 48 patients and 10 healthy volunteers. Localized 31P MRS of the basal ganglia was performed in the 34 patients and in 20 healthy volunteers. The intracellular pH values were calculated from the chemical shift difference between the inorganic phosphate (P) and phosphocreatine (PCr) resonances. The percentage inorganic phosphate (%Pi), phosphocreatine (%PCr) and betaNTP signals, relative to the total 31P signal, and peak area ratios of inorganic phosphate and phosphocreatine, relative to betaNTP were also measured. There were no differences between patients and volunteers in intracellular pH in 31P MR spectra measured from the whole head or the basal ganglia. There was no correlation between the severity of encephalopathy (West Haven criteria) or liver dysfunction (Child score) and intracellular pH values. There was also no significant change in the inorganic phosphate, phosphocreatine or betaNTP resonances in spectra acquired from the whole head. However, in spectra localized to the basal ganglia, there was a significant increase in mean P/NTP (p=0.02) and PCr/NTP (p=0.009). The mean %Pi and mean %PCr were also increased (p=0.06; p=0.05, respectively), but there was no significant change in mean %betaNTP. When the patient population was classified according to the severity of encephalopathy, those with overt disease had a higher mean P/NTP and %Pi (p=0.03; p=0.01), compared to the reference population. Our results suggest that there are detectable bioenergetic abnormalities in patients with minimal hepatic encephalopathy or stable, overt chronic hepatic encephalopathy, but any associated intracellular pH change is probably a secondary, rather than a primary phenomenon.

Complications of cirrhosis III. Hepatic encephalopathy

Hepatic encephalopathy (HE) is a major neuropsychiatric complication of cirrhosis. HE develops slowly in cirrhotic patients, starting with altered sleep patterns and eventually progressing through asterixis to stupor and coma. Precipitating factors are common and include an oral protein load, gastrointestinal bleeding and the use of sedatives. HE is common following transjugular intrahepatic portosystemic stent shunts (TIPS). Neuropathologically, HE in cirrhotic patients is characterized by astrocytic (rather than neuronal) changes known as Alzheimer type II astrocytosis and in altered expression of key astrocytic proteins. Magnetic resonance imaging in cirrhotic patients reveals bilateral signal hyperintensities particularly in globus pallidus on T1-weighted imaging, a phenomenon which may result from manganese deposition. Proton (1H) magnetic resonance spectroscopy shows increases in the glutamine resonance in brain, a finding which confirms previous biochemical studies and results no doubt from increased brain ammonia removal (glutamine synthesis). Additional evidence for increased brain ammonia uptake and removal in cirrhotic patients is provided by studies using positron emission tomography and 13NH3. Recent molecular biological studies demonstrate increased expression of genes coding for neurotransmitter-related proteins in chronic liver failure. Such genes include monoamine oxidase (MAO-A isoform), the peripheral-type benzodiazepine receptor and nitric oxide synthase (nNOS isoform). Activation of these systems has the potential to lead to alterations of monoamine and amino acid neurotransmitter function as well as modified cerebral perfusion in chronic liver failure. Prevention and treatment of HE in cirrhotic patients continues to rely on ammonia-lowering strategies which include assessment of dietary protein intake and the use of lactulose, neomycin, sodium benzoate and L-ornithine-aspartate. The benzodiazepine receptor antagonist flumazenil may be effective in certain cases. A more widespread use of central nervous system-acting drugs awaits a more complete understanding of the precise neurotransmitter systems involved in the pathogenesis of HE in chronic liver failure.

Manganese deposition in basal ganglia structures results from both portal-systemic shunting and liver dysfunction

BACKGROUND & AIMS

Manganese (Mn) deposition could be responsible for the T(1)-weighted magnetic resonance signal hyperintensities observed in cirrhotic patients. These experiments were designed to assess the regional specificity of the Mn increases as well as their relationship to portal-systemic shunting or hepatobiliary dysfunction.

METHODS

Mn concentrations were measured in (1) brain samples from basal ganglia structures (pallidum, putamen, caudate nucleus) and cerebral cortical structures (frontal, occipital cortex) obtained at autopsy from 12 cirrhotic patients who died in hepatic coma and from 12 matched controls; and from (2) brain samples (caudate/putamen, globus pallidus, frontal cortex) from groups (n = 8) of rats either with end-to-side portacaval anastomosis, with biliary cirrhosis, or with fulminant hepatic failure as well as from sham-operated and normal rats.

RESULTS

Mn content was significantly increased in frontal cortex (by 38%), occipital cortex (by 55%), pallidum (by 186%), putamen (by 66%), and caudate (by 54%) of cirrhotic patients compared with controls. Brain Mn content did not correlate with patient age, etiology of cirrhosis, or history of chronic hepatic encephalopathy. In cirrhotic and portacaval-shunted rats, Mn content was increased in pallidum (by 27% and 57%, respectively) and in caudate/putamen (by 57% and 67%, respectively) compared with control groups. Mn concentration in pallidum was significantly higher in portacaval-shunted rats than in cirrhotic rats. No significant changes in brain Mn concentrations were observed in rats with acute liver failure.

CONCLUSIONS

These findings suggest that brain Mn deposition results both from portal-systemic shunting and from liver dysfunction.

Cerebral magnetic resonance imaging in patients with chronic liver disease

Bilateral, symmetrical hyperintensity of the globus pallidus is observed in T1-weighted cerebral magnetic resonance images in from 52 to 100% of patients with chronic liver disease. No significant relationship exists between the presence of these cerebral changes in image signal intensity and the patients' neuropsychiatric status. However, their presence significantly relates to both the severity of the liver disease and the presence and degree of portal-systemic shunting of blood. This shortening of the T1-relaxation time is associated with pallidal deposition of manganese most likely reflecting the presence of an adaptive process designed to improve the efficacy of ammonia detoxification by astrocytes. Future studies employing magnetic resonance imaging techniques to obtain information on cerebral function or combined with magnetic resonance spectroscopy to obtain localized biochemical information might further our understanding of the pathogenesis of hepatic encephalopathy in cirrhotic patients.

Proton magnetic resonance spectroscopy in portal-systemic encephalopathy

Localized proton magnetic resonance spectroscopy (MRS) with short echo times provides unique information of human cerebral metabolism. Studies on patients with portal-systemic encephalopathy (PSE) have been performed to clarify the pathogenesis of this disease and to find a method which allows an objective diagnosis. Spectra of patients with PSE show typical abnormalities. Regional variations of these spectral changes are observed. The metabolic changes correlate with the grade of encephalopathy but the dependence on the Child-Pugh score is controversial. No causal dependence between MRS findings and abnormalities in magnetic resonance imaging is evident. Differences in magnetic resonance spectra in patients compared to controls vanish after liver transplantation, but increase after TIPS. The results of proton magnetic resonance spectroscopy are important for an understanding of the pathogenesis of PSE, but do not aid in the diagnosis of subclinical hepatic encephalopathy.

Role of manganese in the pathogenesis of portal-systemic encephalopathy

Amongst the potential neurotoxins implicated in the pathogenesis of hepatic encephalopathy, manganese emerges as a new candidate. In patients with chronic liver diseases, manganese accumulates in blood and brain leading to pallidal signal hyperintensity on T1-weighted Magnetic Resonance (MR) Imaging. Direct measurements in globus pallidus obtained at autopsy from cirrhotic patients who died in hepatic coma reveal 2 to 7-fold increases of manganese concentration. The intensity of pallidal MR images correlates with blood manganese and with the presence of extrapyramidal symptoms occurring in a majority of cirrhotic patients. Liver transplantation results in normalization of pallidal MR signals and disappearance of extrapyramidal symptoms whereas transjugular intrahepatic portosystemic shunting induces an increase in pallidal hyperintensity with a concomitant deterioration of neurological dysfunction. These findings suggest that the toxic effects of manganese contribute to extrapyramidal symptoms in patients with chronic liver disease. The mechanisms of manganese neurotoxicity are still speculative, but there is evidence to suggest that manganese deposition in the pallidum may lead to dopaminergic dysfunction. Future studies should be aimed at evaluating the effects of manganese chelation and/or of treatment of the dopaminergic deficit on neurological symptomatology in these patients.