Value of regional cerebral blood flow in the evaluation of chronic liver disease and subclinical hepatic encephalopathy

Severity-specific alterations in CBF, OEF and CMRO2 in cirrhotic patients with hepatic encephalopathy

OBJECTIVES

To assess how the severity of hepatic encephalopathy (HE) affects perfusion and metabolic changes in cirrhotic patients and the association between severity and liver disease and anemia.

METHODS

The study groups comprised 31 healthy subjects and 33 cirrhotic patients who underwent MR examinations, and blood and neuropsychological tests. Of the cirrhotic patients, 14 were unaffected, and 11 had covert HE (CHE) and 8 overt HE (OHE). Global cerebral blood flow (CBF), oxygen extraction fraction (OEF), and metabolic rate of oxygen (CMRO2) were noninvasively measured by phase-contrast and T2-relaxation-under-spin-tagging MRI. Correlations were performed between MR measurements, hematocrits, ammonia levels, Child-Pugh scores and neuropsychological test scores.

RESULTS

Compared with the values in healthy subjects, CBF was higher in unaffected patients, the same in CHE patients and lower in OHE patients, OEF was higher in all patients, and CMRO2 was the same in unaffected and CHE patients and lower in OHE patients. Hematocrit was negatively correlated with CBF and OEF, but not with CMRO2. Ammonia level was negatively correlated with CBF and CMRO2, and Child-Pugh score was negatively correlated with CMRO2.

CONCLUSIONS

The severity-associated alterations in cirrhotic patients indicate that homeostasis of oxygen delivery and oxidative metabolism in HE is regulated by multiple mechanisms. These physiological alterations appeared to be associated with the degree of anemia, ammonia level, and liver function.

KEY POINTS

• CBF, OEF and CMRO2 did not change monotonically with HE progression. • Anemia possibly contributed to CBF and OEF changes in cirrhotic patients. • Liver dysfunction mainly contributed to changes in CMRO2 in cirrhotic patients.

Neuromodulation and Palliative Medicine

The palliative care population is generally vulnerable to experiencing medication-induced adverse effects and drug–drug interactions. Neuromodulation may offer particular advantages over systemic medications in this population. Spinal cord stimulation and peripheral nerve stimulation have long been utilized in efforts to provide analgesia for various painful conditions. More recently, deep brain stimulation/motor cortex stimulation has anecdotally been utilized for certain intractable pain states. Although brain electrical stimulation has not been adequately trialed or in some cases even tried at all for management of a variety of symptoms, it is conceivable that in the future it may be a potential therapeutic option in efforts to palliate various severe refractory symptoms (eg, intractable pain, nausea, dyspnea, delirium).

Association of pre-operative brain pathology with post-operative delirium in a cohort of non-small cell lung cancer patients undergoing surgical resection

OBJECTIVE

Post-operative delirium is associated with pre-operative cognitive difficulties and diminished functional independence, both of which suggest that brain pathology may be present in affected individuals prior to surgery. Currently, there are few studies that have examined imaging correlates of post-operative delirium. To our knowledge, none have examined the association of delirium with existing structural pathology in pre-operative cancer patients. Here, we present a novel, retrospective strategy to assess pre-operative structural brain pathology and its association with post-operative delirium. Standard of care structural magnetic resonance imaging (MRIs) from a cohort of surgical candidates prior to surgery were analyzed for white matter hyperintensities and cerebral atrophy.

METHODS

We identified 23 non-small cell lung cancer patients with no evidence of metastases in the brain pre-operatively, through retrospective chart review, who met criteria for post-operative delirium within 4 days of surgery. 24 age- and gender-matched control subjects were identified for comparison to the delirium sample. T1 and fluid-attenuated inversion recovery sequences were collected from standard of care pre-operative MRI screening and assessed for white matter pathology and atrophy.

RESULTS

We found significant differences in white matter pathology between groups with the delirium group exhibiting significantly greater white matter pathology than the non-delirium group. Measure of cerebral atrophy demonstrated no significant difference between the delirium and non-delirium group.

CONCLUSIONS

In this preliminary study utilizing standard of care pre-operative brain MRIs for assessment of structural risk factors to delirium, we found white matter pathology to be a significant risk factor in post-operative delirium. Limitations and implications for further investigation are discussed.

Abnormal regional homogeneity of resting-state brain activity in patients with HBV-related cirrhosis without overt hepatic encephalopathy

BACKGROUND

Many studies have reported that cognitive deficits exist in cirrhotic patients without overt hepatic encephalopathy (OHE). However, the neurobiological mechanisms underlying these deficits are still not fully understood.

AIM

To investigate regional activity abnormalities in patients with hepatitis B virus-related cirrhosis (HBV-RC) without OHE using resting-state functional MRI (Rs-fMRI), and to examine the relationship between regional activity abnormalities and impaired cognition.

METHODS

A newly reported regional homogeneity (ReHo) approach was used to compare the local synchronization of Rs-fMRI signals in 32 patients with HBV-RC without OHE and 32 well-matched healthy controls. Cognition was measured in all patients using psychometric hepatic encephalopathy score (PHES) tests, and the relationship between ReHo variation and PHES was analysed.

RESULTS

Relative to healthy controls, the cirrhosis group showed high ReHo in the prefrontal cortex, and widespread low ReHo in visual association areas (left lingual gyrus, middle temporal gyrus and right middle occipital gyrus), motor association areas (bilateral precentral gyrus and paracentral lobule) and the bilateral precuneus. Correlation analysis of the mean ReHo values in different brain areas and PHES in cirrhotic patients revealed a significantly positive correlation in the left lingual gyrus (r = 0.352; P = 0.048), right middle occipital gyrus (r = 0.453; P = 0.009) and bilateral precentral gyrus (left: r = 0.436, P = 0.013; right: r = 0.582, P < 0.001), paracentral lobule (r = 0.485; P = 0.005) and precuneus (r = 0.468; P = 0.007).

CONCLUSIONS

Our results provide information on the pathophysiological mechanisms underlying cognitive alterations in cirrhotic patients and demonstrate the feasibility of using Rs-fMRI with ReHo analysis as a noninvasive modality with which to detect the progression of cognitive changes in cirrhotic patients.

Pathogenesis of hepatic encephalopathy

Hepatic encephalopathy can be a serious complication of acute liver failure and chronic liver diseases, predominantly liver cirrhosis. Hyperammonemia plays the most important role in the pathogenesis of hepatic encephalopathy. The brain-blood barrier disturbances, changes in neurotransmission, neuroinflammation, oxidative stress, GABA-ergic or benzodiazepine pathway abnormalities, manganese neurotoxicity, brain energetic disturbances, and brain blood flow abnormalities are considered to be involved in the development of hepatic encephalopathy. The influence of small intestine bacterial overgrowth (SIBO) on the induction of minimal hepatic encephalopathy is recently emphasized. The aim of this paper is to present the current views on the pathogenesis of hepatic encephalopathy.

Delirium in elderly adults: diagnosis, prevention and treatment

Delirium is a common and serious acute neuropsychiatric syndrome with core features of inattention and global cognitive dysfunction. The etiologies of delirium are diverse and multifactorial and often reflect the pathophysiological consequences of an acute medical illness, medical complication or drug intoxication. Delirium can have a widely variable presentation, and is often missed and underdiagnosed as a result. At present, the diagnosis of delirium is clinically based and depends on the presence or absence of certain features. Management strategies for delirium are focused on prevention and symptom management. This article reviews current clinical practice in delirium in elderly individuals, including the diagnosis, treatment, outcomes and economic impact of this syndrome. Areas of future research are also discussed.

Delirium in elderly adults: diagnosis, prevention and treatment

Delirium is a common and serious acute neuropsychiatric syndrome with core features of inattention and global cognitive dysfunction. The etiologies of delirium are diverse and multifactorial and often reflect the pathophysiological consequences of an acute medical illness, medical complication or drug intoxication. Delirium can have a widely variable presentation, and is often missed and underdiagnosed as a result. At present, the diagnosis of delirium is clinically based and depends on the presence or absence of certain features. Management strategies for delirium are focused on prevention and symptom management. This article reviews current clinical practice in delirium in elderly individuals, including the diagnosis, treatment, outcomes and economic impact of this syndrome. Areas of future research are also discussed.

Role of Magnetic Resonance in Understanding the Pathogenesis of Hepatic Encephalopathy

A spectrum of neuropsychiatric abnormalities caused by portosystemic venous shunting occurs in hepatic encephalopathy (HE) patients with or without liver dysfunction. It is not completely clear how the astrocyte swelling leads to glial-neuronal dysfunction, and how the symptoms are manifested in HE. A major goal of this work is to review the current status of information available from the existing magnetic resonance (MR) modalities including MR imaging (MRI) and MR Spectroscopy (MRS) as well as other modalities in the understanding the pathogenesis of HE. First, we discuss briefly neuron-histopathology, neurotoxins, neuropsychological and neurophysiological tests. A short review on the progress with single-photon emission computed tomography (SPECT) and positron emission tomography (PET) is then presented. In the remaining part of the manuscript, the following topics pertinent to understanding the pathogenesis of HE are discussed: MRI, diffusion tensor imaging (DTI), one-dimensional MRS based single- and multi-voxel based spectroscopic imaging techniques and two-dimensional MRS.

The role of neuroimaging in elucidating delirium pathophysiology

Understanding of delirium pathogenesis remains limited despite improved diagnosis, and elucidation of risk factors and prognosis. Major advances in neuroimaging offer the possibility of probing the mechanisms and networks involved in delirium and hence improving understanding of this often devastating syndrome. This review describes the current literature of imaging studies in delirium and related conditions, introduces some of the newer capabilities of neuroimaging with magnetic resonance imaging, positron emission tomography, and single photon emission computed tomography, and discusses how these techniques may be applied to the study of delirium. Despite considerable challenges in patient recruitment, study design, intersubject variability, and scanner and contrast agent availability, imaging offers great potential for the identification and clarification of pathogenic mechanisms of delirium and its long-term sequelae.

Cognition in liver disease

BACKGROUND

Cognitive dysfunction has been observed in a range of liver diseases including chronic hepatitis C virus, alcoholic liver disease, primary biliary cirrhosis and Wilson's disease. Such dysfunction may range from mild cognitive changes to overt hepatic encephalopathy, and represents a significant complication of liver disease that may negatively impact the patient's quality of life, and normal activities of daily living (e.g., driving).

METHOD

This article reviews the published evidence relating to cognitive dysfunction in liver disease.

OUTCOME

Issues of definition, diagnosis, epidemiology, aetiology, treatment and outcome are discussed. Particular attention is devoted to identifying the mild cognitive changes that occur in liver diseases of different aetiology.

Functional imaging of the brain in patients with liver cirrhosis

Brain imaging techniques have provided substantial insight into the pathophysiology of hepatic encephalopathy (HE). Magnetic resonance imaging gave hint to the fact that there is an increased deposition of manganese especially in the basal ganglia. Single photon emission computed tomography (SPECT) and positron emission tomography (PET) showed that the preference of the basal ganglia might be due to differences in regional cerebral blood flow and an additional redistribution of blood flow from the cortex to subcortical regions in cirrhotics. PET studies using ammonia as tracer showed that the cerebral metabolism of ammonia and the permeability of the blood brain barrier for ammonia is increased in cirrhotic patients compared to healthy controls. The regional ammonia supply is in accordance with the regional blood flow. In accordance with these findings fluorodesoxyglucose-PET-studies of the brain in cirrhotics showed characteristic alterations of glucose utilisation in the patients with a relative decrease of the glucose utilisation of the cingulate gyrus, the frontomedial, frontolateral, and parieto-occipital cortex, while the glucose utilisation of the basal ganglia, the hippocampus, and the cerebellum was relatively increased. These findings fit well with the clinical characteristics of early stages of HE such as deficits in attention, visuo-spatial orientation, visuo-constructive abilities, motor speed, and accuracy.

Does liver-disease aetiology have a role in cerebral blood-flow alterations in liver cirrhosis?

BACKGROUND

Studies using brain-imaging techniques have shown changes in regional blood flow (rCBF) in patients with liver cirrhosis. It remains unknown whether the aetiology of liver disease accounts for these changes.

AIMS

To evaluate whether the aetiology of liver cirrhosis is associated with different patterns of rCBF.

MATERIALS AND METHODS

A total of 50 patients with end-stage liver disease and no overt encephalopathy were studied. Thirteen age-matched subjects admitted to the neurology department for headache were used as controls. Exclusion criteria were focal brain lesions, severe brain atrophy and any abnormalities found on computed tomography scan suggesting other central nervous system diseases, alcohol intake or use of neuroactive drugs for at least 6 months. rCBF was assessed using single-positron-emission tomography (SPECT) with 99mTc-hexamethylpropylene amine oxime (99mTc-HM-PAO) as a tracer in all patients and controls. The Mann-Whitney U test was used for statistical analysis.

RESULTS

The liver-disease aetiology was as follows: alcoholic (A) in 19 patients; viral (V) (hepatitis B virus, hepatitis D virus, hepatitis C virus) in 14 patients; alcoholic with concomitant viral (A + V) in five patients; and cholestatic (C) (primary biliary cirrhosis, primary sclerosing cholangitis) in 12 patients. SPECT showed significantly lower rCBF in cirrhotic patients than in controls for most cortical and subcortical regions and in alcoholic and viral patients than in cholestatic liver disease patients for some cortical regions. When patients were grouped according to previous alcohol abuse (including cases with a concomitant viral aetiology), rCBF was significantly lower in the frontal superior, medial and temporal inferior regions in the alcoholic group.

CONCLUSIONS

Cerebral blood flow is significantly lower in patients with liver cirrhosis than in controls and, among cirrhotics, it is lower in alcoholic and viral cirrhosis than in cholestatic liver disease. In patients with previous alcohol abuse, cerebral blood flow was significantly more reduced in the frontal and temporal regions compared with patients without previous alcohol abuse.