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Query: UMLS:C0085584 (encephalopathy)
 18,178 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A 67-year-old, non-alcoholic Japanese female case with liver cirrhosis, in the course of admission due to ascites and rupture of the rectal varix, was affected by an unusual type of acute progressive encephalopathy, presenting inattentiveness and slurred speech as initial symptoms. Her consciousness was increasingly clouded. Variable symptoms such as saccadic eye movement, nystagmus, weakness, hyperreflexia, dysmetria, adiadochokinesis and painful dysesthesia were also noted. Laboratory examination disclosed abnormal liver functions, hyponatremia, respiratory alkalosis and normal blood ammonia. Cerebrospinal fluid was xanthochromic and contained slightly increased protein. On CT scan, bilateral symmetrical low density areas were demonstrated in the diencephalon, brainstem and cerebellum. A week after the onset, she was comatose with rigidity of the extremities. Hyperbilirubinemia and severe hyponatremia developed. On the second CT, low density areas extended to the cerebral deep white matter. Her respiration became irregular, and she expired 16 days after the onset. Autopsy disclosed edematous lesions with dark brown discoloration in the medial basal ganglia, ventral diencephalon and mesencephalic tegmentum. Less severely affected lesions with pale yellow discoloration extended into the cerebral white matter, pontine and medullar tegmentum and cerebellar dentate nuclei. In the central lesions, diapedesis of erythrocytes and serum-plasma was marked, with necrosis of the neurons. In the peripheral lesions, diapedesis of less proteinaceous fluid was noted, with less severe neuronal damages. Neither capillary prominence nor gliosis was remarkable. The clinical and pathological features of the present case bore some similarity to those of Wernicke's and Leigh's encephalopathies. However, the patient's age, habitus or clinical course was atypical for the latter.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Acute encephalopathy with symmetrical, widespread, edematous and necrotic lesions--an autopsy case report]. 280 34

Ammonia intoxication allegedly plays a significant role in the pathophysiology of hepatic encephalopathy. In order to understand the pathogenesis of this encephalopathy it is necessary to know the effects of ammonia on the mechanisms by which neurons communicate, i.e., excitatory and inhibitory synaptic transmissions. NH4+ decreases excitatory synaptic transmission mediated by glutamate. Possibly, this effect is related to a depletion of glutamate in presynaptic terminals. NH4+ decreases inhibitory synaptic transmission mediated by hyperpolarizing Cl(-)-dependent inhibitory postsynaptic potentials. This effect is related to the inactivation of the extrusion of Cl- from neurons by NH4+. By the very same action, NH4+ also decreases the hyperpolarizing action of Ca2+- and voltage-dependent Cl- currents. These currents may modify the efficacy of the synaptic input to neurons and increase neuronal excitability. Estimates derived from experimental observations suggest that an increase of CNS tissue NH4+ to 0.5 mumol/g is sufficient to disturb excitatory and inhibitory synaptic transmission and to initiate the encephalopathy related to acute ammonia intoxication. Chronic portasystemic shunting of blood, as in hepatic encephalopathy, significantly changes the relation between CNS NH4+ and function of synaptic transmission. A portacaval shunt increases the tissue NH4+ necessary to disturb synaptic transmission. However, after a portasystemic shunt, synaptic transmission becomes extremely sensitive to any acute increase of NH4+ in the CNS.
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PMID:Synaptic transmission in ammonia intoxication. 281 92

A 40-yr-old man presented with encephalopathy and was found to have hepatocellular carcinoma without cirrhosis. A large vascular hepatic mass was defined by CT scan and angiography; laparoscopy with biopsy confirmed the absence of chronic liver disease. A definitive tissue diagnosis of hepatocellular carcinoma was made at laparotomy; the tumor was unresectable. Peripheral arterial and selective portal and hepatic venous ammonia levels were high, and this finding suggested that the encephalopathy was nitrogenous and hepatic in origin. The proposed mechanisms of the encephalopathy are generation of ammonia from tumor breakdown and portosystemic shunting, a result of partial tumor occlusion of the hepatic veins. An unusually high urinary excretion of orotic acid was found similar to that seen in hereditary orotic aciduria.
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PMID:Hepatic encephalopathy and orotic aciduria associated with hepatocellular carcinoma in a noncirrhotic liver. 282 14

Reye syndrome, a reversible metabolic encephalopathy and hepatopathy, offers a unique opportunity to investigate the pharmacologic mechanisms by which a toxic-metabolic insult to mitochondria is translated into neurochemical and neurologic dysfunction. Similarity of some clinical and metabolic abnormalities between certain inborn errors of organic acid, ammonia, and carbohydrate metabolism and Reye syndrome suggests a common pathophysiologic mechanism at some level. The primary metabolic aberration in Reye syndrome is unknown. Viral, drug, and toxic precipitants in a conductive host alter glial and neuronal function, possibly by direct toxic effects or by altered transmitter metabolism and signal transduction. These events translate into a rather stereotyped progression of the clinical syndrome. Increased ICP, which is a life-threatening epiphenomenon, is the focus of conventional therapy. Investigational treatments, still in preliminary stages, are aimed at early correction of instigating metabolic abnormalities or correction of their consequences on central neurotransmission. Our fragmentary knowledge of neurotransmitter abnormalities in this disorder, which have suggested disparate interpretations, does not allow a cohesive pharmacologic theory of Reye syndrome. The greatest difficulties in interpretation of possible central mechanisms from existing data, which derive largely from peripheral tissues, is in the differentiation of primary from compensatory changes. The unitarian notion that a single pharmacologic disturbance is the source of the encephalopathy is perhaps too simplistic. It is hoped that future studies of disorders such as Reye syndrome will elucidate the intricate relationships between biochemical pathways and neurotransmitter metabolism.
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PMID:Pharmacology of Reye syndrome. 284 66

To obtain a more precise pathophysiological evaluation of the role of ammonia in acute hepatic encephalopathy, we compared the plasma ammonia concentrations and electroencephalographic recordings (EEGs) of rabbits with surgically induced acute hepatic failure (AHF, n = 10) and normal rabbits administered an infusion of ammonium acetate (NH4-Ac, n = 7) over a 10-hr period. AHF was surgically induced by portocaval shunting followed by hepatic artery ligation 48 hr later. In the infusion group the dose of NH4-Ac, initially 0.78 mmol/kg/hr, was increased every 2 hr by 0.13 mmole/kg/hr during a 10-hour period to simulate the arterial NH3 concentrations observed in AHF. Ammonia levels in rabbits administered the NH4-Ac infusion were identical to those observed in AHF, with the exception of the higher initial value in the AHF group. Moreover, the mean rates of increase in grade of encephalopathy in the two groups were similar, although the EEG grades in the infusion group were significantly less at all time points. In conclusion, this study demonstrates that a more pathophysiological approach to identification of the putative toxins in hepatic encephalopathy is feasible. Some of the EEG abnormalities of acute hepatic encephalopathy in rabbits are presumably due to hyperammonemia; the encephalopathy observed in AHF at zero time is probably caused by the previously constructed portocaval shunt via an undefined, but possibly also ammonia-related, mechanism.
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PMID:Continuous intravenous ammonia infusion as a model for the study of hepatic encephalopathy in rabbits. 292 62

An investigation of the mechanism of development of hepatic encephalopathy induced by CCl4 was performed in rats. CCl4 (1.0 ml/kg three times per week for over 10 weeks) caused hepatic encephalopathy in 80% of the treated rats. Accompanying the hepatic encephalopathy were hematemesis, abdominal dropsy, and hyperammonemia, conditions observed in hepatic coma patients. The blood ammonia levels were tremendously increased in only those rats with hepatic encephalopathy. Hepatic activities of carbamylphosphate synthetase (CPS) and argininosuccinate synthetase (ASS), important enzymes of the urea cycle, were significantly inhibited by CCl4. However, the causality between the inhibition of CPS or ASS activity and the increase in blood ammonia levels was not observed. On the other hand, the content of ATP, which is a substrate of CPS and ASS, was decreased by 60% in liver of rats with hepatic encephalopathy. The activity of Mg2+-ATPase which can decompose hepatic ATP was increased by 60 and 300% in mitochondria and microsomes, respectively, of livers of rats with CCl4-induced encephalopathy. There was a good correlation between the decreased hepatic ATP content and the increased mitochondrial Mg2+-ATPase activity. Furthermore, there was also a good correlation between the increase in blood ammonia levels and the increase in Mg2+-ATPase activity in microsomes. These findings suggest that hyperammonemia, which was produced by the decrease in hepatic content and by the inhibition of CPS and ASS, may play an important role in induction of hepatic encephalopathy.
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PMID:Blood ammonia levels and hepatic encephalopathy induced by CCl4 in rats. 296 38

Beta adrenoreceptor blocking drugs have been used for the prevention of haemorrhage from oesophageal varices. However, it is possible that these agents, by virtue of their effects on hepatic blood flow, may impair liver function and precipitate hepatic encephalopathy. We have therefore studied the effect of the beta blocking drug propranolol on hepatic encephalopathy in patients with cirrhosis and portal hypertension. Twenty patients were randomly assigned to receive 4 weeks treatment with propranolol or an identical-looking placebo, the former given in a dose sufficient to reduce resting pulse rate by greater than or equal to 25%. Before and after treatment patients were assessed for the severity of liver disease and the presence of encephalopathy. EEG mean cycle frequency and fasting arterial ammonia concentrations were also measured, and in order to detect latent hepatic encephalopathy, each patient underwent a battery of psychometric tests. Patients were blinded as to their treatment, as were those assessing their responses. Neither propranolol nor placebo had any significant effect on the parameters measured. On propranolol median EEG mean cycle frequency fell from 9.08 ct s-1 (range 8.63-11.0 ct s-1) to 8.73 ct s-1 (range 8.27-11.44 ct s-1), and median fasting arterial ammonia concentration fell from 66 mumol litre-1 (range 40-329 mumol litre-1) to 49 mumol litre-1 (range 37-188 mumol litre-1). Psychometric test values, while initially abnormal and suggestive of latent hepatic encephalopathy in the majority of patients, did not change significantly during the study.
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PMID:The effects of propranolol on hepatic encephalopathy in patients with cirrhosis and portal hypertension. 297 40

Young male ferrets developed hyperammonemia and encephalopathy shortly after eating a diet lacking in arginine. The dietary supplementation of arginine or intraperitoneal injection of ornithine prevented hyperammonemia and shortened the duration of encephalopathy. Therefore, young ferrets were assumed to be unable to meet their ornithine needs from sources other than arginine. Adult ferrets did not develop hyperammonemia and encephalopathy after eating arginine-free diet. Because young ferrets are also susceptible to human influenza infections, they were further tested as animal model of Reye's syndrome. Reye's syndrome is a serious childhood disorder that develops following influenza infections and is characterized in part by an encephalopathy, hyperammonemia and elevated serum transaminases. In young ferrets, concurrent administration of aspirin with human influenza inoculation and an arginine-free diet produced symptoms similar to those seen in humans with Reye's syndrome. The ferret model appears to be useful for studying the roles of various etiologic agents and their interactions in producing Reye's syndrome-like disorders. The ammonia metabolism in ferrets is reviewed and the ferret model for Reye's syndrome and its applications for the better understanding of this disorder in humans are discussed.
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PMID:Arginine deficiency, hyperammonemia and Reye's syndrome in ferrets. 299 54

A new approach to pathogenetic study of hepatic encephalopathy was recently undertaken in order to identify the neurological alterations of the brain which characterize the coma. In this study attention was firstly addressed to a correct and objective evaluation of the comatose state in rats with fulminant hepatic failure induced by galactosamine. For this purpose visual evoked potentials were utilized since this electrophysiological test proved reliable and sensitive on the basis of an extensive pharmacological study. Two different stages of coma were identified in the rat and they were named mild and severe. Receptor binding studies performed on brain membranes of these rats show in the mild stage an increased number of low and high affinity GABA receptors and a decreased affinity of dopamine receptors. The severe stage is characterized by the persistence of only high affinity GABA receptors and a reduced number of dopamine receptors. This imbalance between inhibitory and excitatory receptor systems may explain the generalized central nervous system depression which characterizes the hepatic encephalopathy while the increased number of benzodiazepine receptors found in both stages of coma may account for the brain supersensitivity to sedative administration of patients with liver disease and for the sedative-induced episodes of coma. These receptor alterations may be attributed to a disuse and/or a partial degeneration of nerve terminals due to peripheral neurotoxins (i.e., ammonia, mercaptans, short chain fatty acids) and the decrease of glutamate decarboxylase activity and of zinc levels in brain tissues seems to be respectively a direct and an indirect demonstration of this phenomenon. Bearing in mind the supersensitivity of the GABA-benzodiazepine receptor system and their reciprocal interaction, a benzodiazepine antagonist was administered to rats in mild stage of encephalopathy. Electrophysiological and benzodiazepine binding studies demonstrated that this treatment can temporarily counteract some of the neurological disturbances of the earlier stage of coma and act as antidote of the sedative-induced episodes of coma.
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PMID:Hepatic encephalopathy. Experimental studies in a rat model of fulminant hepatic failure. 299 24

A previous study of the patterns of visual evoked responses (VERs) in rats was interpreted as providing support for the synergistic neurotoxins hypothesis of the pathogenesis of hepatic encephalopathy (HE) due to fulminant hepatic failure (FHF). In contrast, other studies of the patterns of VERs in rabbits with different encephalopathies were interpreted as providing support for the concept that increased GABA-ergic tone may contribute to the neural inhibition of HE due to FHF. To attempt to resolve the discordant findings in these studies, additional studies of VERs have been undertaken in rats. To induce increased tissue levels of ammonia, mercaptans and fatty acids which are found in HE due to FHF, carefully predetermined doses of urease, dimethyldisulphide and octanoic acid were administered. The (pre-seizure) encephalopathy induced by these three agents was associated with abnormalities of the VER waveform that were fundamentally different from the abnormalities of the VER waveform associated with HE due to thioacetamide-induced FHF. However, the VER waveform in this model of HE due to FHF resembled closely that associated with pentobarbital-induced encephalopathy. These findings are in satisfactory agreement with those in the previous analogous studies in rabbits. They do not provide support for the synergistic neurotoxins hypothesis of the pathogenesis of HE, but are entirely consistent with increased GABA-ergic tone contributing to the neural inhibition of HE due to FHF.
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PMID:Hepatic encephalopathy. Application of visual evoked responses to test hypotheses of its pathogenesis in rats. 303 57


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