Review
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World J Gastroenterol. Dec 28, 2013; 19(48): 9240-9255
Published online Dec 28, 2013. doi: 10.3748/wjg.v19.i48.9240
Pathophysiology of cerebral oedema in acute liver failure
Teresa R Scott, Victoria T Kronsten, Robin D Hughes, Debbie L Shawcross
Teresa R Scott, Victoria T Kronsten, Robin D Hughes, Debbie L Shawcross, Institute of Liver Studies, King’s College London School of Medicine at King’s College Hospital, King’s College Hospital, London SE5 9RS, United Kingdom
Author contributions: Scott TR wrote the first draft of this manuscript assisted by Kronsten VT; Shawcross DL revised the manuscript with the help of Hughes RD and responded to the reviewer’s comments.
Supported by Medical Research Council (MRC) Centre for Transplantation, King’s College London, United Kingdom-MRC grant No. MR/J006742/1; The National Institute for Health Research (NIHR) Biomedical Research Centre based at Guy’s and St Thomas’ NHS Foundation Trust and King’s College London
Correspondence to: Dr. Debbie L Shawcross, Institute of Liver Studies, King’s College London School of Medicine at King’s College Hospital, King’s College Hospital, Denmark Hill, London SE5 9RS, United Kingdom. debbie.shawcross@kcl.ac.uk
Telephone: +44-20-32993713 Fax: +44-20-32993167
Received: September 9, 2013
Revised: October 28, 2013
Accepted: November 18, 2013
Published online: December 28, 2013
Processing time: 127 Days and 3 Hours
Abstract

Cerebral oedema is a devastating consequence of acute liver failure (ALF) and may be associated with the development of intracranial hypertension and death. In ALF, some patients may develop cerebral oedema and increased intracranial pressure but progression to life-threatening intracranial hypertension is less frequent than previously described, complicating less than one third of cases who have proceeded to coma since the advent of improved clinical care. The rapid onset of encephalopathy may be dramatic with the development of asterixis, delirium, seizures and coma. Cytotoxic and vasogenic oedema mechanisms have been implicated with a preponderance of experimental data favouring a cytotoxic mechanism. Astrocyte swelling is the most consistent neuropathological finding in humans with ALF and ammonia plays a definitive role in the development of cytotoxic brain oedema. The mechanism(s) by which ammonia induces astrocyte swelling remains unclear but glutamine accumulation within astrocytes has led to the osmolyte hypothesis. Current evidence also supports an alternate ‘Trojan horse’ hypothesis, with glutamine as a carrier of ammonia into mitochondria, where its accumulation results in oxidative stress, energy failure and ultimately astrocyte swelling. Although a complete breakdown of the blood-brain barrier is not evident in human ALF, increased permeation to water and other small molecules such as ammonia has been demonstrated resulting from subtle alterations in the protein composition of paracellular tight junctions. At present, there is no fully efficacious therapy for cerebral oedema other than liver transplantation and this reflects our incomplete knowledge of the precise mechanisms underlying this process which remain largely unknown.

Keywords: Cerebral oedema; Acute liver failure; Ammonia; Hepatic encephalopathy; Intracranial pressure; Intracranial hypertension; Cerebral blood flow

Core tip: Cytotoxic and vasogenic cerebral oedema have been implicated in acute liver failure (ALF) with a preponderance of experimental data favouring cytotoxic mechanisms. Astrocyte swelling is a consistent neuropathological finding in human ALF and ammonia plays a definitive role. The mechanism(s) by which ammonia induces astrocyte swelling remains unclear but glutamine plays a central role inducing oxidative stress, energy failure and ultimately astrocyte swelling. Although complete breakdown of the blood-brain barrier is not evident in human ALF, increased permeation to water and ammonia has been demonstrated. There is no efficacious therapy other than liver transplantation reflecting the incomplete knowledge base.