The liver plays a key role in the regulation of body metabolism, and its functions include the synthesis of essential substances and the degradation of toxins. Liver failure may be accompanied by system-wide disturbances. These are no better exemplified than by the striking cerebral syndromes that occur with hepatic dysfunction.

The brain depends on the gastrointestinal system as a source of nutrition. The neurological disturbances that occur as complications of gastrointestinal disease arise from a wide range of pathological processes and may be quite diverse in presentation.

This chapter focuses on the neurological syndromes that result from various types of liver failure. In addition, it describes the neurological complications of selected gastrointestinal disease.

Neurological complications due to liver disease

The relationship between the liver and the brain has been recognized since the time of Hippocrates. Since then, there have been many accounts of dramatic behavioural disturbances that may occur with liver dysfunction. These have been eloquently reported by Plum and Hindfelt (1976).

The spectrum of nervous system disturbances occurring with liver disease encompasses a wide range of neurological and behavioural disorders. The term ‘hepatic encephalopathy’ is commonly defined as a neuropsychiatric syndrome arising as a complication of liver dysfunction. Although the term ‘encephalopathy’ implies a disturbance of consciousness and behaviour only, the neurological syndromes occurring with liver disease encompass a much broader spectrum of neurological disorders. These diverse manifestations do not lend themselves easily to a single definition. Thus, hepatic encephalopathy cannot be regarded as a single clinical entity.

Furthermore, although hepatic encephalopathy has been defined as a reversible metabolic encephalopathy, and although this may often be true, chronic liver failure does sometimes result in progressive, irreversible neurologic dysfunction. The terminology is additionally confusing in that it is not uncommon to use the term ‘portal systemic encephalopathy’ interchangeably with ‘hepatic encephalopathy’ (Jones & Weissenborn, 1997) because pathological shunting of blood between the portal and systemic circulation frequently develops.

Liver failure may take several forms. Sometimes it develops rapidly, in a most dramatic fashion, but usually the onset is insidious and the evolution is slow, with permanent disturbances in liver system function occurring over time. Often, the course of chronic liver disease is punctuated by episodes of acute neurological deterioration. These episodes are usually reversible and are frequently related to a well-defined cause.