The clinical picture of acute, subacute, or chronic hepatic encephalopathy consists of a derangement of consciousness, presenting first as mental slowing and confusion, occasionally with hyperactivity, followed by progressive drowsiness, stupor, and coma. The confusional state is combined with a characteristic intermittency of sustained muscle contraction; this phenomenon, which was originally described in patients with hepatic stupor by Adams and Foley and called asterixis (from the Greek sterixis, a “fixed position”). It is now recognized as a sign of various metabolic encephalopathies but is most prominent in this disorder (see Chap. 4). It is conventionally demonstrated by having the patient hold his arms outstretched with the wrists extended, but the same tremor can be elicited by any sustained posture, including that of the protruded tongue. We have seen patients in whom asterixis of the large antigravity muscles (e.g., iliopsoas or quadriceps) causes falling. A variable, fluctuating rigidity of the trunk and limbs, grimacing, suck and grasp reflexes, exaggeration or asymmetry of tendon reflexes, Babinski signs, and focal or generalized seizures round out the clinical picture in a few patients.
The EEG is a sensitive and reliable indicator of impending coma, becoming abnormal during the earliest phases of the disordered mental state. Foley et al noted an EEG abnormality consisting of paroxysms of bilaterally synchronous slow or triphasic waves in the delta range, which at first predominate frontally and are interspersed with alpha activity and later, as the coma deepens, displace all normal activity (see Fig. 2-7J). A few patients show only random high-voltage asynchronous slow waves.
This syndrome of hepatic encephalopathy is remarkably diverse in its course and evolution. It usually appears over a period of days to weeks and may terminate fatally; or, with appropriate treatment, the symptoms may regress and then fluctuate in severity for several weeks or months. Persistent hepatic coma of the latter type proves fatal in about half of patients (Levy et al). In many patients, the syndrome is relatively mild and does not evolve beyond the stage of mental dullness and confusion, with asterixis and EEG changes. In yet others, a subtle disorder of mood, personality, and intellect may be protracted over a period of many months or even years; this chronic but nevertheless reversible mental disturbance need not be associated with overt clinical signs of liver failure (jaundice and ascites) or other neurologic signs. Characteristically in these patients, an extensive portal–systemic collateral circulation can be demonstrated (hence the term portal–systemic encephalopathy) and an association established between the mental disturbance and an intolerance to dietary protein as well as raised blood ammonia levels (Summerskill et al).
The diversion of blood from the portal system into the vena cava after ligation of the portal veins was first performed in dogs by Eck in 1877. Probably the first and certainly most striking example in man was the case of pure “Eck” fistula reported by McDermott and Adams, in which a portacaval shunt was created during the removal of a pancreatic tumor. The liver was normal. Episodic coma occurred thereafter whenever dietary protein increased. Consciousness was restored on a protein-free diet, and coma could be induced again by ammonium chloride. Postmortem examination 2 years later confirmed the normal liver and showed cerebral changes of hepatic encephalopathy, as described below.