Lecture: minimal hepatic encephalopathy

Today’s lecture focused on the diagnosis of minimal hepatic encephalopathy, with detail on legal implications.  Hepatic encephalopathy comes in three chronic forms: episodic, persistant and minimal. Minimal hepatic encephalopathy (mHE) is difficult to diagnose, and is not part of the West Haven staging system of HE.

Most of the diagnostic tools are not practical for everyday, clinical use.  One of the prominent clinical features of mHE includes: the inability to filter an ostensibly incorrect, reflexive answer to a presenting problem or question.  This suggests a deficit in higher order thinking.  One problem with some of the findings in this research is that the sample population (patients with compensated cirrhosis) includes cohorts that can have organic brain disease that is independent of a hypertoxemic state (ie. chronic HCV, history of alcoholic liver disease, history of psychoactive medication). 

Nevertheless, the data on mHE and driving is highly suggestive that drivers are indeed impaired, and unaware of it.  While the number of accidents on the road has not been adequately studied, accidents in a driving simulator are more frequent in the mHE population.  The ability to pay attention to details on the dashboard is also impaired, along with reaction time for “balls bouncing into the street.”  It is also clear that these impairments are worse as driving duration increases, ie. fatigue makes the impairment more pronounced. 

The physician is not legally bound to report any encephalopath to the authorities, and, in fact, does not have the power to insist on revoking a driver’s license.  Diagnosis alone is not enough to take away a driver’s license.  Only the RMV is certified to declare somebody incompetent behind the wheel.  For legal purposes, the physician should tell the patient of his/her concern about driving with this diagnosis, and must chart that the discussion took place.  A case of hepatic encephalopathy and physician responsibilities has never gone to court (in Massachusetts, at least). 

In summary, mHE is a frequent complication of portal hypertension, when the fibrotic liver is unable to remove an adequate amount of toxins from the bloodstream.  It is difficult to diagnose, and empiric therapy (even with 100 grams of probiotic yogurt daily) can be attempted.  Rifaximin may be a promising agent in the future, but cost effectiveness studies for this drug have not been conducted.  Patients with mHE believe that they are as good as any driver on the road, though it is clear that they are compromised behind the wheel; a fair compromise with a particularly borderline case of mHE may be to limit the distance/duration behind the wheel.

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