COMMENTARY

Is Minimal Hepatic Encephalopathy Associated With Increased Risk for Motor Vehicle Accidents and Traffic Violations?

David A. Johnson, MD, FACG, FACP

Disclosures

October 23, 2007

Minimal Hepatic Encephalopathy: A Vehicle for Accidents and Traffic Violations

Bajaj JS, Hafeezullah M, Hoffmann RG, Saeian K
Am J Gastroenterol. 2007;102:1903-1909

Summary

It is well known that hepatic encephalopathy is a complication of cirrhosis. However, the spectrum of impact associated with this complication is not as well recognized by clinicians who care for these patients. Although patients with this complication may have very recognizable and overt evidence of impairment, others may exhibit changes in cognitive function that are too subtle to be detected by the standard neurologic status assessments. Such abnormalities are apparent only with neurophysiologic and neuropsychological testing. These more subtle abnormalities have been collectively termed "minimal hepatic encephalopathy (MHE)." This condition is characterized by delays in reaction time and abnormal response inhibition. Although this disorder is termed minimal, the reported prevalence is certainly not; it is present in 20% to 85% of cirrhotic patients.[1] The full clinical implications of this disorder are not well understood, although it is recognized that patients with MHE do not demonstrate normal response on tests of driving ability.[2] Given that impairment of cognitive function (eg, with alcohol or drug use) is a recognized contributing factor to motor vehicle accidents and traffic violations, it would be a logical extension to implicate MHE as a potential contributing factor in this setting as well.

In this study, the investigators identified 200 cirrhotic patients without overt hepatic encephalopathy. From this pool, 115 patients were excluded because of current medication use that had potential psychoactive interference (eg, antidepressants, interferon, antipsychotics, or neuroleptics). The remaining 85 patients underwent a psychometric battery of testing, which demonstrated MHE in 50 patients. An anonymous questionnaire was mailed to all 200 patients -- 115 taking psychoactive medication, 50 who were MHE-positive, and 35 who were MHE-negative. Questions were asked about motor vehicle accidents (MVAs) and traffic violations (TVs) resulting in ticket issuance. Additionally, a validated driving behavior questionnaire inquiring about specific driving behaviors that can result in MVAs or TVs was also sent. An age- and sex-matched control group of 100 patients was developed: 50 volunteers recruited from the community and 50 nonhepatology patients recruited from the gastroenterology clinic.

Results showed that driving duration was similar for the study and control groups. Patients with cirrhosis had a higher percentage of MVAs at 1 year compared with controls (9% vs 1%) and 5 years (17% vs 4%). Similarly, there was a corresponding difference for higher TVs at 1 year (13% vs 2%) and 5 years (25% vs 4%) for cirrhotics vs controls. The MHE-positive cirrhotic patients also had a significantly higher percentage of TVs compared with MHE-negative cirrhotic patients at 1 year (21% vs 4%; P = .003) and 5 years (36% vs 12%; P = .004). Corresponding significant differences in MVAs were also noted between these groups at 1 year (17% vs 0%; P = .03) and 5 years (33% vs 12%; P = .03). Additionally, lower driving behavior questionnaire scores were also apparent for the MHE-positive vs MHE-negative patients (P = .02). By multivariate logistic regression analysis, MHE-positive status was the only risk factor for MVAs and TVs (odds ratio, 7.6; 95% confidence interval [CI], 1.5-37.3).

Viewpoint

Although causation of MVAs and TVs is multifactorial, clearly there is a human behavioral and/or cognitive component that is contributory. This study highlights a very important potential risk for patients with MHE. Whereas not all patients with cirrhosis have MHE, a significant proportion, if not the majority, will have evidence of MHE when specific tests are performed to characterize the disorder. Admittedly, driving skills and the legal implications of deciding fitness to drive are very controversial issues. However, this study raises a very recognizable concern that these patients may pose a risk, not only to themselves but to others. Before overreacting to these findings, some potential weaknesses of this study should be recognized. First, the methodology involved self-reporting tools and a retrospective analysis. Additionally, there was a potential confounding effect on the etiology of the liver disease. Patients with alcoholic liver disease may have residual neurophysiologic abnormalities that persist for years. Moreover, there are some data that suggest that hepatitis C may also affect neuronal tissue, which may further confound this analysis as it relates to MHE.[3] Clearly, additional prospective studies in this area are warranted, particularly to determine whether demonstrated abnormalities may be reversible with medical therapies to improve MHE.

Abstract

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