Skill impairment: Another dimension of the driving difficulties in minimal HE

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Hepatology. 2007 Nov 14

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skill impairment: Another dimension of the driving difficulties in minimal

hepatic encephalopathy.

Bajaj JS, Hafeezullah M, Hoffmann RG, Varma RR, Franco J, Binion DG, Hammeke TA, Saeian K.

Division of Gastroenterology and Hepatology, Medical College of Wisconsin, Milwaukee, WI.

Patients with minimal hepatic encephalopathy (MHE) have attention,

response inhibition, and working memory difficulties that are associated with

driving impairment and high motor vehicle accident risk. Navigation

is a complex system needed for safe driving that requires functioning working

memory and other domains adversely affected by MHE. The

aim of this study was to determine the effect of MHE on navigation skills and

correlate them with psychometric impairment. Forty-nine

nonalcoholic patients with cirrhosis (34 MHE+, 15 MHE-; divided on the basis of

a battery of block design, digit symbol, and number connection test A) and 48

age/education-matched controls were included. All

patients underwent the psychometric battery and inhibitory control test (ICT)

(a test of response inhibition) and driving simulation. Driving

simulation consisted of 4 parts: (1) training; (2) driving (outcome being

accidents); (3) divided attention (outcome being missed tasks); and (4)

navigation, driving along a marked path on a map in a " virtual city "

(outcome being illegal turns). Illegal turns were

significantly higher in MHE+ (median 1; P = 0.007) compared with MHE-/controls

(median 0). Patients who were MHE+ missed more divided

attention tasks compared with others (median MHE+ 1, MHE-/controls 0; P =

0.001). Similarly, accidents were higher in patients

who were MHE+ (median 2.5; P = 0.004) compared with MHE- (median 1) or controls

(median 2). Accidents and illegal turns were

significantly correlated (P = 0.001, r = 0.51). ICT

impairment was the test most correlated with illegal turns (r = 0.6) and

accidents (r = 0.44), although impairment on the other tests were also

correlated with illegal turns.

Conclusion: Patients positive for MHE have impaired navigation skills

on a driving simulator, which is correlated with impairment in response

inhibition (ICT) and attention. This navigation

difficulty may pose additional driving problems, compounding the pre-existing

deleterious effect of attention deficits. (HEPATOLOGY

2008.). PMID: 18000989 [PubMed

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