Fact-sheet: Hepatic encephalopathy
Updated on 02/19/2018 at 9:06 PM
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Definition
A combination of psychiatric, cognitive, and motor signs related to chronic or acute hepatocellular insufficiency.
Occurs in more than 50% of cirrhosis cases.
Secondary to the accumulation of neurotoxic substances, including ammonium and manganese.
Clinical features
- Impaired consciousness, ranging up to coma
- Motor abnormalities: asterixis, bradykinesia, tremor
CT
Bilateral, symmetric cortical edema (sulcal effacement, gray-white matter differentiation loss) may be seen but is most often inapparent.
MRI
Acute hepatic encephalopathy:
- diffuse, symmetric cortical diffusion hyperintensity sparing the occipital and insular cortex, suggestive of cytotoxic edema
- T2 FLAIR cortical hyperintensity
- T2 FLAIR hyperintensity of the corticospinal tracts (inconstant)
- bilateral and symmetric sulcal effacement
- no contrast enhancement
- progression to diffuse cerebral edema and cerebral herniation in the absence of treatment.
These acute abnormalities are secondary to hyperammonemia.
The abnormalities seen on T2-FLAIR and diffusion imaging are proportional to the degree of hyperammonemia and are reversible with treatment.
Chronic hepatic encephalopathy:
- T1 hyperintensity of the basal ganglia, particularly the globus pallidus, due to manganese deposition (slowly reversible after transplantation), best seen on T1 spin-echo sequences
- T1 hyperintensity of the anterior pituitary and hypothalamus (less common)
- atrophy predominating in the cerebellum
- spectroscopy: increased glutamate, with concentration proportional to the severity of hepatic insufficiency, and decreased myoinositol and choline.
Differential diagnosis
Other causes of basal ganglia T1 hyperintensity: - parenteral nutrition - carbon monoxide poisoning - neurofibromatosis type 1 - Fahr disease - Langerhans cell histiocytosis