Hepatic encephalopathy
General description
Hepatic encephalopathy, also known as acute hyperammonemic encephalopathy or portosystemic encephalopathy, is a neuropsychiatric disorder caused by liver dysfunction. It is commonly associated with advanced liver diseases such as cirrhosis or acute liver failure, though in rare cases, congenital urea cycle defects may also lead to the condition.
Hepatic encephalopathy is characterized by impaired consciousness and cognitive dysfunction resulting from the accumulation of ammonia and other toxins in the bloodstream that the liver typically detoxifies. While hyperammonemia plays a central role, the severity of symptoms does not always correlate with blood ammonia levels, indicating that additional mechanisms are involved in its pathogenesis.
Manganese deposition
In chronic liver disease, manganese accumulates in the globus pallidus, substantia nigra, and the anterior lobe of the pituitary gland, leading to T1WI hyperintensity on MRI. In healthy individuals, manganese is efficiently removed by the liver. However, in patients with chronic liver disease, impaired liver function allows manganese to bypass hepatic clearance, resulting in its accumulation in the brain.
T2WI and FLAIR hyperintensity
MRI reveals bilateral symmetric T2WI and FLAIR hyperintensity in the middle cerebellar peduncles, cerebellar white matter, globus pallidus, and cerebral white matter.
Corticospinal tract
The corticospinal tract, including the white matter of the precentral gyrus, posterior limb of the internal capsule, and cerebral peduncle, shows hyperintensity on T2WI/FLAIR and DWI.
Motor cortex
The cerebral cortex of the precentral gyrus exhibits T2WI hypointensity accompanied by DWI hyperintensity.