Learning objectives
To review the clinical setting and MRI typical findings of hepatic encephalopathy (HE).
To review the more classical MRI features of acute toxic and acquired metabolic encephalopathies in order to provide the radiologist the skills to differentiate each entity.
Background
Hepatic encephalopathy can occur in the setting of acute fulminant hepatic failure or as a more chronic disease,
which is usually a more indolent process.
Although its pathogenesis is not clear and many hypotheses have been proposed,
the physiopatothology is thought to be due to the cerebral edema and raised intracranial pressure caused by an increased intracellular osmolytes,
which are usually metabolized by the liver,
such as manganese and ammonia.
The clinical manifestations are secondary to a misbalance between inhibitory and excitatory neurotransmission.
This misbalance...
Findings and procedure details
MRI can show a specific pattern of cerebral metabolic changes and measure abnormal deposits of different substances that under normal circumstances are metabolized by the liver.
T1-weighted images show hyperintense signal in the globus pallidus,
subthalamic region and midbrain (Fig.
1,2,3). The increased T1 signal is due to a rise in manganese concentration (a paramagnetic substance),
with preferential deposition in the globus pallidus and substantia nigra.
This finding has also been seen in patients receiving total parenteral nutrition,
those with occupational exposure to manganese from...
Conclusion
MRI plays an important role in the diagnosis of acute encephalopathic patients.
The knowledge of the typical MRIfindings is essential for an accurate diagnosis.Often the image diagnosis can be a challenge for the radiologist,
but understanding the characteristic imaging features coupled with a detailed clinical history,
can often help to establish the correct diagnosis.
References
A.
Rovira,
J.
Alonso,
J.
Córdoba.
MR Imaging Findings in Hepatic Encephalopathy.
Am J Neuroradiol 2008; 29:1612-21.
P.
Sharma,
M.
Eesa,
J.
N.Scott.
Toxic and Acquired Metabolic Encephalopathies: MRI appearance.
AJR 2009; 193:879-886.
A.M.
McKinney,
B.D.
Lohman,
B.Sarikaya,
E.Uhlmann,
J.Spanbauer,
T.Singewald,
J.R.Brace.
Acute Hepatic Encephalopathy: Diffusion-Weighted and Fluid-Attenuated Inversion Recovery findings,
and correlation with plasma ammonia level and clinical oucome.
Am J Neuroradiol 2010; 31:1471-79.
T.
Naegele,
W.
Grodd,
R.
Viebahn,
U.
Seeger,
U.
Klose,
D.
Seitz,
S.
Kaiser,
I.
Mader,
J.
Mayer,
W.
Lauchart,...