Hepatic encephalopathy

Structural MRI changes

The radiological presentation of the disease strongly depends on the acuteness of the process. In patients with liver cirrhosis and chronic encephalopathy, the most characteristic feature on T1-weighted images (T1WI) is a bilateral and symmetric increase in signal intensity (hyperintensity).

The changes are predominantly localized in the basal ganglia, specifically involving the globus pallidus. An important feature of this MRI pattern is its potential reversibility: clinical observations confirm that following successful liver transplantation, the signal in the globus pallidus completely normalizes.

Proton MR spectroscopy

Single-voxel proton MR spectroscopy is used for a deep assessment of metabolic disorders. Measurements are usually performed in the parietal region, encompassing visually unremarkable white matter.

Key metabolites and their resonant frequencies:

• NAA (N-acetylaspartate) — 2.0 ppm. Acts as a marker of neuronal integrity.
• Glx (glutamine/glutamate) — 2.1–2.5 ppm.
• Cr (creatine/phosphocreatine) — 3.02 ppm.
• Cho (choline-containing compounds) — 3.2 ppm.
• mIns (myo-inositol) — 3.55 ppm.

Dynamics of changes: Before surgery, the spectrum demonstrates a sharp increase in the Glx peak, accompanied by a drop in the concentration of mIns and Cho. Meanwhile, the NAA level remains within normal limits, indicating that the neurons themselves are preserved. Following liver transplantation, the balance of metabolites (Glx, mIns, Cho) completely recovers to normal values.

Acute hepatic encephalopathy

The development of acute hepatic encephalopathy (Acute Hepatic Encephalopathy) requires the analysis of additional MR sequences, such as diffusion-weighted imaging (DWI / DWI), apparent diffusion coefficient maps (ADC maps / ADC maps), as well as T2WI and T2-FLAIR.

Tomograms reveal bilateral hyperintense lesions affecting:

• The cortical grey matter of the temporal and frontal lobes, as well as the insular cortex;
• The thalami;
• The dorsal brainstem.

Key diagnostic criterion of the acute phase is the presence of restricted diffusivity (restricted diffusivity). Pathological areas appear bright on DWI and are confirmed by a dark signal on ADC maps.

Differential diagnosis of metabolic lesions

The MRI presentation of liver dysfunction must be differentiated from other types of metabolic encephalopathies:

1. Hypoglycemic encephalopathy: Also characterized by diffusion restriction, but the lesions are localized in the cortical grey matter, deep brain nuclei, and, most importantly, symmetrically affect both hippocampi.
2. Non-ketotic hyperglycemia: Demonstrates a completely different pattern. In this case, T2WI and T2-FLAIR visualize hypointense (dark) lesions typically located in the right occipital subcortical white matter.

Class and exam questions

What else to study on this topic

• Application of the revised McDonald criteria (2017) and evaluation of the central vein sign in multiple sclerosis.
• MRI patterns in neuromyelitis optica spectrum disorders (NMOSD).
• Neuroimaging in CNS vasculitis and systemic lupus erythematosus (including antiphospholipid syndrome).
• Specific syndromes: CLIPPERS syndrome and acute disseminated encephalomyelitis (ADEM).
• Pattern recognition in adult genetic leukoencephalopathies and reversible cerebral vasoconstriction syndrome (RCVS).

Other topics in the Neuroimaging section

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