Urea Cycle Disorders: A Neuroimaging Pattern Approach Using Diffusion and FLAIR MRI

Area of Science:

• Neurology
• Radiology
• Metabolic Disorders

Background:

• Urea cycle disorders (UCDs) are genetic conditions leading to hyperammonemia.
• Early diagnosis and assessment of neurological impact are crucial for UCD management.
• MRI, particularly diffusion-weighted imaging (DWI) and fluid-attenuated inversion recovery (FLAIR), can reveal brain abnormalities.

Purpose of the Study:

• To evaluate characteristic MRI findings in UCD patients during the first hyperammonemia episode.
• To correlate initial MRI patterns with serum ammonia levels.
• To determine the association between MRI findings, ammonia levels, and neurological outcome severity.

Main Methods:

• Retrospective analysis of MRI scans (DWI and FLAIR) from 10 UCD patients during their first hyperammonemia episode.
• Evaluation of topographical distribution of abnormalities in various brain regions.
• Correlation analysis between MRI patterns, peak serum ammonia levels, and neurological outcomes (>30 days follow-up).

Main Results:

• The UCD cohort included various types of deficiencies (OTC, AS, CPS1, Citrinemia).
• Increased neurological sequela severity correlated with diffuse cerebral cortex or corpus striatum involvement on DWI.
• Peak serum ammonia levels ≥450 µmol/L were associated with grades 2-4 neurological outcomes, while levels <450 µmol/L correlated with grades 0-1 outcomes.

Conclusions:

• More severe neurological outcomes in UCD are linked to diffuse cerebral cortex or corpus striatum involvement on DWI.
• High serum ammonia levels are also associated with poorer neurological outcomes in UCD patients.