Quantitative CT-scan to evaluate cerebral edema secondary to hyperammonemia in ICU: A proof-of-concept study

Hyperammonemia is a critical condition sometimes associated with severe neurological symptoms and cerebral edema. Quantitative CT-scan may help directly assess the impact of ammonia levels on brain structures, offering the potential to improve patient management.

We conducted a retrospective, proof-of-concept study on patients admitted to the ICU with ammonemia >100 µmol/L who underwent one or more brain CT-scans. Weight, volume, and specific gravity of brain structures were assessed using BrainView software (Institut National des Télécommunications).

Seven patients and 14 CT-scans were evaluated. Ammonia levels were positively correlated with whole brain weight (ρ = 0.64 and P=0.014) and volume (ρ = 0.64 and P=0.014), but no association was found with specific gravity. Similar results were found for hemispheres (ρ = 0.62, P=0.018 for weight and ρ = 0.62, P=0.019 for volume), whereas no significant correlations were noted for cerebellum, brainstem, and cerebrospinal fluid. No significant correlation could be found between variations in weight, volume, specific gravity, and variations in ammonemia.

Our findings suggest that total brain weight and volume correlate with ammonia levels, with varying impacts on different brain structures, yet our study could not find any significant association between the variations of ammonemia and the variations of CT measures. Quantitative CT scan could be of interest for evaluating cerebral edema in patients with severe hyperammonemia, paving the way for more targeted therapeutic interventions.