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

Abstract

BACKGROUND AND PURPOSE This study aimed to assess characteristic regions of MRI involvement utilizing diffusion weighted imaging (DWI) and fluid‐attenuated inversion recovery (FLAIR) at urea cycle disorder (UCD) diagnosis to determine the possible association between initial MRI patterns within 10 days of the first hyperammonemia episode, serum ammonia levels, and severity of neurological outcome based on clinical follow‐up of >30 days. METHODS Ten patients with UCDs (4 females; median age: 5.4 years, age range: 6 days‐54 years) were included who underwent MRI during a first episode of hyperammonemia. The topographical distribution of the DWI and FLAIR abnormalities in the cerebral cortex, deep gray matter, white matter, posterior limb of internal capsule, cerebral peduncle, and cerebellum was evaluated. Possible correlations between the brain injury patterns on DWI/FLAIR images, serum ammonia levels, and severity of neurological outcome were investigated by a trend correlation. RESULTS The UCD cohort (n = 10) involved four ornithine transcarbamoylase deficiencies, four argininosuccinic aciduria, one carbomoylphosphate synthetase deficiency, and one citrullinemia type‐1. The observed trend in the distribution of DWI abnormalities as the severity of neurological sequela outcome increased was with diffuse cerebral cortex or corpus striatum involvement. Patients with initial peak serum ammonia ≥450 µmol/L had a grade 2 to 4 outcome, and those with peak ammonia <450 µmol/L had a grade 0 or 1 outcome. CONCLUSIONS The presence of more severe neurological outcome could be associated with diffuse cerebral cortex or corpus striatum involvement on DWI and high serum ammonia levels in patients with UCD.

Neuroimaging in inborn errors of metabolism

“…Blaži oblici hiperamonemije mogu se klinički više nespeci fično prezentirati, što može biti uzrok odgođenom po stavljanju ispravne dijagnoze. 13,14 Neurološki simptomi mogu uključivati konvulzije, bihevioralne poremećaje, iritabilnost, kognitivno zaostajanje i hiperamonije mijsku komu. Tipična neuroradiološka prezentacija MOTKa prikazana je na slici 3.…”

Review of Multi-Modal Imaging in Urea Cycle Disorders: The Old, the New, the Borrowed, and the Blue

“…Importantly, the thalami are typically spared which helps exclude HIE. Diffusion abnormality extent (diffuse cortical and/or striatal) trends negatively with prognosis ( 82 ) ( Figure 5 ). However, not much is known about the expected duration of diffusion abnormalities in and after a hyperammonemic event which may be mechanistically different from those of hypoxic ischemic injury.…”