Investigation of Brain Nitrogen in Partial Ornithine Transcarbamylase Deficiency (OTCD) Using 1 H MRS, DTI, and fMRI

The overall goal of this project is to characterize metabolic, structural and cognitive changes in OTCD using 1H MRS, DTI, volumetric averaging and fMRI with cognitive testing of executive function measures to validate biomarkers for the effect of HA and its treatment on the brain. The investigators will measure gln and mI in blood and brain (using 1H MRS) in affected participants, and mI in brain in controls, fractional anisotropy as a measure of white matter microstructural damage (by DTI) and brain activation pathways alterations with tasks probing working memory (fMRI). As a secondary outcome measure, the investigators will correlate the findings from neuroimaging with cognitive functioning. This protocol is based on the previous 5104 protocol, now includes children to evaluate the age and stage of disease on these indices in a cohort that is undergoing important developmental events against an age matched typically developing cohort.