Hyperinsulinism/Hyperammonemia (HI/HA) syndrome is an orphan disease characterized by fasting and protein-induced hypoglycemia, hyperammonemia, and has high prevalence of epilepsy, developmental delays, and learning disabilities. Understanding the mechanism involved in brain phenotype remains limited. Glutamate weighted chemical exchange saturation transfer (GluCEST) imaging was used to spatially map the glutamate levels of hippocampus. We observed a higher GluCEST contrast in the hippocampus of some of these subjects following a unilateral pattern. This preliminary study demonstrates for the first time the application of GluCEST MRI for studying the abnormal function of glutamate dehydrogenase (GDH) enzyme activity in human subjects with HI/HA syndrome.