GLUD1 and epilepsy: Interestingly, despite having elevated ammonia levels, these patients are often without common symptoms of elevated ammonia such as headaches and encephalopathy.2 The etiology of epilepsy in HI/HA is not completely clear at this time; it is postulated that overactivity of brain GDH depletes glutamate and glutamine, which causes a disequilibrium of glutamate and GABA.