Objective:To report the follow-up findings of 7 children with severe epilepsy as a result of thiamine deficiency in infancy caused by a defective soy-based formula.Methods:The medical records of 7 children aged 5-6 years with thiamine deficiency in infancy who developed epilepsy were reviewed and their clinical data, EEG tracings, and neuroimaging results were recorded. The clinical course and present outcome of these children, now 5 years after exposure to thiamine deficiency, are described.Results:All infants displayed seizures upon presentation, either tonic, myoclonic, or focal. Six infants had an EEG recording at this stage and all showed slow background. Five of them had no epileptic activity and only 1 displayed focal activity. Following a seizure-free period of 1-9 months, the seizures recurred, and all 7 children displayed either myoclonic or complex partial seizures. Multifocal or generalized spike wave complexes were recorded on the EEGs of all 7 patients, and the tracings of 3 children evolved into hypsarrhythmia. The seizures were refractory to most antiepileptic drugs, and 4 children remain with uncontrolled seizures. All children have mental retardation and motor disabilities as well as symptoms of brainstem dysfunction.Conclusions:Our findings indicate that severe infantile thiamine deficiency may result in epilepsy.