Further investigation and history is needed.
Seizures are a symptom. They can be caused by practically anything (fevers, drug or substance ingestion and metabolic issues are things that come readily to mind in that age group). In many people with epilepsy (a tendency to have unprovoked seizures), no specific focus is obvious in the brain on MRI or CT scan because the anomaly can be too subtle.
I'm not sure what you mean by 'mild seizures', but I would want a complete history and an EEG to start with before suggesting a definite cause.
