Reversible splenial edema has been often reported in epilepsy patients. Clinical presentation is reported to be silent in general. We experienced a patient with splenial lesion and cognitive dysfunction. A 21-year-old man underwent video-EEG monitoring for preoperative evaluation. He had suffered from viral encephalitis eight years ago and developed chronic drug-resistant epilepsy. After antiepileptic drugs withdrawal, he developed eight episodes of secondarily generalized tonic-clonic seizures for several hours and some seizures were repeated without recovery of consciousness. Majority of ictal EEG onset presumed to originate from the left frontal region. After seizures he had shown disorientation and irritability with gradual recovery. Brain MRI demonstrated a splenial lesion. Though splenial lesion disappeared on follow-up MRI, neuropsychological test demonstrated frontal lobe dysfunction 6 months later compared with that performed just before the video-EEG monitoring. We report a patient with isolated reversible splenial lesion associated with long term dysfunction of frontal lobe.