MRI lesions masked by brain development: a case of infant-onset focal epilepsy.

A 3-month-old male presented with right-side-dominant focal seizures. Focal spikes were observed on the left side of an electroencephalogram obtained at the time of onset. The immature development in the left middle temporal lobe was observed by initial magnetic resonance imaging (MRI). The hypoperfusion in the left temporal lobe observed with single-photon computed tomography was consistent with MRI findings. These MRI findings were not observed in a second MRI at 11 months of age. This observation may explain one of the causes of infant-onset focal epilepsy.