Pure dysarthria caused by a small cortical infarction is rare. Recent reports have revealed that a small cortical lesion can lead to pure dysarthria, furthermore some reports have revealed that a middle frontal gyrus lesion might cause pure dysarthria. We report a 64-year-old woman who presented only dysarthria and had a small limited cortical infarction located at the left middle frontal gyrus. This case indicated that an isolated middle frontal gyrus lesion can cause pure dysarthria by secondary compromising of the cortical areas related or connected to the corticobulbar tract.