Objective To investigate the clinical and radiographic features of anterior internuclear ophthalmoplegia caused by acute brainstem infarction. Methods Four cases of anterior internuclear ophthalmoplegia were retrospectively reviewed by analyzing their clinical and radiographic data together with anatomical features. Results All 4 cases were caused by brainstem ischemic lesions, demonstrating dotted infraction on thin-sliced diffused-weighted imaging at the dorsal side of pontine and the ventromedial side of the fourth ventricle. Among 4 cases, 1 was cured and the other 3 cases achieved improved adduction and diplopia. Conclusion Anterior internuclear ophthalmoplegia is characterized by its dotted lesion in the brainstem at the dorsal side of pontine and the ventromedial side of the fourth ventricle. Thin-sliced MRI facilitates the detection of these lesions.