Memory impairment due to a small unilateral infarction of the fornix.

A 52-year-old man suffered sudden anterograde and retrograde amnesia without any focal neurological deficit. Assessment using Wechsler Memory Scale-Revised test revealed significant memory impairment with a marked decline of delayed recall and preserved attention and concentration. Wechsler Adult Intelligent Scale-Third Edition indicated poor intelligent quotients. MRI revealed a small infarction at the anterior column of the left fornix. His memory loss persisted for more than 3 months with only slight improvement. This rare case indicates that isolated damage to the anterior column of the unilateral fornix is sufficient to cause significant memory disturbance, and that cerebral infarction should be considered in the differential diagnosis of a patient presenting with amnesia as the only symptom.