Acute Amnesia due to Isolated Mammillary Body Infarct

There are limited reports describing acute amnesia after mammillothalamic tract infarction. Furthermore, acute infarction isolated to the mammillary body has never been reported. We present the first case of anterograde amnesia after isolated acute infarction of the mammillary body in a patient without concurrent or prior thalamic or mammillothalamic tract injury.

A retrospective review of the patient's electronic medical record including inpatient notes and all radiological examinations was performed.

A 50-year-old woman presented with acute onset of confusion and constant repetition of the same questions. Magnetic resonance (MR) imaging of the brain showed isolated acute infarct of the left mammillary body without concurrent abnormality of the thalamus or mammillothalamic tract. MR angiography showed severe stenosis of the proximal posterior cerebral artery at the origin of the perforating mammillary artery.

Isolated injury to the mammillary body is rare. In addition to recognized memory-related structures such as the thalamus and mammillothalamic tract, mammillary body injury may also play a role in memory dysfunction. Knowledge of the vascular supply of memory-related structures is important in diagnosing and understanding memory dysfunction.