MSH: A syndrome characterized by a transient loss of the ability to form new memories. It primarily occurs in middle aged or elderly individuals, and episodes may last from minutes to hours. During the period of amnesia, immediate and recent memory abilities are impaired, but the level of consciousness and ability to perform other intellectual tasks are preserved. The condition is related to bilateral dysfunction of the medial portions of each TEMPORAL LOBE. Complete recovery normally occurs, and recurrences are unusual. (From Adams et al., Principles of Neurology, 6th ed, pp429-30),NCI: A condition characterized by sudden, temporary, usually short-lived memory loss, not associated with a neurologic disorder. Affected individuals lose memory function for recent events and have a decreased ability to retain new information. It is usually a solitary event.