Transient global amnesia.

Transient global amnesia (TGA) is a sudden and severe anterograde memory disturbance accompanied by various degrees of retrograde amnesia and sometimes executive dysfunction. TGA affects elderly individuals and men and women equally. During the episode, patients cannot recall novel episodic information and therefore repeatedly ask the same questions. They are not fully oriented to space and time. Diagnostic criteria first established in 1985, and elaborated in 1990, demand that there is no clouding of consciousness, other impairments of cognition, or a history of epilepsy or head trauma. An episode of TGA resolves within 24 h leaving a memory gap for the length of the attack. While in rare cases TGA might happen repeatedly, it mostly occurs as a single attack. TGA is considered a benign disorder as memory deficits resolve completely and do not lead to long-term sequelae. In up to 90% of reported TGA cases, a precipitating event - mainly described as physical or emotional stress - is present. The cause of TGA has been a matter of long-standing debate among researchers. In search of an answer, several possible causes (ischemia, migraine, epileptic seizures, or, more recently, a disturbance of venous hemodynamics) have been hypothesized. However, to date there is no scientific proof of any of these mechanisms. By using diffusion-weighted MRI 24-48 h after a TGA episode, small dot-like lesions have been detected in the hippocampus. This has led to the implication that the selective vulnerability of CA1 neurons to metabolic stress might play a role in the pathophysiology of TGA.