Amnesi

Amnesi is the plural form of amnesia in some languages and is used to describe conditions characterized by memory loss. In clinical terms, amnesia refers to impairments in the ability to recall past events (retrograde memory) or to form new memories (anterograde memory), or both, beyond ordinary forgetfulness or lapses.

Types include anterograde amnesia, where new information cannot be encoded; retrograde amnesia, where previously stored memories are lost; and global amnesia, where both retrograde and anterograde memories are impaired. Transient global amnesia is a temporary, sudden onset of dense amnesia that usually resolves within hours. Dissociative (psychogenic) amnesia involves memory loss related to psychological factors rather than direct brain injury.

Causes vary and include neurological injuries such as traumatic brain injury, stroke, or brain infections; neurodegenerative diseases like Alzheimer's disease and other dementias; metabolic disturbances (hypoxia, thiamine deficiency); substance effects (alcohol, sedatives); seizures; and psychological factors in dissociative amnesia or psychogenic amnesia.

Symptoms depend on the type but generally involve gaps in memory for events, personal information, or skill-based memory. Confabulation and confusion about identity can occur in some cases. Diagnosis relies on patient history, collateral information, neurologic examination, and neuropsychological testing; imaging or laboratory studies are used to identify treatable causes and rule out other disorders.

Treatment focuses on the underlying cause and on memory rehabilitation and coping strategies. In some forms, such as dissociative amnesia, psychotherapy is employed. Pharmacologic treatment is not universal but may be used for associated conditions. Prognosis varies; brief conditions such as transient global amnesia often recover fully, whereas chronic or progressive cases may persist.