amnesia

Amnesia is a deficit in memory resulting from brain injury, disease, or psychological factors, marked by partial or complete inability to recall past experiences or to form new memories. It commonly affects episodic and autobiographical memory and is distinguished from ordinary forgetfulness by its persistent nature and clear onset.

Amnesia is commonly classified as organic (neurological) or psychogenic (dissociative). Organic amnesia includes anterograde amnesia (inability to form new memories) and retrograde amnesia (loss of past memories), which can occur alone or together as global amnesia. Transient global amnesia is a self-limited form with sudden onset that typically resolves within 24 hours. Psychogenic amnesia arises after psychological stress or trauma and may involve localized or extensive memory gaps, sometimes with periods of travel away from home (dissociative fugue).

Causes include traumatic brain injury, stroke, hypoxia, brain tumors, infections such as encephalitis, seizures, alcohol or drug effects, and neurodegenerative disorders like Alzheimer's disease or Korsakoff syndrome. Certain medications can also affect memory. Psychogenic amnesia is linked to stress, grief, or trauma and does not always have a detectable brain lesion.

Diagnosis relies on clinical history, neurological examination, neuroimaging (MRI or CT), and neuropsychological testing to determine the pattern of memory loss and to exclude other conditions such as dementia, delirium, or psychiatric disorders.

Treatment targets the underlying cause when possible and may involve medical management, cognitive rehabilitation, memory strategies, and psychotherapy for psychogenic forms. The prognosis varies: transient forms such as transient global amnesia typically resolve completely, while other amnesia syndromes may persist or improve only partially, with rehabilitation helping individuals regain independence.