What are the causes of acute amnesia?

From the Guidelines

Acute amnesia can result from several medical conditions that disrupt normal brain function, with the most common causes including traumatic brain injuries, seizures, certain medications, alcohol intoxication, and medical emergencies such as strokes and infections. The causes of acute amnesia can be broadly categorized into several groups, including:

• Traumatic brain injuries from accidents or falls, which can damage memory-processing areas of the brain 1
• Seizures, particularly temporal lobe epilepsy, which can trigger transient amnesia during and after episodes
• Certain medications like benzodiazepines (including diazepam and lorazepam), anesthetics, and some anticonvulsants, which can induce temporary memory loss
• Alcohol intoxication, which frequently causes blackouts, and recreational drugs like ketamine and GHB, which similarly impair memory formation
• Medical emergencies such as strokes affecting the hippocampus or thalamus, infections like encephalitis or meningitis, and oxygen deprivation to the brain, which can all cause acute amnesia
• Psychological trauma, which can trigger dissociative amnesia as a protective mechanism
• Transient global amnesia, which presents as a sudden, temporary inability to form new memories lasting up to 24 hours, often triggered by emotional stress or physical exertion
• Migraine headaches, which occasionally cause temporary memory disruption during attacks

These various causes affect memory by disrupting either the encoding of new memories (anterograde amnesia) or the retrieval of existing memories (retrograde amnesia), depending on which neural pathways or brain structures are affected 1. It is essential to identify the underlying cause of acute amnesia to provide appropriate treatment and management, as some causes may require immediate medical attention to prevent further brain damage or complications 1.

From the Research

Causes of Acute Amnesia

• Acute amnestic syndromes can be caused by various factors, including transient global amnesia (TGA), transient epileptic amnesia (TEA), stroke injuries, traumatic brain injuries, autoimmune encephalitis, and acute toxic metabolic disorders 2
• TGA is characterized by sudden onset of anterograde amnesia lasting less than 24 hours, in the absence of other neurological signs or symptoms 2, 3
• Other causes of acute-onset amnesia include posterior circulation strokes, psychogenic amnesia, post-traumatic amnesia, and toxic/drug-related amnesia 3
• Amnesia can also be a symptom of a psychiatric disorder, such as dissociative amnesia 2

Neurological Etiologies

• Stroke injuries occurring at strategic memory-related sites can present as sudden episodes of amnesia 2
• Traumatic brain injuries can cause amnesia, and donepezil, an acetylcholinesterase inhibitor, has been investigated as a potential treatment for cognitive impairments, including memory problems, after traumatic brain injury 4, 5
• Autoimmune encephalitis can also cause amnesia, and should be included among the differential diagnoses 2

Psychiatric and Toxic Etiologies

• Amnesia can be a symptom of a psychiatric disorder, such as dissociative amnesia 2
• Toxic or drug-related amnesia can occur due to various substances, and should be considered in the differential diagnosis 3
• Alcohol use disorder can also lead to cognitive impairments, including memory problems, and donepezil has been investigated as a potential treatment for alcohol use disorder-related mild cognitive impairment 6