What are the etiologies of acute anterograde memory loss (AMS)?

From the Guidelines

Acute anterograde memory loss (AMS) can result from various etiologies, broadly categorized as neurological, metabolic, toxic, infectious, and psychiatric causes, with the most recent evidence suggesting that neurological etiologies such as stroke, seizures, and intracranial hemorrhage are critical to identify and manage promptly 1. The etiologies of AMS can be broken down into several key categories, including:

• Neurological causes: stroke, seizures (including non-convulsive status epilepticus), traumatic brain injury, and intracranial hemorrhage
• Metabolic causes: hypoglycemia, hyperglycemia, electrolyte abnormalities (particularly sodium, calcium, and magnesium imbalances), hepatic encephalopathy, uremic encephalopathy, thyroid disorders, and hypoxia
• Toxic etiologies: medication side effects, alcohol intoxication or withdrawal, recreational drug use, and exposure to environmental toxins
• Infectious causes: meningitis, encephalitis, sepsis, and systemic infections causing secondary brain dysfunction
• Psychiatric conditions: acute psychosis can also present as AMS When evaluating a patient with acute AMS, a systematic approach is essential, starting with stabilization of airway, breathing, and circulation, followed by rapid assessment for immediately reversible causes like hypoglycemia (check glucose and administer dextrose if low), opioid overdose (consider naloxone 0.4-2mg IV/IM/intranasal), or alcohol withdrawal (benzodiazepines like lorazepam 1-2mg IV) 1. Some key points to consider in the evaluation and management of AMS include:
• The yield of neuroimaging studies in patients with AMS is low, but identifying patients with AMS secondary to acute intracranial pathology is extremely important to guide management and ensure early appropriate triage 1
• Delirium is a defined and diagnosable medical condition that can present with subtle disturbances in consciousness, and early detection and accurate diagnosis are extremely important as mortality in patients may be twice as high if the diagnosis of delirium is missed 1
• New onset psychosis is often listed as a separate subgroup under the AMS category, and medical conditions that may present with psychotic symptoms include endocrine disorders, autoimmune diseases, neoplasms and paraneoplastic processes, neurologic disorders, infections, genetic or metabolic disorders, nutritional deficiencies, and drug-related intoxication, withdrawal, side effects, and toxicity 1 The most recent and highest quality study suggests that a systematic approach to evaluating and managing AMS, including prompt identification and management of neurological etiologies, is critical to improving patient outcomes 1.

From the Research

Etiologies of Acute Anterograde Memory Loss (AMS)

The etiologies of acute anterograde memory loss (AMS) can be diverse and include:

• Neurological causes:
  • Transient global amnesia (TGA) 2, 3
  • Transient epileptic amnesia (TEA) 2, 3
  • Stroke injuries occurring at strategic memory-related sites 2, 3, 4, 5
  • Traumatic brain injuries 2
  • Autoimmune encephalitis 2
• Psychiatric causes:
  • Dissociative amnesia 2
  • Psychogenic amnesia 3
• Vascular causes:
  • Acute type A aortic dissection 6
• Toxic/metabolic causes:
  • Acute toxic metabolic disorders 2
  • Toxic/drug-related amnesia 3

Clinical Presentation

These etiologies can present with sudden onset of anterograde amnesia, which can be accompanied by other neurological symptoms or be isolated 2, 3, 4, 5, 6.

Diagnostic Approach

A thorough diagnostic approach is necessary to establish the underlying cause of AMS, including:

• Clinical evaluation 2, 3
• Neuropsychological assessment 3
• Imaging studies (e.g., MRI, CT) 4, 5, 6
• Laboratory tests (e.g., blood tests) 6