Makindo Medical Notes

Memory disorders impair the ability to encode, store, or retrieve information and can severely affect quality of life. ⚠️ Always consider thiamine deficiency as a reversible cause, especially in alcohol misuse or malnutrition. Unlike delirium, memory impairment in these disorders occurs in a state of normal consciousness.

🧬 Aetiology

Memory relies on a network of brain structures — damage to any can produce an amnestic syndrome:

• 📍 Medial Temporal Lobes: Critical for encoding & retrieval.
• 📍 Hippocampi: Essential for new memory formation → bilateral damage causes profound anterograde amnesia.
• 📍 Fornices: White matter tracts linking hippocampus to other limbic structures.
• 📍 Mamillary Bodies: Vulnerable to thiamine deficiency → classic in chronic alcoholism.

⚠️ Common Causes of Memory Disorders

• 🍺 Wernicke-Korsakoff Syndrome: From thiamine deficiency (often alcohol misuse, malnutrition). – Triad = confusion, ataxia, ophthalmoplegia. – Untreated → irreversible amnesia with confabulation.
• ⏳ Transient Global Amnesia (TGA): Sudden, short-lived memory loss (hours), often after stress/exertion. No other neuro deficits.
• 🥖 Thiamine Deficiency: Direct cause of impaired mamillary body & limbic function → treat with thiamine urgently.
• 🦠 Herpes Simplex Encephalitis: HSV-1 affects temporal lobes → profound short & long-term memory loss.
• 💥 Severe Head Injury: Traumatic disruption of hippocampal/temporal structures → post-traumatic amnesia.
• 🫁 Cerebral Anoxia: Seen post-cardiac arrest; hippocampus highly oxygen-sensitive.
• 🧠 Bilateral Tumour/Infarction: e.g. PCA infarcts → severe amnesia.
• ☠️ Arsenic Poisoning: Rare cause; produces CNS toxicity including memory impairment.
• 🍬 Hypoglycaemia: Repeated/profound episodes → neuronal injury affecting cognition.
• 🚬 Carbon Monoxide Poisoning: Causes global hypoxia → delayed cognitive & memory decline.

🔎 Clinical Pearl

Amnestic syndrome = profound memory loss but with preserved attention & normal consciousness. This distinguishes it from delirium, seizures, or psychiatric conditions.

🩺 Anticipation of Symptoms

⏰ Early recognition is vital → treat reversible causes promptly. 💉 In suspected Wernicke-Korsakoff or malnutrition → give IV thiamine BEFORE glucose to prevent precipitating irreversible Korsakoff’s syndrome. Many cases are preventable if managed early.

💡 Exam Pearl: – Think of Wernicke’s triad (confusion + ataxia + ophthalmoplegia) in alcoholics → treat with thiamine. – TGA is always short-lived and benign. – HSV encephalitis → temporal lobe + memory loss + seizures.