Makindo Medical Notes

Introduction

• Transient Global Amnesia (TGA) = benign, temporary, isolated episode of anterograde amnesia lasting <24h, without focal neurological deficits.
• 📜 First described by Fisher & Adams (1964).
• 🧠 Characterised by sudden onset of memory loss + confusion for recent events, while identity and long-term memory remain intact.
• ❓ Etiology unclear: vascular, migrainous, epileptic, or stress-related triggers proposed.
• ⚠️ Commonly misdiagnosed as TIA or seizure — but prognosis is excellent.

📊 Epidemiology

• Incidence: 5–10 per 100,000 annually; higher in >50 years.
• 👵 Typical age: 50–70 years.
• 👨 Slight male predominance.
• 🔁 Recurrence: 5–25% (usually single repeat episode).

⚙️ Etiology & Pathophysiology

• 💧 Venous congestion → transient hippocampal dysfunction.
• ⚡ Migrainous aura pathways implicated.
• 🩸 Ischaemia: transient hypoperfusion (but no consistent vascular occlusion).
• ⚡ Epileptic activity unlikely (EEG typically normal).
• ⏱️ Triggers: immersion in cold water, exertion, emotional shock, sexual activity, medical procedures.

🩺 Clinical Presentation

• Sudden anterograde amnesia with repetitive questioning.
• ✅ Identity & long-term memory preserved.
• ✅ Alert, responsive, no LOC.
• ✅ No focal deficits.
• ⏳ Duration: 1–24h (commonly 4–6h) with full recovery.
• ⏮️ Retrograde amnesia (hours–days before) may persist.
• Emotional distress common (patient aware something is wrong).

✅ Diagnostic Criteria

• Witnessed episode of amnesia.
• Inability to form new memories during attack.
• No clouding of consciousness or identity loss.
• No focal neurological deficits or seizure features.
• Duration <24h.
• No recent head trauma.

🧾 Differential Diagnosis (without table)

• 🧩 Transient Ischaemic Attack (TIA): usually with focal deficits (weakness, aphasia, visual loss); isolated amnesia is rare.
• ⚡ Epileptic Amnesia: lasts minutes; automatisms, impaired awareness; abnormal EEG.
• 🧠 Psychogenic Amnesia: often identity loss, linked to psychological stressors.
• 🤕 Head Injury: trauma history, concussion features.
• 🍷 Wernicke–Korsakoff: thiamine deficiency in alcoholics, with confabulation + ataxia.
• 💊 Drug-induced: benzodiazepines, sedatives.

🧪 Investigations (if atypical)

• 🧲 MRI (DWI): punctate hippocampal lesions may appear after 24–48h (supportive, not diagnostic).
• 🖼️ CT: usually normal; excludes acute pathology.
• 📉 EEG: typically normal; rules out epilepsy.
• 🧪 Bloods: exclude metabolic causes (glucose, electrolytes).
• 🫀 Cardiac/vascular: ECG, echo, carotid Doppler if TIA suspected.

💊 Management

• ✅ Reassurance: benign, self-limiting.
• 👀 Observe until full recovery; exclude mimics.
• 🚫 Avoid unnecessary anticoagulation or antiepileptics if classical features present.
• 🧘 Address stressors if identifiable.
• 🔁 Follow-up if atypical or recurrent.

📈 Prognosis

• 🌟 Excellent: most only have a single episode.
• 📉 No ↑ risk of stroke or epilepsy.
• 🧠 Full cognitive recovery.
• 🔁 Recurrence: 5–25% (usually once).
• 🚗 Driving: single episode = no restriction; ≥2 episodes → stop driving & notify DVLA.

💡 Teaching Pearls

• 🗣️ Repetitive questioning is the hallmark OSCE clue.
• 🌊 Often triggered by immersion in cold water, exertion, or stress.
• ❌ TIA → has focal deficits; Seizure → minutes not hours; Psychogenic → identity loss.
• 👨‍⚕️ Reassurance = main treatment.

Conclusion

TGA is a self-limited amnestic syndrome with sudden onset, full recovery, and excellent prognosis. Recognising its clinical pattern prevents misdiagnosis as stroke or seizure, avoids unnecessary investigations, and provides reassurance to patients and families.

📚 References

• Hodges JR, Warlow CP. Syndromes of transient amnesia. J Neurol Neurosurg Psychiatry. 1990;53:834-843.
• Fisher CM, Adams RD. Transient global amnesia. Trans Am Neurol Assoc. 1964;89:143-147.
• Bartsch T, Deuschl G. TGA: functional anatomy and clinical implications. Lancet Neurol. 2010;9:205-214.
• Sattler JM, Rabinstein AA. Transient global amnesia. Mayo Clin Proc. 2019;94:662-672.