In the latest in our series, Dr Roger Henderson asked what might be the cause of this patient’s sudden-onset confusion and memory loss. Answer revealed below!
A previously well 65-year-old woman attended the GP surgery as an emergency, having been brought there by her family. That morning she had suddenly become confused in time and place, forgetting where she lived, what job she did and who her family members were.
She was repeatedly asking questions about where she was, and who the people around her were, and did not seem to understand she was in a doctor’s surgery. Although she had some recall about events that had happened years previously, she was unable to say what had happened in recent days or weeks. Her family said she had been under severe stress in recent weeks due to concerns she had about the possibility of being made redundant from her job.
There was no history of similar episodes, or any seizures or psychiatric problems. Her family said she did not smoke or take any recreational drugs.
Examination showed her to be confused but fully alert, normotensive, with no clinical evidence of a cerebrovascular event. A full detailed physical examination showed no obvious abnormalities, no fever and her blood glucose level was normal. On MMSE she was unable to answer the year, address or the name of the Prime Minister. She was subsequently admitted to hospital for further investigations.
These showed her to have entirely normal blood tests – including inflammatory markers, thyroid function and toxicology screening – a normal CXR and ECG, and a normal EEG. An MRI scan of her brain did not show any abnormality. She was admitted for observation as she remained extremely confused.
After 24 hours and with no specific treatment, the patient had developed orientation in time, place and person again and she was discharged home feeling well 48 hours later with no obvious adverse effects from the episode.
What is going on?
Answer
The diagnosis was transient global amnesia (TGA) – a syndrome characterized by loss of antegrade memory with less prominent loss of retrograde episodic memory that typically resolves within 24 hours.
TGA affects up to 30 in 100,000 people over the age of 50, usually presenting in the seventh decade. During an episode, patients with TGA typically ask repeated questions about their surroundings.
Diagnosis is based on the rapid recovery and exclusion of other potential diagnoses. Of note, it is vital to exclude TIA which is sometimes incorrectly diagnosed as TGA.
Another important differential is transient epileptiform amnesia (TEA). This can present almost identically to TGA. Distinguishing features are:
• TEA episodes are usually shorter than TGA episodes.
• TEA is more likely to recur.
• More retrograde amnesia in TEA than in TGA.
• EEG may be abnormal in TEA.
The underlying cause of TGA is unclear, but it is thought that stress may be a trigger in some patients. It should be considered a possible diagnosis for sudden memory loss in a patient with no medical history and with a normal physical examination.
Dr Roger Henderson is a GP based in Scotland
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