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In 1889, the British neurologist John Hughlings Jackson described the case of Dr Z, a medical practitioner who suffered from an unusual variety of epilepsy. During his seizures, he retained consciousness and was able to engage in complex, purposeful behaviour for which he was later amnesic. On one occasion he felt the onset of a seizure while examining a patient. During this attack, he correctly diagnosed pneumonia, prescribed treatment and wrote in the patient’s notes, but later had no recollection of having done so (fig 1).
Reports of pure amnestic seizures have appeared sporadically in the literature over the past 50 years. Recent work, however, has suggested that such cases are underrecognised and appear to have several clinical features in common.
A 69 year old, retired teacher of French, was staying with her daughter over the Christmas period. She awoke one morning and asked her husband “Where are we? What day is it? Why are we here?” She had no recollection for events of the previous few days and, when reminded, appeared to be unable to retain the information. She was understandably concerned by this, but her appearance and behaviour were otherwise normal. By the time she had got up, dressed and had breakfast, her repetitive questioning had stopped and memories for the past had returned. She had a hazy recollection of what had just happened to her. Apart from treated hypertension and hypercholesterolaemia, her past medical history was unremarkable, there were no symptoms of depression or anxiety and physical examination was normal. A diagnosis of transient global amnesia (TGA) was made and she was reassured that the problem was unlikely to recur.
However, she went on …