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Transient global amnesia (TGA) is a well defined and not uncommon clinical entity, comprising the sudden development of a dense anterograde amnesia, usually accompanied by repetitive questioning, without alteration in consciousness or other epileptic phenomena, or the development of focal neurological features. Behaviour during the episode may otherwise appear normal and recovery is complete within 24 hours, except for an amnesic gap for the duration of the attack together with a short and variable period of retrograde amnesia.1 The cause of TGA is not known, but it seems to be strongly associated with migraine, although other causes, including transient cerebral ischaemic attacks and epilepsy, have been reported. Attacks of TGA have apparently been precipitated by various physical and emotional stresses, including sexual intercourse.1
The wife of a 64 year old man complained that on five separate occasions between March 1977 and October 1995, her husband had exhibited stereotyped attacks of amnesia after intercourse. During these events he would repeatedly ask questions such as “What are we doing?”, “What time of year is it?”, and “What time of day is it?”, but readily recognised his wife and subsequently other people during the amnestic period. He seemed aware that he was experiencing difficulties but there was no alteration in conscious level, and his activities during intercourse and afterwards were otherwise unremarkable. The amnestic state lasted about 30–60 minutes on each occasion and he then recovered completely, except that he had no memory for the period of intercourse and only a very hazy recollection of foreplay. He had no associated headache with these episodes, but gave a 20 year history of migraine without aura, and he had also experienced previous episodes of coital cephalalgia, with severe occipitonuchal headache at climax lasting some 20 minutes. He had never experienced TGA attacks under other circumstances, and had had intercourse without developing neurological symptoms on many other occasions.
His cardiovascular and neurological examinations were normal, and brain CT and extracranial ultrasound studies were normal. His EEG showed some sharply contoured theta activity in the right frontotemporal area.
The history of recurrent TGA attacks, together with the EEG abnormalities, raises the possibility of an epileptic aetiology in this patient, but this seems unlikely. Patients with epileptic TGA nearly always develop typical complex partial seizures within a year of the first TGA attack.1 Pure amnestic seizures are characterised by similar selective memory impairment with preservation of other cognitive abilities, but are much briefer, not accompanied by retrograde amnesia, and patients are unaware that there is anything wrong during attacks.2 Also, such attacks almost invariably occur in patients who have other, more typical complex partial seizures.2 TGA in this patient therefore seems likely to be a manifestation of migraine.
The fact that a person can repeatedly experience selective amnesia for sexual intercourse, but otherwise function normally during the amnestic period, raises interesting social and medicolegal considerations!
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