GPAtlas🧭 When to suspect
Transient global amnesia (TGA) is a striking but benign syndrome of sudden, isolated, profound anterograde amnesia – an abrupt inability to lay down new memories – in an otherwise well, fully conscious adult, usually aged over 50. The clinical hallmark is persistent, stereotyped, repetitive questioning ("What are we doing?", "Where am I?") asked in the same tone every few minutes, while personal identity, language and complex skills (making tea, driving, dressing) remain entirely intact.
Episodes typically last 2–12 hours (mean around 6) and, by definition, resolve fully within 24 hours, leaving a permanent gap in memory for the event itself but no other deficit. There is often a recognised precipitant – vigorous physical exertion, emotional or psychological stress, immersion in cold or hot water, a Valsalva manoeuvre, or sexual intercourse.
Two clinical skills matter most in primary care. First, TGA is a diagnosis of exclusion: during the acute episode it cannot be reliably distinguished from stroke, TIA, seizure or hypoglycaemia, so a patient who is still amnesic is a medical emergency. Second, once the diagnosis is secure, the news is reassuring – TGA is benign, needs no drug treatment, and does not increase the future risk of stroke, epilepsy or dementia.
| Diagnostic criterion (Hodges & Warlow) | Clinical note |
|---|---|
| Witnessed attack | A capable observer must be available – the diagnosis rests on the collateral history, as the patient cannot recall the event. |
| Clear anterograde amnesia | Cannot retain new information for more than a few seconds during the attack; mild retrograde amnesia may coexist. |
| Preserved consciousness and identity | No clouding of consciousness; the patient knows who they are and recognises family. |
| Cognition limited to amnesia | No aphasia, apraxia or agnosia – attention, language and visuospatial skills are intact. |
| No focal or epileptic features | No limb weakness, sensory loss, visual field defect or seizure activity. |
| No recent head injury or active epilepsy | These point to alternative diagnoses (post-traumatic or epileptic amnesia). |
| Resolution within 24 hours | Most settle within 2–12 hours; an episode lasting longer than 24 hours is not TGA. |
TGA is not rare: incidence is around 3–8 per 100,000 per year, rising in those over 50, with a mean age of about 62 and a roughly equal sex distribution. The strongest recognised association is with a history of migraine.
Source: Practical Neurology · NEJM review
🔒 Sign up free to read the full topic
You're viewing a free preview. Create a free account to unlock the rest.
Sign up free →Sample topics are open to everyone in the Free Sample Bundle.