Sudden memory loss may be a temporary condition, or a symptom of something more serious.
“My mind just went blank,” says Try, who works from her Wellington home as an IT consultant. “I couldn’t remember where I’d been, what I’d been doing or what I was supposed to be doing.”
She managed to find her way home, but once she got there, she still couldn’t remember where she’d been. Notes she’d taken at a tax workshop that morning made no sense, and when a client rang, she couldn’t remember who she was.
“It was just a total blank for the first few minutes, then I started to recognise things, but I couldn’t process information or make sense of it.”
Try didn’t call her husband to tell him what was happening. If she had, she would almost certainly have repeatedly asked him where she was and what she was meant to be doing.
Asking the same question over and over is characteristic of transient global amnesia (TGA), the condition Try was diagnosed with after seeing her GP the next day. He immediately contacted the neurology department at Wellington Hospital, where staff concluded she had had an episode of TGA.
Alan Barber, a neurologist at Auckland City Hospital and medical consultant to the Stroke Foundation, says although the symptom of TGA – sudden memory loss – is frightening, doctors familiar with the condition can quickly distinguish it from potentially life-threatening conditions such as strokes.
“Once you’ve seen TGA, you’ll never forget it, because it has a characteristic clinical pattern,” he says. “The patient is alert, but keeps asking the same question over and over again. If they’re in a car, they might ask, ‘Where are we going?’, then a minute later they’ll ask it again.”
He says people experiencing TGA – which can last for up to 24 hours – know who they are and who their spouse is. However, they are temporarily unable to lay down any new memories. “The constant questioning can be distressing for anyone who is with them.”
The symptoms are so alarming that many affected people head straight to the accident and emergency department. Barber says that’s a good thing, because it means doctors can rule out other possible causes of their symptoms, including a rare kind of stroke that affects memory. Other possibilities include migraines, which are thought to be a predisposing factor for TGA and epilepsy, which can also affect memory.
TGA occurs in about five in 100,000 people and is more common in those over 40. No one knows what causes it, though it can be triggered by sudden immersion in hot or cold water, strenuous physical activity or having sex.
It doesn’t require any treatment and it’s rare to have a second episode. Once symptoms have gone, most people can get on with their lives – though their doctor may suggest not driving for a month. However, pilots and air-traffic controllers who have been diagnosed with TGA are grounded for a year to make sure they don’t have a second episode. Bus and truck drivers are also expected to stop driving for at least six months.
Barber says anyone who experiences sudden memory loss should go to hospital. “Don’t muck about or call the GP for an appointment – just call an ambulance.” Going to a hospital is even more important if they’re also experiencing symptoms associated with a stroke, such as a drooping face, weakness in one arm or difficulties speaking. “With a stroke, you can lose two million brain cells a minute, so we want you here five minutes ago,” he says.
Even if those stroke-like symptoms disappear after 20 minutes or so – which typically happens after a transient ischaemic attack (TIA) or “mini stroke” – it’s important to seek medical treatment immediately.
“If something happens that’s not normal, and it’s scary for people watching it, get to hospital. You can’t know whether it’s TGA or TIA or something else, so you need to be seen by someone who does.”
This article was first published in the June 15, 2019 issue of the New Zealand Listener.