A mini-stroke fades away, but it often comes before a major one
A transient ischaemic attack brings stroke symptoms such as a drooping face, lost vision or slurred words, then vanishes, sometimes within minutes. Because the brain recovers, it is easy to shrug off. Yet many people who have one go on to suffer a major stroke within 48 hours.
Every kind of stroke comes from interrupted blood flow to the central nervous system. In a TIA the supply is cut briefly and restored before brain tissue dies, so imaging afterwards shows no significant damage. That distinguishes it from a full stroke, where dead tissue is visible, and from a silent stroke, where damage appears on a scan without any noticed symptoms. One person can experience all three, in any order.
Definitions have shifted. The classic rule was symptoms lasting under 24 hours, but a pooled study of 808 patients from 10 hospitals found that 60 percent of attacks ended within an hour and only 14 percent went past six hours. The American Heart Association and American Stroke Association now use a tissue-based definition: a short episode of vascular neurological dysfunction, typically under an hour, without significant infarction on imaging. Symptoms lasting longer than an hour are more often linked to permanent damage.
Typical signs are focal: weakness or numbness on one side, often opposite the affected hemisphere, sudden painless loss of sight in one eye, double vision, or trouble producing or understanding speech. One-sided weakness points more strongly to a TIA than memory lapses, headache or blurred vision, which are more often caused by look-alike conditions. Low blood sugar, for instance, can mimic an attack. Witnesses who can say exactly when symptoms began and ended are valuable.
The usual culprit is a clot. Atrial fibrillation, an irregular heart rhythm, can let clots form in the heart and travel to a brain artery; fatty plaque near the fork of the carotid artery in the neck can shed fragments too; and narrowed vessels can starve tissue. The middle cerebral artery is most often involved worldwide. Guidelines call for brain imaging within 24 hours of onset, preferably MRI with diffusion sequences, which detects fresh and old lesions better than CT. Risk factors doctors look at include age over 55, smoking, high blood pressure, diabetes and raised blood fats.
Source: Transient ischemic attack
