Transient Ischemic Attacks. Minor Strokes
- Transient ischemic attacks (TIAs) are episodes of transient focal ischaemia.
- Sudden onset of loss of focal brain or monocular function.
- They are usually from 2 to 30 min in duration and last less than 24 hours. The onset is sudden and symptoms usually reach maximal intensity within 2 min. The episodes usually resolve rapidly with a 50% recovery in 1 h and a 90% recovery in 4 h. The frequency varies. Some patients experience a single attack, whereas others experience multiple attacks at different intervals.
Epidemiology
- About 50 per 100 000 per year
- Middle-aged and elderly, incidence increases with increasing age
- Gender; M=F (age <55 y), M>F (age 55-75 y), F>M (age >75 y)
Etiology
- TIAs are symptoms of disease of:
- The arteries (extracranial large artery atherothromboembolism, intracranial large artery atheroma, intracranial small artery lipohyalinosis/microatheroma, non-atheromatous arterial disease) – 75-80%
- Heart disease – 20%
- Haematological disease - <5% (anemia, polycythemia, hyperviscosity, thrombocythemia, cerebral venous thrombosis, bacterial endocarditis)
- Most TIAs are caused by emboli, usually from carotid or vertebral arteries
- Uncommonly, TIAs result from impaired perfusion due to severe hypoxemia, reduced O₂-carrying capacity of blood (e.g., profound anaemia, carbon monoxide poisoning), or increased blood viscosity (e.g., severe polycythemia), particularly in brain arteries with pre-existing stenosis.
- Systemic hypotension does not usually cause cerebral ischemia unless it is severe or arterial stenosis pre-exists because autoregulation maintains brain blood flow at near-normal levels over a wide range of systemic BPs.
- In subclavian steal syndrome, a subclavian artery stenosed proximal to the origin of the vertebral artery “steals” blood from the vertebral artery (in which blood flow reverses) to supply the arm during exertion, causing signs of vertebrobasilar ischemia.
- Occasionally, TIAs occur in children with a severe cardiovascular disorder that produces emboli or a very high Hct.
Clinical Symptoms
Focal neurological symptoms
Motor:
- Contralateral hemiparesis or hemiplegia (weakness or clumsiness of one side of the body, in whole or in part)
- Simultaneous bilateral weakness
- Difficulty in swallowing
Speech/language disturbances:
- Difficulty understanding or expressing spoken language
- Difficulty in reading or writing
- Slurred speech
- Difficulty in calculating
Somatosensory:
- Contralateral numbness, coldness, or paresthesias involving one side of the body only, in whole or in part
Visual:
- Dimness of vision or loss of vision in one eye, in whole or in part
- Homonymous hemianopia (loss of vision in the left or the right half of the visual field)
- Bilateral blindness
- Double vision