Crescendo transient ischemic attacks (TIAs)

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  1. TIAs are brief reversible episodes of focal, nonconvulsive ischemic neurologic disturbance with duration less than 24 hours
  2. Attacks lasting up to one hour and leave no permanent signs are different from those of longer duration which are more likely due to embolism
    1. a single TIA is different from repeated ones because the latter are more often a warning sign of impending vascular occlusion while the former are usually due to an embolus
    2. approximately 25% of people who have a TIA develop either a full stroke or a myocardial infarction
    3. recurrent attacks of the same pattern suggest atherosclerosis and thrombosis
    4. crescendo TIAs consist of a series of increasingly frequent TIAs in one vascular territory
      1. patients with crescendo TIAs are more likely to progress to a stroke and more likely to have embolic causes for their symptoms than patients with ordinary TIAs
      2. patients commonly suffer from a clot in a carotid artery but may also come from a cardiac source
  3. crescendo TIA distribution is mostly posterior circulation if the posterior cerebral arteries are included in the posterior circulation
    1. posterior circulation TIAs are more likely to lead to full stroke
    2. posterior circulation symptoms: dizziness, diplopia, dysarthria, ataxia
  4. anticoagulation treatment: crescendo TIAs, stroke in evolution, cerebral emboli caused by atrial fibrillation, valvular heart disease, MI, paradoxical embolization
    1. atrial fibrillation is associated with a 1% risk of stroke in the 50-59 year old population and 23.5% in the 80-89 year old population
    2. warfarin reduces the risk of stroke 81% when compared to placebo and should be started in most patients with this condition who are >75 years
      1. aspirin is effective prophylaxis for patients who are at low risk for stroke (about 70% of patients under age 75 are low risk based on an absence of hypertension, prior stroke of left ventricular dysfunction) but only 30% over the age of 75 fit the low risk criteria
    3. recurrent stroke is not prevented by high dose aspirin
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