Prolonged hypoperfusion and early stroke after transient ischemic attack.

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Abstract
Many patients suffer a stroke early after a transient ischemic attack, but the reason why is often unclear. We studied 12 patients with <75% stenosis of the internal carotid artery and a single hemispheric transient ischemic attack lasting <1 hour who had a normal neurologic examination 3-13 hours later and a normal computed tomogram 24-36 hours later. Single-photon emission computed tomography using technetium-99m HM-PAO .ltoreq.50 hours after the attack showed no abnormality in eight patients, but in the other four there was an area with 30-50% reduction in perfusion ipsilateral to the transient ischemic attack. Three of these four patients developed an ipsilateral infarct 3-7 days later, but none of the eight patients with normal single-photon emission computed tomograms had a stroke during the following weeks. No difference in therapy, risk factors, severity of internal carotid artery disease, or timing of the technetium-99m study could explain these findings. We suggest that some transient ischemic attacks, though clinically identical to others, may be associated with persisting focal hypoperfusion, which predisposes to early stroke.