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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=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. |
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