Regular blood transfusions were shown by DeBaun and coworkers to reduce the incidence or recurrent strokes from 14 to 6 percent over 3 years in sickle cell disease. Lee and colleagues demonstrated that exchange transfusions with monitoring of the velocities of flow in the middle cerebral artery by transcranial Doppler examination reduce the risk of this important neurologic complication. In the stroke prevention trial of sickle cell anemia, the risk of first stroke was reduced by 90 percent in 63 children who received periodic transfusions as compared to 67 children who received only supportive care.
Inevitably, most patients are seen first by clinicians who may not be expert in all the fine points of cerebrovascular disease. Situations arise in which critical decisions must be made regarding anticoagulation, further laboratory investigation, and the advice and prognosis to be given to the family. The following are some of the situations encountered by the authors that may be of value to students and residents and to nonspecialists in the field.
The Patient With a History of an Ischemic Attack or Small Stroke in the Past
The patient may be functioning normally when examined, but it has been ascertained by the history or radiologic procedures that a stroke or TIA occurred in the past. The problem is what measures should be taken to reduce the risk of further strokes. This is particularly problematic if a surgical procedure is planned. A brief focal TIA, several minutes or less in duration, or many stereotyped spells usually represent severe stenosis of the internal carotid artery on the side of the affected cerebral hemisphere. If the symptoms have occurred recently, these may be forerunners of complete occlusion. If the TIA was far in the past—more than several weeks previously—the immediate risks of occlusion are reduced. The initial approach is to establish the patency of the carotid arteries by ultrasonography or MRA. If there is a reduction in diameter of greater than 70 percent when compared with an adjacent normal segment of vessel, and probably if there is a severely ulcerated but not critically stenotic plaque, carotid surgery (or angioplasty with stenting) is advisable. If a single TIA lasted more than 1 h or the neurologic examination discloses minor signs referable to the region of the hemisphere affected by the TIA, a search for a source of embolus is indicated. Appropriate diagnostic studies include electrocardiography (ECG), a transesophageal echocardiogram, monitoring for cardiac arrhythmia, ultrasonography of the carotid arteries, and a CT or MRI if it has not already been performed. Control of elevated blood pressure and addressing high cholesterol levels are ancillary steps. The mistake is to ignore the potential significance of a prior small stroke or TIA.
The Patient With a Recent Stroke That May Not Be Complete
If hours have passed since the first symptoms of stroke but the syndrome is fluctuating or advancing, the basic problem is whether a thrombotic infarction (venous or arterial) will spread and involve more brain tissue; or if embolic, whether the ischemic tissue will become hemorrhagic or another embolus will occur; or if there is an arterial dissection, whether it will give rise to emboli. Therapies are controversial in most of these circumstances. In some centers, it is the practice to try to prevent propagation of a thrombus by administering heparin (or low-molecular-weight heparin) followed by warfarin, as discussed earlier. Some stroke deficits fluctuate with blood pressure, suggesting occlusion of the carotid or of another large vessel. Attention to adequate cerebral perfusion by omitting the patient’s usual blood pressure medications, ensuring adequate hydration and avoiding hemoconcentration, and potentially utilizing a head-down position may all assist in stabilizing the situation.
The Inevident or Misconstrued Syndromes of Cerebrovascular Disease