The natural history of stroke in sickle cell disease

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The occurrence and progression of strokes in patients with sickle cell disease and the resultant structural and functional defects were investigated by an indepth study of 35 patients, 32 of whom are part of a natural history study of 537 patients. The relative frequency for all ages is 6 per cent. Strokes are predominantly seen in patients with sickle cell anemia (33 with sickle cell anemia and two with heterozygous hemoglobin S and C (SC) disease). Twenty-five of the patients were less than 20 years old at the time of the first stroke—9.1 per cent of all patients observed during this age range. The actuarial or predictive risk of an initial stroke during the first two decades is 0.761 episodes per 100 person years whereas after age 20 the risk is 0.524 episodes per 100 person years. Children significantly at risk (p < 0.01) for cerebral infarction have a mean age at onset of 7.7 years (modal age of 5 years). Contrarily, adults have a significant risk for intracranial hemorrhage (p < 0.05). Five of the 23 patients who had a cerebral infarct died. No predictive factors such as prior illness rate, hemoglobin level, fetal hemoglobin content or previous neurologic symptoms identified the patient “at risk” prior to the first stroke. Follow-up of the patients with cerebral infarction for a mean observation time of nine years revealed a reoccurrence rate of 67 per cent. Temporal clustering of the recurrence within 36 months is the outstanding clinical feature of this group of patients, and 80 per cent of subsequent strokes occurred before 36 months. Each patient who survived showed a functional neurologic improvement immediately after the stroke but never regained the intellectual or neurologic status they had before the stroke. Residual neurologic deficit increased with each reoccurrence and 11 of the patients have permanent paralysis. Computerized tomography demonstrated structural damage with low density areas in all patients with cerebral infarcts. These patients were not treated with a transfusion program of antisickling agents. Subarachnoid or intracerebral hemorrhage occurred in 11 young adults ages 14 to 36 years, all with SS. Six of the 11 died, and structural vascular defects such as aneurysms were found in four. The susceptible person with SS experiences a definitive period of risk marked by recurrent stroke episodes following which no further strokes are likely to occur. Factors contributing to this cessation are unknown.