Transcranial Doppler sonography in children with sickle cell disease and silent ischemic lesions

Background

Sickle cell disease (SCD) is considered the most frequent cause of stroke in childhood. According to the STOP (stroke prevention trial in sickle cell anemia study) criteria, patients with abnormal values (>200 cm/s) of time-averaged mean velocities of maximum blood flow (TAMM), detected by transcranial Doppler sonography (TCD), should undergo blood transfusion in order to reduce the risk of ischemic stroke. However, patients with normal TAMM might harbor silent strokes on magnetic resonance imaging (MRI) scan. Our aim was to verify whether SCD patients with normal velocities but with a significant side-to-side asymmetry of TAMM are more prone to develop silent strokes.

Subjects and methods

Thirty-one consecutive SCD patients, (15 females; mean age: 9.23 ± 3.66 years), categorized as “normal” according to the STOP protocol (<170 cm/s) and without a history of blood transfusions and TIA/stroke, underwent a cerebral MRI scan and complete TCD evaluation in order to detect significant asymmetries in the main intracranial arteries. Then, we subdivided this cohort into two groups according to the detection of TAMM asymmetry: “normal and symmetric” (NS), “normal and asymmetric” (NA).

Results

We found 13/31 patients (41.9%) harboring a significant TAMM asymmetry (NA group), while brain MRI detected silent ischemic lesions in 13/31 (41.9%) patients. No significant differences were found between NA and NS regarding silent strokes frequencies (Chi-square test with continuity correction, χ² = 0.598), lesion number (t-student test, p = 0.09) and lesion burden (t-student test, p = 0.227).

Conclusion

According to our study, TAMM asymmetry is not a significant predictor of silent cerebral ischemia.