MRA OF THE INTRACRANIAL CIRCULATION IN ASYMPTOMATIC PATIENTS WITH SICKLE-CELL DISEASE

Background. MR angiography (MRA) provides a mechanism for non-invasive ly studying blood flow thus providing a new opportunity to study the i ntracranial circulation in asymptomatic sickle cell disease (SCD) pati ents. Although conventional angiography is the gold standard for the d epiction of vascular anatomy, this is too invasive for an asymptomatic population. Objective. To establish the range of appearances in asymp tomatic SCD patients and to correlate brain MRI results (either sub-cl inical abnormalities or normal brain parenchyma) with the MRA findings . Materials and methods. Brain MRT and MRA of the intracranial circula tion was performed on 22 patients (13 male and 9 female, median age 7. 5 years, range 1.3-20 years). Fourteen were homozygous SS and eight we re SC. The median haematocrit at the time of MRI was 25.9 (range 13.8- 33.3). Results. On MR imaging, four patients had infarcts in eight vas cular territories (six anterior and two posterior). In 3/4 of anterior vascular territories with infarction, long (greater than or equal to 6 mm) segments of abnormal signal were seen at the internal carotid ar tery bifurcation with associated reduced distal now. Short focal areas of abnormal signal were commonly seen where vessels branched, bifurca ted or curved and were not associated with infarcts. These areas proba bly represent turbulence-related dephasing secondary to high velocity flow found in SCD. Conclusion. Long segments (greater than or equal to 6 mm) of abnormal signal with reduced distal flow correlated with sub -clinical infarction.