Introduction
Although a monogenic blood disorder, sickle cell disease (SCD) presents
with a progressive vasculopathy triggered by free heme, which causes
activation of endothelial cells, reticulocytes, neutrophils and
platelets1,2. Consequent nitric oxide depletion leads
to vasoconstriction, upregulation of adhesion molecules and endothelial
intima proliferation3,4. As a direct consequence of
this, SCD patients are prone to several complications including chronic
lung disease, leg ulcers and stroke5. The latter is
the most devastating of the complications and it is ischemic in affected
children, in whom it occurs in about 11% before the age of 20 years if
no specific intervention is instituted6. Arterial
stenosis usually occurs in the large vessels of the Circle of Willis,
especially the internal carotid, the middle and anterior cerebral
arteries.
Stroke tends to be recurrent in SCD; therefore, there is a need for
primary and secondary prevention by identifying patients at
risk6. Transcranial Doppler ultrasound imaging (TCDI)
is used for screening children with SCD and the STOP guidelines call for
patients with abnormal time-averaged mean of the maximum velocity
(TAMMV) of >200 cm/s to start prophylactic blood
transfusions to reduce the concentration of HbS7.
Hydroxyurea has also been shown to be effective for primary stroke
prevention, especially in resource-poor populations8.
Kuwaiti patients with SCD uniformly carry the Arab/India (A/I) haplotype
and have elevated HbF levels9,10. Stroke is relatively
rare in these patients, just as has been reported for other Arab Gulf
patients with SCD11. A previous TCDI study carried out
in Kuwait about 10 years ago did not identify any patients with abnormal
or conditional TAMMV in any of the cerebral
arteries12. The present study was therefore designed
to repeat TCDI as a follow up on the same patients to see if or how
their parameters have changed in the intervening years. Would the TAMMV
values remain in the normal range or would the effects of cumulative
vasculopathy be evident in elevated velocities? Or will the effects of
age produce lower velocities than in the initial study?