ASSESSMENT OF STROKE RISK BY DETERMINING CEREBRAL BLOOD FLOW VELOCITIES AND OTHER SELECTED FACTORS IN CHILDREN WITH SICKLE CELL ANAEMIA IN LAGOS

Abstract

Sickle cell anaemia confers a higher risk of childhood stroke than any other paediatric disease..
The risk of stroke in sickle cell anemia is predictable and preventable. This risk can be determined
by using transcranial Doppler ultrasonography to measure cerebral blood flow velocities in the
major arteries of Circle of Willis and prophylatically transfusing with genotype AA blood those
with more than 200cm/seconds by maintaining haemoglobin S concentration at less than 30%, thus
reducing the stroke risk by 92%, hence making primary prevention a reality.
A descriptive cross sectional study was done to assess stroke risk by determining the pattern
cerebral blood flow velocities and other selected factors in children with sickle cell anaemia in
Lagos. The study was carried out among three hundred and fifteen children with sickle cell
anaemia and three hundred and fifteen children with genotype AA, aged and gender matched,
systematically recruited from the Paediatric Haematology, Well Child and Out-Patient Clinics of
Lagos University Teaching Hospital and at the Sickle Cell Foundation-Nigeria, both in Idi-Araba
over a period nine months Ethical approval was obtained prior to study At every clinic, consent
and assent were obtained, semi-structured questionnaires were distributed to collect clinical data
and venepuncture were carried out to collect blood for haematological data. Transcranial Doppler
scan was used to measure their cerebral blood flow velocities. The mean cerebral blood flow
velocities were significantly higher in subjects than controls (p< 0.05). All the children in the
HbAA group had normal cerebral blood flow velocities. The highest velocities were recorded in
the middle cerebral artery and internal carotid artery in both studied population. The pattern of
stroke risk classification in children with sickle cell anaemia using Adam’s criteria showed that 173 (54.9%), 115 (36.5%) and 27 (8.6%) had standard, conditional and high risks respectively.
Higher diastolic blood pressure, lower haemoglobin, higher total white cell count, and lower
arterial oxygen saturation were predictors of abnormal cerebral blood flow velocities and without
exception increased stroke risk in children with sickle cell anaemia
This study showed that children with sickle cell anaemia have considerably high elevated cerebral
flow velocities (TAMMV > 170 cm/sec) presenting in 46% with 8.6% out of every hundred at
risk of primary stroke (TAMMV > 200 cm/sec). However none of the children with HbAA
genotype had elevated cerebral blood flow velocities. Thus those with these selected factors that
predicted high cerebral blood flow velocities should be given priority for transcranial Doppler
examination especially in resource-limited areas. In addition routine use of transcranial Doppler
to measure cerebral blood flow velocities should be advocated by all paediatricians and health
policy makers in order to reduce the burden of primary stroke

ASSESSMENT OF STROKE RISK BY DETERMINING CEREBRAL BLOOD FLOW VELOCITIES AND OTHER SELECTED FACTORS IN CHILDREN WITH SICKLE CELL ANAEMIA IN LAGOS