Background In a retrospective analysis over 15 years (1988-2002) we estimated the incidence of stroke in our paediatric sickle cell disease (SCD) patients to be 5.4%(1), significantly less than figures from North America. We now report the initial results of our prospective study, against a background of on-going Tran-Cranial Doppler (TCD) studies, which have been shown to be effective in identifying children with SCD who are at an increased risk of stroke.

Objectives Using close monitoring by TCD, to estimate the annual incidence of stroke and stroke risk in a cohort of Nigerian children with SCD.

Methods Sixty-six consecutive children screened for stroke risk by TCD were followed up for a period of 12 months. All those with standard risk (SR) velocities (<170 cm/sec) had a repeat TCD scan one year after the first examination while those with abnormal velocities (>170 cm/sec) had a repeat study every 3 months. All were assessed for clinical signs of stroke and any significant changes in their cerebral blood flow velocities, leading to a classification of stroke risk. All the children with high risk velocities were offered the option of periodic blood transfusion for primary stroke prevention.

Results Forty-two males and 24 females were studied. Their ages ranged from 37 to 197 months, (mean +/- SD, 98 +/- 40). At first TCD examination, 40 (60.6%) had SR velocities, 21 (31.8%) had conditional risk (CR) velocities and 5 (7.6%) had high risk (HR) velocities. At subsequent TCD examinations, 4 (19%) of the 21 children with CR velocities had converted to high risk and 6 (15%) of the 40 children with SR velocities had become CR. Two children developed a stroke, one in the HR group and one in the CR group. This gives a stroke incidence rate of (2/66) 3.0% overall, but (1/21) 4.8% and (1/5) 20.0% for CR and HR, respectively.

Conclusion These data suggest that the incidence of stroke in Nigerian children is actually different from the rates in North America. If similar figures are confirmed as our study progresses, it would be important to find explanations for this observation.