The significance of inadequate transcranial Doppler studies in children with sickle cell disease

Abstract

Sickle cell disease (SCD) is a common cause of cerebrovascular disease in childhood. Primary stroke prevention is effective using transcranial Doppler (TCD) scans to measure intracranial blood velocities, and regular blood transfusions or hydroxycarbamide when these are abnormal. Inadequate TCD scans occur when it is not possible to measure velocities in all the main arteries. We have investigated the prevalence and significance of this in a retrospective audit of 3915 TCD scans in 1191 children, performed between 2008 and 2015. 79% scans were normal, 6.4% conditional, 2.8% abnormal and 12% inadequate. 21.6% of 1191 patients had an inadequate scan at least once. The median age of first inadequate scan was 3.3 years (0.7–19.4), with a U-shaped frequency distribution with age: 28% aged 2–3 years, 3.5% age 10 years, 25% age 16 years. In young children reduced compliance was the main reason for inadequate TCDs, whereas in older children it was due to a poor temporal ultrasound window. The prevalence of inadequate TCD was 8% in the main Vascular Laboratory at King’s College Hospital and significantly higher at 16% in the outreach clinics (P<0.0001), probably due to the use of a portable ultrasound machine. Inadequate TCD scans were not associated with underlying cerebrovascular disease.

Transcranial Doppler and Magnetic Resonance in Tanzanian Children With Sickle Cell Disease

“…Absent/low CBFv in the ICA/MCA may be secondary to extracranial stenosis or occlusion with low distal flow (not excluded as neck vessel imaging was not performed), as well as intracranial disease, demonstrated on MRA in 50% of low and 42% of absent TCD in this study, or to difficulties in obtaining signal through a thick skull. 10…”

“…Magnetic resonance angiography (MRA) detects intracranial arteriopathy. 8 Stenosis or occlusion of the intracranial arteries may be detected with transcranial Doppler (TCD), measuring cerebral blood flow velocity (CBFv); abnormal internal carotid artery (ICA)/middle cerebral artery (MCA) CBFv (>200 cm/s) occurs in 2.8% to 10% of children 9,10 and predicts clinical stroke. 11 Low anterior cerebral artery and MCA CBFv may also predict stroke and SCI, 12 but there is an overlap with those with inadequate TCD; 10 there are few data comparing TCD with MRA in this group.…”

Practice patterns for stroke prevention using transcranial Doppler in sickle cell anemia: DISPLACE Consortium

“…Practice standards vary as to whether lower parameters are applied for categorizing TCDi results. According to some investigators, there is consensus that parameters set in STOP protocol for dedicated Doppler can be applied to TCDi. However, McCarville et al recommended parameters for classifying TCD results using TCDi that are 10% lower than STOP protocol for dedicated Doppler, that is, TAMM values of 180 cm/s or more for abnormal result, and 153 to 179 cm/s for conditional result.…”

“…A recent study conducted in the United Kingdom applied more stringent criteria than STOP to better characterize inadequate TCD findings in children with SCA. This protocol defined inadequate as any study in which none of the 10 vessels could be measured for any reason . Most frequently, our study site PIs defined inadequate in accordance with STOP protocol; however, approximately two‐thirds of sites used other methods, which may represent adoption of protocols similar to those used in the United Kingdom.…”

“…Among individuals in STOP studies who experienced stroke, fewer (9%) had an inadequate TCD immediately prior to the stroke event than normal, conditional, or abnormal . In their in‐depth exploration of inadequate TCD results, Greenwood et al found that nearly 75% of individuals with an inadequate scan had a subsequent normal scan; <5% had a subsequent abnormal scan and none had subsequent stroke. A poor temporal window and lack of patient cooperation were the most common causes for an inadequate result.…”