Professor David Rees is a consultant in paediatric haematology at King’s College Hospital, London. He has research and clinical interests in paediatric sickle cell disease, and other inherited red cell abnormalities, including porphyrias, thalassaemia and enzymopathies.
He trained at Cambridge University and St Thomas’ Hospital Medical School and has previously worked in London, Oxford and Sheffield. He spent six years in the Weatherall Institute of Molecular Medicine in Oxford doing research on haemoglobin disorders. He is involved in the care of more than 500 children with sickle cell disease and thalassaemia in southern England and active in clinical and laboratory-based research on haemoglobinopathies. He is a medical adviser to the Sickle Cell Society in the UK.
Abstract: Extracranial causes of stroke in sickle cell disease
Sickle cell disease (SCD) is one of the commonest causes of cerebrovascular disease in children in many countries. There is increasing evidence that the establishment of transcranial Doppler (TCD) screening as part of primary stroke prevention is reducing the incidence of overt stroke, and the epidemiology of cerebrovascular disease is changing in children with SCD.
Previously, most new overt strokes involved stenosis of large arteries in the anterior circulation, particularly the middle cerebral artery. This picture is decreasing in incidence, with a relative increase in ‘atypical’ strokes. In particular, stenosis of the extracranial internal carotid artery (eICA) is emerging as a cause of stroke, particularly in those with apparently normal TCD velocities. These extracranial strokes tend to occur in older children, and possibly adults, and stenosis of the eICA on Doppler ultrasound seems to be associated with an increased risk of overt stroke. It is not clear whether this type of stroke is preventable by the institution of regular blood transfusions blood transfusions or anti-platelet agents. eICA stenosis is often part of more generalised cerebrovasculopathy, but can occur in isolation. It is detectable using Doppler ultrasound, which can be undertaken during routine TCD studies using imaging technologies. Similarly, stenosis of the ICA within the petrous temple bone is increasingly recognised as a cause of stroke, which is not routinely detected using TCD. Skull infarction resulting in extradural haemorrhage is also a rare but recognised cause of stroke.
We have recently seen two cases in children, one of which was fatal. This may be part of the more general phenomenon of skull infarction which also causes proptosis and facial swelling. This is not linked to cerebrovascular disease and optimal management is not clear. The role of paradoxical embolism and thrombophilia is unclear in stroke in SCD.
In summary, TCD screening is changing the epidemiology of stroke in SCD, with extracranial causes becoming relatively more common.