- Stroke is a Major complication of sickle cell disease
- The naive clinician may assume that sickle cell anaemia is associated predominantly with sickling within small vessels as the mechanism of stroke, but this would be wrong.
- There is a poorly understood strong predisposition to large vessel intracranial disease with narrowing and occlusion of the internal carotids and middle cerebral vessels.
- The prevalence of Cerebral infarction by the age of 20 is 11%.
- Sickle cell related stroke disease often commences in childhood after the age of 2.
- Sickle cell disease is in fact the most common cause of stroke in children.
Age adjusted prevalence
|Sickle cell disease (homozygous) || 4.01% |
|S-ß0 thalassemia || 2.43% |
|S-ß+thalassemia ||1.29% |
|SC disease ||0.84% |
Sickle cell disease
- Sickle cell disease (SCD) is a group of inherited red blood cell disorders.
- People with SCD have abnormal haemoglobin, called haemoglobin S
- Those with SCD inherit two abnormal haemoglobin genes, one from each parent.
- These make haemoglobin S. When a person has two haemoglobin S genes, this is sickle cell anaemia the most severe kind of SCD.
- Haemoglobin SC disease and haemoglobin Sß thalassemia (thal-uh-SEE-me-uh) are two other common forms of SCD.
|Manifestations of Stroke and Sickle cell disease|
|Large vessel stroke disease : occlusion of MCA/ACA|
|Small vessel stroke disease |
|Silent infarction is common |
|Moyamoya type syndrome |
|Haemorrhagic stroke |
- Strokes are due to a culmination of large and small vessel disease and altered cerebral autoregulation
- Some are typically due to large-artery vasculopathy of the intracranial internal carotid arteries and proximal MCAs and occasionally the ACAs.
- Silent infarcts may be seen on MRI T2 may be seen in 21.8% of children between 6 and 19 years of age with SCD-SS
- Children with Transcranial doppler showing high velocities (suggests narrowing) of the MCA at increased risk.
- Red cell adherence to the endothelium mediated by von Willebrand's protein my be important.
- There may be collateralisation and a Moyamoya syndrome picture can develop.
- There is a risk of both Cerebral infarction and haemorrhage.
- SCD itself will cause fatigue, anaemia, haemolysis, sickling crises.
- Stroke related presentations will be related to ischaemia and strokes involving the large vessel MCAs and Carotid territory infarcts with related clinical syndromes in children.
- Penetrating small vessel strokes are often silent. Watershed infarction also seen.
- FBC: anaemia. U&E, LFT: Evidence of haemolysis
- Hb Electrophoresis: HbSS or HbSC
- Transcranial Doppler of the MCA: Useful for detecting intracranial stenoses and a velocity > 200 cm/second suggests at risk and at risk children should have annual screening as this is a major stroke risk factor.
- Non-Contrast CT acutely can determine if there is infarction and/or haemorrhage
- MRI/A for more detailed assessment: this may show occlusive intracranial internal carotid disease. There may be frank large vessel infarcts on borderzone lesions.
- Hb Electrophoresis
- ABC. Stroke Unit. Oxygen to achieve SAO2 94-98% and IV fluids as needed. Urgent Haematology consult. The role and risk and benefits of thrombolysis and thrombectomy is unclear.
- Acutely needs Manual or automated exchange transfusion to keep HbS at <30% and keeping Hb > 10g/dl suppresses erythropoiesis.
- Exchange transfusion: The STOP study showed that high risk children defined by high flow (> 200 cm/sec) on transcranial doppler benefited significantly from a programme of chronic transfusion. However chronic transfusions can be associated with risk of iron overload. Target is a HbS level < 30% of total Haemoglobin.
- Aspirin and Hydroxyurea (Hydroxycarbamide) may be considered and increases HbF. Hydroxycarbamide increases HbF. Aspirin is commonly also used but it may increase risk of haemorrhage.
- Prevention with prophylactic chronic transfusions is advised but associated with severe iron overload which may require chelation therapies.
- Stem cell transplantation is only long-term cure but is associated with multiple possible serious complications.
- Revascularisation surgery may be considered in those with a typical Moyamoya arteriopathy.