Overt strokes occur in approximately 5-10% of children with sickle cell disease.
Most common types of sickle disease genotypes associated with stroke are SS and S/beta thalassemia.
Ischemic stroke has a bimodal distribution -in children and older adults with sickle cell disease.
Ischemic strokes less common in adults aged 20-29, while hemorrhagic stroke more frequent at this age.
Most commonly recognized cause of neurologic injury are silent cerebral infarcts which are ischemic lesions detected on MRI exams.
Silent strokes are cerebral infarcts with a signal abnormality of minimal 3 mm on MRI in both axial and coronal views and which do not cause other neurologic examination abnormalities, but are associated with cognitive difficulties.
Among adults with sickle cell anemia, overt stroke is reported in 11% by age 20 years, and 24% by age 45.
Cumulative risk of stroke is 11.5% by 18 years of age, and 12.8% by 20 years of age.
Silent cerebral infarcts occur in 20-40% of children with sickle cell anemia.
The rate of silent ischemic stroke is estimated to be 53% in unselected adults with sickle cell anemia.
Patients with hemoglobin SS on the hiatus risk for stroke, both overt and silent.
The risk of ischemic stroke and sickle cell disease patients increases with age.
Transcranial Doppler ultrasound can detect patients with high stroke risk in children months-years before the stroke occurs.
Transcranial Doppler ultrasound measures blood flow velocity in the large arteries of the circle of Willis.
Because of anemia the velocity of the blood in the larger arteries of the circle of Willis are elevated, and become elevated in a focal manner when reduces the arterial diameter.
The velocity of 200 cm/S in children is associated with the highest risk for stroke, which is approximately 0.5-1% per year in children with sickle cell disease.
Presently there is no way to predict stroke adults with sickle cell disease.
Chronic blood transfusions reduces annual risk of stroke in children from 10% to less than 1%.
Transcranial Doppler ultrasound velocities can be reverted to low risk or moderate risk from high risk by transfusion therapy.
In the TWITCH study (transcranial Doppler with Transfusions Changing to Hydroxyurea) hydroxy urea work as well as blood transfusion as a substitute for an indefinite blood transfusion therapy children with elevated risk of stroke.
Presently, no optimal stroke prevention strategy for adults with sickle cell anemia exists, except for controlling comorbid conditions associated with stroke such as hypertension, hyperlipidemia, renal disease, atrial fibrillation, and coagulopathy.
Best diagnostic modality for patients with acute neurological symptoms and sickle cell disease is MRI with diffusion weighted imaging.
MRI imaging should occur within the first hour of onset of neurologic abnormalities.
MRI can differentiate between an ischemic or hemorrhagic stroke and can determine if the ischemic event occurred within the previous 10 days.
Treatment for acute stroke is an emergency exchange blood transfusion.
Initially, a simple blood transfusion can be provided if ahe hemoglobin is 10gm/dL or less.
Additional supportive measures iclude oxygen therapy to keep oxygen saturation above 95%, and blood cultures, antipyretics and antibiotics if required.
A second stroke or silent cerebral infarct occurs in 45% of children with sickle cell disease despite chronic blood transfusion therapy.