Transcranial Doppler in Children With Hemoglobinopathies

Hemoglobinopathies

Transcranial Doppler ultrasonography (TCD) is a noninvasive, portable technique for evaluating the intracranial vasculature. TCD ultrasonography is performed placing a low frequency (≤ 2 MHz) transducer on the scalp of the patient, in order to visualize the intracranial arterial vessels through specific acoustic windows, where bone is thinner, and evaluate cerebral blood flow velocity (CBFV) . Patients diagnosed to have hemoglobinopathy conditions with its most common forms thalassemia and sickle cell disease manifest both biochemical and clinical evidence of hypercoagulability conditions include deep venous thrombosis, pulmonary emboli and recurrent arterial occlusion . Cerebrovascular accidents can be identified using transcranial Doppler ultrasonography which enables evaluation of cerebral artery blood flow velocity with a sensitivity of 90% and specificity of 100 % when compared with cerebral angiography . According to the stroke prevention trial in sickle cell anemia (STOP) study ,TCDs were classified based on blood velocity in the circle of Willis, expressed as time averaged mean of the maximum velocity (TAMMV). Children with abnormal, high velocities (\>200cm/s) were at increased risk of stroke, which was reduced by 90% after starting regular blood transfusions. TAMMVs less than 170cm/s were classified as normal with annual TCD scanning recommended, whereas velocities between 170 and 200cm/s were called conditional, and followed up more closely without starting transfusion.

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