Therapy Insight: Stroke Risk and Its Management in Patients With Sickle Cell Disease

Fenella J. Kirkham

Disclosures

Nat Clin Pract Neurol. 2007;3(5):264-278. 

In This Article

Imaging

When a child with SCD presents with acute neurological problems, the priority is to conduct an exchange transfusion. As these patients are often admitted to a peripheral hospital without facilities for emergency imaging under general anesthesia, the literature on acute imaging is scanty. CT often does not show abnormalities within the first 24 hours after the onset of neurological symptoms. By contrast, diffusion-weighted MRI[22,23,44] (Figure 3A) can show ischemic regions within minutes—that is, before irreversible infarction has occurred—and T2-weighted MRI is usually abnormal within a few hours.

Diffusion and perfusion MRI. (A) Diffusion MRI shows abnormalities (arrows) in the patient with ciclosporin toxicity (Figure 1G). (B) Perfusion MRI abnormality throughout the right hemisphere and posteriorly on the left in an 11-year-old boy with sickle cell anemia who developed headaches after a chest crisis and was found to have high internal carotid artery and middle cerebral artery velocities on transcranial Doppler ultrasound (right vessels 200 cm/s; left vessels 161 cm/s).

In patients presenting with clinical stroke, neuroimaging might reveal a large infarct in the distribution of the middle cerebral artery,[45] or an abnormality in the basal ganglia, or deep white or grey matter of the border zones.[46] The involvement of these territories indicates proximal arterial pathology, whereas parieto-occipital or thalamic involvement should suggest venous sinus thrombosis.[25] Subarachnoid and intracerebral hemorrhage also occur, often in the context of acute hypertension,[20] or as a result of venous sinus thrombosis,[25] rupture of aneurysms (usually located at the bifurcations of major vessels, particularly in the vertebrobasilar circulation)[47] or rupture of fragile collaterals.[48]

Although it was assumed in the past that stroke in SCD was the result of sickling of red blood cells in the small cerebral vessels, this does not seem to be the direct cause in most cases. Between 60% and 90% of children with SCD and acute stroke in an arterial distribution have abnormal findings on conventional angiography or magnetic resonance angiography (MRA),[49] and there is also an association with seizures[8] (Figure 4). Typical abnormalities include stenosis (Figure 5A,B) or occlusion (Figure 5C) of the distal internal carotid or middle cerebral arteries,[10,50,51,52] which can be diagnosed as high time-averaged maximum velocity on transcranial Doppler ultrasound (TCD; Figure 4), a clinically important risk factor for stroke (see below).[53] Vertebral or internal carotid dissection,[12] moyamoya syndrome[48] (bilateral severe stenosis or occlusion of the internal carotid arteries with collateral formation; Figure 5D) and, occasionally, rarer patterns such as small-vessel vasculitis have also been documented. Moyamoya syndrome is associated with an increased risk of stroke recurrence.[48,54] Venous sinus thrombosis[24,25,42,43] (Figure 1E, Figure 6) is probably underdiagnosed because many patients do not undergo acute vascular imaging; if emergency MRA is available and the results are found to be normal, magnetic resonance or CT venography should be considered.

Transcranial Doppler velocities. Abnormal right middle cerebral artery (220 cm/s) and normal left middle cerebral artery (130 cm/s) in a 10-year-old girl with sickle cell anemia, focal tonic seizures (right side), transient ischemic attacks and headaches, on an exchange-transfusion program. Magnetic resonance angiography shows right proximal stenosis of the middle cerebral artery (bottom panel).

Magnetic resonance angiography (MRA). (A) Grade 1 turbulence in an asymptomatic child with sickle cell anemia and silent infarction. (B) Grade 2 turbulence in the right terminal internal carotid artery, A1 segment of the right anterior cerebral artery, right middle cerebral artery (M1 and M2 segments) and in the M1 segment of the left middle cerebral artery in a boy with HbSβ0-thalassemia (Figure 1B). (C) Middle cerebral artery occlusion in the girl with the large middle cerebral artery territory occlusion (Figure 1A). (D) Moyamoya in a child with sickle cell anemia and recurrent transient ischemic attacks.

Magnetic resonance venogram showing obliteration of the left transverse, sigmoid and straight sinuses in a patient with sickle cell anemia. The patient presented with headache, vomiting, drowsiness, papilledema and a sixth nerve palsy.

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