Abstract
The Stroke Prevention Trial has confirmed that utilization of transcranial Doppler ultrasonography (TCD), which examines blood flow in large intracranial vessels, can identify children with sickle cell disease (SCD) who are at high risk of developing a premature stroke. It is not known to what extent the vasculopathy in SCD involves small vessels and whether the abnormalities, if present, correlate with large-vessel vasculopathy. Eighteen children with SCD were examined with TCD to determine middle cerebral artery (MCA) velocity and computer-assisted intravital microscopy (CAIM) to determine bulbar conjunctival vessel velocity during the same visit for vasculopathy correlation. High MCA velocity (> or = 200 cm/sec) was found by TCD in 4 patients who also showed abnormal conjunctival velocity (< 0.2 mm/sec or intermittent trickle flow) by CAIM. Three patients had conditional (> or = 170 cm/sec and < 200 cm/sec) MCA velocity: 2 showed abnormal (trickle) and 1 showed normal conjunctival velocity (1.9 mm/sec). One patient with unmeasurable MCA velocity had abnormal (trickle) conjunctival velocity. Of the remaining 10 patients who had normal MCA velocity, 2 showed abnormal (0.05 mm/sec and 0.1 mm/sec) and 8 showed normal conjunctival velocities (1.1-2.4 mm/sec). The MCA velocities correlated significantly with bulbar conjunctival flow velocities (P < or =.008, Fisher exact test). A correlation exists between MCA (large-vessel) and conjunctival (small-vessel) flow velocities. CAIM is a noninvasive quantitative technique that might contribute to the identification of SCD patients at high risk of stroke. Small-vessel vasculopathy might be an important pathological indicator and should be further explored in a large-scale study. (Blood. 2001;97:3401-3404)
Highlights
Cerebrovascular disease, the most serious complication in homozygous (HbSS) sickle cell disease (SCD) patients, most often results from occlusion or reduction of cerebral blood flow of major intracranial arteries.[1,2] Cerebral infarction with acute neurologic deficits affects 5% to 17% of SCD patients by 15 years of age.[1,2,3,4,5,6] The Cooperative Study of SCD recently reported the chances of having a first cerebrovascular accident by 20, 30, and 45 years of age were 11%, 15%, and 24%, respectively, for HbSS patients.[7]
Small vessels can readily be noninvasively assessed in the bulbar conjunctiva, but it is not known whether large-vessel (MCA) vasculopathy correlates with small-vessel abnormalities
Adams et al clearly showed that SCD patients having middle cerebral artery (MCA) or internal carotid artery (ICA) velocities more than 200 cm/sec have a 40% chance of having a stroke during a 40-month period, while patients with velocities between 170 and 200 cm/sec had only a less than 7% chance of stroke during the same period.[2,10,18]
Summary
Cerebrovascular disease, the most serious complication in homozygous (HbSS) sickle cell disease (SCD) patients, most often results from occlusion or reduction of cerebral blood flow of major intracranial arteries.[1,2] Cerebral infarction with acute neurologic deficits affects 5% to 17% of SCD patients by 15 years of age.[1,2,3,4,5,6] The Cooperative Study of SCD recently reported the chances of having a first cerebrovascular accident by 20, 30, and 45 years of age were 11%, 15%, and 24%, respectively, for HbSS patients.[7]. Transcranial Doppler ultrasonography (TCD) has been used to measure blood flow velocity in the intracranial arteries of the circle of Willis, including the internal carotid artery (ICA) and the middle cerebral artery (MCA).[10,11] Focal elevation of velocity, via TCD measurement, usually indicates arterial stenosis because flow velocity is directly related to cerebral blood flow and inversely related to arterial diameter.[10] The Stroke Prevention Trial in Sickle Cell Anemia (STOP) has confirmed that utilization of TCD to identify high MCA velocity is predictive of high risk and vulnerability for stroke in children with SCD.[2,3,8,10] Small vessels can readily be noninvasively assessed in the bulbar conjunctiva, but it is not known whether large-vessel (MCA) vasculopathy correlates with small-vessel (conjunctival) abnormalities. Solely to indicate this fact, this article is hereby marked ‘‘advertisement’’ in accordance with 18 U.S.C. section 1734
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