Article Figures & Data
Figures
- Fig 1.
Range of abnormalities shown by MR images of young patients with hemoglobin SS sickle cell disease.
A, T1-weighted MR image of a 4.3-year-old boy with bilateral lacunae in the centrum semiovale and paraventricular white matter. Image section is 3 cm thick. Image shows multiple lacunae, the largest of which is approximately 7 mm in diameter.
B, T1-weighted MR image of a 5.0-year-old girl with multiple small bilateral white matter lacunae in the centrum semiovale and the corona radiata. Image section is 3 cm thick. Image shows several lacunae, the largest of which is approximately 7 mm in diameter.
C, T1-weighted MR image of a 5.4-year-old boy with bilateral lacunar infarcts involving both frontal lobes and the centrum semiovale on both sides. Image section is 3 cm thick. Image shows two lacunae, the largest of which is approximately 6 mm in diameter.
D, Fluid-attenuated inversion recovery image of an 8.4-year-old boy with bilateral leukoencephalopathy in the centrum semiovale. Image section is 3 cm thick. Image shows abnormally high signal intensity. Because fluid-attenuated inversion recovery images null signal intensity from CSF, this is not a partial volume effect from the ventricle.
Tables
- TABLE 1:
Summary of abnormal MR imaging findings for patients with hemoglobin SS sickle cell disease
Finding No. of Patients Affected Proportion (%) Tortuous intracranial vessels by MR angiography 16 33 Any lacunar infarction 11 22 Tortuous intracranial vessels by MR angiography with no other abnormality 10 20 Multiple, bilateral frontal white matter lacunae 8 16 Mild-to-moderate arterial stenosis by MR angiography 7 14 Single frontal white matter lacune 4 8 Lacunar infarction in corona radiata/centrum semiovale 4 8 Encephalopathy/leukoencephalopathy 3 6 Note.—A total of 57% (28 of 49 patients) had abnormalities shown by either MR imaging or MR angiography, whereas 43% (21 of 49 patients) had abnormalities shown by MR imaging alone. The proportion of patients with any abnormal finding was calculated from a total of 49 patients evaluated. Because findings are not mutually exclusive, many patients are tabulated under more than one finding. Lacunar infarction was seen in 22% of all patients, and the majority of all lacunar infarctions were in white matter.
- TABLE 2:
Psychometric test scores of patients with sickle cell disease stratified by MR imaging findings
Comparison Normal MR Imaging Findings Abnormal MRI Δ Pooled t Test P < No. Mean ± SD No. Mean ± SD Mean hematocrit 30 25.0 ± 4.8 15 23.0 ± 5.8 −8.0% NS Full-scale IQ 33 81.1 ± 11.0 16 78.6 ± 16.1 −3.1% NS WISC-R FSIQ 10 83.0 ± 8.0 5 90.2 ± 10.5 +8.6% NS WISC-III FSIQ 23 80.2 ± 12.1 11 73.4 ± 15.7 −8.5% NS Verbal IQ 23 84.6 ± 12.3 11 74.1 ± 15.2 −12.4% 0.02 Performance IQ 23 78.9 ± 12.5 11 77.5 ± 16.3 −1.8% NS WISC-III factor scores VC factor 22 86.0 ± 12.9 11 74.4 ± 13.5 −13.5% 0.01 PO factor 23 80.0 ± 13.2 11 75.7 ± 16.4 −5.4% NS FD factor 22 89.0 ± 11.9 11 86.2 ± 17.2 −3.1% NS PS factor 20 85.3 ± 14.0 11 93.7 ± 19.9 +9.9% NS Note.—IQ indicates intelligence quotient; WISC-R (FSIQ), Wechsler Intelligence Scales for Children-Revised full-scale intelligence quotient; WISC-III FSIQ, Wechsler Intelligence Scales for Children-Version III full-scale intelligence quotient; VC, verbal comprehension; PO, perceptual organization; FD, freedom from distractibility; PS, processing speed; NS, not significant. When MR imaging findings were used to partition patients into those with normal MR imaging findings and those with abnormal MR imaging findings; few significant differences in psychometric test scores were observed. The Δ value was calculated as the percent reduction in psychometric test scores in the abnormal MR imaging group, as compared with test scores in the normal MR imaging group. A one-way pooled t test was used to test for significance because of a prediction that patients with abnormal MR imaging findings would have lower psychometric test scores. Patients with normal MR imaging findings were not significantly younger than patients with abnormal MR imaging findings, nor was there a significant difference in hematocrit.
- TABLE 3:
Psychometric test scores of patients with sickle cell disease stratified by hematocrit
Comparison Hematocrit ≥ 27 Hematocrit < 27 Δ Pooled t test P < No. Mean ± SD No. Mean ± SD Mean hematocrit 17 29.2 ± 3.2 28 21.4 ± 3.7 −26.7% 0.0001 Full-scale IQ 17 86.0 ± 13.8 28 76.9 ± 11.3 −10.6% 0.006 WISC-R FSIQ 6 90.5 ± 9.0 9 82.0 ± 8.1 −9.4% 0.04 WISC-III FSIQ 11 83.5 ± 12.4 19 74.5 ± 12.0 −10.8% 0.03 Verbal IQ 11 87.1 ± 12.5 19 77.1 ± 12.9 −11.5% 0.02 Performance IQ 11 82.7 ± 12.6 19 76.2 ± 12.2 −7.9% NS WISC-III factor scores VC factor 10 89.9 ± 13.4 19 77.0 ± 11.7 −14.3% 0.006 PO factor 11 84.0 ± 13.7 19 75.8 ± 12.9 −9.8% NS FD factor 10 96.2 ± 12.1 19 85.3 ± 13.3 −11.3% 0.02 PS factor 10 88.6 ± 11.7 18 87.7 ± 18.5 −1.0% NS Note.—IQ indicates intelligence quotient; WISC-R (FSIQ), Wechsler Intelligence Scales for Children-Revised full-scale intelligence quotient; WISC-III FSIQ, Wechsler Intelligence Scales for Children-Version III full-scale intelligence quotient; VC, verbal comprehension; PO, perceptual organization; FD, freedom from distractibility; PS, processing speed; NS, not significant. When hematocrit was used to partition patients into those with low hematocrit values (<27) and those with more normal hematocrit values (≥27), significant differences in psychometric test scores were observed: The Δ value was calculated as the percent reduction in the comparison value in the low hematocrit group, compared with the value in the more normal hematocrit group. A one-way pooled t test was used to test for significance because of a prediction that patients with low hematocrit would have lower psychometric test scores. Patients with low hematocrit were not significantly younger than patients with more normal hematocrit (9.6 versus 9.4 years, P = .43).
- TABLE 4:
Relationship of hematocrit to WISC-III scores in children with sickle cell disease
Test Measure or Factor Score Sample Size Correlation r = ANOVA P < Adjusted R2 WISC-III FSIQ 30 0.50 0.005 22.7 Verbal IQ 30 0.42 0.02 14.8 Performance IQ 30 0.46 0.01 18.8 WISC-III factor scores VC factor 19 0.50 0.006 22.2 PO factor 20 0.46 0.01 18.8 FD factor 19 0.39 0.04 12.2 PS factor 18 0.13 NS 0.0 Note.—WISC-III indicates Wechsler Intelligence Scales for Children-Version III; ANOVA, analysis of variance; FSIQ, full-scale intelligence quotient; IQ, intelligence quotient; VC, verbal comprehension; PO, perceptual organization; FD, freedom from distractibility; PS, processing speed; NS, not significant. Regression of hematocrit with full-scale intelligence quotient and with various sub-tests or factor scores of the WISC-III. The correlation (r) is reported, together with the level of significance calculated by analysis of variance. The proportion of variance in psychometric measures, explained by hematocrit (R2), is expressed as a percentage.
- TABLE 5:
Full-scale intelligence quotient as a function of MR imaging findings and hematocrit
Hematocrit ≥ 27 Hematocrit < 27 Average FSIQ Normal MR imaging findings 86.8 ± 9.9 77.5 ± 9.8 81.2 ± 10.7 n = 8 n = 12 n = 20 Abnormal MR imaging findings 75.0 ± 16.5 69.3 ± 14.3 71.0 ± 14.3 n = 3 n = 7 n = 10 Average FSIQ 83.5 ± 12.4 74.5 ± 12.0 77.8 ± 12.7 n = 11 n = 19 n = 30 Note.—FSIQ indicates full-scale intelligence quotient, as measured by the WISC-III in children cross-stratified by hematocrit and MR imaging findings. Multivariate analysis showed a significant effect of MR imaging findings on full-scale intelligence quotient (one-tailed, P = .016) and of hematocrit on full-scale intelligence quotient (one-tailed, P = .038). There was no significant interaction between MR imaging and hematocrit (P = .717), suggesting these factors are independent predictors of full-scale intelligence quotient.
Test Instrument Patient Score No. Control Score No. Reference WISC-R 88.8 126 Armstrong et al., 1996 77.7 21 94.3 21 Swift et al., 1989 82.7 43 88.0 30 Wasserman et al., 1991 72.3 28 73.5 19 Knight et al., 1995 85.7 31 92.0 31 Noll et al., 2001 85.4 15 Present study WISC-III 82.8 165 Wang et al., 2001 83.9 156 90.3 76 Bernaudin et al., 2000 81.8 41 Brown et al., 2000 86.0 30 92.1 15 Watkins et al., 1998 78.0 34 Present study Weighted mean 83.6 89.1 Note.—Mean full-scale intelligence quotient for 690 patients with sickle cell disease, as compared with 192 control participants. Data are from testing of patients and age- and race-similar control participants with the WISC-R or WISC-III. The weighted mean is an average of data from all studies, weighted for the number of study participants in each of the studies. If a conservative assumption is made that the SD of patient and control scores is ± 15, as in Wechsler normative data, then the difference in weighted mean between patients and control participants is significant (P < .000003). To be even more conservative, we then excluded studies that did not include control data collected concurrent with patient data or that derived control data from non-siblings, and we assumed that the sample size of patients was equivalent to the sample size of control participants. This left four studies (underlined), with a sample size of 142 patients and 142 control participants; the full-scale intelligence quotient difference between patients and control participants was still significant (P < .00001).
