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(Stroke. 2003;34:2664.)
© 2003 American Heart Association, Inc.
Original Contributions |
From the Stroke Center, Neurological Institute (C.S., A.V.K., C.H., H.M., J.P.M.), Interventional Neuroradiology (H.C.S., J.P.-S.), and Medicine (R.R.S.), Columbia University College of Physicians and Surgeons, New York, NY; Department of Neurology, Universitätsklinikum Benjamin Franklin, Freie Universität Berlin, Berlin, Germany (C.S., A.H.); and Department of Neurology, Hôpital Lariboisière, Paris, France (C.S.).
Correspondence to C. Stapf, MD, Stroke Center/Neurological Institute, Columbia University College of Physicians and Surgeons, 710 W 168th St, New York, NY 10032. E-mail cstapf{at}neuro.columbia.edu
| Abstract |
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Methods The 542 consecutive patients from the prospective Columbia AVM database (mean±SD age, 34±15 years) were analyzed. Univariate statistical models were used to test the effect of age at initial presentation on clinical (AVM hemorrhage, seizures, headaches, neurological deficit, other/asymptomatic) and morphological (AVM size, venous drainage pattern, AVM brain location, concurrent arterial aneurysms) characteristics.
Results Hemorrhage was the presenting symptom in 46% (n=247); 29% (n=155) presented with seizures, 13% (n=71) with headaches, 7% (n=36) with a neurological deficit, and 6% (n=33) without AVM-related symptoms. Increasing age correlated positively with intracranial hemorrhage (P=0.001), focal neurological deficits (P=0.007), infratentorial AVMs (P<0.001), and concurrent arterial aneurysms (P<0.001); an inverse correlation was found with seizures (P<0.001), AVM size (P=0.001), and lobar (P<0.001), deep (P=0.008), and borderzone (P=0.014) location. No age differences were found for sex, headache, asymptomatic presentation, and venous drainage pattern.
Conclusions Our data suggest a significant interaction of patient age and clinical and morphological AVM features and argue against uniform AVM characteristics across different age classes at initial presentation. In particular, AVM patients diagnosed at a higher age show a higher fraction of AVM hemorrhage and are more likely to harbor additional risk factors such as concurrent arterial aneurysms and small AVM diameter. Longitudinal population-based AVM data are necessary to confirm these findings.
Key Words: aneurysm cerebral arteriovenous malformations intracranial hemorrhages seizures stroke
| Introduction |
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In this study, we analyzed the effect of patient age at initial presentation on demographic, clinical, and morphological AVM characteristics at the time of initial presentation.
See Editorial Comment, page 2669
| Subjects and Methods |
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2 times the width of the arterial vessel that carried the dilatation. They were further classified as feeding artery aneurysms, intranidal aneurysms (both considered AVM associated), and aneurysms unrelated to blood flow to the AVM (nonassociated aneurysms).16 A feeding artery was defined as any intracranial vessel that angiographically contributed arterial flow to the malformation. The AVM nidus was defined as the vascular mass included in the AVM size measurement. Intranidal aneurysms were coded when visualized early after angiographic injection, eg, before substantial venous filling had occurred. Infundibula, arterial ectasias (ie, dilated feeding vessels), and intranidal aneurysmal dilatations seen during the venous angiographic phase only were not coded as arterial aneurysms. Arterial aneurysms were coded as unrelated to the AVM when located on intracranial arteries not contributing blood flow to the AVM.
Statistical Analysis
Several standard statistical models (level of significance,
=0.05) were applied to test the effect of age on demographic (female sex), clinical (mode of presentation), and morphological (AVM size, anatomic location, venous drainage pattern, presence of arterial aneurysm subtypes) characteristics at the time of the diagnostic event.
In a first model, age at presentation was stratified into subsequent age classes in 10-year increments, as illustrated in Figures 1 through 4 ![]()
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, and comparisons were made with
2, analysis of variance (ANOVA), and Tukeys honestly significant difference (HSD) statistics. Based on Spearmans rank correlation, a second model analyzed age at presentation as a continuous variable and tested for linear correlations with the study variables. A third model tested for nonlinear correlations with squared continuous age values using logistic standardized likelihood estimates. If both linear and nonlinear correlations were found, additional log-linear models (likelihood ratio) and ANOVA statistics were applied to test the goodness of fit for each correlation. All analyses have been considered purely exploratory; therefore, no additional
level downward adjustments or multiple comparison procedures have been undertaken.
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| Results |
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60 years of age. The overall mean±SD age of the sample was 34±15 years.
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Demographic Characteristics
No significant sex differences were found between the predefined age classes, and no significant linear or nonlinear correlations with increasing age were seen (Table 2).
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Clinical Presentation
Almost half of the patients (247, 46%) initially presented with intracranial hemorrhage. The relative frequency of hemorrhagic AVM presentation differed significantly between age classes (Table 2). Figure 1 illustrates that the highest bleeding frequencies were found among patients in the lowest and highest age groups. As suggested by the shape of the age distribution for AVM hemorrhage, a squared correlation between age and hemorrhagic AVM presentation was found.
The relative frequency of seizures at initial presentation (155, 29%) was significantly different among the age classes (Table 2), with the highest values seen among AVM patients 20 to 29 and 30 to 39 years of age and no seizures detected after 60 years of age (Figure 1). A significant negative correlation between seizure occurrence and increasing age was found for both linear and squared age values (Table 2). The goodness-of-fit analysis was significant for the linear [
2 (df=1), 8.94; P=0.003], squared [
2 (df=1), 15.90; P<0.001], and both effects combined [
2 (df=2), 22.71; P<0.001].
Among patients presenting with a sudden or slowly progressing focal neurological deficit (unrelated to hemorrhage), no significant differences across different age groups were found (Table 2). The second statistical model analyzing age as a continuous variable, however, suggested a linear correlation with increasing age. Figure 1 illustrates that the highest relative frequencies were detected in patients 50 to 59 and
60 years of age.
As for headache and asymptomatic AVM presentation, neither showed significant differences between age classes or correlations with increasing age (Table 2).
Morphological Characteristics
Overall, the mean±SD maximal AVM nidus diameter in the sample was 33±17 mm. Size measurements differed significantly across different age classes (Table 2), with the largest nidus diameters seen in AVM patients 20 to 29 years of age (mean±SD maximal diameter, 37±17 mm; Figure 2). In the posthoc comparison (Tukeys HSD procedure; df=532,
=0.05), mean maximal size measurements differed significantly between the latter age class and patients 50 to 59 (mean±SD maximal diameter, 27±15 mm) and those
60 (mean±SD maximal diameter, 27±16 mm) years of age. Overall, significant linear and logarithmic correlations were seen between AVM size and increasing age. The goodness-of-fit analysis, however, was significant only for the linear (F(1.536), 6.19; P=0.013) not the squared (F(1.536), 2.74; P<0.098) trend, suggesting that the linear correlation may suffice to describe the effect of age on AVM size.
The relative frequency of a lobar AVM location showed significant differences across age classes (Table 2), with the highest numbers seen in the 3 median age groups. As suggested by the shape of the age distribution for lobar AVMs (Figure 3), no linear correlation with increasing age was found, but a negative logarithmic correlation with age was seen.
No significant differences between age classes were seen for AVMs in a deep brain location. In the second statistical model, however, a significant negative correlation with increasing age was found (Table 2). Figure 3 illustrates different proportions for deep brain AVMs, ranging from 22% patients in the lowest age group to 4% in those 50 to 59 years of age. No cases with a deeply located AVM were diagnosed in patients >60 years of age (Figure 3).
The occurrence of infratentorial AVMs showed significant differences between age classes, with the highest proportion seen among patients
60 years of age (Figure 3). Also, significant linear and logarithmic correlations with increasing age were found (Table 2). The goodness-of-fit analysis was significant for the linear [
2 (df=1),12.81; P<0.001], squared [
2 (df=1), 28.63; P<0.001], and both effects combined [
2 (df=2), 41.00; P<0.001].
Borderzone AVMs occurred in significantly different proportions across different age groups (Table 2), and significant negative correlations (both linear and logarithmic) with increasing age were found (Table 2). The additional goodness-of-fit analysis was significant for the linear [
2(df=1), 6.19; P=0.013], squared [
2 (df=1), 7.00; P=0.008], and both effects combined (
2 (df=2), 10.73; P=0.005).
The relative distribution of AVM patients harboring concurrent arterial aneurysms of any subtype showed significant differences between age classes (Table 2). Figure 4 illustrates the proportions, ranging from 3 (13%) in the lowest to 19 (63%) in the highest age group. Accordingly, Spearmans
statistics confirmed a significant linear correlation with increasing age. Similarly, robust linear correlations were found for both feeding artery and unrelated aneurysms, but none was seen for intranidal aneurysms (Table 2). Nonetheless, all 3 subtypes, including intranidal aneurysms, showed significantly different proportions across age classes (Table 2 and Figure 4).
No age effect was found for relative frequencies of different venous drainage pattern; neither could a correlation with increasing age be determined.
| Discussion |
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The clinically most relevant mode of AVM presentation, intracranial hemorrhage, occurred at significantly different proportions across age classes. In addition, the observed frequency of factors favoring the risk of AVM rupture such as AVM size7,11,17,18 and the presence of associated aneurysms8,16,1921 showed significant differences relative to age. For other modes of AVM presentation, the occurrence of symptomatic seizures also showed a significant association with age. The additional association of age with AVM size and borderzone location, both known predictors for AVM-related seizures,15,22,23 further supports the plausibility of these findings.
As for invasive treatment modalities, AVM size and deep venous drainage are recognized morphological risk predictors for surgical therapy outcome and are the basis for the well-established Spetzler-Martin grading scale.2427 Both factors may also play a role in risk prediction for endovascular treatment.2830 Although in our study venous drainage pattern did not show significant differences across different age classes, the mean maximal nidus size was significantly associated with age, trending toward lower AVM diameters with increasing age at presentation. One recent series already suggested an independent effect of age on the risk of AVM surgery,30 but further studies are necessary to confirm these findings.
Patients presenting after 60 years of age assemble several clinical and morphological features that may be unique to this subgroup. Clinically, no case presenting with AVM-related seizures was detected in these patients, but the highest proportion of hemorrhagic presentation (73%) was seen. None had been diagnosed with a deeply located AVM, but this group harbored the highest proportion of concurrent arterial aneurysms. Most surprisingly, this age class showed the smallest mean AVM diameter in the entire study cohort. This observation challenges the widely accepted notion that AVMs represent an embryonic disorder that, once it emerges, grows steadily over time. The significantly smaller nidus diameters in patients
60 years of age support the idea of late-onset AVMs, which may develop after birth and even during adulthood.31 The possibility of spontaneous AVM regression32 may add to the trend toward smaller nidus diameters at higher age, but because evidence for common AVM regression is lacking, its overall impact on the size curve may be limited. The relatively large nidus diameters seen in children <10 years of age may indicate relatively rapid AVM enlargement after the initial lesion has emerged. Whether the possibility of fast AVM growth is limited to young patients (as described for AVM recurrence after complete removal33,34) or may also occur in adults remains to be determined.
Patient age characteristics are a factor illustrating the limited comparability between referral center studies. A recently published comparison of 1289 AVM patients from 4 international treatment centers demonstrated significant age differences between the samples, most likely a result of local referral bias.35 The overall mean age of patients included in this meta-analysis (31 years; 95% confidence interval [CI], 30 to 32) is significantly different from the figure found in our own sample (34 years; 95% CI, 33 to 35) and clearly differs from prospective population-based estimates in the ongoing New York Islands AVM Study2 (35 years; 95% CI, 33 to 37; 2-tailed t test, P<0.001). These comparisons emphasize that in AVM natural history and treatment studies, only limited inferences on the total population of AVM patients can be made on the basis of single-center experience alone.
This is also true for our own analysis to which some additional methodological limitations may apply. All variables investigated were coded at the time of the diagnostic event and do not include follow-up data on possible changes in AVM characteristics. Hence, this cross-sectional study is merely observational and does not provide a longitudinal risk analysis. The patient sample is drawn from a large prospective data set, but because of as-yet-unknown population-based case fatality rates after AVM hemorrhage, referral center cohorts such as ours may underestimate the overall frequency of incident AVM hemorrhage and associated risk factors.36,37 Finally, referral bias to specialized treatment centers may significantly influence demographic, clinical, and morphological characteristics of the local patient cohort.35 The possibility of a systematic error in the data analysis can therefore not be excluded.
Overall, our data argue against the assumption of uniform AVM characteristics across different age classes at initial presentation. In particular, AVM patients diagnosed at a higher age seem to bear a higher proportion of AVM hemorrhage and are more likely to show additional risk factors (ie, concurrent arterial aneurysms and small AVM size). These findings suggest a
dynamic
risk exposure at different ages and may caution against stable annual risk predictions in patient counseling.38,39 Slowly accumulating data from prospective longitudinal and population-based surveys will allow more adequate risk predictions regarding AVM-related morbidity and mortality.2,40
| Acknowledgments |
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This work was supported by NIH grant R01 NS 4079201 (principal investigator, Dr Mohr). We thank S. Marshall for his reliable help and W.L. Young, MD, for his effort during the data collection process.
Received April 16, 2003; revision received May 15, 2003; accepted June 13, 2003.
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