Variations of Intracranial Dural Venous Sinus Diameters from Birth to 20 Years of Age: An MRV-Based Study

DISCUSSION

Our study of 429 MR venograms demonstrates the patterns of development of the major sinuses of the DVS system from birth to 20 years of age. Three important findings are evident: First, dural venous sinuses, in general, demonstrated maximal growth between 0 and 7 years of age, and most sinuses reached adult size around 7–10 years of age. This finding emphasizes the postnatal plasticity of the DVS system. Second, a higher prevalence of the persistent prenatal sinuses was found in younger age categories compared with older categories, implying that involution of these sinuses continues to take place after birth into childhood but largely ceases in early adulthood. Finally, we found no difference in patterns of transverse venous sinus drainage across age categories, suggesting that transverse venous sinus dominance patterns are maintained into early adulthood.

The main finding from our study is that postnatal growth of the DVS system continues until 10 years of age after which diameters remain stable. These findings track closely with the rates of head circumference growth as well as growth of the intracranial arteries across time.⁶ There are important clinical implications to understanding the rate of change of the cerebral venous system across time. For example, with the growing use of venous sinus stent placement for treatment of idiopathic intracranial hypertension in adults, there have been several reports in the literature describing venous sinus stent placement to treat pediatric patients.^7⇓-9 An understanding of normal age-related venous sinus diameters would be important for device sizing and treatment planning in these patients. There are also growing reports on mechanical endovascular recanalization of venous sinus thrombosis in the pediatric population, and again, having an understanding of the normal venous sinus diameters would be important for sizing of thrombectomy devices.^10,11

Our data suggest a gradual involution of the occipital and persistent falcine sinuses from birth to 20 years of age. The occipital sinus originates from the torcular plexus and is discernable as early as the third gestational month.^12,13 Secondary to increased hemodynamic burden within the developing posterior fossa, the occipital sinus demonstrates a rapid expansion in the fourth and fifth gestational months, followed by diminution in the sixth and seventh months.^12,13 The presence of an occipital sinus in postnatal life is, therefore, less commonly observed. Similar to the pattern observed in the current study, Widjaja and Griffiths⁵ found an occipital sinus in 9 of 50 patients (18%), most of whom were younger than of 2 years of age, and none were found in those older than 9 years of age. Additionally, Mizutani et al¹⁴ found that 6 of 13 infants (46.2%) had an occipital sinus, compared with only 3 of 35 adults (8.6%), suggesting that persistent occipital sinuses largely regress by adulthood.

Persistent falcine sinuses are exceptionally rare and are typically present in the context of absent, hypoplastic, or occluded venous outflow tracts.^15,16 This observation implies that alterations in cerebral venous flow dynamics may result in recanalization of the falcine sinus. In the current study, we observed a trend in which the prevalence of the persistent falcine sinus decreased across age categories; this trend may suggest that venous outflow dynamics normalize with increasing age, thereby prompting involution of the falcine sinus. One separate study found no difference in the prevalence of persistent falcine sinuses between infants and adults.¹⁴ This finding is likely due to small sample sizes, however, given that persistent falcine sinuses have an exceptionally low prevalence overall. The findings of the current study relating to the prevalence of the falcine and occipital sinuses demonstrate the dynamic nature of the DVS system in younger age categories.

Prenatal formation of the transverse venous sinuses is characterized by rapid expansion in the fourth fetal month, which is followed by contraction to a relatively stable diameter at 7–8 months of fetal life.^12,13,17 Much variation exists within the anatomic patterns of the transverse venous system. Although many individuals have a codominant transverse venous system, a large proportion of the population exhibits unilateral dominance, typically on the right, suggesting that a single transverse sinus is sufficient in providing outflow for the superficial venous system.^13,18 Nevertheless, changes in transverse sinus dimensions to compensate for altered flow mechanics may occur.¹⁹ Our data here demonstrate that transverse sinus patterns do not change as a result of increasing age, suggesting that the in utero establishment of a transverse sinus–dominance pattern is sufficient for maintaining adequate venous drainage from birth into adulthood. Our study may be limited in the conclusions that may be drawn in this regard; however, the transverse sinuses were found to be codominant in every age group other than the 6- to 10-year-old patients, suggesting that the dural venous sinuses are still developing in younger children and that 1 transverse sinus becomes unilaterally dominant by 6–10 years of age. If this scenario were the case, however, this pattern of transverse sinus dominance would be prevalent in adulthood as well. Given that this pattern was not found to be prevalent, this issue suggests a potential sampling error in our study. Further study is, therefore, warranted to more fully elucidate developmental patterns of the transverse sinus system.

Fetal development of the cerebral DVS system is highly complex and begins early in fetal development.^5,13 The findings from our study highlight the incredibly dynamic nature of the dural venous sinus system with rapid growth of some sinuses and regression of others in postnatal life and into early childhood. The dynamic character of the cerebral venous system and its role in the pathogenesis of various intracranial vascular malformations has only recently been acknowledged.² For example, several reports of de novo formation of vascular malformations with venous components imply active pathogenetic involvement of the venous system.^20⇓-22 Our understanding of the role of the venous system in various pathologic states continues to evolve.

Important limitations of this report must be considered. Our study population was heavily skewed toward those 16–20 years of age; therefore, the prevalence of embryonic sinuses may be underestimated in the younger age categories. Our study is prone to selection bias for 2 reasons: All those who had MRV studies had a clinical indication for imaging, and the patient population was obtained from a single quaternary referral center.

Most important, a minority of studies (n = 23.8) were not performed with contrast, possibly resulting in suboptimal measurements. Our measurements were made on 3D MR venograms, which may make it difficult to ascertain the true diameter of a 2D structure (ie, the diameter of the lumen of a given venous sinus). Ideally, measurements would be made on a 2D image on which the image section is perpendicular to the long axis of the vessel. However, our validation analysis found no differences between measurements made on 3D and 2D; therefore, our measurement protocol was sufficient for the purposes of this study. Future studies should adopt stringent quality control measures with regard to the technical aspects of each study because various physiologic and imaging-based parameters may potentially affect the measured diameter of each DVS system component. Future studies should also consist of multiple measurements made by multiple authors for validation purposes.