Tentorial Venous Anatomy: Variation in the Healthy Population

Abstract

Background and purpose: A new transtentorial venous system consisting of medial, intermediate, and lateral tentorial veins, connecting infra- and supratentorial compartments, was recently shown in 2 cadaver dissections and 2 patient scans. We sought to characterize the venous patterns within the tentorium and their relation to measures of skull development in a cohort of healthy adults.

Materials and methods: We retrospectively reviewed tentorial venous anatomy of the head using CTA/CTV performed for routine care or research purposes in 238 patients. Included studies had adequate contrast opacification of venous structures and a section thickness of ≤2 mm; we excluded cases with space-occupying lesions and vascular pathologies. Tentorial angle, dural sinus configurations, and measures of skull base development were assessed as predictors of tentorial venous anatomy variation via Cramér V association, the binary encoded Pearson correlation, and nearest-point algorithm with the Euclidean distance metric for clustering.

Results: Tentorial vein development was related to the ringed configuration of the tentorial sinuses (P < .005). There were 3 configurations. Groups 1A and 1B (n = 50/238) had ringed configuration, while group 2 did not (n = 188/238). Group 1A (n = 38/50) had a medialized ringed configuration, and group 1B had a lateralized ringed configuration (n = 12/50). Measurements of skull base development were predictive of these groups. The ringed configuration of group 1 was related to the presence of a split confluens, which correlated with a decreased internal auditory canal-petroclival fissure angle. Configuration 1A was related to the degree of petrous apex pneumatization (P value = .010).

Conclusions: Variations in the transtentorial venous system directly correlate with cranial development.

FIG 1.

Transtentorial veins. A–C, 3D volumetric reconstruction of delayed-phase CTA of the head and neck; parenchyma (0–40 HU) has been segmented out, leaving the intracranial vessels filled with contrast. A, Reconstructed volume of the head is shown from the anteroposterior view with a 30° downward rotation to show the plane of the tentorium. B, The same reconstruction as in A is rotated to show the left side. C, The same reconstruction rotated to show the right side, which is symmetric. D–F, Source axial images for the volumetric reconstruction of this scan are shown; MTV, ITV, and LTV are labeled. ICV indicates the internal cerebral vein; SS, straight sinus; SPS, superior petrosal sinus; VGC, vein of Galen confluens; TS, transverse sinus; MTV, medial tentorial sinus.

FIG 2.

Schematic representation of 3 transtentorial vein configurations. The 2 groups of tentorial sinus configurations are shown; group 1, which is subdivided, has an RC, while group 2 does not. Regions of variation are shaded in purple, cross-hatching denotes sinuses, and veins are blue. The split confluens is shown for groups 1A and 1B. The degree of petrous apex pneumatization for each group is also shown. A, Configuration 1A has a medialized RC, and the ITV is interrupted by plexiform anastomosis to the RC or LTS. B, Configuration 1B has a lateralized RC, and the ITV is uninterrupted. C, In configuration 2, the RC is absent; the LTV connects the MTS to the LTS and the LTS to the superior petrosal sinus. Relevant draining sinuses are also shown. CS indicates cavernous sinus; ATV, apical tentorial vein; CBV, cerebellar bridging vein; ICS, intercavernous sinus; ISS, inferior sagittal sinus; MBV, mesencephalic bridging vein; PA, plexiform anastomosis; SpPS, sphenoparietal sinus; SS, straight sinus; SSS, superior sagittal sinus; VGC, vein of Galen confluens; VG, vein of Galen; TS, transverse sinus; SPS, superior petrosal sinus; C, confluens; TBV, tentorial bridging vein; ICV, internal cerebral vein.

FIG 3.

Association and correlation with clustering highlights common tentorial vein configurations. Left, Cramér V association heat map, a symmetric measure of associations among categoric variables, presents 2 intercorrelated variable groupings. The first shows a high-to-perfect association among the MTS origin, RC, ITV, and LTV. The second shows a moderate-to-high association among the cavernous sinus, LTS origin, transverse sinus, and MTV. Right, The Pearson correlation heat map reveals 2 primary configurations, one of which also has an alternate configuration based on the presence or absence of the ring connection of the MTS and LTS. In the first configuration, the RC is medialized. Due to the presence of the medialized RC originating from the MTS at the straight sinus, the tentorial veins have the following connections: The ITV is interrupted by the RC, and the LTV is lateralized, draining to the superior petrosal sinus. An alternate and slightly less common configuration comprises a lateralized RC and resultant medialized LTV. The second primary configuration has no RC, the ITV is interrupted by the LTS, and the LTV is also interrupted by the LTS. In this configuration, the MTS may be present or absent. IAC-PCF (left) and (right) (degrees); petrosagittal angle (left) and (right) (degrees); CC-JB distance (left) and (right) (millimeters); remaining variables are categoric. The ITV was categorized as 0 through 4 as per the result of preliminary categorization. LTV was categorized as 1 through 3 per results of preliminary categorization. female = 0; M1, male = 1.

FIG 4.

Tentorial vein and skull base measurement subset correlation with clustering and distribution plots. Left, The Pearson correlation heat map further characterizes the medialized RC with the ITV and LTV. This characterization confirms that when the RC of the MTS and LTS is present and medialized, the ITV and LTV originate from this connection and are lateralized (group 1A). The strongest associated configuration comprises this; the lateralized RC is confirmed (group 1B). The configuration with the absent RC between the tentorial sinuses is also again confirmed (group 2). This configuration appears related to the CC-JB distance and the tentorial angle in the heat map. Right, Y-axes in all charts are patient numbers. Probability density functions and kernel density estimates for skull base measurements, grouped by tentorial vein categories, reveal additional relationships. The distribution plots are shown for the right side of the tentorium only because symmetry is upheld as shown in the heat map. The probability density functions for LTV 3 and ITV 4 (configuration 1A) are nearly identical; this is inversely related to male sex, CC-JB distance, and petrous apex pneumatization 0 (less complete). This group is positively correlated to petrous apex pneumatization 1 (more complete). Group 1B has no correlation with petrous apex pneumatization; however, it is distinguished from group 2 by oppositional correlation to the IAC-PCF. The probability density functions and kernel density estimates of ITV 2 and LTV 1 (group 2) are very similar. IAC-PCF (left) and (right) (degrees); petrosagittal angle (left) and (right) (degrees); CC-JB distance (left) and (right) (millimeters); the remaining variables are categoric. ITV was categorized as 0 through 4 per the results of preliminary categorization. LTV was categorized as 1 through 3 per the results of preliminary categorization. F0 indicates female = 0; M1, male = 1; R, right; L, left.

FIG 5.

Dural sinus and skull base measurement subset correlation with clustering and distribution plots. Left, The Pearson correlation heat map further characterizes the relationship among the dural sinuses, cavernous sinuses, and skull base measurements. This confirms that an LTS originating in the transverse sinus is linked with a patent cavernous sinus. As a corollary, an LTS originating in the transverse sinus–sigmoid sinus junction is linked with a diminutive cavernous sinus. The clustering also reiterates the relationship between the RC presence and the location of the origin of the MTS. Right, Y-axes in all charts are patient numbers. Probability density functions and kernel density estimates for skull base measurements, grouped by dural sinus categories, provide additional support for the determined anatomic configurations. The distribution plots are shown for the right side of the RC only because symmetry was upheld as shown in the heat map. The probability density functions for LTS originating from the transverse sinus (LTS origin 0) and patent cavernous sinus (cavernous sinus 2) are similar; these show a weak positive correlation with the absent RC (configuration 2). Conversely, the probability density functions for LTS originating at the transverse sinus–sigmoid sinus junction (LTS origin 1) and a congenitally diminutive cavernous sinus (cavernous sinus 1) are similar, showing a weak positive correlation with the RC (configuration family 1). IAC-PCF (left) and (right) (degrees); petrosagittal angle (left) and (right) (degrees); CC-JB distance (left) and (right) (millimeters); the remaining variables are categoric. The ITV was categorized as 0 through 4 per the results of preliminary categorization. The LTV was categorized as 1 through 3 per the results of preliminary categorization. F0 indicates female = 0; M1, male = 1; R, right; L, left.