Anatomical Variations of Superior Sagittal Sinus and Tributary Bridging Veins: A Cadaveric Study

Background and objective

Injuries to the parasagittal cerebrovenous structures may lead to devastating complications. Being aware of the inherent anatomical heterogeneity in the region might lower the rate of undesirable outcomes. In this study, our goal was to characterize the superior sagittal sinus (SSS) positioning in relation to the midline and depict tributary bridging veins (BVs) distribution over the lateral surface of the cerebral hemispheres.

Methods

We performed anatomical dissections of the brain in 10 cadaveric specimens (five females and five males; median age: 52 years, range: 44-74 years). Measurements (in mm) of the SSS width and deviation of its lateral margin from the midline were obtained along the entire length of the structure at six craniometric points [at mid-distance between Nasion and Bregma (½ N-B); at Bregma (B); in the middle of the Bregma-Lambda segment (½ B-L); at Lambda (L); halfway between Lambda and Inion (½ L-I); and at Inion (I)]. The count, diameter, and lateral insertion points of the draining BVs were also documented in three segments [Nasion-Bregma (N-B), Bregma-Lambda (B-L), and Lambda-Inion (L-I)].

Results

The width of the SSS increased progressively along the direction of the blood flow (p<0.01). There was an SSS lateral deviation bias to the right, but the comparison failed to reach the significance level (p=0.12). The maximal lateralization of the SSS in the pre-Lambdal interval was 13.1 mm on the right side and 11.7 mm on the left side. These values increased up to 19.8 mm and 15.1 mm in the torcular area on the right and left sides, respectively. A total of 191 BVs were identified (a mean of 19.1 ± 2.5 per individual). The L-I segment showed a lower number of BVs as compared to its N-B and B-L counterparts (mean: 0.9 ± 0.6 vs. 8 ± 1.8 and 10.2 ± 2, respectively, p<0.01). Along the entire span of the SSS, the average diameter of the BVs was larger on the right side (mean: 1.4 ± 0.9 mm vs. 1.1 ± 0.8 mm on the left, p<0.01). The average lateralization of BVs dural entry points was lower on the left side in the B-L segment (mean: 5.6 ± 6.4 mm vs. 8.8 ± 6.7 mm on the right, p<0.01). There was a statistically significant trend of decreasing BVs lateralization with each consecutive SSS segment (mean: 10.9 ± 7.4 mm in the N-B segment, 7.3 ± 6.7 mm in B-L, and 1.6 ± 1.2 mm in L-I, p<0.01). The maximal lateral deviation of BVs insertion points was 33.6 mm in N-B, 30 mm in B-L, and 4.1 mm in L-I portions of the SSS.

Conclusions

In most cases, the SSS deviated laterally from the midline, up to 13 mm in the pre-Lambdal segment and up to 20 mm in the torcular area. Right-sided BVs were of larger average diameters. The lateral insertion points of BVs decreased along the rostrocaudal span of the SSS.

Imaging of Neurologic Disorders Associated with Pregnancy and the Postpartum Period

Diverse pathologic conditions affect the central nervous system (CNS) and pituitary gland during pregnancy and the puerperium. Some are specific to the physiologic process of reproduction (eg, eclampsia, postpartum cerebral angiopathy, Sheehan syndrome, lymphocytic adenohypophysitis). Others are nonspecific but occur more often in pregnant women (eg, cerebral infarction, dural venous thrombosis, pituitary apoplexy). Recognition of the characteristic imaging findings in eclampsia, for example, may allow exclusion of other disorders. Even when imaging changes are nonspecific, knowledge of those entities associated with pregnancy and awareness of the increased likelihood of certain diseases in pregnancy will allow a more informed differential diagnosis. Differentiation of primary nonaneurysmal subarachnoid hemorrhage (SAH) from aneurysmal SAH is an example. Moreover, earlier use of imaging will result in fewer delayed diagnoses. For example, magnetic resonance venography allows early diagnosis of cerebral venous thrombosis. Even when the imaging changes are less specific, knowledge of likely possibilities will lead to more appropriate earlier use of imaging. For example, the stimulatory effects of pregnancy on prolactinoma, meningioma, hemangioblastoma, vestibular schwannoma, and metastatic tumors such as breast cancer and choriocarcinoma suggest the early use of CNS imaging to avoid the consequences of a delayed diagnosis.