The relationship between jugular foramen asymmetry and superior sagittal venous sinus laterality

The reason for asymmetry of the jugular foramen (JF) size is unclear, with previous suggestions including that handedness may influence development of a larger IF on the ipsilateral side of handedness. Intracranial venous asymmetry has not previously been considered in relation to IF size. We aim to investigate if the asyminetry of the superior sagittal venous sinus (SSVS) drainage is related to IF size. Two hundred and forty-five skulls from collections in Otago, New Zealand (Indian skulls) and Coimbra, Portgual (European skulls) were assessed for JF size and SSVS laterality. Data were analysed to determine relationships between the variables IF symmetry, side of drainage of SSVS (laterality), location of the skull collection, and sex using chi-squared and proportion tests (P < 0.05). Two hundred and forty skulls were included in the final analysis (140 Otago, 100 Coimbra). A significant relationship was seen between larger IF and SSVS laterality, with ipsilateral SSVS laterality and larger JF more frequent (54.6%). Differences were noted between location: Otago had significantly more right-sided combinations (66.4% vs. 38%), Coimbra had significantly more that were equal-sided (10% vs. 4.3%). IF size was significantly different across the samples: a larger right IF was more frequent (60%). There were also significant differences between location: Otago showed a higher incidence of larger, right IF (74.3% vs. 40%), while Coimbra had more that were equal (34% vs. 5.7%). Drainage side of SSVS was different across, but not between, skull locations; sex had no effect on any variable. The findings demonstrate an association between the ipsilateral SSVS drainage laterality and a larger IF, and support previous findings of asymmetry in IF size. Further investigations are necessary using imaging techniques to explore the nature of the association between IF asymmetry and SSVS drainage laterality.