petrosquamous sinus petrosquamous sinus the petrosquamous sinus is a fetal vein that generally disappears by birth and, when present, runs backward along the junction of the squama and petrous portion of the temporal, and opens into the transverse sinus. petrosquamous sinusdetailsidentifierslatinsinus petrosquamosusta98a12.3.05.107ta24851fma50777anatomical terminology