Anatom3DSigmoid sinus
Sinus sigmoideus · Esovitý splav
Veins
Looks like
An S-shaped channel curving down in a groove behind the ear, just inside the mastoid bone.
What it does
Continues the transverse sinus down to the jugular foramen, where it becomes the internal jugular vein.
Keeping it well
A middle-ear or mastoid infection can clot it: ear pain with high fever, headache and swelling behind the ear needs urgent care.