An infection of the mastoid air cells spreads to the sigmoid sinus via a valveless channel that connects the sigmoid sinus to the posterior auricular and occipital veins. This channel is the:

• A Mastoid emissary vein ✓
• B Petrosquamous sinus
• C Condylar emissary vein
• D Sphenoparietal sinus

Explanation

The mastoid emissary vein passes through the mastoid foramen in the temporal bone, linking the sigmoid sinus extracranially with the posterior auricular or occipital veins. Because emissary veins are valveless, infection can spread retrogradely into the sinus, producing septic thrombosis of the sigmoid sinus. The condylar emissary vein uses the condylar canal near the occipital condyle, and the sphenoparietal sinus drains along the lesser wing of the sphenoid.

Reference: Gray's Anatomy, 42nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.