We describe the MRI features of sigmoid sinus thrombosis following mastoiditis in a 3-year-old girl.

T2-weighted coronal MRI can diagnose both patency of the sigmoid sinus and epidural hematoma extending along the sinus groove.

Conclusions: Erosion of the cortical plate overlying the sigmoid sinus is the most sensitive and specific CT finding for distinguishing coalescent from noncoalescent acute mastoiditis.

Conclusions: Fistulas of the transverse- sigmoid sinuses with cortical reflux may require sacrifice of the parent sinus for cure.