Figure 7b. Dural venous phlebothrombosis in a 4-year-old girl with left acute mastoiditis. (a, b) Axial CT scans of the temporal bone (a obtained inferior to b) show increased attenuation of the left mastoid air cells with a clear defect in the posterior and lateral mastoid cortex (arrow). (c) Axial contrast-enhanced cranial CT scan shows asymmetric enhancement of the sigmoid sinus (arrow). (d) Axial T2-weighted MR image shows hyperintense material in the left mastoid cells with a hyperintense thrombus at the level of the sigmoid sinus (arrow). (e) Axial MR venogram shows absence of normal venous flow with occlusion at the level of the mid transverse sinus on the left side and some evidence of adjacent collateralization (arrow).