Potential pitfalls in imaging of paediatric cerebral sinovenous thrombosis.

Paediatric cerebral sinovenous thrombosis (CSVT) is a rare but serious condition. The imaging signs may be subtle with a number of potential pitfalls. We present a pictorial essay of the pitfalls of diagnosis of CSVT on CT and MRI. We describe, using examples, potential pitfalls on both imaging modalities including anatomical variants of the cerebral venous system, extra-axial fluid collections and enhancement of chronic thrombus. Pitfalls particular to CT are discussed including beam-hardening artefact, image windowing and neonatal physiological intravascular hyperdensity. We review the potential variability in the appearance of thrombus on MRI, dependent largely on the stage of thrombus evolution and the pulse sequence. The signal intensity of thrombi, although described as evolving in a typical pattern on T1- and T2-weighted MRI, may be affected by variability in the degree of oxygenation of red cells in the forming thrombus, dilution and secondary propagation of thrombosis. Individual MRI sequences should not be interpreted in isolation, but as a set, and compared with CT images if available.