Incidence of the empty delta sign in computed tomography in the paediatric age group

The computed tomographic (CT) appearances of dural sinus thrombosis are variable, but include visualization of thrombus within the sinus on post‐contrast images (the ‘empty triangle’or ‘empty delta’sign). This review of 104 consecutive examinations was undertaken to assess the incidence of the empty delta sign in a paediatric group undergoing CT examinations. The number of examinations in which a sagittal sinus filling defect was seen in three or more images, was unexpectedly high. An overall incidence of 18% was noted. Defects due to bone artifact and defects seen on only one or two slices were excluded. The age distribution of abnormal scans was markedly skewed towards young infants. Nine of 27 examinations (33%) in infants less than 1 month of age, were positive for filling defects, compared with six of 21 (29%) aged between 1 and 12 months, and four of 56 (7%) aged over 1 year. This review suggests that the finding of a filling defect or empty delta sign in the sagittal sinus is not pathognomonic for sinus thrombosis that results in clinically apparent manifestations. Second, a filling defect apparent on CT may resolve spontaneously. The incidence of non‐occlusive sinus thrombosis may be significantly higher than previously recognized, particularly in young infants where predisposing conditions including dehydration, infection or prematurity coexist. Previous studies have indicated that the sensitivity of the empty delta sign is approximately 30%. This study implies that either the empty sign has limited specificity in the paediatric population, or that unrecognized non‐occlusive sinus thrombosis is much more frequent than previously described.