title: Differentiation of transverse sinus thrombosis from congenitally atretic cerebral transverse sinus with CT.
abstract: OBJECTIVE
  Transverse sinus thrombosis can have nonspecific clinical and radiographic signs. We hypothesized that the novel "sigmoid notch sign" (on head CT) can help differentiate transverse sinus thrombosis from a congenitally atretic sinus among individuals with absent signal in 1 transverse sinus by MR venography.
  
  
  METHODS
  We retrospectively evaluated 53 subjects with a unilaterally absent transverse sinus signal on MR venography. Eleven had true transverse sinus thrombosis and 42 had an atretic transverse sinus. Reviewers were trained in the sigmoid notch sign: "positive" if 1 of the sigmoid notches was asymmetrically smaller than the other, consistent with a congenitally absent transverse sinus on that side. This sign was scored on CT scans by 2 blinded reviewers to determine if signal dropout was clot or atretic sinus. A consensus rating was reached when the reviewers disagreed. Characteristics of the sigmoid notch sign as a diagnostic test were compared with a gold standard of full chart review by an independent reviewer.
  
  
  RESULTS
  Each reviewer had a sensitivity of 91% (detecting 10 of 11 clots based on a negative sigmoid notch sign) and specificity of 71% to 81%; consensus specificity increased to 86% (36 of 42 individuals with an atretic sinus had a positive notch sign, detecting atretic sinuses based on presence of the sign).
  
  
  CONCLUSIONS
  Asymmetries of the sigmoid notches on noncontrast brain CT is a very sensitive and specific measure of differentiating transverse sinus thrombosis from an atretic transverse sinus when absence of transverse sinus flow is visualized on MR venography.
authors.affiliation: Sinai Hospital, and Department of Neurology, Johns Hopkins University School of Medicine, Johns Hopkins Bayview Medical Center, 301 Mason F. Lord Building, Baltimore, MD 21224, USA.
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Chik
authors.forename: Rebecca F
authors.initials: RF
authors.lastname: Gottesman
authors.forename: Steven R
authors.initials: SR
authors.lastname: Zeiler
authors.forename: Jason
authors.initials: J
authors.lastname: Rosenberg
authors.forename: Rafael H
authors.initials: RH
authors.lastname: Llinas
mesh_terms: D003937:Diagnosis, Differential; D006801:Humans; D020227:Lateral Sinus Thrombosis / Q000151:congenital* / Q000175:diagnosis* / Q000000981:diagnostic imaging; D012189:Retrospective Studies; D016037:Single-Blind Method; D014057:Tomography, X-Ray Computed / Q000592:standards*; D054064:Transverse Sinuses / Q000002:abnormalities* / Q000000981:diagnostic imaging*