Table 1. Presence or absence of sigmoid notch sign on CT.

Distribution of films read as positive or negative sigmoid notch sign by gold standard diagnosis of transverse sinus thrombosis or congenitally atretic sinus.

	“Positive” sigmoid notch sign	“Negative” sigmoid notch sign	Total	Percent with “Positive” sign	95% CI	Percent with “Negative” sign	95% CI
Transverse sinus thrombosis	1	10	11	9.1% (FALSE NEGATIVE RATE)	-9.2%, 27.3%	90.9% (SENSITIVITY)	72.7%, 109.2%
Congenitally atretic sinus	36	6	42	85.7% (SPECIFICITY)	74.7%, 96.7%	14.3% (FALSE POSITIVE RATE)	3.3%, 25.3%