Prediction of vascular abnormalities on CT angiography in patients with acute headache

OBJECTIVES: Patients with acute headache increasingly undergo CT‐angiography (CTA) to evaluate underlying vascular causes. The aim of this study is to determine clinical and non‐contrast CT (NCCT) criteria to select patients who might benefit from CTA. METHODS: We retrospectively included patients with acute headache who presented to the emergency department of an academic medical center and large regional teaching hospital and underwent NCCT and CTA. We identified factors that increased the probability of finding a vascular abnormality on CTA, performed multivariable regression analyses and determined discrimination with the c‐statistic. RESULTS: A total of 384 patients underwent NCCT and CTA due to acute headache. NCCT was abnormal in 194 patients. Among these, we found abnormalities in 116 cases of which 99 aneurysms. In the remaining 190 with normal NCCT we found abnormalities in 12 cases; four unruptured aneurysms, three cerebral venous thrombosis’, two reversible cerebral vasoconstriction syndromes, two cervical arterial dissections and one cerebellar infarction. In multivariable analysis abnormal NCCT, lowered consciousness and presentation within 6 hr of headache onset were independently associated with abnormal CTA. The c‐statistic of abnormal NCCT alone was 0.80 (95% CI: 0.75–0.80), that also including the other two variables was 0.84 (95% CI: 0.80–0.88). If NCCT was normal no other factors could help identify patients at risk for abnormalities. CONCLUSIONS: In patients with acute headache abnormal NCCT is the strongest predictor of a vascular abnormality on CTA. If NCCT is normal no other predictors increase the probability of finding an abnormality on CTA and diagnostic yield is low.