Doing More with Less: Diagnostic Accuracy of CT in Suspected Cauda Equina Syndrome.

BACKGROUND AND PURPOSE: Cauda equina syndrome typically requires emergent MR imaging to detect compressive lesions on the cauda equina, which may require surgical decompression. While CT is sometimes performed as a complementary imaging technique to evaluate osseous integrity in patients with cauda equina syndrome, the accuracy of CT in detecting significant spinal stenosis and cauda equina impingement is not well-defined in the literature. We hypothesized that percentage thecal sac effacement on CT of the lumbar spine would have high sensitivity and high negative predictive value in evaluating significant spinal stenosis and cauda equina impingement. MATERIALS AND METHODS: We analyzed imaging studies for 151 consecutive patients with clinically suspected cauda equina syndrome. The percentage thecal sac effacement (<50%, ≥50%) was determined on CT and MR imaging. The presence or absence of cauda equina impingement was determined on MR imaging. Using MR imaging as the reference standard, we performed statistical analysis to determine the accuracy of CT in predicting significant spinal stenosis (percentage thecal sac effacement, ≥50%) and cauda equina impingement. RESULTS: Forty of 151 patients had a percentage thecal sac effacement of ≥50% on MR imaging. Nineteen of 40 had cauda equina impingement. Readers determined that there was a CT percentage thecal sac effacement of <50% in 97/151 cases, and CT percentage thecal sac effacement of ≥50% in 54/151 cases. Reader sensitivity for the detection of significant spinal stenosis (MR percentage thecal sac effacement of ≥50%) was 0.98; specificity, 0.86; positive predictive value, 0.72; and negative predictive value, 0.99. No cases read as CT percentage thecal sac effacement of <50% were found to have cauda equina impingement. CONCLUSIONS: CT percentage thecal sac effacement of ≥50% predicts significant spinal stenosis on MR imaging in patients with clinically suspected cauda equina syndrome. CT percentage thecal sac effacement of <50% appears to reliably rule out cauda equina impingement. This imaging marker may serve as an additional tool for the clinician in deciding whether MR imaging can be deferred.

Percentage insula ribbon infarction of >50% identifies patients likely to have poor clinical outcome despite small DWI infarct volume.

BACKGROUND AND PURPOSE: Large admission DWI infarct volume (>70 mL) is an established marker for poor clinical outcome in acute stroke. Outcome is more variable in patients with small infarcts (<70 mL). Percentage insula ribbon infarct correlates with infarct growth. We hypothesized that percentage insula ribbon infarct can help identify patients with stroke likely to have poor clinical outcome, despite small admission DWI lesion volumes. MATERIALS AND METHODS: We analyzed the admission NCCT, CTP, and DWI scans of 55 patients with proximal anterior circulation occlusions on CTA. Percentage insula ribbon infarct (>50%, ≤50%) on DWI, NCCT, CT-CBF, and CT-MTT were recorded. DWI infarct volume, percentage DWI motor strip infarct, NCCT-ASPECTS, and CTA collateral score were also recorded. Statistical analyses were performed to determine accuracy in predicting poor outcome (mRS >2 at 90 days). RESULTS: Admission DWI of >70 mL and DWI-percentage insula ribbon infarct of >50% were among significant univariate imaging markers of poor outcome (P < .001). In the multivariate analysis, DWI-percentage insula ribbon infarct of >50% (P = .045) and NIHSS score (P < .001) were the only independent predictors of poor outcome. In the subgroup with admission DWI infarct of <70 mL (n = 40), 90-day mRS was significantly worse in those with DWI-percentage insula ribbon infarct of >50% (n = 9, median mRS = 5, interquartile range = 2-5) compared with those with DWI-percentage insula ribbon infarct of ≤50% (n = 31, median mRS = 2, interquartile range = 0.25-4, P = .036). In patients with admission DWI infarct of >70 mL, DWI-percentage insula ribbon infarct did not have added predictive value for poor outcome (P = .931). CONCLUSIONS: DWI-percentage insula ribbon infarct of >50% independently predicts poor clinical outcome and can help identify patients with stroke likely to have poor outcome despite small admission DWI lesion volumes.