The crescent sign on ocular ultrasound and correlation with elevated intracranial pressure: A prospective cohort study.

Objectives: While lumbar puncture (LP) remains gold standard for assessing intracranial pressure (ICP), LP can be difficult to perform and lead to complications. Noninvasive correlations for elevated ICP via ocular ultrasound (OUS) have shown mixed results. The primary objective of this study is to identify the frequency and test characteristics of the crescent sign on OUS for elevated ICP. Secondary objectives include comparison of test characteristics to optic nerve sheath diameter (ONSD) and optic disc elevation (ODE).

Design: Single center, prospective, observational cohort study enrolling adults (age ≥ 18 years) who presented to an outpatient Neurology LP clinic. An OUS protocol was performed prior to scheduled LP, with measurement of the opening pressure (OP) by manometry. Patients were excluded if LP was unable to be completed (for any reason) or if completed in the sitting position. Elevated OP was defined as ≥25cmH2O.

Results: In total, 68 patients were enrolled; seven were excluded due to no OP measured, leaving 61 patients for analysis. Forty-six patients had normal OP, while 15 had elevated OP. The crescent sign was observed in 19 patients (31 %). Overall sensitivity, specificity, and accuracy of the crescent sign was 67 %, 80 %, and 74 %, respectively. Comparison of accuracy between the six other OUS findings demonstrated no significant differences between test characteristics (p > 0.10 for each).

Conclusions: The crescent sign was observed in 31 % of patients, with moderate sensitivity, specificity, and accuracy for elevated ICP. This study has several limitations and evaluations in the acute care setting are needed.