Comparison of ultrasonographic measurement of optic nerve sheath diameter (ONSD) versus direct measurement of intracranial pressure (ICP) in traumatic brain injury patients

Abstract

Aim. To compare ultrasonographic measurement of optic nerve sheath diameter (ONSD) with direct measurement of intra- cranial pressure (ICP) and evaluate the correlation between them in traumatic brain injury patients. Patients and methods. Twenty traumatic brain injury patients were enrolled in the study. Patients had a median Glasgow Coma Scale (GCS) score of 5. All patients underwent noninvasive measurement of ICP by ultrasonographic measurement of ONSD and invasive ICP measurement using an intraventricular catheter. We used MedCalc to analyze data. Results. We compared the ONSD measurement in patients with ICP less than 20 cm H2O with patients with ICP greater than 20 cm H2O. The mean ONSD for 8 patients with ICP > 20 cmH2O was 7.6 0.8 mm, and for 18 patients with ICP < 20 cm H2O was 5.6 0.6 mm. Student t-test comparison between these two groups showed a statistically significant mean difference of 1.99 (95 % CI = 1.4-2.6). The ROC curve showed that the optimal cutoff value of ONSD for predicting ICP > 20 cm H2O was 6.1, with sensitivity of 100% and specificity of 83 %. (the area under the curve was 0.98, 95 % CI = 0.825- 0.990). In this study, the usually used cutoff of ONSD > 5 mm gives a sensitivity of 100 %, but a specificity of only 22%. Conclusion. Ultrasonographic measurement of ONSD correlates with direct measurement of ICP. This method has potential as a screening test for elevated ICP in traumatic brain injury.