Ultrasonography of the optic nerve sheath may be useful for detecting raised intracranial pressure after severe brain injury

Objective: To assess at admission to the ICU the relationship between optic nerve sheath diameter (ONSD) and intracranial pressure (ICP) and to investigate whether increased ONSD at patient admission is associated with raised ICP in the first 48 h after trauma. Design and setting: Prospective, blind, observational study in a surgical critical care unit, level 1 trauma center. Patients and participants: 31 adult patients with severe traumatic brain injury (TBI; Glasgow coma scale = 8) requiring sedation and ICP monitoring, and 31 control patients without brain injury requiring sedation. Measurements and results: ONSD was measured with a 7.5-MHz linear ultrasound probe. Two TBI groups were defined on the basis of ICP profile. If ICP exceeded 20 mmHg for more than 30 min in the first 48 h ( before any specific treatment), patients were considered to have high ICP; if not, they had normal ICP. The largest ONSD value (the highest value for the right and left eye) was significantly higher in high ICP patients (6.3 +/- 0.6 vs. 5.1 +/- 0.7mm in normal ICP patients and 4.9 +/- 0.3 mm in control patients). There was a significant relationship between the largest ONSD and ICP at admission (r = 0.68). The largest ONSD was a suitable predictor of high ICP (area under ROC curve 0.96). When ONSD was under 5.7 mm, the sensitivity and negative predictive values for high ICP were 100%. Conclusions: In the early posttraumatic period, ocular ultrasound scans may be useful for detecting high ICP after severe TBI.