A Novel Triage Tool: Optic Nerve Sheath Diameter in Traumatic Brain Injury and its Correlation to Rotterdam Computed Tomography (CT) Scoring

Background: Optic nerve sheath diameter (ONSD) evaluated in CT imaging as well as Rotterdam CT Score (RCTS) are proven independent predictors of outcome in patients with traumatic brain injury (TBI). To date, no study has correlated ONSD on admission CT scan with RCTS.

Material/Methods: Retrospective cohort study comprised of consecutive patients undergoing CT imaging for traumatic brain injury recruited between January and October 2015. Bilateral ONSD was measured 3 mm behind the eyeball in axial and sagittal planes and mean value was calculated. RCTS was assessed on the same CT images, bias was eliminated by blinding RCTS to ONSD measurement.

Results: 150 patients were included; mean age in the group was 42.94±16.7 years. ONSD in mild TBI, RCTS 2 and 3 were 3.3 mm (SD 0.39 mm) and 4.1 mm (0.047 mm), respectively. Mean ONSD in moderate and severe TBI (RCTS score 4 and above) was 4.83 mm and above, SD 0.4 mm. Mean ONSD correlated with occurrence of diffuse cerebral oedema, presence of subdural and extradural hematoma; however in isolation there was no statistical significance.

Conclusions: Higher ONSD was observed in patients with moderate and severe TBI, correlating with admission RCTS of 4 and above. Subsequent increase in ONSD was also found with increase in RCTS. ONSD could serve as an initial triage tool in the emergency department as well as a method of determining the need for sequential CT in patients with mild TBI.