Optic nerve sheath diameter on CT brain as a predictor of morbidity and mortality in patients with traumatic brain injury

Abstract

Background: Traumatic Brain Injury (TBI) is very common in our setting and puts a strain on the healthcare system and social welfare services. There are no formal statistics reported locally, however we treat many patients with TBI due to assaults, motor vehicle accidents (MVA) and falls at the two major hospitals in Johannesburg. TBI is a common cause of major disability and loss of income among young and middle aged South Africans. The development of a reliable prognostic factor in addition to existing ones would help guide therapy and allow prioritization of resources for TBI patients. Other studies have demonstrated the direct correlation between measured Intracranial pressure (ICP) and Optic Nerve Sheath Diameter (ONSD), however there is no consensus regarding the normal ONSD. ONSD varies in children, adults and among different populations. Objectives: Establish an average ONSD among adult patients presenting at Chris Hani Baragwanath Academic Hospital and Charlotte Maxeke Johannesburg Academic Hospital. To measure the ONSD on CT brain and correlate with outcome upon discharge or thirty days (whichever comes first) in adult patients with severe traumatic brain injury in our setting using a Glasgow Outcome Scale (GOS) score. Methods: We conducted a prospective observational study from July to December 2015 at two major hospitals with neurosurgical facilities in Johannesburg. Study subjects were adult male and female patients (>18yrs) with severe TBI as well as adult patients with normal scans performed within the study period (Controls). Results: 40 severe TBI patients and 42 controls were enrolled in the study. Most patients in the study were young adult males (n=37) who sustained their injuries due to assaults (43%) and MVA/PVA (28%). Admission GCS had 3 categories, with the majority of patients in the GCS category 3 (45%). ONSD average in normal subjects was 5.36mm, while in TBI patients the average ONSD was 5.6mm. There were 12 deaths, 18 patients with poor outcome and 10 patients with good outcome. Conclusion: Our results showed that the ONSD is not a reliable prognosticator in severe TBI patients. The ONSD correlation with GOS and Rotterdam score was not statistically significant with a p-values of 0.096 and 0.876 respectively.