Is optic nerve sheath diameter a promising screening tool to predict neurological outcomes and the need for secondary decompressive craniectomy in moderate to severe head injury patients? A prospective monocentric observational pilot study.

Background: Optic nerve sheath diameter (ONSD) has been shown to be a noninvasive and quick method to calculate intracranial pressure (ICP) and subsequent neurologic outcomes, although with variable cutoffs. ICP can be indirectly assessed by noninvasive methods such as transcranial Doppler, ONSD, tympanic membrane displacement, and fundoscopy. Knowledge regarding the diagnostic accuracy of ONSD for predicting unfavorable outcomes within 72 hours (h) of moderate and severe head injury is limited. The objective of this study was to measure ONSD measurements at 24-h intervals in moderate to severe head injury patients and to find its association with clinical outcomes in the target population.

Methods: This prospective observational study was done on moderate to severe head injury patients. ONSD was measured twice at 24-h intervals over 48 h. The clinical outcome was divided into the favorable group (patients who were in conservative treatment with a stable Glasgow Coma Scale [GCS] score and discharged following treatment) and the unfavorable group (patients who had a drop in GCS motor score of one or more, or expired or underwent surgical intervention) within 72 h following traumatic brain injury. The Kruskal-Wallis test, Mann- Whitney test, and receiver operating characteristic curves were used to establish the association between ONSD and clinical outcomes.

Results: ONSD values measured at 24-h intervals >6.1 mm ( < 0.0146) and 6.2 mm ( < 0.0001) were found to be predictors of unfavorable outcomes (expired or underwent surgery), and hence the need for a secondary decompressive craniectomy (DC).

Conclusion: ONSD is an efficient screening tool to assess neurological outcomes in severe head injury patients. It can reliably predict the need for secondary DC at an earlier stage before secondary brain damage ensues in these patients.