Correlation of optic nerve sheath diameter with intracranial pressure monitoring in patients with severe traumatic brain injury

Aims and objectives: To assess the feasibility and reliability of using optic nerve sheath diameter (ONSD) as an objective measure of intracranial pressure (ICP) in patients of severe head injury. Methods and materials: This prospective study was carried out in Neurosurgery ICU over a 3month period (April-June 2012). All patients with severe traumatic brain injury (admission GCS <= 8) who had ICP monitoring using Codman (R) intraparenchymal transducer had serial bedside ONSD measurements taken by a single neurosurgeon using a 7.5 MHz linear probe on the same ultrasound machine (Sonosite Micromaxx (R)) were enrolled in the study. Patients with significant ocular trauma to either eye were excluded. Results: A total of 20 patients were enrolled during the study period. The mean age was 27 years (range 2-43 years) with M:F ratio of 3:1 and mean GCS of 6 (range 4-8). The mean ONSD in patients with ICP >20 was 6.6 + 0.45mm as compared to 5.9 + 0.57mm in patients with ICP <20 (p = 0.028). The Pearson Correlation Coefficient between ONSD (average of both eyes) and ICP was 0.499 (p = 0.041). A cutoff of 6.3 mm detected ICP >20 mmHg with 100% sensitivity and 72.7% specificity. Conclusion: ONSD is a technically simple, non-invasive method of assessing ICP and correlates well with actual ICP in patients of severe traumatic brain injury. A cutoff of 6.3 mm can be used to plan therapeutic interventions when ICP monitoring is unavailable or contraindicated. Copyright (C) 2013, Neurotrauma Society of India. All rights reserved.