Bedside Ultrasonographic Assessment of Optic Nerve Sheath Diameter As a Means of Detecting Raised Intracranial Pressure in Neuro-Trauma Patients

Abstract

Background: Optic nerve sheath diameter (ONSD) measurement is emerging as a noninvasive method to estimate raised ICP. It is helpful in situations where imaging of brain or direct ICP monitoring is not available or feasible. Use of ONSD is still limited, so this study was planned to determine whether the bedside sonographic measurement of ONSD can reliably predict elevated ICP in neuro-trauma patients. Methodology: After approval from Hospital Ethics Committee, this cross-sectional study was conducted in hundred traumatic brain injury (TBI) patients with suspected elevated ICP, admitted to neurosurgical ICU. The severity of brain injury was assessed according to Glasgow coma scale (GCS), initial CT scan findings, and revised trauma score (RTS). All patients underwent ONSD sonography of the eye and CT scan subsequently. ONSD of ≥5.0 mm was considered as a benchmark of raised ICP. Results: Mean ONSD of the study group with ONSD ≥5.0 mm was 5.6 ± 0.3 mm. ONSD was raised in 46% of patients, more so in patients with low GCS (3-6). The relationship of ONSD with GCS, CT scan findings, and RTS was highly significant. The sensitivity of the bedside sonographic measurement ONSD to detect raised ICP was 93.2% and specificity was 91.1% when compared with CT scan. Positive Predictive Value of the ONSD measurement was 89.1% and the negative predictive value was 94.4%. Conclusion: Ultrasonographic assessment of ONSD is a reliable modality to detect raised ICP in neurotrauma patients. It can be helpful in the early initiation of treatment of elevated ICP, thus preventing secondary brain damage.

Bedside ultrasonographic evaluation of optic nerve sheath diameter for monitoring of intracranial pressure in traumatic brain injury patients: a cross sectional study in level II trauma care center in India

“…This shows that ONSD and CT scan findings had a significant correlation. Similar findings were seen in other studies [ 8 ].…”

“…In the present study, we found no significant correlation between age and gender, similar to other studies [ 8 , 12 ]. Other studies have shown that GCS has significant correlation with ONSD, where they found that low GCS significantly correlates with higher ONSD [ 8 ].…”

“…In the present study, we found no significant correlation between age and gender, similar to other studies [ 8 , 12 ]. Other studies have shown that GCS has significant correlation with ONSD, where they found that low GCS significantly correlates with higher ONSD [ 8 ]. Similar results are seen in our study as patients with low GCS had a mean ONSD of 6.4±1.0 mm, and patients with moderate GCS had an ONSD of 4.7±0.4 mm.…”

“…Here, we observed that ONSD assessment with ultrasound has good sensitivity and specificity (86.42% and 64.29%, respectively), with a 93.33% positive predictive value to identify increased ICP at an accuracy of 83.16%. Compared to CT scans, Kaur et al [ 8 ] found a correlation between ONSD and ICP using ONSD assessment to detect elevated ICP in neurological trauma patients, with a sensitivity and specificity of 93.2% and 91.1%, respectively. The ONSD test had an accuracy of 92% and a positive predictive value to detect elevated ICP of 89.1% and a negative predictive value of 94.4%.…”

“…The sample size was calculated by assuming the mean ONSD in increased ICP patients as 5.6±0.3 mm, at a statistical power of 0.90 (alpha=0.05) [ 8 ], leading to an estimated sample size of 95 subjects.…”