Analysis of dynamic changes in optic nerve sheath diameter (ONSD) with ultrasound in post-craniotomy patients: Trends and correlation with computed tomography ONSD and Glasgow coma scale in post-operative period

Objectives

Intracranial pressure (ICP) monitoring in patients with intracranial tumors undergoing craniotomy is usually done in perioperative period in intensive care unit. Invasive measurement of ICP, though considered as the gold standard, has its own limitations such as availability of expertise, equipment, and associated complications. Period of raised ICP in post-operative period may impact patient outcomes. Post-craniotomy computed tomography (CT) assessment is done routinely and may need to be repeated if indicated during post-operative stay. Utility of sonographic serial optic nerve sheath diameter (ONSD) assessment in post-operative monitoring of patients who have undergone elective craniotomy was explored in this study. The primary objective of the study was to measure the dynamic change in ONSD as compared to baseline pre-operative measurement in the first 3 postoperative days after elective craniotomy. The secondary objective of the study was to evaluate correlation between ONSD value with Glasgow Coma Scale (GCS) and post-operative CT findings.

Materials and Methods

In this prospective, observational, and cohort study, we studied adult patients undergoing craniotomy for intracranial tumors. GCS assessment and sonographic measurement of ONSD were done preoperatively, immediate post-operative period, and 12, 24, and 48 h after surgery. CT scan to detect raised ICP was done at 24 h post-operative. Correlation of ONSD with GCS at respective period and correlation of CT scan finding with respective ONSD assessment were evaluated.

Results

A total of 57 patients underwent elective craniotomy for intracranial tumors. Significant difference was observed in ONSD value depending on time of measurement perioperatively (χ2 = 78.9, P = 0.00). There was initial increase in the first 12 h followed by decrease in ONSD in the next 48 h. Negative correlation was observed between baseline ONSD and 12 h GCS (ρ = -0.345, P = 0.013). There was significant change in GCS scores based on the status of ONSD (raised or normal) at 12 h after surgery (P = 0.014). Significant correlation between USG ONSD and CT ONSD was observed (ρ = 0.928, P = 0.000). Optimal cutoff value of ONSD to detect raised ICP with reference to CT signs was 4.8 mm with 80% sensitivity and 95% specificity.

Conclusion

ONSD undergoes dynamic changes, correlates with CT scan, and has good diagnostic accuracy to detect raised ICP post-craniotomy for intracranial tumors. It may serve as a useful tool in monitoring in resource-limited setup.

Mean value of B-mode optic nerve sheath diameter as an indicator of increased intracranial pressure: a systematic review and meta-analysis

Objectives

Timely diagnosis and treatment of increased intracranial pressure can decrease morbidity and prevent mortality. The present meta-analysis aims to determine the mean value of the ONSD measured in patients with various elevated ICP etiologies under different clinical settings, as well as comparing the value of ONSD between patients with and without elevated ICP.

Methods

This meta-analysis complied with the Preferred Reporting Items for Systematic Reviews and Meta-analysis Statement8. PubMed, Embase, and Cochrane Library were searched to identify ONSD measured by US for patients with increased ICP from establishment to October 2020.

Results

A total of 779 patients with elevated ICP among 22 studies were included in the present meta-analysis. Studies were published between 2003 and 2020. Eighteen were comparative (18/22, 81.8%), and four were single-armed study (4/22, 18.2%). Twenty were prospective studies (20/22, 90.9%). There was moderate-to-high heterogeneity based on the prediction ellipse area and variance logit of sensitivity and specificity.

Conclusions

The mean value of the ONSD among patients diagnosed with increased ICP was 5.82 mm (95% CI 5.58–6.06 mm). Variations were observed based on etiology of intracranial hypertension, clinical settings where ONSD was measured, and standards for diagnosing intracranial hypertension. The US-ONSD among patient with elevated ICP was significantly higher than the normal control. Although a cut-off value is not clearly determined, these mean values can be implemented to evaluate the sensitivity and specificity of US-ONSD in diagnosing intracranial hypertension in future studies.

Evaluation of Bedside Sonographic Measurement of Optic Nerve Sheath Diameter for Assessment of Raised Intracranial Pressure in Adult Head Trauma Patients

Aim:

The aim was to evaluate the use of bedside sonographic measurement of the optic nerve sheath diameter (ONSD) in the assessment of elevated intracranial pressure in patients with head injury coming to the emergency department (ED).

Methods:

A prospective study of ED patients presenting with a history of acute head injury, an ocular ultrasound was performed for ONSD measurement, followed by a computed tomography (CT) of the brain. Three measurements were taken for each eye, then, the mean binocular ONSD measurement for each patient was obtained to ensure accuracy. A mean bipolar ONSD >5 mm was considered abnormal.

Results:

A total of 175 patients were considered for the study. Of 175 patients, only 56 (32%) had intracranial pathology detected on CT brain with mean ONSD of 5.7 mm (standard deviation [SD]: 0.59). The mean ONSD for 119 (68%) patients, who had normal CT brain, was 4.5 mm (SD: 0.42). The mean ONSD measured for the right eye was 4.86 mm with SD 0.88, and the mean ONSD for the left eye was 4.90 mm with SD 0.85. When comparing ONSD measurement with CT findings of raised intracranial pressure, the ONSD sensitivity was 87.5% (95% confidence interval [CI]: 85%–96%) and specificity was 94.1% (95% CI: 85%–96%), with a positive predictive value of 87.5% and a negative predictive value of 94.1%. The area under the receiver operator characteristic curve obtained was 0.90 (95% CI: 0.85–0.96).

Conclusion:

The study has shown a bedside measurement of ONSD through sonography as an efficient tool to assess elevations in intracranial pressure in head injury patients.