Sonographic diameter of optic nerve sheath in differentiation of ischemic and hemorrhagic strokes; a diagnostic accuracy study

POCUS, how can we include the brain? An overview

Point-of-care ultrasound (POCUS) is an essential tool to assess and manage different pathologies in the intensive care unit, and many protocols have been proposed for its application in critical care literature. However, the brain has been overlooked in these protocols.

Brain ultrasonography (BU) is easily available, and it allows a goal-directed approach thanks to its repeatability and immediate interpretation and provides a quick management and real time assessment of patients’ conditions. Based on recent studies, the increasing interest from intensivists, and the undeniable benefits of ultrasound, the main goal of this overview is to describe the main evidence and progresses in the incorporation of BU into the POCUS approach in the daily practice, and thus becoming POCUS-BU. This integration would allow a noninvasive global assessment to entail an integrated analysis of the critical care patients.

Optic nerve sheath diameter at high altitude: standardized measures in healthy volunteers

Background

Increases in the diameter of the optic nerve sheath (ONSD) on ultrasound are associated with high intracranial pressure (hICP). The normal value varies with altitude and the population studied. The objective of this study is to describe the normal values of the ONSD in a healthy adult population of the city of Bogotá, Colombia, at 2640 meters above sea level (masl).

Patients and methods

A prospective observational study was conducted on a total of 247 healthy individuals recruited from May 2021 to May 2022 who were subjected to the color, low power, optic disk, safety, elevated frequency, dual (CLOSED) protocol for measuring the bilateral ONSD adjusted to the eyeball transverse diameter (ETD).

Results

A total of 230 individuals were analyzed; the average ONSD of the right eye (RE) was 0.449 cm (range 0.288–0.7) and that of the left eye (LE) was 0.454 cm (range 0.285–0.698); the correlation between RE and LE was 0.93 (p < 0.005), and the correlation of the ONSD/ETD ratios for the RE and LE was lower (r² = 0.79, p < 0.005). A total of 10.8% of the studied population had values greater than 0.55 cm.

Conclusions

The median ONSD and ONSD/ETD ratio in the city of Bogotá are similar to those described in other populations; however, approximately 10.8% of the healthy population may present higher values, which would limit the use of ONSD on its own for clinical decision-making, only repeated measurements with significant changes in the ONSD and ONSD/ETD or asymmetries between the measurements of both eyes linked to clinical findings would allow the diagnosis of hICP.

The role of optic nerve sheath diameter measurement on CT in differentiating transient ischemic attack and acute ischemic stroke

OBJECTIVE

This study aimed to determine if optic nerve sheath diameter (ONSD) measurement on computed tomography could differentiate transient ischemic attack (TIA) from acute ischemic stroke (AIS). Both TIA and AIS are the rings of the same disease chain. To exclude hemorrhagic stroke and stroke mimics in these patients, brain computed tomography (CT) remains the first step imaging modality.

PATIENTS AND METHODS

In this retrospective study, ONSDs of patients with TIA and AIS within three hours from symptom onset to initial CT was measured. The right, left, mean, and delta ONSD measurements were compared between AIS and TIA groups. Then diagnostic accuracy metrics were calculated.

RESULTS

A total of 196 patients (128 in the AIS group and 68 in the TIA group) were included. Both mean and delta ONSD of AIS patients were higher than those of the TIA group. The area under the receiver operating curve of mean and delta ONSD for predicting AIS were 0.746 with a sensitivity of 82.8% and a specificity of 42.7% (cut-off: 5.00 mm), and 0.826 with a sensitivity of 67.2% and a specificity of 86.8% (cut-off: 0.50 mm), respectively.

CONCLUSION

Increased mean or delta ONSD measured on initial CT could alert emergency physicians for an impending stroke.

Ultrasound measurement of the optic nerve sheath diameter in traumatic brain injury: a narrative review

Background : Raised intracranial pressure (ICP) needs to be investigated in various situations, especially in traumatic brain injury (TBI). Ultra-sonographic (US) measurement of the optic nerve sheath diameter (ONSD) is a promising noninvasive tool for assessing elevated ICP. Objectives : This narrative review aimed to explain the history of and indications forUS measurement of ONSD. We focused on the detection of elevated ICP after TBI and discussed the possible improvements in detection methods. Conclusions : US measurement of ONSD in TBI cases provides a qualitative but no quantitative assessment of ICP. Current studies usually calculate their own optimum cutoff value for detecting raised ICP based on the balance between sensitivity and specificity of the method when compared with invasive methods. There is no universally accepted threshold. We did not find any paper focusing on the prognosis of patients benefiting from it when compared with usual care. Another limitation is the lack of standardization. US measurement of ONSD cannot be used as the sole technique to detect elevated ICP and monitor its evolution, but it can be a useful tool in a multimodal protocol and it might help to determine the prognosis of patients in various situations.

Measuring the Optic Nerve Sheath Diameter with Ultrasound in Acute Middle Cerebral Artery Stroke Patients

BACKGROUND

Measurement of the optic nerve sheath diameter (ONSD) with ultrasound enables non-invasive and indirect assessment of increased intracranial pressure (ICP). Although most of the studies were employed with traumatic brain injury patients, it's increasingly popular in acute ischemic stroke (AIS) studies.

OBJECTIVES

Evaluating whether using ONSD as a follow-up measurement would help monitor the thrombolytic therapy (TT) effectiveness and determine the high-risk patients for malignant middle cerebral artery (MCA) syndrome.

METHODS

This prospective observational study was conducted between August 1, 2019, and February 1, 2020, in a tertiary hospital. Forty-four patients were eligible. We determined the TT moment as the time when the first ocular ultrasound measurement would be made (time 0). Also, we decided on the 24^th h after the treatment as the time to perform the second ocular ultrasound measurement (time 24). The National Institute of Health Stroke Scale (NIHSS), the Glasgow Coma Scale (GCS), and the Alberta Stroke Program Early Computed Tomography (ASPECT) scores were evaluated blindly at the time-0 and the time-24. The cut-off value of ONSD was 0.55 mm.

RESULTS

There was no difference in ONSD results before and after the TT (p = 0.414). But, patients with an equal or higher value than cut-off had an increased risk for complications such as malignant-MCA, bleeding, seizure, etc. (p = 0.05). Malignant-MCA was observed in four patients with higher ONSD values. At the time-24, NIHSS decreased, GCS and ASPECT scores increased. Finally, ONSD was positively correlated with the NIHSS and negatively correlated with the GCS at the time-24.

CONCLUSIONS

Monitoring ONSD values in both the emergency department and the intensive care unit may be useful in the early diagnosis of MCA stroke complications and the follow-up of TT's effectiveness.

Optic nerve sheath diameter change in prediction of malignant cerebral edema in ischemic stroke: an observational study

Background

In acute large anterior circulation infarct patients with large core volume, we evaluated the role of optic nerve sheath diameter (ONSD) change rates in prediction of malignant progression.

Methods

We performed a retrospective observational study including patients with anterior circulation acute ischemic stroke with large ischemic cores from January 2010 to October 2017. Primary outcome was defined as undergoing decompressive surgery or death due to severe cerebral edema, and termed malignant progression. Patients were divided into malignant progressors and nonprogressors. Malignant progression was divided into early progression that occurred before D1 CT, and late progression that occurred afterwards. Retrospective analysis of changes in mean ONSD/eyeball transverse diameter (ETD) ratio, and midline shifting (MLS) were evaluated on serial computed tomography (CT). Through analysis of CT at baseline, postprocedure, and at D1, the predictive ability of time based change in ONSD/ETD ratio in predicting malignant progression was evaluated.

Results

A total of 58 patients were included. Nineteen (32.8%) were classified as malignant; 12 early, and 7 late progressions. In analysis of CT_{postprocedure}, A 1 mm/hr. rate of change in MLS during the CT_baseline-CT_{postprocedure} time phase lead to a 6.7 fold increased odds of early malignant progression (p < 0.05). For ONSD/ETD, 1%/hr. change lead to a 1.6 fold increased odds, but this association was trending (p = 0.249). In the CT_D1, 1%/day change of ONSD/ETD in the CT_baseline-CT_D1 time phase lead to a 1.4 fold increased odds of late malignant progression (p = 0.021) while 1 mm/day rate of change in MLS lead to a 1.5 fold increased odds (p = 0.014).

Conclusions

The rate of ONSD/ETD changes compared to baseline at D1 CT can be a predictor of late malignant progression along with MLS. ONSD/ETD change rates evaluated at postprocedure did not predict early malignant progression.