Name: optic nerve sheath point of care ultrasound: image acquisition
Uploaded: 2023-08-18T13:50:00
Description: Watch this Scientific Journal Video about Optic Nerve Sheath Point of Care Ultrasound: Image Acquisition at JoVE.com

This effort was partially sponsored by the US Government under Other Transactions (W81XWH-15-9-0001/W81XWH-19-9-0015) and the Medical Technology Enterprise Consortium (MTEC) under 19-08-MuLTI-0079.

This procedure is in accordance with the ethical standards of the institutional committee on human experimentation and with the Helsinki Declaration of 1975. Ultrasound is considered minimal risk procedure, so written consent from the patient is not required.
1. Probe selection
NOTE: ONSD POCUS can be performed with a multitude of different transducers. To evaluate abnormalities in suspected cases of increased ICP, choose a linear high-frequency (5-14...

<ol>
	<li>Hansen, H. C., Helmke, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Validation+of+the+optic+nerve+sheath+response+to+changing+cerebrospinal+fluid+pressure:+ultrasound+findings+during+intrathecal+infusion+tests.">Validation of the optic nerve sheath response to changing cerebrospinal fluid pressure: ultrasound findings during intrathecal infusion tests.</a> Journal of Neurosurgery. 87 (1), 34-40 (1997).</li><li>Bauerle, J., Lochner, P., Kaps, M., Nedelmann, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intra-+and+interobsever+reliability+of+sonographic+assessment+of+the+optic+nerve+sheath+diameter+in+healthy+adults.">Intra- and interobsever reliability of sonographic assessment of the optic nerve sheath diameter in healthy adults.</a> Journal of Neuroimaging. 22 (1), 42-45 (2012).</li><li>Lochner, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intra-+and+interobserver+reliability+of+transorbital+sonographic+assessment+of+the+optic+nerve+sheath+diameter+and+optic+nerve+diameter+in+healthy+adults.">Intra- and interobserver reliability of transorbital sonographic assessment of the optic nerve sheath diameter and optic nerve diameter in healthy adults.</a> Journal of Ultrasound. 19 (1), 41-45 (2016).</li><li>Shokoohi, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optic+nerve+sheath+diameter+measured+by+point-of-care+ultrasound+and+MRI.">Optic nerve sheath diameter measured by point-of-care ultrasound and MRI.</a> Journal of Neuroimaging. 30 (6), 793-799 (2020).</li><li>Montorfano, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mean+value+of+B-mode+optic+nerve+sheath+diameter+as+an+indicator+of+increased+intracranial+pressure:+A+systematic+review+and+meta-analysis.">Mean value of B-mode optic nerve sheath diameter as an indicator of increased intracranial pressure: A systematic review and meta-analysis.</a> The Ultrasound Journal. 13 (1), 35 (2021).</li><li>Jeon, J. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Correlation+of+optic+nerve+sheath+diameter+with+directly+measured+intracranial+pressure+in+Korean+adults+using+bedside+ultrasonography.">Correlation of optic nerve sheath diameter with directly measured intracranial pressure in Korean adults using bedside ultrasonography.</a> PLoS One. 12 (9), e0183170 (2017).</li><li>Maissan, I. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrasonographic+measured+optic+nerve+sheath+diameter+as+an+accurate+and+quick+monitor+for+changes+in+intracranial+pressure.">Ultrasonographic measured optic nerve sheath diameter as an accurate and quick monitor for changes in intracranial pressure.</a> Journal of Neurosurgery. 123 (3), 743-747 (2015).</li><li>Sedwick, L. A., Burde, R. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Unilateral+and+asymmetric+optic+disk+swelling+with+intracranial+abnormalities.">Unilateral and asymmetric optic disk swelling with intracranial abnormalities.</a> American Journal of Ophthalmology. 96 (4), 484-487 (1983).</li><li>Chen, L. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrasonic+measurement+of+optic+nerve+sheath+diameter:+a+non-invasive+surrogate+approach+for+dynamic,+real-time+evaluation+of+intracranial+pressure.">Ultrasonic measurement of optic nerve sheath diameter: a non-invasive surrogate approach for dynamic, real-time evaluation of intracranial pressure.</a> British Journal of Ophthalmology. 103 (4), 437-441 (2019).</li><li>Copetti, R., Cattarossi, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optic+nerve+ultrasound:+artifacts+and+real+images.">Optic nerve ultrasound: artifacts and real images.</a> Intensive Care Medicine. 35 (8), 1488-1489 (2009).</li><li>Aspide, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+proposal+for+a+new+protocol+for+sonographic+assessment+of+the+optic+nerve+sheath+diameter:+The+CLOSED+protocol.">A proposal for a new protocol for sonographic assessment of the optic nerve sheath diameter: The CLOSED protocol.</a> Neurocrit Care. 32 (1), 327-332 (2020).</li><li>Robba, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrasound+non-invasive+measurement+of+intracranial+pressure+in+neurointensive+care:+A+prospective+observational+study.">Ultrasound non-invasive measurement of intracranial pressure in neurointensive care: A prospective observational study.</a> PLoS Medicine. 14 (7), e1002356 (2017).</li><li>Anas, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transorbital+sonographic+measurement+of+normal+optic+sheath+nerve+diameter+in+Nigerian+adult+population.">Transorbital sonographic measurement of normal optic sheath nerve diameter in Nigerian adult population.</a> The Malaysian Journal of Medical Sciences. 21 (5), 24-29 (2014).</li></ol>

The most critical steps of this protocol are ensuring the correct settings are used, such as ophthalmic or small parts, to minimize the energy transmitted to the eye. Additionally, ensuring that the optic nerve and not a blooming artifact is being measured is important.
Within diagnostic POCUS, the evaluation of the ONSD is well-suited to investigating patients with traumatic brain injury to evaluate if there is increased ICP. Although invasive intracranial monitoring remains the gold standard...

The goal of this protocol is to allow bedside providers to rapidly evaluate patients for intracranial hypertension in a non-invasive fashion using point-of-care ultrasound. In recent years, bedside decision-making and treatment have been augmented by the emergence of point-of-care ultrasound (POCUS). POCUS involves the use of ultrasound for diagnostic or procedural guidance by a patient&#39;s primary treatment provider. This article focuses on the diagnostic POCUS of the optic nerve sheath.
The rationale behind this technique is that the optic nerve and sheath communicate with the central nervous system. Specifically, the subarachnoid space extends from inside the skull around the optic nerve. Thus, when the intracranial pressure increases, the optic nerve sheath increases in size. It has been shown in studies with magnetic resonance imaging (MRI) and computed tomography (CT) that the optic nerve does not change in size with increased ICP, but the optic nerve sheath does. The vitreous of the eye provides excellent transmission of sound waves, resulting in the optic nerve being clearly visible as a hypoechoic structure inserted on the posterior eye, with the sheath visible around it. For these reasons, ultrasound of the optic nerve sheath has been used to detect elevated ICP, thus allowing the diagnosis of potentially life-threatening instances of increased ICP1.
However, despite its clinical significance, the proficiency of physicians in using ONSD POCUS is variable2,3, which limits the appropriate use of this modality4. This study aims to describe a time-efficient yet thorough image acquisition protocol for diagnostic ONSD POCUS and to illustrate the abnormal findings commonly found in clinical practice. Multiple imaging protocols have been described in the literature, and they present variations in the structural interpretation, ultrasound settings, marker placement, and scan technique5. Different marker points have varying sensitivity to changes in ICP, and the placement affects the ability to distinguish between patients with normal and high ICP. For these reasons, in this paper, we outline a standard technique to obtain optic nerve sheath images and measure them consistently.
Differences in the measurement location and technique have resulted in widely different thresholds of what is considered to be an abnormal optic nerve sheath5,6. In a recent meta-analysis, the average ONSD for patients without intracranial hypertension was 4.1 mm, and the average ONSD for those with increased ICP was 5.6 mm. A generally accepted threshold for a dilated ONSD is 5.5 mm, but a change in ONSD from a normal baseline is much more predictive if a baseline is available. In the context of severe TBI, the ONSD of both eyes seems to change together7.&#160;There are some individual cases of increased ONSD on one side, but this is rare8.
There are additional challenges in the measurement of ONSD in the severe traumatic brain injury (TBI) population. Patients with severe TBI (defined as having a Glasgow coma score of &#60;8) are not alert enough to follow commands. This means a different approach is required to measure the nerve in this population compared to in patients being evaluated in an ophthalmology office in an elective fashion for neuritis. An A-scan can be used to measure the optic nerve in a cooperative patient that can hold their eye still for a length of time, but this is not a useful technique in TBI patients, so a B-scan is the standard technique (see step 2.7 below).
The use of this method and protocol should be considered for patients for whom there are concerns regarding intracranial hypertension but who do not have an intracranial monitor in place. Specific patient populations that may benefit are trauma patients with a clinical concern for traumatic brain injury in the prehospital or emergency room setting. Additionally, patients in the ICU with a sudden change in neurologic status are good candidates for ONSD POCUS.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Butterfly iQ+ with USB-C 2.0</td>
			<td>Butterfly</td>
			<td>n/a</td>
			<td>Used to obtain one of the images</td>
		</tr>
		<tr>
			<td>Clarius L7HD Portable Ultrasound Machine</td>
			<td>Clarius</td>
			<td>n/a</td>
			<td>Used to obtain one of the images</td>
		</tr>
		<tr>
			<td>Ultrasound Gel</td>
			<td>Parker</td>
			<td>n/a</td>
			<td>Used to obtain all images</td>
		</tr>
		<tr>
			<td>Transparent dressing</td>
			<td>3M</td>
			<td>9534HP</td>
			<td>Used to protect eye</td>
		</tr>
	</tbody>
</table>

optic nerve sheath point of care ultrasound: image acquisition

The goal of this protocol is to develop a standardized method for acquiring images of the optic nerve sheath and measuring the optic nerve sheath diameter (ONSD). Diagnostic ultrasound of the ONSD to detect intracranial hypertension has traditionally faced many problems because of methodologic discrepancies. Due to inconsistencies in the measuring techniques, the potential for ONSD to become a non-invasive bedside monitoring tool for ICP has been hampered. However, establishing a transparent, consistent methodology for measuring the ONSD would support its use as a valid and reliable method of identifying intracranial hypertension. This is important as it has both high sensitivity and specificity in acute care settings. This narrative review describes ONSD POCUS image acquisition, including patient positioning, transducer selection, probe placement, the acquisition sequence, and image optimization. Further, visual aids are provided to assist in real-time during image acquisition. This method should be considered for patients for whom there are concerns regarding intracranial hypertension but who do not have an intracranial monitor in place.

There are several findings that can be seen on the POCUS of the optic nerve sheath and several pitfalls that can occur in the measurements. As can be seen in Figure 5, the nerve typically heads back from the eye at an angle when the eye is in a neutral position. In patients undergoing elective ultrasound of the eye for optic neuritis, for example, the patient is typically asked to move the eye and straighten the nerve to facilitate the measurement of the diameter along the axis of the nerve....

Watch this Scientific Journal Video about Optic Nerve Sheath Point of Care Ultrasound: Image Acquisition at JoVE.com

Optic Nerve Sheath Point of Care Ultrasound: Image Acquisition

Point-of-care ultrasound (POCUS) of the optic nerve sheath diameter (ONSD) has been shown to be useful in identifying patients with increased intracranial pressure (ICP). However, the non-standardized technique for this POCUS has hampered its use. We present a standardized image acquisition protocol for use in the acute care setting.

The goal of this protocol is to develop a standardized method for acquiring images of the optic nerve sheath and measuring the optic nerve sheath diameter ...

Point of Care Ultrasound of the Optic Neuro Sheath Diameter is a useful technique in identifying patients with elevated intracranial pressure. It can be used outside of an ICU because it does not require any invasive techniques, so it can be used in the emergency room or potentially even in the pre-hospital setting. This technique can be used immediately upon the patient's arrival and is easily repeatable.However, the lack of standardization has hampered its widespread use. Here, we present a standardized acquisition protocol. This technique is targeted to patients with severe traumatic brain injury.It can help determine if there is elevated intracranial pressures, which may require specific therapies. To begin, press the select scanner tab on an ultrasound machine and select a linear high frequency probe. Allow the probe to connect wirelessly.For setting up the ultrasound, go to applications and choose ocular or small parts. Check the frequency of the scanner. Set the depth to four centimeters for adult patients.Adjust the depth by scrolling up or down on the touch screen. Set the focal zone to 2.5 centimeters. Check the mechanical index and thermal index.Set the video capture length to at least four seconds. Then select the mode as B mode, and select two dimensional gray scale ultrasound. Patients that are candidates for this procedure are those with concern for intracranial hypertension, such as those with severe traumatic brain injury.Exclude patients with ocular trauma. Position the patient in the default position with the head of the bed at 30 degrees. To perform the scan, apply the ultrasound gel to cover the length of the transducer.Close the patient's eyelid and use a transparent film dressing to hold it closed to prevent corneal abrasion or eye damage. Position the probe for the transverse view over the pupil. Center the probe over the pupil and sweep or fan it over the eye.The globe will be hypoechoic with a distinct transition visible at the back of the eye. Identify the optic nerve as a linear hypoechoic structure posterior to the globe. The sheath will be visible as a hypoechoic boundary of the nerve.Attempt to obtain a view with the nerve headed directly posterior from the back of the eye. Ensure the nerve is visible three millimeters posterior to the globe. Once the adequate view is acquired, take a video of the optic nerve sheath.Then scroll back on the video until the maximum diameter of the optic nerve sheath is seen. Alternatively, press the freeze button when at the maximum ONSD, and use the review slider to ensure that the maximum ONSD has been captured. To measure the nerve, press the annotation button, select the distance caliper.Using the caliper function, measure three millimeters posterior from where the optic nerve attaches to the retina. Press the distance caliper again and measure the outermost lateral borders of the optic nerve sheath. Save the annotated image by pressing the save button on the bottom right of the screen.To obtain a sagittal view, center the probe on the eye. Follow the same steps. As for the transverse view, obtain an adequate image and measure the ONSD.When taking measurements, when the eye is in a neutral position, the nerve typically heads back at an angle. Patients can be requested to move the eye so that the nerve is headed straight back. In cases where commands cannot be followed, for example, in patients with traumatic brain injury, the nerve will head back at an angle.It is recommended to measure along the axis of the nerve if it does not head straight back. It is also essential to be aware of potential pitfalls such as mistaking the optic nerve for its sheath, or not using settings or probes with sufficient resolution to distinguish the sheath and nerve. Also, acoustic artifacts like blooming can create interference and misreading.A blooming artifact from structures on the posterior eye shows that there is no rounded nerve head, no sheath, and the shadow appears very rectangular. Whereas when the optic nerve and sheath are visible, the rounded head of the nerve and the sheath are clearly seen. A common struggle in Point Of Care Ultrasound for the Optic Nerve Sheath Diameter is finding the nerve on a sweep.This can be mitigated by gently rocking the probe back and forth until it comes into view, and by angling the probe slightly towards the midline. Additional to this technique, you can also use color flow doppler to help identify the optic nerve. This can help differentiate it from other artifacts that may be present in the image.

Research

JoVE Journal

Medicine

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