Letter to the Editor
May 2023
Effect of Interscalene Brachial Plexus Block on Intracranial Pressure: Are the Measures of Optic Nerve Sheath Diameter Standardised with B-Scan?
By
Mario Graziano, Marco Gioia, Danilo Biondino
Affiliations
- Department of Opthalmology, University of Salerno, Salerno, Italy
doi: 10.29271/jcpsp.2023.05.596
Sir,
We read with great interest the original article by Gundogdu et al. about the evaluation of the optic nerve sheath diameter (ONSD) measurement by ultrasound (US) to evaluate the effect of Interscalene Brachial Plexus Block on Intracranial Pressure (ICP).1 We laud our colleagues for their interesting article, but we would like to make some comments.
In this study, the authors have applied US B-scan technique and the measurements were obtained with a portable US device and a 6-10 MHz linear probe.
B-scan is very sensitive in detecting small optic nerve calcifications as in cases of optic nerve drusen,2 but it is not so reliable in case of measurements.
We are aware that evaluation of the ONSD by US B-scan has been applied as a non-invasive technique to identify an increased ICP, but unfortunately, a considerable number of artefacts could make that evaluation not strictly accurate.3
To avoid these complications, a more accurate investigation could have been achieved with the so-called standardised A-scan technique.4
Moreover, the authors have examined the patients putting the probe on closed eyelids. Thus, it is not clear if the eye is in the primary gaze position.
Changing of eye position leads to a variation of the cerebrospinal fluid amount that surrounds the optic nerve and a different ONSD value.
Furthermore, close eyelids cause an attenuation of US, so they lead to a reduction of image quality, with an even more uncertain outcome.
So, it has been recommended to examine all the patients with open eyelids and with eyes in the primary position using the anaesthetic eyedrops and utilising methylcellulose as a coupling medium between the eye and the US probe.5
REFERENCES
- Gundogdu O, Avci O. Evaluation of the effect of interscalene brachial plexus block on intracranial pressure using optic nerve sheath diameter and internal jugular vein collapsibility index. J Coll Physicians Surg Pak 2022; 32(10):1249-54. doi: 10.29271/jcpsp.2022.10.1249.
- Rosa N, De Bernardo M, Abbinante G, Vecchio G, Cione F, Capasso L. Optic nerve drusen evaluation: a comparison between ultrasound and OCT. J Clin Med 2022; 11(13): 3715. doi: 10.3390/jcm11133715.
- De Bernardo M, Vitiello L, Cornetta P, Rosa N. Ocular ultrasound evaluation of optic nerve sheath diameter in military environments. Mil Med Res 2019; 6:16. doi: 10.1186/s40779-019-0207-8.
- Rosa N, De Bernardo M, Di Stasi M, Cione F, Capaldo I. A-scan ultrasonographic evaluation of patients with idiopathic intracranial hypertension: Comparison of optic nerves. J Clin Med 2022; 11(20):6153. doi: 10.3390/jcm11206153.
- Graziano M, Di Paola I, Marotta G, Cornetta P, Capasso L. Letter to Editor: The Cushing reflex and the vasopressin-mediated hemodynamic response to increased intracranial pressure during acute elevations in intraabdominal pressure. Surgery 2022; 172(2):777. doi: 10.1016/j.surg. 2022.01.047.
Authors Reply Section
By
Oguz Gundogdu
Affiliations
- Dr. Oguz Gundogdu, Department of Anesthesiology and Reanimation, Sivas Cumhuriyet University, Sivas, Turkey
AUTHOR'S REPLY:
Sir,
We would like to thank you for your interest in our article. To our knowledge, most of the optic nerve sheath diameter (ONSD) measurements were performed in B-scan mode.1-3 However, A-scan mode is preferred recently, because of some artefacts and blooming problems in B-scan mode. We think the best ONSD examination method is the combined use of A-scan and B-scan. There is a recent article supporting this idea.4 Unfortunately, our portable US did not have A-scan mode. So, we could not perform ONSD measurements in A-scan mode.
Our patients in the study did not have any sedative agents, and they were cooperative. They had been ordered to look across and not to move their eyes to limit the change of position of the primary gaze. The preferred measurement method includes closed eyelids because of the possibility of eye infection. Furthermore, most of the ONSD measurements were performed in the closed eyelid positions.5-7
REFERENCES
- Raghunandan N, Joseph M, Nithyanandam S, Karat S. Role of ultrasonographic optic nerve sheath diameter in the diagnosis and follow‑up of papilledema and its correlation with Frisén’s severity grading. Indian J Ophthalmol 2019; 67:1310-3.
- Raj G, Singh R, Deodhar M, Chauhan A, Kumar T, Gaur M. B-scan measurement of optic nerve sheath diameter as a marker of elevated intracranial pressure. Int J Res Med Sci 2017; 5(6):2397-400.
- Kerscher SR, Zipfel J, Groeschel S, Bevot A, Haas-Lude K, Schuhmann MU. Comparison of B-Scan ultrasound and mri-based optic nerve sheath diameter (ONSD) measurements in children. Pediatr Neurol 2021; 124:15-20.
- Vitiello L, Salerno G, De Bernardo M, D’Aniello O, Capasso L, Marotta G, et al. Ultrasound detection of intracranial hypertension in brain injuries. Front Med (Lausanne) 2022; 9:870808. doi: 10.3389/fmed.2022.870808.
- Kerscher SR, Zipfel J, Groeschel S, Bevot A, Haas-Lude K, Schuhmann MU. Comparison of B-scan ultrasound and mri-based optic nerve sheath diameter (ONSD) measurements in children. Pediatr Neurol 2021; 124:15-20. doi: 10.1016/ j.pediatrneurol.2021.08.002
- Chen LM, Wang LJ, Hu Y, Jiang XH, Wang YZ, Xing YQ. Ultrasonic measurement of optic nerve sheath diameter: A non-invasive surrogate approach for dynamic, real-time evaluation of intracranial pressure. Br J Ophthalmol 2019; 103(4):437-41. doi: 10.1136/bjophthalmol-2018-312934.
- Rajajee V, Fletcher JJ, Rochlen LR, Jacobs TL. Comparison of accuracy of optic nerve ultrasound for the detection of intracranial hypertension in the setting of acutely fluctuating vs stable intracranial pressure: Post-hoc analysis of data from a prospective, blinded single centre study. Crit Care 2012; 16(3):R79. doi: 10.1186/cc11336.