Indian Journal of Critical Care Medicine
Volume 27 | Issue 6 | Year 2023

Reply: Optic Nerve Sheath Diameter in Hyponatremia: A Closer Look

Upendra Hansda1https://orcid.org/0000-0002-5703-4135, Ijas Muhammed Shaji2https://orcid.org/0000-0001-6338-2892, Sanjeed Uttanganakam3https://orcid.org/0000-0002-2322-5400

1–3Department of Trauma and Emergency, All India Institute of Medical Sciences, Bhubaneswar, Odisha, India

Corresponding Author: Upendra Hansda, Department of Trauma and Emergency, All India Institute of Medical Sciences, Bhubaneswar, Odisha, India, Phone: +91 6742476400, e-mail: uhansdah@gmail.com

How to cite this article: Hansda U, Shaji IM, Uttanganakam S. Reply: Optic Nerve Sheath Diameter in Hyponatremia: A Closer Look. Indian J Crit Care Med 2023;27(6):453.

Source of support: Nil

Conflict of interest: None

Keywords: Hyponatremia, Optic nerve sheath diameter, Ultrasonography.

Dear Editor,

Thanking the authors for reading our article with interest and appraising a few facets. Yes, we agree about the influence of scattering and blooming effect of ultrasonographic waves by using a B-scan. However, the B-scan is easier to use, can be done quickly, and used in patients with altered sensorium. It is commonly used in the emergency department. Also, a fixed distance from the globe on the optic nerve can be chosen which is difficult with A-scan.1

In our study, the investigators were not blinded as per the study methodology. The optic nerve sheath diameter (ONSD) was measured at two-time points, one at presentation to the emergency department and the other at the time of discharge. So, the second measurement could not be blinded as it was measured after the correction of hyponatremia at the time of discharge. Another study can be planned where blinding can be done in serial measurements of the ONSD during the correction of hyponatremia.2

The reply for the alteration of cerebrospinal fluid (CSF) production and dynamics in hypovolemia is that the CSF production is constant and is actively secreted by the choroidal plexus through the combined activity of numerous membrane proteins irrespective of choroidal blood flow.3 We believed to take the ONSD values separately on each side instead of an average of either side. Because optic nerve sheaths could have septation and trabeculations.4


Upendra Hansda https://orcid.org/0000-0002-5703-4135

Ijas Muhammed Shaji https://orcid.org/0000-0001-6338-2892

Sanjeed Uttanganakam https://orcid.org/0000-0002-2322-5400


1. Newman WD, Hollman AS, Dutton GN, Carachi R. Measurement of optic nerve sheath diameter by ultrasound: A means of detecting acute raised intracranial pressure in hydrocephalus. Br J Ophthalmol 2002;86(10):1109–1113. DOI: 10.1136/bjo.86.10.1109.

2. Arunachala S. Optic Nerve Sheath Diameter and Sodium Levels: A Friend of a Friend is Still a Stranger. Indian J Crit Care Med 2023;27(4):235–236. DOI: 10.5005/jp-journals-10071-24444.

3. Simon MJ, Iliff JJ. Regulation of cerebrospinal fluid (CSF) flow in neurodegenerative, neurovascular and neuroinflammatory disease. Biochim Biophys Acta 2016;1862(3):442-451. DOI: 10.1016/j.bbadis.2015.10.014.

4. Killer HE, Jaggi GP, Miller NR. Papilledema revisited: is its pathophysiology really understood? Clin Exp Ophthalmol. 2009;37(5):444–447. DOI: 10.1111/j.1442-9071.2009.02059.x.

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