Highlights
- •Optic nerve sheath dilation follows a logarithmic time course.
- •Sheath diameters (ONSD) correlate to applied subarachnoid pressure levels.
- •Dilation starts rapidly (10–20 s) and saturates after 200 s.
- •Relative changes of ONSD may be a future target for neuromonitoring.
Abstract
Background
Optic nerve sheath (ONS) dilation indicates intracranial pressure elevation under
clinical conditions but limited data exist with regard to the dynamics of sheath expansion.
Objective
To assess the time course of ONS widening and its stability under controlled pressure
conditions in vitro.
Methods
Pre-defined pressure steps up to 65 mmHg were applied to the perineural space of ex-vivo
human optic nerves (n = 16). Using ultrasound, the optic nerve sheath diameter (ONSD) was monitored over
500 s. Re-tests at low-pressure levels concluded each experimental series.
Results
In most cases, 50% of the total diameter-change were achieved within 50 s after pressure
onset and 95% of the maximal diameter after 200 s. The diametric gains in each experiment
were strongly correlated with the applied pressure levels (coefficient of variance
0,96) within preparations with variability of the transfer function across preparations.
The time course of the dilation was found to follow an approximate natural logarithmic
function (R2 = 0.93–0.99). The re-test condition revealed unchanged time course properties (5%
significance level) despite starting regularly from a higher baseline-diameter after
preceding exposures.
Conclusions
ONS dilation commences rapidly after pressure exposure with a predictable time course
over 3–4 min. Elasticity changes presumably affecting trabecular structures cause
upward shifts of the optic nerve sheath pressure response. Clinically, ONSD shifts
should be considered in serial measurements for increasing intracranial pressure monitoring,
but relevant response delays are absent for lower or higher changes of intracranial
pressure.
Keywords
Abbreviations:
ON (optic nerve;), ONSD (optic nerve sheath diameter), ICP (intracranial pressure), SAS (subarachnoid space), CSF (cerebrospinal fluid), SD (standard deviation), ME (modulus of elasticity)To read this article in full you will need to make a payment
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Article info
Publication history
Published online: July 31, 2022
Accepted:
July 25,
2022
Received in revised form:
July 4,
2022
Received:
April 21,
2022
Identification
Copyright
© 2022 Published by Elsevier B.V.
