Effects of acute intracranial pressure change on human and pig optic nerve head using optical coherence tomography

Abstract

Purpose : We assessed the effect of acute intracranial pressure (ICP) decrease after lumbar puncture (LP) in humans and acute ICP increase in a pig model on the optic nerve head (ONH) morphology. We hypothesized that acute ICP increase would lead to anterior shift of lamina cribrosa (LC) and acute ICP decrease a posterior LC shift.

Methods : LP study: ONH imaging (12 enhanced depth imaging (EDI) radial sections; Cirrus HD-OCT), intraocular pressure (IOP), CSF opening (OP) and closing (CP) pressures were obtained in 19 subjects before and after LP. Bruch’s membrane opening diameter (BMOD) and anterior lamina cribrosa depth (ALCD) were measured by 2 graders for all 12 radial sections after importing the images into Image J software. Repeated measures ANOVA evaluated differences in BMOD and ALCD before and after LP.
Pig study: ICP was increased in 5mm Hg increments using lumbar drain in 3 anesthetized pigs, while ICP was monitored by a parenchymal monitor (Integra Camino). At each ICP level (stabilized to ±2mm Hg for 10 minutes), ONH imaging of right eye (12 EDI radial sections; Spectralis OCT), IOP of left eye (Pneumotonometery) were obtained. ONH images were graded as above. Change for each variable was calculated and modeled as a fixed effect for longitudinal data. Slopes were evaluated for statistical significance to determine if changes in ICP were associated with changes in BMOD and ALCD.

Results : LP study: Mean CSF-OP was 15.5mm Hg (range: 4- 31mm Hg); mean ICP change was 8mm Hg (range: 2.6-17.7mm Hg). There was a small, statistically insignificant IOP decrease after LP in IIH patients (1.2mm Hg) vs. non-IIH (0.3mm Hg).
Pig study: Baseline ICP was 4.5 mm Hg (range 1.5-8 mm hg) and maximal stable ICP ranged from 18-32 mm Hg. Acute ICP elevation led to IOP increase in pig models (discussed separately).
In both studies, no significant changes of BMOD and ALCD were seen in all 12 radial sections following ICP changes.

Conclusions : Acute ICP changes did not produce measurable changes of ONH morphology in humans and pig. The LC appears resistant to significant displacements despite large changes of ICP possibly from compensatory mechanisms such as IOP changes. Study limitations include small sample size and/or small effect size.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.

 

Measurement of BMOD and ACLD of ONH images in Image J in pigs (c- baseline; d- raised ICP)