Optic Disc Edema in Raised Intracranial Pressure

TLDR

The study examined 21 optic nerve heads from 13 rhesus monkeys with papilledema induced by chronically raised intracranial pressure via subarachnoid balloon implantation, using light and electron microscopy, and applied horseradish peroxidase tracer to nine eyes. Histopathology revealed severe axonal swelling and cytoid body formation with mild interstitial edema and vascular leakage in laminar and retrolaminar regions, while glial cells showed no intracellular edema, indicating that axonal swelling chiefly accounts for the optic disc edema seen ophthalmoscopically.

Abstract

Optic nerve heads of 21 eyes from 13 rhesus monkeys that had developed papilledema secondary to chronically raised intracranial pressure from balloon implantation in the subarachnoid space were studied by light and electron microscopy. Nine eyes were also examined with the horseradish peroxidase tracer technique. The pathologic changes in the optic nerve head included severe axonal changes and mild interstitial edema. Axonal alteration ranged from axonal swelling to formation of cytoid bodies. Interstitial edema and vascular leakage of horseradish peroxidase were noted in the posterior lamina retinalis, lamina choroidalis and lamina scleralis (prelaminar and lamina cribrosa regions), as well as in the retrolaminar myelinated optic nerve. No intracellular edema of the glial elements was noted. Axonal swelling was so prominent that it appeared to be primarily responsible for the overall swelling of the optic disc observed ophthalmoscopically.