Optic nerve axoplasm and papilledema.

A detailed review of optic nerve axoplasm is presented. A number of hypotheses have been postulated for the pathogenesis of papilledema associated with increased intracranial pressure. These hypotheses, mechanical and nonmechanical, are critically evaluated in relation to five essential features of papilledema. Theories, as well as clinical and experimental studies, of axonal transport are reviewed, and a new hypothesis is proposed: Papilledema is primarily a mechanical, nonvascular phenomenon in which an excess amount of extracellular fluid is present in the prelaminar region of the optic disc and the accumulation of that fluid results from the leakage of axoplasm from optic nerve fibers which are compressed posterior to the lamina cribrosa of the optic disc. The authors believe that this is the only existing hypothesis consistent with all the known facts about papilledema. Discussions by Drs. J. Terry Ernest, Thomas R. Hedges, and S. S. Hayreh follow the review.