PATTERN OF AXONAL LOSS IN LONGSTANDING PAPILLEDEMA DUE TO IDIOPATHIC INTRACRANIAL HYPERTENSION

There is both clinical and histopathologic evidence for peripheral vis ual field loss and optic nerve degeneration in longstanding papilledem a due to idiopathic intracranial hypertension (IIH). The purpose of th is study was to look at the extent and distribution of axonal dropout in secondary optic atrophy due to IIH. Both optic nerves from a 29-yea r-old man with a two year history of IIH were examined histologically and morphometrically. A high-contrast lipid (myelin) stain, paraphenyl enediamine (PPD), and a semiautomated image analysis system were emplo yed to resolve sufficiently the optic nerve fiber images for counts an d for measurement. There were 80% and 90% losses of axons, respectivel y, in the right and left optic nerves consequent to IIH. The axonal lo ss in the peripheral area of each optic: nerve was much more severe th an that in inner sectors (= 0.001 for the right optic nerve and = 0.00 5 for the left). This pattern of axonal dropout is consistent with the preservation of good central visual acuity despite devastating optic nerve atrophy, and with the severe peripheral visual field loss noted in this patient.