Figure 15-7 Sarcoidosis. A, Low-magnification photomicrograph of the optic nerve with discrete noncaseating granulomas (arrows). B, Higher magnification shows multinucleated giant cells (arrow) in the granulomas. (Courtesy of Hans E. Grossniklaus,

MD.)

Sarcoidosis of the optic nerve is often associated with retinal, vitreal, and uveitic lesions (Fig 15- 7; see also Chapter 12, Fig 12-8). Unlike the characteristic noncaseating granulomas in the eye, optic nerve lesions may feature necrosis.

Degenerations

Optic Atrophy

Injury to the retinal ganglion cells and to the axons of the peripheral optic nerve (that portion of the nerve near the retina) results in axonal swelling. This swelling manifests clinically as optic disc edema (Fig 15-8). Axonal swelling and loss of retinal ganglion cells are followed by retrograde degeneration of axons (ascending atrophy, Wallerian degeneration) toward the lateral geniculate body. Pathologic processes within the cranial cavity or orbit result in descending atrophy toward the retinal ganglion cells (see BCSC Section 5, Neuro-Ophthalmology).

Figure 15-8 Optic disc edema. Swollen prelaminar axons demonstrate vacuolar alteration (red arrows) and displace the retina laterally (red arrowhead) from its normal termination just above the end of the Bruch membrane (black arrowhead). Juxtapapillary serous intraretinal fluid/hard exudates (black arrows) and serous subretinal fluid (asterisk) are also observed.

(Courtesy of Tatyana Milman, MD.)

Axonal degeneration is accompanied by loss of myelin and oligodendrocytes. The optic nerve shrinks despite the proliferation of astrocytes and of fibroconnective tissue in the pial septa (Fig 15- 9).

Cavernous optic atrophy of Schnabel is characterized microscopically by large cystic spaces that are posterior to the lamina cribrosa and contain mucopolysaccharide material, which stains with alcian blue stain (Fig 15-10). Although the changes associated with cavernous optic atrophy were initially observed in glaucomatous eyes after acute intraocular pressure elevation, the condition has been increasingly identified in nonglaucomatous elderly patients with generalized arteriosclerotic disease. The mucopolysaccharide was originally thought to be vitreous, forced by increased intraocular pressure into the ischemic necrosis–induced cavernous spaces, but it is more likely produced in situ, within the atrophic spaces of the optic nerve.

Giarelli L, Falconieri G, Cameron JD, Pheley AM. Schnabel cavernous degeneration: a vascular change of the aging eye. Arch Pathol Lab Med. 2003;127(10):1314–1319.

Figure 15-9 Atrophic optic nerve. A, Gross appearance of atrophic optic nerve. B, Low-magnification photomicrograph. Note the widened subdural space (asterisks). C, High magnification. Transverse or cross section of atrophic nerve shows loss of axons (arrowheads), accompanied by glial proliferation and widening of fibrovascular pial septa (arrows). D, Glaucomatous optic atrophy. Masson trichrome stains the collagen of the sclera, lamina cribrosa, and meninges dark blue and the axonal fascicles pink. The optic nerve demonstrates advanced cupping (red arrow), accompanied by posterior bowing of the lamina cribrosa (arrowheads). Axonal atrophy and thickening of pial septa are present. The intermeningeal space is widened due to severe optic nerve atrophy (double-ended arrow). CRA = central retinal artery, P = pia, A =

arachnoid, D = dura. (Part A courtesy of Debra J. Shetlar, MD; parts C and D courtesy of Tatyana Milman, MD.)