Ocular Pathology

Anatomy and pathology of the human eye. Use it to review eye pathology for Ophthalmology Board Review or OKAP.

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Wednesday, February 07, 2007

Cavernous Atrophy of the Optic Nerve

Cavernous Optic Atrophy of Schnabel
Definition: degeneration of the optic nerve characterized by cystic spaces in the anterior portion.
Incidence/ Prevalence: The prevalence is 2.1% in an autopsy series. These changes occur commonly in patients with glaucoma after acute IOP elevation, but are perhaps more common in nonglaucomatous elderly patients with generalized arteriosclerotic disease (Ref 1.)
Etiology: In most cases it is thought that vascular disease plays the primary role. The cystic spaces are created by the loss of neuronal tissue that is more sensitive to ischemic injury than the surround supportive connective tissue. In some cases it is associated with glaucoma, perhaps by a vascular mechanism.
Clinical Findings: Most of the patients are elderly (mean age 88), most in women (81%), the condition is usually unilateral (82%). Glaucoma was present in only 23.7% of patients in this series (Reference 1).

Histopathology: Cavernous optic atrophy of Schnabel is characterized microscopically by large cystic spaces (surrounded by arrows 1 in gross and microscopic figures) containing mucopolysaccharide material, which stains with alcian blue dye, posterior to the lamina scleralis. The intracystic material is thought to be vitreous that penetrates into the parenchyma through the internal limiting membrane of the optic nerve head.
In the illustration below, we interpret this to be a focal infarction of the optic nerve that is the beginning of cavernous atrophy. The arrows surround the lighter area that forms a myxoid or cystic appearance. The arachnoid space (number 2) is widened and the dura is thickened (number 3). Most patients are believed to have arteriosclerosis as was evident in narrowing and hyalinization of central retinal artery wall. In this patient the vessels appear patent (arrow 5).
Ganglion cells and nerve fiber layer loss are present in the retina in this case (arrow 4). Cupping and retrodisplacement of the lamina scleralis are also evidence of co-existent glaucoma especially if in combination with patent and normal appearing central retinal arteries. At higher magnification the cystic spaces are lined by thin septa forming a web of neurofibrillary material. This case had only a hint of alcian blue material suggesting it is really a very early lesion.
Treatment: By definition, the diagnosis of cavernous atrophy is made once an eye has been removed and the optic nerve has been sectioned. The fellow eye should be examined in cases to determine if glaucoma is present.

Giarelli L, Schnabel cavernous degeneration Arch Pathol Lab 2003:10:1314-9.

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