A Child Presenting With Optic Nerve Edema

Monica Pacheco, MD; Kimberly G. Yen, MD

Disclosures

October 02, 2007

Discussion

Pseudopapilledema is a term that refers to optic nerve head anomalies that may give the appearance of true optic nerve edema. True optic nerve edema may be secondary to increased intracranial pressure, in which case it is referred to as papilledema. True optic disc edema may be also caused by compressive optic neuropathies, papillitis, anterior ischemic optic neuropathy, central retinal vein occlusion, juvenile diabetic papillopathy, and optic disc vasculitis. It is important to make the correct diagnosis because of the differences in outcomes and treatment of the 2 entities, as well as to avoid unnecessary testing in those cases in which testing is not needed.

The most common cause of pseudopapilledema is optic nerve head drusen. Optic nerve head drusen are round, whitish yellow, refractile bodies that are often calcified. Drusen are usually found buried within the optic nerve in childhood and gradually surface over the years. They produce elevation of the disc and blurring of its margins, similar to optic nerve head edema. They are bilateral but asymmetric in 66% to 78% of cases,[1,2,3] and their prevalence is estimated at 2%, from autopsy in population studies.[4] Optic nerve drusen usually occur sporadically, but familial cases of optic drusen have also been described in the literature. Theories aimed at explaining the pathogenesis of optic disc drusen include: axonal degeneration of the optic nerve head,[5] mesodermal dysgenesis of the optic nerve head resulting in a small sclera canal with vascular anomalies,[6] and aberrant axoplasmic transport.[7]

Clinical differences that are generally present in true optic nerve edema and not in pseudopapilledema are:

  1. The presence of optic disc hyperemia, associated with congestion of optic disc microvasculature;

  2. The presence of disc surface microvascular abnormalities, such as capillary dilation, telangiectasia, and flame hemorrhages; and

  3. Optic disc margin blurring with obscuration of retinal vessels secondary to nerve fiber layer edema.

The presence of any one of these factors would be suggestive of true optic nerve edema.

Most patients with optic disc drusen are asymptomatic; hence, optic disc drusen are incidental findings on routine eye exams. Occasionally, transient visual obscurations may be associated with optic nerve head drusen. When asymmetric, they may be associated with an RAPD.

Ultrasonography is the gold standard for optic nerve head drusen identification but may also be documented on CT scan. (Because the optic nerve drusen were seen on CT scan, an ultrasound was not necessary in our patient.) Although optic nerve head drusen are rarely associated with visual acuity reduction (studies suggest an incidence of 0.65% to 1.4% of cases[8,9]), they may be associated with visual field defects of varying severity that progress slowly over years.[10,11] Therefore, although there is no need to treat them, it is important that they be identified. Visual field defects commonly associated with optic disc drusen are enlarged blind spot, inferior arcuate, sector or altitudinal or both,[11] and visual field constriction.[12,13] Morbidity associated with drusen include retinal hemorrhages,[14,15] which may or may not be associated with peripapillary neovascular membranes,[14] ischemic optic neuropathy,[16] amblyopia, retinal dystrophies, optic nerve gliomas, macular telangiectasia, and angioid streaks.[14] Drusen are generally found incidentally on routine eye examination, and no routine screening for this condition is recommended or available.

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