Chapter 11

OPTIC DISC EDEMA

Several disorders can simulate optic disc swelling, and numerous conditions can cause it. Table 11–1 lists the possible conditions that result in optic disc edema. This chapter is intended to help clarify the nature of the problem when the physician observes that the optic disc is swollen.

Clinically distinguishing among the various causes of optic disc swelling requires careful review of the history and the elements of the eye examination (see Section I). The history should clarify whether or not there is subjective vision impairment, either transient or persistent. If persistent, was the onset abrupt or gradual? Is the disorder unilateral or bilateral? Is eye pain or headache a symptom? Are there associated systemic or neurologic diseases? Have there been symptoms of increased intracranial pressure such as headache, transient visual obscurations on standing, pulsatile tinnitus, or nausea and vomiting? Has there been any indication of an orbital disorder?

The examination should indicate the level of mental alertness of the patient and the systemic blood pressure. The status of the vision, by measuring the best corrected visual acuity, the color vision, and the visual fields, is important in clarifying the problem. It is important to recall that there can be substantial impairment of vision without reduction of visual acuity. Observing the briskness of the pupil reaction to light helps estimate the function of the optic nerve. Evaluation for possible orbital abnormalities would include assessing exophthalmometry, orbital resiliency, and the presence of an orbital or cranial bruit. At times, performing fluorescein angiography to assess the circulation to the optic disc is of value. Although normal discs have late staining of the disc itself, extension of the leakage beyond the optic disc margins indicates pathologic swelling. Are there anomalous vessels on the disc surface that produce more than two branches of a parent vessel (trifurcations or tetrafurcations)?

Table 11–1 indicates possible diagnostic considerations when there appears to be optic disc edema. The initial issue to resolve is whether there is truly pathologic acquired swelling of the disc, or just that the disc itself is congenitally elevated, that is, “pseudopapilledma,” best typified by optic nerve drusen. The lack of obscuring of the vessels as they pass over the edge of the elevated optic disc is a reliable indicator that the elevated disc is an anomaly, and that the disc is not pathologically swollen. The presence of anomalous vessels on the disc is common in pseudopapilledema. If the disc is truly swollen, the task then is to determine if it is papilledema (due to increased intracranial pressure) or another cause of optic disc edema.

BROAD CATEGORY 1: PSEUDOPAPILLEDEMA

OPTIC DISC DRUSEN (SEE CHAPTER 23)

Classic Presentation^1,2

• The patient may be asymptomatic or have any symptom that is unrelated to the optic nerves (Fig. 11–1).

• Can be unilateral (32%) or bilateral (68%), and occurs in all age groups.

• Visual acuity is almost always normal, but nerve fiber bundle visual field defects are common.

• A relative afferent pupil defect can occur if the optic nerve dysfunction is greater in one eye than in the other.

• Small hemorrhages on the optic disc surface can rarely occur, and rarely peripapillary choroidal neovascularization can develop that may require laser photocoagulation.

• The suspected presence of optic disc drusen can be confirmed by the presence of autofluorescence of the disc with fundus photography (Fig. 11–1c,d), or by demonstrating the drusen with ultrasonography or computed tomographic (CT) scans.

• Some optic discs can be elevated despite our inability to demonstrate drusen, and either represent “buried” drusen deeper in the nerve, or simply more optic nerve tissue than normal, which is a congenital anomaly of the disc. Persons with congenital tortuosity of the retinal vessels or with substantial hyperopia also can have elevated discs that are not pathologically swollen.

HYPEROPIC DISCS

Classic Presentation

• The patient may be asymptomatic or have any symptom that is unrelated to the optic nerves.

• The patient is hyperopic.

• There is normal visual function.

• The discs are elevated, but there are no hemorrhages, obscuration of the vessels as they cross the disc margin, engorged veins, or cotton wool spots.

Red Flag

The presence of any additional fundus abnormalities should prompt pursuit of an alternative diagnosis.

BROAD CATEGORY 2: PAPILLEDEMA

When it is evident that there is pathologic optic disc swelling with obscured vessels, and perhaps associated hemorrhages and/or exudates, noting whether there is unilateral or bilateral involvement is important. It should be stressed that the term papilledema should be used to indicate optic disc swelling secondary to elevated intracranial pressure (ICP). It is almost always bilateral, and only rarely asymmetric (Fig. 11–2). When there is unilateral optic disc swelling, one considers as possible causes a local optic disc inflammation (the “papillitis” variant of optic neuritis, as opposed to “retrobulbar” optic neuritis) (Fig. 11–3); a vasculopathy such as ischemic optic neuropathy or papillophlebitis (Fig. 11–4); poorly understood inflammatory disorders such as neuroretinitis³ (Fig. 11–5), or the acute idiopathic blind spot enlargement (AIBSE) syndrome,^4–6 or a neoplasm (as with an optic nerve sheath meningioma or glioma) (Fig. 11–6);^4,5,7 With bilateral optic disc swelling, in addition to papilledema, one considers the possibilities of bilateral involvement with optic neuritis or ischemic optic neuropathy, systemic arterial hypertension, or diabetic papillopathy (Fig. 11–7).^7–9

PAPILLEDEMA

• Bilateral, similar optic disc edema with good optic nerve function (Fig. 11–2).

• Symptoms of elevated intracranial pressure such as headache, nausea, vomiting, or diplopia due to an esotropia caused by cranial nerve VI dysfunction.

• Transient obscurations of vision lasting 5 to 10 seconds, especially with posture changes.

• Early in the course, the visual acuity is normal, and visual fields show enlarged blind spots.

• Degree of fundus vascular changes (hemorrhages, exudates) relates to rapidity and severity of the rise in ICP.

• With protracted and severe papilledema, ischemic insults to the optic nerves can cause inferior nasal visual field defects initially, though generalized peripheral visual field loss and even blindness can occur with severe involvement.

The diagnosis of pseudotumor cerebri as the cause for papilledema should not be made until neuroimaging excludes the possibilities of hydrocephalus, a mass, or a dural venous sinus thrombosis, and a lumbar puncture reveals an elevated ICP with normal cerebrospinal fluid10 (see Chapter 17).

In an asymptomatic patient, the presence of true papilledema is uncommon, but normal optic discs do not rule out elevated intracranial pressure.

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