Ординатура / Офтальмология / Английские материалы / Neuro-Ophthalmology_Kidd, Newman, Biousse_2008

edema” refer to generic disc swelling, whereas we reserve papilledema for swelling because of increased pressure in the brain.

Experiments by Tso and Hayreh1 showed that “axoplasmic stasis” was the basic mechanism of any cause of disc swelling, whether it resulted from papilledema (inflated intracranial balloons and high-dose radiation to the brain) or from ocular hypotension (ciliary body destruction). They demonstrated that axoplasmic stasis occurred at the lamina cribrosa. Other researchers confirmed these findings and also observed that edema occurred after tying a ligature around the retrobulbar portion of the optic nerve.2,3 Therefore, swelling of the axons causes the nerve to swell. An atrophic nerve cannot swell; thus, a functional nerve must have axons. The features that we look for in papilledema are related to axonal swelling.

OPHTHALMOSCOPIC FEATURES (FIG. 12–1)

To recognize true disc swelling, a review of specific characteristics is needed.4

Is the disc elevated? When viewing the disc monocularly through an ophthalmoscope, one should look for clues that elevation is present. Do the arteries and veins appear to drape over the top of the disc? In addition, one should focus the ophthalmoscope on the plane of the retina and then focus the ophthalmoscope at the top of the disc. Is there a change in the diopters that suggests an elevated optic disc? (Fig. 12–1A).

Is a cup present? In true papilledema, the cup is preserved until very late in the swelling process, whereas a disc in which the cup is absent has a greater chance of being associated with pseudo-swelling (Fig. 12–1B).

Is the disc hyperemic? Although this is one of the least useful signs of true disc swelling, it is present in most cases of papilledema. Hyperemia can occur because there are small dilated capillaries on the disc (Fig. 12–1C).

Is the nerve fiber layer thickened and blurred? In true swelling, the vessels will be lost in the nerve fiber because of this thickened layer. In pseudoswelling, the vessels appear to drape over the top of the disc (Fig. 12–1D).

Is there anomalous branching? In papilledema, the vessels are usually normal, although anomalous discs can occasionally show papilledema. Most anomalous discs may have abnormal branching patterns such as trifurcations or tetrafurcations.

Are the veins dilated? In papilledema, the venous structures are generally dilated. An older term for papilledema is “choke”: the vessels and the disc are squeezed, but the veins are not particularly swollen (Fig. 12–1E).

Are there venous pulsations? One should view one of the large trunks of the

veins at the disc margin. Hedges found that 70% of those with healthy eyes and brains, but no increased pressure, had venous pulsations.5 Venous pulsations can be viewed at http://medlib.med.utah.edu/NOVEL/Moran/ index3.html. One should be cautious in interpreting these findings: indivi-

duals with normal ICP may have no venous pulsations, and pulsations have been documented in patients with elevated ICP.4

Incidental Findings with True Disc Swelling

Is there hemorrhage? In true disc swelling, hemorrhage can be present. However, this is not absolute, because a splinter hemorrhage can be present in some forms of pseudo-swelling (Fig. 12–1F).

G H

Figure 12–1 Cont’d—G, Retinal exudates. H, Retinal folds.

Are there exudates? Although exudates are not usually present until papilledema is fully established, their presence can signal an active process (Fig. 12–1G).

Are there retinal folds? On occasion, retinal folds will accompany papilledema. Although this is not required for disc swelling, it is an incidental finding (Fig. 12–1H).

Table 12–1 shows the Lars Frise´n staging scheme, which is used to classify

papilledema.6 Knowing the classification of disc swelling enables the clinician to determine an improvement or worsening of the swelling and to communicate the findings to others.

What Kinds of Disc Abnormalities Can Be Mistaken for Papilledema? What Is Pseudopapilledema? (Fig. 12–2)

Normal variations of the disc can be mistaken for papilledema or for what some have termed pseudopapilledema. Table 12–2 summarizes the diagnostic criteria of papilledema and pseudopapilledema. The most common cause of pseudopapilledema is a hyperemic, small, crowded disc. The “little red disc,” a term coined by Corbett and Thompson, is often seen in hyperopia and appears almost elevated because of crowding that occurs when axons are traveling through a very small lamina cribrosa (Fig. 12–2A).4 Other causes of pseudopapilledema include persistent membranes on the disc, tilted discs, and myelinated nerve fibers (Fig. 12–2B to D). Another common cause of pseudopapilledema is discs with drusen. Optic disc drusen are small hyaline bodies that are usually congenital, inherited, and refractile. They may be buried in the disc or visible with an ophthalmoscope by using the red-free light or shining the slit-beam at an oblique angle. Buried drusen pose more difficulty in diagnosis because they are often not visible because of elevation of the nerve. Orbital ultrasound, which often shows a special echo resulting from the calcium in these discs, or a computerized tomogram (CT scan) will generally correctly diagnose buried drusen.

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TABLE 12–1 Papilledema Staging Scheme by Lars Frise´n

Stage 0 is a normal disc with minimal swelling of nasal margin of the disc; nerve fiber layer is clear; no obscuration of the vessel is observed; and the cup (if present) is not obscured. This individual had a documented opening pressure of 350 mm cerebrospinal fluid (CSF).

Stage 1 is a C-shaped swelling of the nasal, superior and inferior borders. Usually the temporal margin is normal with sharp disc margins. The cup is maintained. No vessel obscuration.

Stage 2 involves elevation of the temporal margin and 360-degree swelling. There is a blur of the nerve fiber layer (NFL); some vessel obscuration may be present. The cup begins to fill in.

Stage 3 involves elevation of the entire disc with obscuration of the retinal vessels at the disc margin. NFL is moderately opaque with 360-degree swelling, hyperemia, and vascular obscuration at disc margin. The cup may be totally obscured.

In Stage 4 there is complete obliteration of the cup and obscuration of the vessels on the surface of the disc. NFL is opaque with 360-degree swelling and advanced hyperemia of the disc; vessels are largely obscured on the disc surface.

In Stage 5 there is a dome-shaped appearance and all vessels are obscured.

Modified from Frise´n L: Swelling of the optic nerve head: A staging scheme. J Neurol Neurosurg Psychiatry 1982;45:13–18.

Figure 12–3 shows examples of buried (Fig. 12–3A) and visible (Fig. 12–3B) drusen as well as ultrasound (Fig. 12–3C) and CT (Fig. 12–3D) appearances.

How Long Does It Take True Papilledema to Develop?

Most investigators have shown that it takes 1 to 7 days to develop papilledema after an acute increase in ICP.7,8 Not everyone with increased ICP develops papilledema.9 Reasons for this finding are thought to be related to differences in size of the optic canal.10 Laboratory investigations demonstrate that the first sign of papilledema is usually blurring of the disc margin by the swelling of the axons, followed by hyperemia of the disc. Swelling progresses from the

upper and lower pole to the nasal margin, with the temporal margin being the last to swell.11,12

What Are the Symptoms of Papilledema?

Similar symptoms characterize papilledema no matter what its cause. First, patients will often report transient visual obscurations. These are often described as a spontaneous dimming of the light in one or both eyes over seconds, often occurring without positional changes. Diplopia is another common visual complaint. Giuseffi et al.13 found that about 38% of patients with idiopathic intracranial hypertension (IIH) had diplopia. A sixth nerve palsy is the most common cause. Rarely, vertical diplopia and ophthalmoplegia have been reported.10

D

Figure 12–2 Common causes of pseudopapilledema. A, Crowded disc, sometimes called a “little red disc” or a hyperopic disc. B, Membranes on the disc. C, Tilted discs. D, Myelinated nerve fiber.

The most common nonvisual symptom of papilledema is headache, which is reported by more than 90% of patients with IIH. Headaches associated with high pressure are said to be holocranial, continuous, and worsened by Valsalva maneuver. Often, there may be superimposed migraine-like symptoms of photophobia, phonophobia, nausea, and vomiting. Pain can also be experienced behind the eyes as well as in the neck. Both these symptoms are thought to be caused by dilation of the dural sheath because of increased pressure.14 As noted

later in the discussion of papilledema-associated headache, severity of the headache and height of the elevated ICP do not correlate.15,16

Intracranial noise, another common nonvisual symptom, may be overlooked unless the patient is queried specifically about it. On questioning by an otolaryngologist, almost 90% of patients reported intracranial noise.17 Patients often describe the noise as whooshing, buzzing, or “wind-like.” In addition, pulsatility may be a component of the noise. On occasion, the pulsatile tinnitus can be auscultated.13

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TABLE 12–2 Differentiating Papilledema from Pseudopapilledema

(Anomalous Discs)

Signs of Papilledema

What signs besides the presence of disc swelling will convince the clinician that the swelling is the result of increased ICP rather than another process? First, the visual acuity is usually normal unless there has been very severe papilledema with fluid in the macula or infarction of the disc. Wall and George18 showed that only 13% of patients who presented with IIH had visual acuity worse than 20/20. In many of those cases, patients had severe visual field loss despite their normal visual acuity. If visual acuity loss is observed at presentation, and if causes for the visual loss are not readily identifiable, one should consider another cause of disc swelling such as optic neuritis.

C D

Figure 12–3 Disc drusen. A, Buried drusen. B, Visible drusen. C, Ultrasound of buried drusen. D, Computed tomography scan of drusen.

Looking for a relative afferent pupillary defect is important when papilledema is noted. In symmetrical papilledema without visual loss, an afferent defect should not be present. Optic neuritis or another process causing disc swelling may be the cause of an afferent defect.

Assessment of visual fields is essential in the evaluation of any cause of papilledema. Because confrontational visual fields are of limited use, quantitative static perimetry (e.g., Humphrey visual field) or kinetic perimetry (Goldmann perimetry) are required. Wall and George’s18 prospective study of patients with IIH showed that more than 90% of patients with either type of perimetry had abnormalities at the time of presentation. Types of visual field abnormalities seen in papilledema, no matter what the cause, include enlarged blind spot because of a swollen disc. Other common findings include arcuate defects

TABLE 12–3 Differentiating Papilledema from Other Causes of Disc Swelling

Figure 12–5 Fluorescein angiogram in papilledema.

A scan echography of the orbit has been shown to correlate with increased ICP.21 Ultrasound can also determine if buried drusen are present.

Magnetic resonance imaging (MRI) and other techniques are often important if one suspects papilledema. Brain tumors and other space-occupying tumors can be seen. Other MRI findings can help diagnose elevated ICP; for example, one may be able to see an empty sella or dilated nerve sheaths on axial views. Magnetic resonance venography (MRV) helps exclude venous thrombosis.10

If imaging studies are normal, lumbar puncture (LP) is suggested with careful measurement of the opening pressure in the lateral decubitus position. Papilledema is usually associated with elevated pressures (>200 mm cerebrospinal fluid [CSF]).