Bilateral optic disk edema secondary to increased intracranial pressure.
Epidemiology: Epidemiologic data from the 1950s describe papilledema in as many as 60% of patients with brain tumors. Since then, advances in neuroradiology have significantly reduced the incidence of papilledema. The diagnostic importance of the disorder has decreased accordingly.
Etiology: An adequate theory to fully explain the pathogenesis of papilledema is lacking. Current thinking centers around a mechanical model in which increased intracranial pressure and impeded axonal plasma flow through the narrowed lamina cribrosa cause nerve fiber edema. However, there is no definite correlation between intracranial pressure and prominence of the papilledema. Nor is there a definite correlation between the times at which the two processes occur. However, severe papilledema can occur within a few hours of increased intracranial pressure, such as in acute intracranial hemorrhage. Therefore, papilledema is a conditional, unspecific sign of increased intracranial pressure that does not provide conclusive evidence of the cause or location of a process.
In approximately 60% of all cases, the increased intracranial pressure with papilledema is caused by an intracranial tumor; 40% of all cases are due to other causes, such as hydrocephalus, meningitis, brain abscess, encephalitis, malignant hypertension, or intracranial hemorrhages. The patient should be referred to a neurologist, neurosurgeon, or internist for diagnosis of the underlying causes.
Every incidence of papilledema requires immediate diagnosis of the underlying causes as increased intracranial pressure is a life-threatening situation.
The incidence of papilledema in the presence of a brain tumor decreases with increasing age; in the first decade of life it is 80%, whereas in the seventh decade it is only 40%. Papilledema cannot occur where there is atrophy of the optic nerve, as papilledema requires intact nerve fibers to develop.
❖ Foster Kennedy syndrome: This refers to isolated atrophy of the optic nerve due to direct tumor pressure on one side and papilledema due to increased intracranial pressure on the other side. Possible causes may include a meningioma of the wing of the sphenoid or frontal lobe tumor.
❖ Hypotension papilledema: This refers to a nerve fiber edema due to ocular hypotension. Possible causes may include penetrating trauma or fistula secondary to intraocular surgery.
Symptoms and diagnostic considerations: Visual function remains unimpaired for long time. This significant discrepancy between morphologic and functional findings is an important characteristic in differential diagnosis. Early functional impairments can include reversible obscurations. Perimetry testing may reveal an increase in the size of the blind spot (Fig. 13.10c). Central visual field defects and concentric narrowing of the visual field are late functional impairments that occur with existing complex atrophy of the optic nerve.
Papilledema is characterized by significant morphologic findings and only slight visual impairment.
The following phases may be distinguished by ophthalmoscopy:
Early phase (Fig. 13.10a): First the nasal margin and then the superior and inferior margins of the optic disk are obscured because of the difference in the relative densities of the nerve fibers (see optic disk). The optic cup is initially preserved. This is important in a differential diagnosis to exclude pseudo-papilledema and optic disk drusen. The optic disk is hyperemic due to dilatation of the capillaries, and there is no pulsation in the central retinal vein. Edema can produce concentric peripapillary retinal folds known as Paton's folds.
Acute phase (Fig. 13.10b): This is characterized by increasing elevation of the optic disk, radial hemorrhages around the margin of the optic disk and grayish white exudates. The optic cup is often no longer discernible. The color of the optic disk will be red to grayish red.
Chronic phase. Significant optic disk edema is present. The optic cup is obliterated, and the hyperemia will be seen to subside.
Atrophic phase. Proliferation of astrocytes results in complex or secondary atrophy of the optic nerve.
Differential diagnosis: This includes pseudopapilledema, optic disk drusen (Table 13.1), abnormalities of the optic disk without functional impairment, optic disk edema with hypertension, and optic neuritis.
Treatment: Intracranial pressure should be reduced by treating the underlying disorder (see Etiology). Once intracranial pressure has been normalized, the papilledema will resolve within a few weeks. Usually complex atrophy of the optic nerve will remain. The severity will vary according to the duration of the papilledema.
370 13 Optic Nerve Papilledema. -
b Acute stage: The optic disk is increasing elevated and has a gray to grayish red color. Radial hemorrhages around the margin of the optic disk and grayish white exudates are observed. The optic disk can no longer be clearly distinguished.
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