Generality
Papilledema (or optic disc edema) is the swelling of the optic disc, that is the portion of the retinal plane that corresponds to the origin of the optic nerve (II pair of cranial nerves). At this level, in fact, the axons converge by about one million ganglion cells of the retina, about to leave the ocular globe to head towards the diencephalon. In other words, the optic disc represents the beginning of the nerve pathways involved in vision, capable of transmitting information from the retina to the visual cortex.
Papilledema in the strict sense is caused by increased pressure inside the brain (intracranial hypertension) and can be associated with trauma, tumors, abscesses or cerebral hemorrhages. Unfortunately, this pathological event does not cause early symptoms, although vision may be transiently disturbed.
The diagnosis is made through ophthalmoscopy, followed by further examinations, usually neuroradiological, aimed at identifying the cause.
The therapy is directed to the underlying disease and must be set in the shortest possible time in order to avoid permanent outcomes for the visual apparatus or worse consequences secondary to intracranial hypertension.
Optic disc: what is it?
The optic disc (or optic disc) is a small oval area of the retinal plane, with a diameter of 1.5-2 millimeters and whitish in color. Located low and medial to the posterior pole of the eye, nasally to the macula, this area has well-defined margins and a flat or excavated surface in the center.
The optic disc is the only blind area of the retina, as it is devoid of photoreceptors.
From the center of the optic disc, the blood vessels that supply the eye emerge.
Pathogenesis
Optic disc edema secondary to intracranial hypertension is almost always bilateral, so both optic nerves appear swollen.
The occurrence of this sign depends on the "increase in pressure in the area between the arachnoid meninges and pia mater that surround the optic nerve, communicating with the endocranial subarachnoid space and filled with cerebrospinal fluid (also called CSF or cerebrospinal fluid). The increase in intracranial pressure, therefore, is transmitted through the CSF also inside the optic nerve sheath, causing compression around it and swelling of the axons posterior to the optic disc. This phenomenon also hinders the venous return through the central vein of the retina, which runs inside the optic nerve and drains the blood from the eye.
In the initial phase, the optic disc is hyperemic and without the normal physiological excavation; the margins swell, rising up on the retinal plane, and become more blurred. Subsequently, the venous stasis of the papillary veins appears, which appear congested and can undergo frequent bleeding.
In the more advanced stages, the optic disc can undergo atrophy, a condition that involves the degeneration of the optic nerve and the onset of severe visual disturbances.
Causes
Papilledema is a sign of elevated intracranial pressure.
Causes include:
- Primary or secondary brain tumor;
- Brain abscess;
- Head trauma;
- Cerebral hemorrhage;
- Meningitis;
- Encephalitis;
- Arachnoid adhesions;
- Thrombosis of the cavernous or dural sinus;
- Pseudotumor cerebri (idiopathic intracranial hypertension).
Symptoms
Optic disc edema does not initially affect vision: visual acuity and pupillary light reflex are usually normal. In later stages, however, visual blurring, intermittent scotomas, visual field defects, and diplopia appear. In addition, patients may present with symptoms attributable to "increased intracranial pressure: jet vomiting, headache, tinnitus, paraesthesia and alterations in consciousness.
On the other hand, a clear decrease in visual capacity occurs with the onset of progressive atrophy of the optic nerve, which is preceded by episodes of fleeting amaurosis (transient blindness).
Diagnosis
Clinical evaluation of papilledema begins with observation of the fundus with the ophthalmoscope. This examination reveals congested and tortuous retinal veins and a hyperemic optic disc with soft edges. At the ophthalmoscopic examination, furthermore, hemorrhages may be found in the papillary and peripapillary areas, but not in the retinal periphery.
Ophthalmoscopy can provide a finding similar to that of papillary infarction of the optic nerve, papillitis or intraorbital optic neuritis, therefore the outcome of the investigation must necessarily be integrated with anamnesis, examination of the visual function and neuroimaging investigations. Visual field examination can detect an enlargement of the blind spot of the eye.
If there is clinical suspicion of papilledema, gadolinium magnetic resonance imaging (MRI) or contrast computed tomography (CT) should be done immediately. These tests are necessary to rule out the presence of an intracranial mass. Once the presence of a space-occupying intracranial lesion has been ruled out, lumbar puncture and cerebrospinal fluid pressure (CSF) measurement should be performed.
Differential diagnosis
The term "papilledema" is strictly reserved for the swelling of the optic disc referred to an increase in intracranial pressure. An isolated swelling of the optic disc without CSF hypertension (caused, for example, by optic neuritis or ischemic optic neuropathy) is instead referred to simply as "optic disc edema".
The swelling of the optic disc, in fact, is also found in other pathological processes. In particular, it can result from inflammation (including optic neuritis, uveitis and papillitis), vascular events (arterial hypertension, ischemia, thrombosis and obstruction of blood vessels), trauma, infectious infiltration, orbital and intraocular tumors, hereditary factors (pseudo-papillitis ) and toxicity from drugs or exogenous agents (eg poisoning by arsenic and inorganic lead).
Differential diagnosis requires a thorough ophthalmological evaluation. Papilledema secondary to intracranial hypertension is typically bilateral. The edema of the optic disc, on the other hand, is often unilateral and involves early visual disturbances and alterations in the chromatic sense.
Treatment
The treatment must be set up as soon as possible. The type of therapeutic intervention depends on the etiology of papilledema and has the aim of reducing intracranial pressure.
If this is not brought back to normal values, in fact, an "atrophy of the optic nerve can ensue. This complication involves a severe reduction of vision associated with other serious neurological sequelae.
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