Fig. 9.1 a, b (a) Optic nerve swelling in the right eye. The disc margins are blurry, and there is no central cup. (b) Sagittal section of a swollen optic nerve.
9.1 Mechanisms of Optic Nerve Edema
Mechanisms of optic nerve edema include the following:
Local optic nerve injury, such as from inflammation (anterior optic neuritis or papillitis), ischemia (anterior ischemic optic neuropathy), fluctuations in intraocular pressure (high, as in acute glaucoma, or low, as in ocular hypotony), and toxicity
Blockage of retrograde axonal transport from optic nerve compression (optic nerve tumor or orbital mass) and raised intracranial pressure (papilledema)
9.2 Differentiating True Disc Edema from Pseudoedema
Differentiating true optic nerve head edema from pseudoedema is essential (▶ Table 9.1, ▶ Fig. 9.2 and ▶ Fig. 9.3). In most cases, pseudoedema appearance results from a congenital anomaly of the optic nerve and does not require any workup, whereas true disc edema is associated with numerous concerning disorders.
True disc edema (▶ Fig. 9.2) | Pseudoedema (▶ Fig. 9.3) |
Elevated optic nerve | Elevated optic nerve |
Margins blurry | Sharp margins |
Vessels obscured | Vessels not obscured |
Venous dilation and tortuosity | Absence of central cup |
Peripapillary hemorrhages and exudates | Anomalous retinal vasculature (arterial branching) |
Leakage on fluorescein angiogram | No leakage on fluorescein angiogram |
Fig. 9.2 a, b (a) True disc edema with (b) leakage on fluorescein angiography (late phase).
Fig. 9.3 a, b (a) Pseudoedema with (b) no leakage on fluorescein angiography (there is late staining only).
9.3 Differential Diagnosis of Disc Edema
Disc elevation without true swelling:
Optic disc anomalies
Myelinated nerve fibers (▶ Fig. 8.50 and ▶ Fig. 9.4)
Drusen (▶ Fig. 8.44 and ▶ Fig. 9.5)
Tilted disc (▶ Fig. 8.49)
Crowded disc
Optic disc infiltration
Leber hereditary optic neuropathy
True disc swelling:
Elevated intracranial pressure (papilledema) (▶ Fig. 9.6)
Inflammatory optic neuropathy (▶ Fig. 9.7)
Demyelinating
Sarcoidosis or other inflammatory diseases
Infectious
Neuroretinitis
Vascular optic neuropathy
Anterior ischemic optic neuropathy (▶ Fig. 9.8)
Nonarteritic
Arteritic
Diabetic papillopathy
Central retinal vein occlusion (▶ Fig. 9.9)
Carotid-cavernous fistula
Malignant systemic hypertension (▶ Fig. 9.10)
Compressive optic neuropathy
Neoplastic
Meningioma (▶ Fig. 9.11)
Hemangioma
Lymphangioma
Non-neoplastic
Thyroid ophthalmopathy
Orbital inflammatory pseudotumor
Infiltrative optic neuropathy
Neoplastic
Leukemia
Lymphoma
Glioma
Non-neoplastic
Sarcoidosis
Toxic
Metabolic/nutritional deficiencies
Traumatic optic neuropathy
Intraocular hypotony (low intraocular pressure)
Fig. 9.4 Myelinated nerve fibers.
Fig. 9.5 Optic nerve head drusen.
Fig. 9.6 Bilateral papilledema.
Fig. 9.7 a,b (a) Right anterior optic neuritis with moderate disc edema. (b) Axial T1-weighted magnetic resonance imaging of the orbits with contrast and fat suppression, showing enhancement of the right optic nerve (arrow).
Fig. 9.8 a,b (a) Right anterior ischemic optic neuropathy with mild disc edema and a few peripapillary hemorrhages. (b) Corresponding inferior altitudinal visual field defect on a 30–2 Humphrey visual field test.
Fig. 9.9 Central retinal vein occlusion with disc edema and numerous retinal hemorrhages distant from the swollen optic nerve.
Fig. 9.10 Malignant systemic hypertension with severe disc edema, retinal hemorrhages, and retinal exudates.
Fig. 9.11 a, b (a) Left optic nerve sheath meningioma with disc edema and shunt vessels. (b) Axial computed tomography of the orbits with contrast showing enhancement along the left optic nerve (arrows).
9.4 Evaluation of the Patient with Disc Edema
Once optic disc edema is confirmed, it should be determined whether it is related to an optic nerve disorder (optic neuropathy) or to raised intracranial pressure. Papilledema is the term used to describe optic disc edema resulting from raised intracranial pressure (▶ Fig. 9.12). All other optic disc edema is termed disc edema or swollen optic nerve. ▶ Table 9.2 compares the characteristics of disc edema from anterior optic neuropathy with those from raised intracranial pressure.
Fig. 9.12 Bilateral asymmetric (right eye worse than left) mild papilledema from raised intracranial pressure.
Optic neuropathy with disc edema | Papilledema (raised ICP) |
Decreased visual acuity | Normal visual acuity (until late) |
Decreased color vision | Normal color vision |
Central, arcuate, or altitudinal visual field defect | Enlarged blind spot, nasal defects, constriction of visual fields |
Disc edema more often unilateral | Disc edema almost always bilateral |
Often isolated (or associated with symptoms or signs related to underlying disease) | Other symptoms and signs of raised ICP (headache, nausea, diplopia from sixth nerve palsies, pulsatile tinnitus, transient visual obscurations) |
Focal neurologic symptoms if focal intracranial process | |
Abbreviation: ICP, intracranial pressure. | |
The mechanisms responsible for raised intracranial pressure and papilledema are as follows:
Hydrocephalus (▶ Fig. 9.13)
Intracranial mass
Tumor, abscess (▶ Fig. 9.14)
Intracerebral hemorrhage
Subdural/epidural hemorrhage
Large vascular malformation
Meningeal process
Infectious
Inflammatory
Neoplastic
Increased venous pressure
Cerebral venous thrombosis
Idiopathic intracranial hypertension
Fig. 9.13 Axial head computed tomography without contrast showing obstructive hydrocephalus (dilated ventricles).
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
