What causes papilledema?

Causes of Papilledema

Papilledema is primarily caused by increased intracranial pressure (ICP), which can result from various underlying conditions including space-occupying lesions, hydrocephalus, cerebral venous abnormalities, and idiopathic intracranial hypertension. 1, 2

Primary Causes of Increased ICP Leading to Papilledema

1. Intracranial Space-Occupying Lesions

• Brain tumors
• Abscesses
• Hematomas
• Cysts

2. Hydrocephalus

• Obstructive
• Communicating

3. Cerebral Venous Abnormalities

• Cerebral venous sinus thrombosis
• Venous outflow obstruction
• Arteriovenous fistulas 1

4. Idiopathic Intracranial Hypertension (IIH)

• Defined as elevated intracranial pressure without evidence of structural lesions or hydrocephalus
• Normal cerebrospinal fluid composition
• Most common in overweight women of reproductive age
• Also occurs in prepubertal children (affects boys and girls equally) 1

Secondary Causes of Papilledema

1. Medication-Induced

• Tetracycline-class antibiotics
• Vitamin A and retinoids
• Steroids
• Growth hormone
• Thyroxine
• Lithium 1, 2

2. Endocrine Disorders

• Addison disease
• Hypoparathyroidism 1

3. CSF Flow/Absorption Issues

• Decreased CSF outflow
• Mechanical blockage of CSF outflow channels
• Rarely, increased CSF production 3

Pathophysiological Mechanism

Papilledema develops through the following process:

1. Elevated ICP is transmitted to the subarachnoid space surrounding the optic nerve
2. This pressure hinders axoplasmic transport within ganglion cell axons
3. The disruption leads to axoplasmic flow stasis and potential intraneuronal ischemia 3, 4

There remains controversy whether the primary mechanism is:

• Physical compression of axons
• Microvascular ischemia 3

Diagnostic Criteria for Papilledema

For true papilledema, the following should be present:

1. Optic disc edema
2. Evidence of increased ICP (>280 mm CSF in children, or >250 mm CSF if not sedated/obese) 1
3. Normal neurological examination (except possible sixth nerve palsy) 1
4. Normal brain parenchyma on imaging (no mass, hydrocephalus, or abnormal meningeal enhancement) 1
5. Normal CSF composition 1

Radiological Findings Associated with Increased ICP

MRI may show:

• Empty sella
• Flattening of the posterior aspect of the globes (56% sensitivity, 100% specificity)
• Distention of the perioptic subarachnoid space
• Transverse sinus stenosis
• Intraocular protrusion of the optic nerve (40% sensitivity, 100% specificity)
• Horizontal tortuosity of the optic nerve (68% sensitivity, 83% specificity)
• Enlarged optic nerve sheath compared to normal (mean 4.3 versus 3.2 mm)
• Smaller pituitary gland size compared to normal (mean 3.63 versus 5.05 mm) 1, 2

Important Clinical Considerations

• Papilledema is a late sign of increased ICP, appearing after pressure has been elevated for some time 5
• Visual function is usually preserved in acute papilledema but can deteriorate in chronic cases 3
• Papilledema may be asymmetric between eyes and rarely presents in only one eye 5
• Papilledema requires urgent evaluation as it can lead to permanent vision loss if the underlying cause is not addressed 3
• The presence of papilledema is particularly critical to detect in patients with noncompliant ventricles or extraventricular blockage of CSF flow 5

Understanding the cause of papilledema is essential for appropriate management, as treatment should target the underlying etiology to prevent permanent visual impairment.