**Question:** Tumours arising from all of the following structures can induce papilloedema except:

A. Optic nerve sheath meningioma
B. Pituitary adenoma
C. Choroid plexus papilloma
D. Retinal vein occlusion

**Core Concept:**
Papilloedema is a clinical condition characterized by the presence of edematous swelling of the optic disc, which can be caused by increased intracranial pressure (ICP). Optic nerve sheath meningiomas, pituitary adenomas, and choroid plexus papillomas are examples of tumours that can increase intracranial pressure and lead to papilloedema. Retinal vein occlusion, on the other hand, is a condition that results from blockage in the retinal veins and typically presents with acute vision loss rather than papilloedema.

**Why the Correct Answer is Right:**
The correct answer (D) is retinal vein occlusion because it does not cause an increase in intracranial pressure. Retinal vein occlusion is caused by blockage in retinal veins, leading to decreased cerebral perfusion and acute vision loss. This condition does not typically result in elevated intracranial pressure or papilloedema.

**Why Each Wrong Option is Incorrect:**
A. Optic nerve sheath meningioma: Meningiomas are tumors that may cause increased intracranial pressure and can lead to papilloedema due to their potential to compress the optic nerve.
B. Pituitary adenoma: Pituitary adenomas can also increase intracranial pressure and result in papilloedema. They can compress the optic nerve and surrounding structures.
C. Choroid plexus papilloma: Choroid plexus papillomas are tumors that can lead to increased intracranial pressure and papilloedema by compressing the optic nerve.

**Clinical Pearl:**
A thorough understanding of the pathophysiology of papilloedema is essential for making a correct diagnosis. Papilloedema can be caused by various conditions, including increased intracranial pressure from brain tumors, trauma, or other pathologies. It is crucial for medical professionals to differentiate between different causes of papilloedema to initiate appropriate treatment and prevent unnecessary interventions.