Which condition is NOT a main cause of papilledema?

Papilledema refers to the swelling of the optic nerve head due to increased intracranial pressure. It is typically associated with conditions that either directly cause increased intracranial pressure or lead to disturbances in cerebrospinal fluid dynamics.

Malignant hypertension, pseudotumor cerebri, and increased intracranial pressure are all well-documented causes of papilledema. Malignant hypertension leads to severe elevations in blood pressure that can result in cerebral edema and increased intracranial pressure. Pseudotumor cerebri is characterized by increased intracranial pressure without a detectable mass, commonly seen in young, overweight women, and it frequently presents with papilledema. Increased intracranial pressure itself, regardless of the underlying cause, directly results in papilledema as it affects the optic nerve.

In contrast, diabetes mellitus is not a primary cause of papilledema. While it can lead to various ocular complications, such as diabetic retinopathy, it does not inherently cause increased intracranial pressure or papilledema. Thus, among the options presented, diabetes mellitus stands out as the condition that does not contribute to the development of papilledema.