Purpose: To report a case of unilateral papilledema caused by an arachnoid cyst.
Methods: Interventional case report.
Results: A 36-year-old woman presented with unilateral papilledema in the left eye. Magnetic resonance imaging (MRI) of the brain demonstrated a large fronto-temporo-parietal arachnoid cyst in the left hemisphere. The papilledema resolved after placement of a cysto-peritoneal shunt that drained the cerebrospinal fluid directly from the arachnoid cyst into the peritoneum.
Conclusion: Papilledema caused by increased intracranial pressure is usually bilateral; unilateral papilledema is possible under special anatomical circumstances.