Spontaneous development of a de novo suprasellar arachnoid cyst. Case report.

Arachnoid cysts are commonly thought to arise from either congenital defects or trauma. In this article the authors report the spontaneous development of a suprasellar third ventricular arachnoid cyst whose origin was not clearly congenital or traumatic. At the age of 4 months, the patient presented with hypertonia, and a magnetic resonance (MR) imaging study showed no abnormalities. At the age of 2 years, the boy presented with headaches and projectile emesis, symptoms that prompted further imaging studies. An MR image of the brain revealed a suprasellar cyst and obstructive hydrocephalus. The cyst was endoscopically fenestrated, which led to long-term symptom resolution.