PURPOSE: We present a case of a 4-year-old child who was incidentally found to have a suprasellar arachnoid cyst (SAC) after initial CT imaging at 6 weeks of age but who demonstrated no anomalies. This is only the sixth case of intracranial de novo ACs documented in the English literature and only the second case of SAC to arise de novo. METHODS: Case review after an SAC was found on an MRI scan at 4 years of age which had not been present on a previous CT of the head. RESULTS: Apparent de novo SAC formation in a healthy 4-year-old female without a history of intracranial infection, surgery or trauma. CONCLUSION: The pathophysiology leading to the formation of the cyst might well be congenital, although there is some question as to how early in development the cysts are formed as our child was a 32-week GA preemie with an initial scan at 38 weeks GA. With the use of fast MRI scans instead of CT scans and the continued neuroimaging of premature infants, we can take a better look at the anatomy and better determine the timing of development of the SAC.