Spontaneous resolution of arachnoid cysts: review and features of an unusual case.

Most intra-cranial arachnoid cysts are quiescent and remain asymptomatic throughout life. Within the natural course of arachnoid cyst evolution, spontaneous resolution has been known to occur rarely, but its frequency is probably underestimated due to lack of systematic detection and long-term observation. We illustrate the spontaneous regression of arachnoid cysts with a patient which was conjointly diagnosed with an arachnoid cyst and a post-traumatic epidural haematoma. Cyst regression was observed 16 months later, upon examination following a second benign cranial trauma. Mechanisms underlying the resolution of the arachnoid cyst are discussed.