Non-traumatic intradiploic arachnoid cyst is a rare condition. We describe a young man with typical trigeminal neuralgia and intradiploic arachnoid cyst at the greater wing of the sphenoid. The patient was successfully treated with medical therapy. To our knowledge, this is the first case report of a possible correlation between trigeminal neuralgia and intraosseous arachnoid cyst. We describe the clinical case, the possible pathogenetic mechanism and briefly review the literature.