Traumatic rupture into the subdural space without evidence of hemorrhage of the arachnoid cysts that localized in middle cranial fossa is a rare anomaly. We described the clinical and radiologic findings of a case 24-year-old man who was presented with a ruptured arachnoid cyst of the middle cranial fossa , and produced a subdural hygroma with trauma. Although arachnoid cysts account for 1% of all intracranial space occupying lesions, the association between arachnoid cysts and subdural hygroma is rare and only 23 cases have been previously reported in the literature. There are two procedures used in the surgery, the first is cyst fenestration and the second is a cysto-peritoneal shunt. In this patient although we applied all the possible surgical choices and we couldn’t achieve any slightest regression on radiological findings, the patient had full recovery clinically.