Three cases of cerebral aerocele are reported. The sintomatology and valvulate mechanism involved in this kind of pathology are discussed. The author desagree that only this valvulated mechanism explains the aerocele without rhinorrhea. Negative pressure generated by cerebral pulsation and the upstand position in presence of osteo-dural fissure, will aspirate air which will expand by body temperature. This together with cerebral pulsations will permit partial elevation of the inner air temperature with the cold out air. This continuous and partial change will detain a little more volumes of air in more and more pressure. When the pressure is sufficient to colapse the capilaries vessels in the neighbouring tissue necrosis will undergo. This repeatitive mechanism generates the aerocele.