Arachnoid cysts of the middle cranial fossa presented as subdural hematomas

The aim of the study was to present the authors' own experience and discuss the treatment method of arachnoid cysts of the middle cranial fossa disclosed as subdural hematoma. Three cases of male patients operated on because of chronic subdural hematoma are presented. Control CT studies after evacuation of hematomas revealed arachnoid cysts of the middle cranial fossa and all patients were qualified for delayed cystocisternostomy by open craniotomy. Indirect signs of presence of arachnoid cysts in the form of bony abnormalities and expanded the middle cranial fossa in the first CT were seen in all patients. Cysts were asymptomatic until the injury in all cases. The volumes of cysts in MRI scans were: 17.8 ml, 52.9 ml and 92.4 ml, respectively. All cysts were type II according to Galassi classification. After control MRI described above made to evaluate cyst appearance, delayed cystocisternostomy to basal cisterns was undertaken in two cases with full success. No complications were observed. The third patient refused surgery. During surgery the thick and non-transparent medial cyst wall and arachnoidea of tentorial notch cisterns were observed impeding the exact identification of neurovascular structures. In our opinion arachnoid cysts of the middle cranial fossa revealed as subdural hematoma should be operated on in two stages: in the first step subdural hematoma should be evacuated and in the second step cystocisternostomy should be performed. With regard to observed morphological changes of arachnoidea and cyst walls we think that open cystocisternostomy is treatment of choice in these cases.