Abstract
The dynamics of cerebrospinal fluid in twelve cases of arachnoid cysts in the middle cranial fossa was examined by using CT-cisternography. RI-cisternography was also performed in nine patients combined with CT-cisternography. According to the results of CT-cisternography obtained from twelve cases, the cysts were classified into four types. The classification was based on the kinetics of cyst fluid, namely the extent of entry and stasis of Metrizamide into the cyst and early clearance from it. Type I showed early filling of Metrizamide into the cyst and early clearance from it. Type II showed early filling of Metrizamide and delayed clearance. Type Ill showed delayed filling of Metrizamide and delayed clearance. Type IV demonstrated no intracystic filling of Metrizamide. In Type I, II and III, there existed communication between the cyst and its adjacent subarachnoid space. Namely they were communicating cysts. Type IV were non-communicating cyst. Type I and II were all clinically asymptomatic. All cases with intracranial hypertension belonged to Type N. Accordingly, it can be said that there were close correlations between CT-cisternographic results and the clinical findings. On the other hand, RI-cisternography demonstrated communicating cysts in all nine cases. Thus there was no clear relationship between RI-cisternographic findings and clinical symptoms. Using nonirritating radioisotope in a small quantity as a tracer RI-cisternography can provide useful information concerning the flow pattern of cerebrospinal fluid. However, the spatial resolution of RI-cisternography in the present state of technology does not reach that of CT-cisternography. Thus, it can be concluded that CTcisternography is very useful in determining the surgical indication and is also of great value in detecting a possible recurrence of the cyst. From the present study it seems to be obvious that CT-cisternography is more useful than RI-cisternography in the study of arachnoid cysts in the middle cranial fossa.
