Dynamic study of arachnoid cysts with metrizamide.

Intracranial arachnoid cyst do not usually present diagnostic problems when studied by CT, since they appear as low density images similar to those produced by CSF, do not change on intravenous contrast perfusion, and are located extraparenchymatously. Sometimes, however, their diagnosis can become difficult or doubtful mainly in cases of deep, basal or paramedian cysts [12, 18, 22, 24]. On the other hand, the functional or dynamic aspects of these structures remain unknown when the study is limited to simple CT. Computed cisternography with metrizamide (CCM) and time control will not only show the relationship between these structures and the arachnoid space but also their dynamic aspect, which may determine the surgical treatment.