Use of metrizamide in computerized tomography to diagnose the Chiari I malformation.

To properly diagnose and treat the Chiari I malformation, it is necessary to know: 1) the position of the cerebellar tonsils; 2) the degree of compression of the upper cervical cord and medulla; 3) the status of the spinal cord, particularly whether a syringohydromyelic condition exists; 4) whether basal arachnoiditis is present; 5) the nature of the communication between the fourth ventricle and the subarachnoid space; and 6) the overall ventricular size. The use of computerized tomography (CT) alone is not sufficient to furnish all of this information. The addition of metrizamide to the CT study enables the exact delineation of the basic pathology of the Chiari I malformation and its associated complications. A total of seven patients with surgically proven Chiari I malformation were included in this study. In all of these cases, CT with metrizamide was the essential diagnostic procedure. Plain films appear to be necessary only to facilitate the diagnosis of an associated Klippel-Feil syndrome or scoliosis.