[Metrizamide CT cisternography in skull base tumors (author's transl)].

Twenty-three cases suspected of skull base tumors were examined by CT cisternography (CTC) with CT scanner (EMI 1010) from April, 1977 to March, 1978. The lesions in 20 cases were diagnosed as positive and confirmed by operation and/or autopsies. These include five acoustic neurinomas, six pituitary adenomas, two craniopharyngiomas, two skull base meningiomas, one arachnoid cyst and miscellaneous tumors. Isotonic Metrizamide solution four of 2-10 ml was injected via lumbar route. Patients were kept in 30 degrees Trendelenburg position for 60 minutes until the first scanning. Scannings were obtained 1, 3, 6, 24 and in some cases 48 hours after lumbar injection. No side effects except for headache, nausea, vomiting occurred. There were no convulsions. In diagnosing cerebellopontine angle tumors, the indirect signs such as asymmetrical ambient cisterns are of importance, when combined with direct signs, i.e. a shadow defect. Parasellar tumors are usually difficult to diagnose with conventional CT due to streak artifact caused by adjacent bony structure. In CTC the extrasellar extension of pituitary tumors were clearly visible. The size, shape, dimensions and the relationship to the adjacent structures of the craniopharyngiomas were easily demonstrated with CTC especially when a coronal view was added. In arachnoid cyst, CTC demonstrated the delayed turnover of Metrizamide between the cyst cavity and the adjacent subarachnoid space. In conclusion, CTC is an useful neuroradiological diagnostic adjunct because of minimal bony streak artifact and high spatial resolution. It would be expected that small tumors of even 2-3 mm in diameter might be diagnosed, from the fact that the middle cerebral artery in the suprasellar cistern is clearly visible as a shadow defect.