The value of CT after total block on myelography. Experience with 25 patients.

Twenty-five patients having a total block on conventional myelography underwent spinal CT. The myelographic and CT findings were compared to surgical findings. The commonest cause of the block was a tumour in 14 cases. In four cases a herniated disc was found, and in three cases the block was caused by degenerative spinal stenosis. Localization of the lesion was more reliably estimated by CT than by conventional myelography. Both the size and localization may be inadequately demonstrated by myelography; in seven cases there was a discrepancy between the myelographic and surgical findings. The intradural lesions were precisely localized on conventional myelography, if the examination was performed through both the lumbar and cervical routes. With extradural lesions there was a significant discrepancy between the myelographic and surgical findings in some cases. Correlation between surgical and CT findings was good, and paraspinal extension of the lesion was also seen on CT. A CT examination is recommended to complement myelography, particularly for the localization of extradural processes. CT also gave additional qualitative information about the lesions, calcifications and cysts being demonstrated by CT only. Destructive, erosive, or degenerative bone changes were better seen with CT.