Diagnosis of cystic lesion within the spinal cord

We report the cases of cystic myelopathy with intramedullary contrast accumulation on delayed CT myelography. The purpose of this report is to compare MRI with delayed CT myelogram and to discuss the pathogenesis of the intramedullary contrast accumulation on delayed CT myelography. Thirty patients with intramedullary contrast accumulation on delayed CT myelography were studied with High Resolution Computed Tomography (Siemens Somatom II) and Magnetic Resonance Imaging (MRI) (0.15 T imager, Toshiba MRT 15 A). MRI were routinely obtained in both axial plane and sagittal plane. Short spin-echo sequences (30 msec TE, 500 msec TR) were used. This series included 6 cases of cervical disc disease, 5 cases of Chiari malformation, 4 cases of lipomeningocele, 4 cases of adhesive arachnoiditis, 2 cases of thoracolumbar spondylosis, 2 cases of trauma, one case of spinal arachnoid cyst, one case of spinal epidural cyst, and 5 cases of idiopathic type. In 17 out of the 30 patients (57 %), the region corresponding to the region of contrast medium collection, which was visualized on delayed CT myelography, was seen as an area of the low signal intensity on MRI. In 11 cases out of 17, the syrinx cavity was confirmed at surgery. In 13 cases, delayed CT myelogram showed collection of intramedullary contrast medium, but MRI failed to reveal an area of low signal intensity. This group included all cases of cervical disc disease, thoracolumbar spondylosis, spinal arachnoid cyst, and spinal epidural cyst. Their spinal cords were normal or small. All cases of intramedullary contrast material seen on delayed CT myelography may not represent the cavity. They may represent the microcyst formation or the myelomalacia, which were not visualized as an area of abnormal signal intensity on MRI. We emphasize that the patient with suspected cystic myelopathy should be examined by both delayed CT myelography and MRI. (J.P.N.)