Abstract
Intramedullary tumors are conventionally regarded as fusiform enlargement of the spinal cord shadow on myelography and computed tomography myelography. With exophytic growth, however, these tumors resemble intradural extramedullary tumors, since a cap defect of the metrizamide column and a shift of the spinal cord are seen on contrast studies.
Seventeen cases of intramedullary tumors were evaluated, six of which involved exophytic tumor growth documented radiologically and at surgery. These tumors were predominantly located from the lower cervical to the upper thoracic region or in the conus medullaris. They were infrequently associated with a syrinx or cyst, and occupied shorter segments of the spinal axis than do tumors without exophytic growth. These tumors could be divided into two types. Type I tumors were accompanied by swelling of the spinal cord and, in some cases, a cap defect of the metrizamide column on the rostral side. Those of Type II had no cord swelling but cord deformity was present, and they were seldom associated with a syrinx or cyst. Cap defects were observed on both the rostral and caudal sides of the tumors. Thus, Type I tumors are mainly intramedullary, whereas Type II tumors are extramedullary. Since it is difficult to differentiate Type II tumors from intradural extramedullary tumors, one should keep in mind the possibility of exophytic growth of intramedullary tumors.
