Intramedullary spinal cord neoplasms are rare, accounting for about 4%10% of all central nervous system tumors. Despite their rarity, these lesions are important to the radiologist because magnetic resonance (MR) imaging is the preoperative study of choice to narrow the differential diagnosis and guide surgical resection. On contrast materialenhanced MR images, intramedullary spinal tumors almost always manifest as expansion of the spinal cord and show enhancement. Syringohydromyelia and cystic lesions are frequently associated with intramedullary tumors. Nontumoral cysts tend to be located at the poles of the tumors and do not enhance on contrast-enhanced MR images, whereas cysts within the substance of the tumor are considered tumoral cysts and typically demonstrate peripheral enhancement. Spinal cord ependymomas are the most common type in adults, and cord astrocytomas are most common in children. Both entities constitute up to 70% of all intramedullary neoplasms. A central location within the spinal cord, presence of a cleavage plane, and intense homogeneous enhancement are imaging features that favor an ependymoma. Intramedullary astrocytomas are usually eccentrically located within the cord, are ill defined, and have patchy enhancement after intravenous contrast material administration. Even with these characteristics, it may not be possible to differentiate these two entities on the basis of imaging features alone. Cord hemangioblastomas are the third most common type of intramedullary spinal tumor. Gangliogliomas commonly extend over more than eight vertebral segments. Paragangliomas and primitive neuroectodermal tumors have an affinity for the filum terminale and cauda equina. Other spinal cord tumors include metastatic disease, which is characterized by prominent cord edema for the size of the enhancing portion, and primary lymphoma.

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SUMMARYBy the direct Fick or the indocyanine-green or both, methods and by renal clearance of inulin and para-aminohippurate (PAH), simultaneous cardiorenal hemodynamic observations were made before and during isoproterenol infusion (0.9-2.6 jug/ min) into three patients without, and 10 patients with, heart disease. Although a consistent increase in cardiac output (11 to 147%) was noted in all patients, no significant change in glomerular filtration rate or renal blood flow was observed. The percentage of the cardiac output delivered to the kidney during drug infusion decreased in all subjects. The renal extraction of PAH, measured in three patients, was not changed during isoproterenol administration. The infusion of isoproterenol to normovolemic and hypervolemic dogs (10 dogs) increased the cardiac output in all animals but produced no significant change in glomerular filtration rate or renal blood flow. Because the renal blood flow is not affected by the increased cardiac output produced by isoproterenol, the data suggest that there is either a weak or an absent beta-receptor response in the kidney in the dog and man.

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