Diagnosis of cerebral lesions by Thallium 201

A new water-soluble myelographic contrast agent with more hydrophilic properties than metrizamide was developed and tested in the primate (Macaca mulatta) and the cat. A new animal model that allows study of the convulsive effects of intrathecally administered contrast agents in the awake monkey was designed. With this sensitive model the new contrast agent was shown to have a remarkable reduced convulsive effect when compared with metrizamide and other media. Intrathecal hypertonic solutions in the cat depress the evoked cortico-spinal responses whereas the neurotoxic effects of the iodinated water-soluble contrast media increase them. The net effect is a combination of the two actions.