Evaluation of the neurotoxicity of water-soluble myelographic contrast agents by electrophysiological monitors.

The effects of subarachnoid injection of Conray (methylglucamine iothalamate) and its dimer (methylglucamine locarmate) in various concentrations were compared using electrophysiological monitors of the cortical evoked response (CER) and the H-reflex. Significant concentration-dependent differences were noted in the H-reflex, less marked with the dimer. No significant difference in the CER was noted. This differential alteration in neurophysiological parameters was independent of changes in blood and cerebrospinal fluid pressure, implying that these water-soluble contrast media have a direct toxic effect on the nervous system, possibly situated in the larger (group 1) root fibers.