Endotoxin as a cause of aseptic meningitis after radionuclide cisternography

The role of pyrogens in aseptic meningitis after radionuclide cisternography was studied by means of the Limulus test, a sensitive detector of endotoxin. During a 15-month period, 39 reactions associated with cisternography were reported. Ten samples of specific lots of the radioactive drugs implicated in 20 of these reactions were tested and all reacted strongly positive to the Limulus test. The less sensitive rabbit pyrogen test was negative for these preparations when tested on a dose-per-weight basis. Our findings apparently provide clinical evidence for the observation made in animals that endotoxin is at least 1,000 times more toxic intrathecally than intravenously. The data implicate endotoxin contamination as a cause of adverse reactions to radionuclide cisternography. We conclude that the USP pyrogen test is insufficiently sensitive for intrathecal injectables and should be supplemented by the Limulus test.