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In Reply.
—Dr Rush is concerned that we quoted a statement from his article out of context. The citation was taken from the "Results" section. The sentence in question was preceded by the results of 33 computed tomographic (CT) scans and followed by the results of 41 CSF studies in 63 patients. The exact citation is, "The availability of computed tomographic scanning at our institution has precluded routine lumbar puncture in some patients with increased intracranial pressure." (We deleted the italicized words.)To preclude means "to make impossible by necessary consequence," according to Webster's New Collegiate Dictionary. Therefore, Dr Rush's statement implies that the lumbar puncture has been made, at best, optional or, at worst, obsolete by the CT scan. However, the contents of the CSF cannot be measured by CT scan. Because the CSF pressure must be elevated and the contents must be normal to make the diagnosis of pseudotumor cerebri