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April 1986

Critical Frequency of Photic Driving in the Diagnosis of Multiple Sclerosis

Author Affiliations

Neurology and Research Services Veterans Administration Wadsworth Medical Center and Department of Neurology Reed Neurological Research Center UCLA School of Medicine Los Angeles, CA 90073

Arch Neurol. 1986;43(4):315. doi:10.1001/archneur.1986.00520040005007

To the Editor.  —Ramani et al1 raised interesting questions in their article comparing critical frequency of photic driving (CFPD) with pattern visual evoked response (PVER) in the diagnosis of multiple sclerosis (MS). The authors reviewed the initial article by Celesia and Daly2 and our initial study3 and found "disagreement about the relative sensitivities" of PVER and CFPD testing.In reevaluating this technique, Ramani et al1 reliably replicated our methods for testing CFPD, with only "minor differences." They state that their results and conclusions did not replicate those of our laboratory or those of Celesia and Daly.2There are several possible reasons for this that are not adequately discussed in their article.First, they report that we found CFPD to be "somewhat more sensitive than PVER." In fact, in our initial report on 27 patients, we found CFPD to be "slightly more sensitive" and we emphasized