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We thank Erro and colleagues for their interest in our recent article regarding the reasons for poor outcomes following botulinum toxin treatment of patients with cervical dystonia. Erro and colleagues provide additional observations regarding the potential value of polymyography for obtaining good results. In our series, approximately half of the subjects had EMG while half did not. When comparing those who had EMG with those who did not, there were no obvious differences in patient satisfaction, the number of trials or injection sites required to reach a satisfactory outcome, or the doses required. However, our study was not designed to evaluate the role of EMG, so we cannot make any firm conclusions regarding its usefulness.
While our clinical intuitions suggest EMG may be useful in some cases, intuitions are sometimes wrong. Our intuitions ideally should be verified by empirical scientific evidence. The assessment of the efficacy of any intervention (including EMG) requires a proper comparison group, to control for any placebo effect of the added procedure on the patients or investigator bias in interpreting outcomes that are partly subjective. While some prior studies have suggested a benefit from EMG, other studies showed no meaningful differences among patients who had EMG and those who did not. The uncontrolled observations provided by Erro and colleagues regarding the possible value of EMG are intriguing. However, like many prior studies including our own, their study design was not adequate to make any firm conclusions. A more rigorously designed scientific study is required before we can recommend that EMG become a routine part of botulinum toxin procedures for cervical dystonia.
H. A. Jinnah, M.D., Ph.D.
Stewart Factor, D.O.
H. A. Jinnah, Departments of Neurology, Human Genetics and Pediatrics, Emory University, Suite 6300 Woodruff Memorial Building, 101 Woodruff Circle, Atlanta, GA, 30322, USA.
Stewart Factor, Department of Neurology, Emory University, Atlanta, GA, 30322, USA.