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TO THE EDITOR: We read with interest the meta-analysis by Mohammed et al.2 on magnetic resonance–guided focused ultrasound (MRgFUS) ablations for treating tremor (Mohammed N, Patra D, Nanda A: A meta-analysis of outcomes and complications of magnetic resonance–guided focused ultrasound in the treatment of essential tremor. Neurosurg Focus 44(2):E4, February 2018). We are delighted to see such work, as the subject is of course of interest and significance, and its timing germane now that a number of relevant studies have been published. However, we found several relevant factual errors in the representation of data from one of our publications3 cited in this work,2 which unfortunately casts a shadow on the overall analysis: 1) Our study was cited as retrospective when in fact it had been performed in a prospective manner. 2) In-procedure complications were reported for 5 patients (Table 3), although our publication reported them in only 4 patients. 3) Figure 3B suggests the occurrence of in-procedure nausea/vomiting and Fig. 3C and E suggest the occurrence of paresthesia (event rates stated as 0.071), although we did not report this. 4) Fig. 3D and F suggest that ataxia persisted at 3 and 12 months (event rates stated as 0.333 and 0.071, respectively), although our study stated that signs of ataxia “resolved within 3 months.” 5) Relatedly, we only reported a maximum follow-up of 6 months. 6) Finally, “persisting limb weakness” at 3 months after the intervention was reported in Table 4, although we did not report any paresis. We are also uncertain why our quality of life data, as measured by the standard Quality of Life in Essential Tremor (QUEST) tool and stated in the abstract, were omitted from the analysis. Additional minor inaccuracies—for example, in stating the age of our study participants inconsistently and incorrectly twice (Table 1 and text)—add to these concerns. Even without cross-checking the accuracy of data points derived from all other included publications, one wonders about the validity of the authors’ results, although overall their conclusions might be similar to those reported in other publications.4 We would also like to express our concerns with the use of a funnel plot for the evaluation of publication bias when only 8 studies were included; in order for such a test to give valid results, it has been argued that at least 30 studies of sufficient power would be necessary, and its interpretation should therefore be done with caution.1 Meta-analyses are powerful scientific tools used to condense findings from individual studies in an accessible way, and their popularity is hence increasing steadily. However, as with other scientific endeavors, their validity depends on the accurate and meticulous execution of all necessary steps involved, and thus, the following of publication standards and guidelines is nice but ultimately pointless if primary data are not handled adequately.

Letter to the Editor. Errors in the meta-analysis of outcomes and complications of MRgFUS