Methods Used and Application of the Mouse Grimace Scale in Biomedical Research 10 Years on: A Scoping Review

SIMPLE SUMMARY: The Mouse Grimace Scale (MGS) was developed as a tool for the measurement of pain in laboratory mice. There have been a number of studies focused on the technique’s validity in different models, and across pain types. With this new information, it is important that a review following systematic methodology is performed on these studies to summarise the methods used, the validity across model types, and the effects of external variables. In this review, we present all of the available evidence on the MGS, together with an indication of the extent of the evidence available for each parameter considered. This review will provide an increased strength of evidence to guide researchers, ethics committees, and policy makers on the use and application of the MGS in biomedical research. ABSTRACT: The Mouse Grimace Scale (MGS) was developed 10 years ago as a method for assessing pain through the characterisation of changes in five facial features or action units. The strength of the technique is that it is proposed to be a measure of spontaneous or non-evoked pain. The time is opportune to map all of the research into the MGS, with a particular focus on the methods used and the technique’s utility across a range of mouse models. A comprehensive scoping review of the academic literature was performed. A total of 48 articles met our inclusion criteria and were included in this review. The MGS has been employed mainly in the evaluation of acute pain, particularly in the pain and neuroscience research fields. There has, however, been use of the technique in a wide range of fields, and based on limited study it does appear to have utility for pain assessment across a spectrum of animal models. Use of the method allows the detection of pain of a longer duration, up to a month post initial insult. There has been less use of the technique using real-time methods and this is an area in need of further research.