New reliable scoring system, Toyama mouse score, to evaluate locomotor function following spinal cord injury in mice

BACKGROUND: Among the variety of methods used to evaluate locomotor function following a spinal cord injury (SCI), the Basso Mouse Scale score (BMS) has been widely used for mice. However, the BMS mainly focuses on hindlimb movement rather than on graded changes in body support ability. In addition, some of the scoring methods include double or triple criteria within a single score, which likely leads to an increase in the deviation within the data. Therefore we aimed to establish a new scoring method reliable and easy to perform in mice with SCI. FINDINGS: Our Toyama Mouse Score (TMS) was established by rearranging and simplifying the BMS score and combining it with the Body Support Scale score (BSS). The TMS reflects changes in both body support ability and hindlimb movement. The definition of single score is made by combing multiple criteria in the BMS. The ambiguity was improved in the TMS. Using contusive SCI mice, hindlimb function was measured using the TMS, BMS and BSS systems. The TMS could distinguish changes in hindlimb movements that were evaluated as the same score by the BMS. An analysis of the coefficient of variation (CV) of score points recorded for 11 days revealed that the CV for the TMS was significantly lower than the CV obtained using the BMS. A variation in intra evaluators was lower in the TMS than in the BMS. CONCLUSION: These results suggest that the TMS may be useful as a new reliable method for scoring locomotor function for SCI models.