The assessment of locomotor function in spinal cord injured rats: the importance of objective analysis of coordination

The Basso, Beattie and Bresnahan (BBB) locomotor rating scale is the most widely used open field test and has been accepted as a valid way to assess locomotor function after spinal cord contusion injury in the rat. A limitation within the BBB locomotor rating scale is the correct assessment of forelimb (FL)-hindlimb (HL) coordination. This limitation can have major implications for the final assessment of locomotor function. In the present study, we show an objective method to assess coordination based on the regularity index (RI), achieved through the use of the CatWalk method. The RI grades the degree of coordination as the result of the number of normal step sequence patterns multiplied by four and divided by the total amount of paw placements. Using the RI, single walkway crossings can be objectively analyzed on coordination. Integration of the CatWalk based coordination into the BBB scale indicates that objective analysis of coordination results in reliable and more sensitive assessment of locomotor function. This new method has been tested successfully in determination of positive effects of enriched housing on functional recovery after spinal cord injury (SCI).