Adaptation of the Basso-Beattie-Bresnahan locomotor rating scale for use in a clinical model of spinal cord injury in dogs

Abstract

Background: Naturally occurring acute spinal cord injury (SCI) in pet dogs provides an important clinical animal model through which to confirm and extend findings from rodent studies; however, validated quantitative outcome measures for dogs are limited.

New method: We adapted the Basso Beattie Bresnahan (BBB) scale for use in a clinical dog model of acute thoracolumbar SCI. Based on observation of normal dogs, modifications were made to account for species differences in locomotion. Assessments of paw and tail position, and trunk stability were modified to produce a 19 point scale suitable for use in dogs, termed the canine BBB scale (cBBB). Pet dogs with naturally occurring acute SCI were assigned cBBB scores at 3, 10 and 30days after laminectomy.

Results: Scores assigned via the cBBB were stable across testing sessions in normal dogs but increased significantly between days 3 and 30 in SCI-affected dogs (p=0.0003). The scale was highly responsive to changes in locomotor recovery over a 30day period, with a standardized response mean of 1.34.

Comparison with existing methods: Concurrent validity was good, with strong correlations observed between the cBBB and two other locomotor scales, the OSCIS (r=0.94; p<0.001) and the MFS (r=0.85; p<0.0001). cBBB scores inversely correlated with other assessments of recovery including mechanical sensory threshold (r=-0.68; p<0.0001) and coefficient of variation of stride length (r=-0.49; p<0.0001).

Conclusions: These results support the use of the cBBB to assess locomotor recovery in canine clinical translational models of SCI.

Keywords: Canine; Clinical spinal cord injury; Intervertebral disc extrusion; Translational model.

Fig. 1

The cBBB can be applied across a spectrum of injury severities. Median (closed circle) and range of cBBB scores in normal dogs (n = 20) and dogs with clinical SCI (n = 30) at 3, 10, and 30 days after injury. Scores differ between normal and SCI-affected dogs at all three time points after injury. * denotes statistical difference from normal dogs, p < 0.0001.

Fig. 2

cBBB preserves psychometric properties of the original scale. cBBB scores for normal dogs are stable across three testing sessions (A). Scores for individual SCI-affected dogs show an upward trajectory in every case, consistent with expected improvement in locomotor function (B). Frequency of scores assigned to any limb at any time point in SCI-affected dogs are well-distributed across the scale over the 30 day recovery period (C).

Fig. 3

cBBB scores improve over time in SCI-affected dogs. Box plots for cBBB scores assigned at day 3 and day 30 after injury. cBBB scores are significantly higher on day 30 compared to day 3, consistent with expected improvement in locomotor status. *p = 0.0003.

Fig. 4

cBBB scores correlate with other independent measures of recovery after SCI. Sensory threshold, as measured by an electronic von Frey anesthesiometer, is inversely correlated with cBBB score in SCI-affected dogs (r = −0.68; p < 0.0001), indicating that as acute hypoalgesia declines toward normal, locomotor status as measured by the cBBB also improves (A). For dogs who are able to ambulate unassisted (cBBB score ≥ 11), coefficient of variance of hind limb stride length (COV SL) is also inversely correlated with cBBB scores across a 30 day recovery period (r = −0.49; p ≤ 0.0001), such that SL becomes more consistent as locomotor score improves (B).