Forelimb locomotor assessment scale (FLAS): novel assessment of forelimb dysfunction after cervical spinal cord injury

Abstract

We describe here a novel forelimb locomotor assessment scale (FLAS) that assesses forelimb use during locomotion in rats injured at the cervical level. A quantitative scale was developed that measures movements of shoulder, elbow, and wrist joints, forepaw position and digit placement, forelimb-hindlimb coordination, compensatory behaviors adopted while walking, and balance. Female Sprague-Dawley rats received graded cervical contusions ranging from 200 to 230 ("mild," n=11) and 250-290 kdyn ("moderate," n=13) between C5 and C8. Rats were videotaped post-injury as they walked along an alley to determine deficits and recovery of forelimb function. Recovery of shoulder and elbow joint movement occurred rapidly (within 1-7 days post-injury), whereas recovery of wrist joint movement was slower and more variable. Most rats in all groups displayed persistent deficits in forepaw and digit movement, but developed compensatory behaviors to allow functional forward locomotion within 1-2 weeks post-injury. Recovery of forelimb function as measured by the FLAS reached a plateau by 3 weeks post-injury in all groups. Rats with mild contusions displayed greater locomotor recovery than rats with moderate contusions, but exhibited persistent deficits compared to sham controls. Reliability was tested by having seven raters (three internal, four external) from different laboratories, independently and blindly score videos of all rats. The multivariate correlation between all raters, all animals, and all time points ranged from r(2)=0.88-0.96 (p<0.0001), indicating a high inter-rater reliability. Thus, the FLAS is a simple, inexpensive, sensitive, and reliable measure of forelimb function during locomotion following cervical SCI.

Figure 1

The mean FLAS recovery pattern is influenced by contusion force. All animals with mild contusions compared to moderate contusions compared to sham injury. Scores for each group represent the mean scores and the 95% confidence interval from all of the raters for all animals within that group (*p<0.001). In each case, results from mild injury are less than those from moderate injury.

Figure 2

FLAS recovery is correlated to contusion force and spared lateral tissue. A, The scatterplot shows the negative correlation between contusion force and mean FLAS score at the end of the experiment, B, the positive correlation between the percentage of spared lateral tissue and mean FLAS scores, and C, no correlation between the percentage of spared ventral gray matter at the epicenter of the lesion and mean FLAS scores. The encircled points represent the 95% (α level) bivariate normal density ellipses depicting the degree of correlation between a dependent variable and independent variable.

Figure 3

Lesion level has minor influence on FLAS recovery pattern. A, animals with a mild contusion at spinal level C5, C6, or C7/8. Animals with a C5 or C6 mild injury exhibit greater recovery of forelimb locomotion compared to animals with a C7/8 mild injury (*p<0.05). B, animals with a moderate contusion at C6 or C7/8 (no significant differences). Scores for each animal represent the mean and the 95% confidence interval from all 7 raters.

Figure 4

Inter-rater reliability is high regardless of experience or laboratory location. A, naïve versus expert raters. B, internal versus external raters (n = naïve; e = expert; IN = internal; EX = external). The encircled points represent the 95% (α level) bivariate normal density ellipses depicting the degree of correlation between a dependent variable and independent variable.

Figure 5

Multivariate correlation between all raters (n=7), all animals (n=28), and all time points (n=11) shows high reliability. (IN = internal; EX = external; n = naïve; e = expert). The encircled points represent the 95% (α level) bivariate normal density ellipses depicting the degree of correlation between a dependent variable and independent variable.