All 18 cerebellar subjects completed all three visits. The six and 12-month follow-up visits occurred, on average, 6.78±0.37 and 13.33±0.40 months after the baseline visit. There were no differences in these values between static and degenerative groups (p=0.87 and p=0.53, respectively).
show total ICARS scores and posture and gait ICARS subscores for both cerebellar groups. Total ICARS scores did not differ between cerebellar groups at baseline (p=0.17). For the degenerative but not the static group, there was a significant worsening of ICARS scores over the three visits (p=0.012); scores increased over the year (baseline vs. 12-month visit, p=0.029) and over the second six-month period (six-month vs. 12-month visit, p=0.028). In contrast, scores tended to remain stable, and in some cases improved, in the static group (p=0.163). Similar results were noted for posture and gait ICARS subscores (). Specifically, there was no significant difference in posture and gait subscores between groups at baseline (p=0.09), however the degenerative group showed a trend towards worsening of posture and gait subscores over the three visits (p=0.067). The static group showed no such difference across visits (p=0.86). For the other ICARS subscores, there were neither any significant between-groups differences at baseline (limb kinetics, p=0.24; speech, p=0.20; oculomotor, p=0.82), nor any differences between visits. However there was a trend towards significant worsening of limb kinetics subscores within the degenerative group (p=0.058). See for details of the other ICARS subscores at each visit.
Selected results from the comparison of control, cerebellar static and cerebellar degenerative groups over time
Additional results for the cerebellar groups
Static balance testing results are depicted in . At baseline, mean sway amplitudes differed among all three groups (p<0.001), with the degenerative group showing worse postural sway compared to either the control group (post hoc, p<0.001) or the static group (post hoc, p=0.008), but no difference between control and static groups (post hoc, p=0.74). Similarly, the factorial analysis showed an overall increase in postural sway in the degenerative group compared to the static group (group effect, p=0.04), but no effects of visit or any group × visit interaction, indicating that neither cerebellar group appeared to demonstrate much change in static postural sway over the course of the year (). Sway variance also differed across the groups at baseline (p=0.002). Again, differences were attributable to impaired postural control in the degenerative (degenerative vs. control, p=0.002; degenerative vs. static, p=0.019) but not the static group (static vs. control, p=0.85; ). There were no changes in sway variance over the three visits, nor any interaction effects. Dynamic weight shifting performance did not differ across groups at baseline (lateral, p=0.38; fore-aft, p=0.56) or across visits (see ).
At baseline, we found significant differences across groups for many of the walking parameters: cerebellar subjects generally took shorter strides (p=0.02), wider steps (p=0.04), spent more time in stance (p=0.001) and walked slower (p=0.02) than controls. However there were no differences between degenerative and static groups on any of these measures (all p>0.49). There were no significant differences between the three groups in cadence (p=0.22) or percent double support time (p=0.63; see ).
Over time, the static cerebellar group tended to walk faster and take longer strides, whereas the degenerative cerebellar group tended to walk slower and take shorter strides (group × visit interactions, p=0.007 and p=0.042, respectively; ). There were no significant post hoc differences between visits for walking speed or stride length. There was a significant effect of visit for percent double support time (p=0.02). The cerebellar group as a whole increased double support times at the six-month follow up (post hoc, p=0.02) and at the 12-month follow up compared to baseline (post hoc, p=0.01). We found no significant changes across groups or visits for stride width, cadence or percent stance time (see ).
show the correlations between ICARS scores and gait performance for the individuals in the cerebellar degenerative group at the 12 month visit. We selected gait performance measures of walking speed, stance time and stride width for these analyses because these parameters have been specifically reported to be impaired in individuals with cerebellar disorders and shown to be strongly related to balance function4
. Correlations between total ICARS scores and walking performance were strong and significant (; speed, r=−0.737; stance time, r=0.621; stride width, r=0.719). Correlations between posture and gait ICARS subscores and walking were also significant (; speed, r=−0.818; stance time, r=0.688; stride width, r=0.830). Notably, each of these produced a higher correlation coefficient and greater statistical significance than the corresponding correlation using total ICARS scores.
Scatterplots showing the correlation between specific walking parameters and ICARS scores for all subjects in the cerebellar degenerative group
To determine whether the ICARS could predict later gait performance, we calculated correlation coefficients between ICARS scores at baseline and walking performance at the 12 month follow-up. Overall, total ICARS scores were not a significant predictor of gait measures one year later. The correlations between total ICARS score and walking speed, stance time and stride width were r=−0.439 (p=0.176), r=0.438 (p=0.177) and r=0.551 (p=0.079), respectively. However, posture and gait ICARS subscores did predict all three walking measures (see ; speed, r=−0.613; stance time, r=0.639; stride width, r=0.774).