Our results in all patients showed a clear difference in outcomes at the 12-month cutoff as revealed by the simple regression and a trend that reached significance at the 24-month cutoff as assessed by the multiple regression. These results are consistent with those discussed, especially those that specifically used the Nurick score. We further showed that the influence of duration of symptoms on outcomes is dependent on age. Our simple regression analysis suggested that this dependence was evident for symptom durations of 12 and 24 months only in the younger cohort. However, our multiple regression analysis showed that the effect of symptom duration on outcomes is evident only in patients aged >65 years who have had symptoms for 24 months. The stark difference in results between the simple and multiple regressions is probably due to the several potentially confounding variables that were controlled for in the multiple regression analysis. Of course, it should be noted that a statistically nonsignificant difference does not necessarily translate into a clinically nonsignificant difference.
Our results are consistent with the few studies that describe the influence of the interplay between age and duration of symptoms on postoperative outcomes in CSM. For example, Handa and colleagues5 retrospectively reviewed 61 patients who underwent expansive laminoplasty for CSM and stratified them according to age greater or less than 70 years. Compared with the younger patients, duration of symptoms in the 22 elderly patients correlated with a significant difference in outcomes as assessed by the mJOA, with a cutoff of 1 year.5 Similarly, Yamazaki and colleagues19 evaluated 64 patients who also underwent expansive laminoplasty for CSM and stratified them according to age greater or less than 65 years. Duration of symptoms in 35 elderly patients significantly correlated with outcomes as assessed by the JOA scale, such that those considered to have an excellent outcome had a mean duration of symptoms of 11.1 months compared to the 39 months of symptoms in those considered to have a fair outcome.19 In contrast to those studies, we found that 24 months rather than 12 months was significant. However, we also evaluated outcomes using the Nurick score rather than the JOA. The JOA is a more detailed instrument, and this may be the reason for the discrepancy. Nonetheless, our results are consistent with the extant literature and add to the limited number of studies that have commented on the combined interactions of symptom duration and age in postoperative outcomes for CSM.
There are several strengths and limitations to this study. One strength is the relatively large sample size of patients. However, there was an uneven distribution in the number of patients in each age cohort. Ideally, there would have been an equal number of patients in each age group. The fact that all patients were operated on by the same surgeon minimizes variability in outcomes due to surgeon skill. We also controlled for multiple variables that are known to affect CSM outcomes, but we did not have quantitative data with respect to degree of compression or cross-sectional area of the affected spinal cord, which have been described as significant variables in outcomes of CSM. Furthermore, we did not evaluate the results using several outcome measures such as the JOA in addition to the Nurick score, and this limits the comparability of our work to some of the existing literature. This study also suffers from the inherent biases and shortcomings of retrospective studies, and the fact that this was not a multicenter study may limit generalizability of the results. However, given the dearth of literature on this topic, our work adds to the literature. Further studies will be needed to more clearly elucidate this topic.
This study demonstrated that duration of symptoms may be a significant factor in the recovery of patients undergoing surgical decompression for CSM, but only in patients aged >65 years who have had symptoms for 24 months.
This paper will be judged for the Resident Writer’s Award.