Original Research

The Effect of Age on the Benefits of Early Decompression for Cervical Spondylotic Myelopathy

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References

Simple regression analysis of data of all patients revealed a statistically significant negative relationship between duration of symptoms and postoperative change in Nurick score (P = .044). There was no relationship between duration of symptoms and preoperative Nurick score (P = .482). When stratified according to duration of preoperative symptoms by 12 or 24 months, the relationship between duration of symptoms and change in Nurick score was statistically significant for cutoffs of 12 months (P = .03) and 24 months (P = .007). There was no relationship between duration of symptoms and preoperative Nurick score for any threshold of preoperative symptom duration. When these results were stratified according to age, patients aged ≤65 years showed a statistically significant association between duration of preoperative symptoms and change in Nurick score for cutoffs of 12 months (P = .016) and 24 months (P = .019). However, patients aged >65 years did not show a statistically significant association for cutoffs of 12 or 24 months (P = .85 and .29, respectively). There was also no relationship between duration of symptoms and preoperative Nurick score for any threshold of preoperative symptom duration in either age cohort.

Multiple regression analysis of the previously described findings was undertaken to assess the influence of potential confounding variables. These included age, gender, diabetes, cocaine use, alcohol use, tobacco use, signal change on preoperative MRI, severity of myelopathy, total levels fused, prior surgery, surgical approach (anterior vs posterior), and procedure performed (Table 4). Analysis of the relationship between duration of symptoms and change in Nurick score for all patients initially revealed a statistically nonsignificant correlation (P = .22). Significant factors in this model included diabetes status and tobacco use that correlated with decreasing change in Nurick score (P = .02 and .0001, respectively) and severity of myelopathy that correlated with increasing change in Nurick score (P = .0002). Notably, combined procedures also correlated with decreasing change in Nurick score (P = .03), but the performance of individual procedures did not correlate with change in Nurick score. There was no association between duration of symptoms and preoperative Nurick score (P = .76). When stratified according to duration of symptoms of 12 or 24 months, only 24 months was found to be statistically significant (P = .03). There was no relationship between duration of symptoms and preoperative Nurick score for any threshold of symptom duration. When further stratified according to age, the younger cohort did not show a statistically significant association between duration of preoperative symptoms and change in Nurick score for either threshold of symptom duration (P = .15 and .43, respectively). Diabetes status, tobacco use, number of levels fused, severity of myelopathy, and combined procedures remained significant predictors of change in Nurick score for both thresholds of symptom duration. In contrast, the older cohort showed a statistically significant association between duration of symptoms and postoperative change in Nurick score only for a threshold of 24 months (P = .01). In contrast to the younger cohort, the only other significant predictors in this group were preoperative severity of myelopathy, anterior approach (all ACDF procedures), and signal change on preoperative MRI (P = .02, .04, and .03, respectively). There was no relationship between duration of symptoms and preoperative Nurick score for any threshold of preoperative symptom duration in either age cohort.

DISCUSSION

Several studies have attempted to describe the prognostic influence of preoperative symptom duration on surgical outcomes for CSM. Few studies suggest that duration of symptoms does not correlate with functional outcomes. For example, Naderi and colleagues6 concluded in a retrospective study of 27 patients that there is no correlation as assessed by the modified Japanese Orthopedic Association scale. Handa and colleagues5 similarly concluded in a retrospective study of 61 patients that duration of symptoms was not significant, but only in patients aged <70 years. Furlan and colleagues7 conducted a prospective study of 81 patients with a mean follow-up of 10 months and concluded that there is no association as assessed using the modified Japanese Orthopedic Association (mJOA) and Nurick score. In contrast, the majority of studies support the notion that duration of symptoms adversely affects outcomes. Several of these studies do not provide a clear cutoff beyond which outcomes are significantly affected.17-19,22

Of the studies that provide a cutoff, a fair number of studies suggest a limit of 12 months and a few suggest 24 months. In a retrospective study of 109 patients with cervical radiculopathy and 55 with cervical myelopathy, Bertalanffy and Eggert8 found that duration of symptoms beyond 12 months significantly correlated with worse outcomes as assessed by the evaluation criteria set forth by Roosen and Grote.23 Using the more common European Myelopathy Score, Heidecke and colleagues9 arrived at the same conclusion from a retrospective review of 106 patients. In a large retrospective review of 248 patients, Pumberger and colleagues11 found that patients who did not improve following surgical decompression for CSM, where improvement was defined as a reduction of at least 1 Nurick grade, had an average of 17.85 months of preoperative symptoms, whereas those who did improve had symptoms for an average of 11.21 months. In a prospective study of 98 patients, Suzuki and colleagues10 found that recovery rate of the JOA scale was significantly decreased in those with >1 year of preoperative symptoms. Both Chagas and colleagues14 and Suri and colleagues13 conducted prospective studies that revealed a significant difference in Nurick score improvement in patients with >2 years of symptoms. In reviews of the literature, both Holly and colleagues15 and Yoon and colleagues16 found a low level of evidence for the significance of symptom duration on outcomes. Similarly, Tetreault and colleagues24 found that duration of symptoms was predictive of outcomes as assessed by both mJOA and Nurick score.

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