We found that, in patients who had lost their ability to walk for more than 48 h due to MSCC, hip flexion strength before surgery, primary tumor grade, and postoperative complications were associated with regaining walking ability one month after surgery. Regained ambulation resulted in longer survival after surgery.

Prognostication of neurological improvements after surgery remains challenging for MSCC because multiple variables may influence patient outcomes. Previous studies have identified neurological deficit duration, preoperative bladder function, KPS, degree of paralysis, and speed of neurological deterioration as predictive factors for regained walking ability [6, 7, 9,10,11,12,13,14,15,16,17]. The preoperative ambulation status is the strongest and most consistent predictor of postoperative ambulatory outcomes after surgery for MSCC [7, 17]. Most patients with preserved walking ability at the time of surgery remain ambulatory after surgery [3, 5, 7, 17]. In patients who lost their ability to walk before surgery, preoperative motor function and surgical timing are likely the most important predictors for regained ambulation [7, 12, 17]. In our study, half of the patients regained ambulation after surgery despite the duration of neurological deterioration of more than 48 h before surgery. Even though the timing of surgery for MSCC is considered a key component of neurological recovery, the association between the duration of neurological symptoms and neurological recovery has also been reported to be of low evidence [7]. Several studies have reported that > 48 h between the loss of ambulation and surgery has a negative effect on the ability to regain ambulation [5, 11, 13, 16]. In their study of 121 patients, Quraishi et al. reported that surgery for MSCC 48 h after acute presentation with neurological symptoms was associated with poor neurological outcomes [13]. Only 8 of the 53 patients who underwent surgery 48 h after they lost their ability to walk regained ambulation in their study.

The speed of neurological deterioration was highlighted in a systematic review and meta-analysis by Liu et al. [17], who reported a lower chance of regaining ambulation with a greater speed of neurological deterioration. In the present study, the speed of onset of neurological symptoms was not associated with ambulation after surgery. This may be explained by the fact that relatively few patients in our study experienced rapid onset (≤ 24 h) of neurological deterioration. On the other hand, we found that the primary tumor grade, reflected by the speed of tumor growth, was significantly associated with neurological recovery. Patients with slow-growing tumors, such as breast, prostate and thyroid cancer, and intermediate-growing tumors, such as kidney or ovarian tumors, had better neurological outcomes than patients fast-growing tumors, such as lung, gastrointestinal, esophageal and pancreatic tumors.

In our study, the extent of MSCC reflected by the ESCC scale was not associated with neurological outcome one month after surgery, which is in line with the study of Uei et al. [20], who did not find an association between the severity of neurological deficits and the ESCC scale in 467 patients with MSCC. Sphincter dysfunction was previously considered a negative prognostic sign [7] but was not associated with neurological outcome in our study. However, only six of our patients with sphincter dysfunction regained the ability to walk. A sharper definition of complete loss of anal sphincter function may have altered the association for regained ambulation, but few patients who underwent surgery completely lost sphincter function, which limited the statistical analysis for such a definition.

In the present study, the severity of preoperative neurological deterioration represented by preoperative hip flexion strength was associated with ambulation recovery after surgery. Our results suggest that the preoperative strength of hip flexion could be used as a prognostic indicator for neurological recovery even if the duration of ambulation loss exceeds 48 h. Some previous studies have shown that muscle strength in lower extremities equal to or greater than grade 3 is associated with postoperative recovery of ambulation [6, 7, 12, 16]. The association between preoperative hip flexion strength and postoperative ambulation has also been questioned. Ohashi et al. [21] reported a significant association between hip flexion strength before surgery and postoperative walking ability in their univariate analysis, but this variable was not statistically significant in their multivariate analysis. The prognostication of regained ambulation after surgery is thus complex. Surgery within 48 h has been demonstrated to be associated with favorable outcomes [7, 13], but no true timeframe has yet been defined for patients for whom surgery is ineffective. The identification of preserved hip flexion in patients with a duration of lost walking ability for > 48 h may thus add clinical value for adequate selection for surgery in these groups of patients with MSCC.

In our study, regained walking ability had a significant effect on postoperative survival, the difference in survival was relatively large with a median survival of 5 month for the nonambulatory patients compared to 16 month for the patients that regained walking ability. The association between regained ambulation and survival are in line with several other studies [16, 22, 23]. Walking ability has a significantly effect not only on postoperative survival, but also the quality of life [23, 24, 25]. This highlights the importance of identifying variables that may influence neurological recovery when making decisions about surgery in patients with longer durations of ambulation loss.

The limitations of our work are the retrospective study design and that the treatments for MSCC were not randomized. The wide range of years included in the study is another limitation due to the innovation of surgical techniques and adjuvant therapies for specific tumors over time, which may have influenced the results. Furthermore, this study limits the possibility to draw conclusion about even longer time spans of lost ambulation, and it is important to highlight that MSCC is a surgical emergency that should be addressed as soon as possible. A strength of this study is the large sample size of patients with MSCC who lost their ability to walk for more than 48 h before surgery.