Prognosis Following Surgery for SCI

In the acute period of traumatic SCI, interventions are aimed primarily at preserving or improving long-term function. Although recovery of neurologic function after injury is notoriously difficult to predict, much work has gone into identifying prognostic factors that might help guide individual expectations for long-term function. In general, prognosis and neurological outcome are described using outcomes tools including changes in the AIS motor score, and the Frankel grade, which is general measure of functional independence.

Discussion

Park et al. (2017) performed a prognostic factor analysis to determine variables that might influence prognosis for traumatic SCI. In summary, they found that at one-year follow-up, the presenting neurological status of the individual, as well as their mean arterial pressure during the acute phase of hospital stay, was associated favourably with AIS motor score improvement.

Another potential determinant of neurological outcome is the overall medical state of the individual both before injury, and in terms of their complication profile after injury. Kreinest (2016) retrospectively reviewed a heterogenous series of individuals with SCI and found that long-term AIS motor score changes were adversely affected if the individual had previous spinal co-morbidities such as ankylosing conditions, or significant degenerative conditions. It is unclear whether spinal comorbidities are primary drivers of outcome or whether they may act as a surrogate for increased age, for example. Interestingly, further analysis of these individuals showed that other pre-injury comorbidities, as well as common in-hospital complications such as urinary tract infection and pneumonia, had no effect on AIS motor score improvements in these individuals.

Walking ability is clearly an important functional outcome after traumatic SCI. In a population of individuals with thoracolumbar SCI, Abdel-Fatah (2017) demonstrated that walking ability at one year was strongly related to the level of injury, with T12 and L1 injuries having significantly more function, and T10 and T11-injured individuals not regaining the ability to walk. This may potentially be due narrowing of the spinal canal at T10-11.

Another retrospective review was performed by Razaq (2018) who reported an SCI cohort with mixed neurology, demonstrating an overall AIS motor grade conversion of 45% at follow-up, with AIS A individuals demonstrating a substantially lower chance of improvement than those with incomplete injuries.

Despite the clear focus on early surgical decompression of traumatic SCI for improved outcome, there is some evidence that individuals undergoing delayed treatment can still experience neurological recovery. Konomi et al. (2018) assessed a retrospective cohort of individuals with late surgery and found that those individuals with severe cord compression still demonstrated neurologic improvement (2 or more AIS grades) in 30% of cases when late surgery was performed. This compared favourably to no improvement in the same individuals without surgery. In contrast, the subgroup of individuals with only mild-moderate ongoing cord compression demonstrated similar rates of recovery in surgical vs nonsurgical groups, and this rate was lower (11-18%) than the severe group.

Lehre et al. (2015) report a series of surgical individuals from a resource-limited setting in Ethiopia. In their series, 17% of individuals did not survive to follow-up, but among survivors 17% of complete SCI and 42% of incomplete individuals with SCI demonstrated motor recovery on examination. The authors propose that even in resource-limited settings, individuals can still derive benefit from surgical management of SCI.

McKinley et al. (2004) describe a retrospective comparison between nonsurgical, early surgery, and late surgery with respect to long-term motor improvement. They reported that nonsurgical individuals demonstrated a higher AIS motor score improvement at follow-up, as well as higher scores on the Functional Independence Measure. This was felt to be a confounded result due to the higher proportion of incomplete SCI in the nonsurgical group, who have a greater rehabilitation potential. Otherwise no differences were found with respect to prognosis between early and late surgery.

One well-recognized pattern of SCI is so-called hyperextension injury, which can occur as a dynamic process resulting in cord impingement without structural damage to the spine itself. In terms of AIS motor score improvement, these individuals tend to demonstrate a consistent improvement after 1 year (Kawano et al. 2010), and surgical intervention seems not to affect recovery. This is intuitive as there is not necessarily a structural process to correct in the setting of this injury.

In a (2008) study, Singhal et al. compared the motor recovery of 37 individuals with cervical SCI who were managed conservatively and with surgery. Despite not finding a statistical difference, they did report preservation of sensation below the injury as an important prognostic factor.

Conclusion

There is conflicting level 2, 3, and 4 evidence (based on several mixed studies) that a number of prognostic factors are important in the neurological outcomes after surgery for SCI which may include, but are not limited by, prior neurological and general medical status, mean arterial pressure, spinal co-morbidities, age, complications (e.g., pneumonia, urinary track infections), walking ability, level and completeness of injury, and timing of surgery.