Elsevier

World Neurosurgery

Volume 86, February 2016, Pages 112-119
World Neurosurgery

Original Article
The Association of Cervical Spine Alignment with Neurologic Recovery in a Prospective Cohort of Patients with Surgical Myelopathy: Analysis of a Series of 124 Cases

https://doi.org/10.1016/j.wneu.2015.09.044Get rights and content

Background

Cervical spine sagittal malalignment has been demonstrated to correlate with the severity of disease in patients with cervical spondylotic myelopathy (CSM). The impact of spinal alignment on neurologic recovery has not been investigated thoroughly. The goal of this study was to evaluate the variable impact of preoperative sagittal alignment on neurologic recovery among surgical myelopathic patients.

Methods

An analysis of prospectively collected data was performed on surgical CSM patients treated at a tertiary neurosurgical center. Demographic data and preoperative and postoperative measures of neurologic disability (modified Japanese Orthopedic Association [mJOA] score, Nurick grade, Neck Disability Index) were analyzed for dependency on cervical spine alignment (kyphotic vs. lordotic) as well as preoperative disease severity and spinal cord magnetic resonance imaging.

Results

Thirty-four percent of 124 CSM patients had preoperative kyphosis. Surgical intervention was more frequently anterior or combined anterior/posterior among this group than those with preserved lordosis. Most patients exhibited postoperative neurologic improvement; however, the extent was dichotomous, with greater improvement among patients with preoperative lordosis (ΔmJOA 3.1) than with preoperative kyphosis (ΔmJOA 1.4, P = 0.02). More severe preoperative disease and quantitative magnetic resonance imaging T2 hyperintensity also predicted poorer recovery (α = 0.05). Lordotic patients exhibited similar improvement when approached anteriorly or posteriorly, whereas kyphotic patients exhibited greater improvement when approached by an anterior or combined approach. It is unclear whether restoring lordosis protects against adjacent segment disease.

Conclusions

The majority of patients with CSM showed postoperative neurologic improvement. Patients with preoperative lordotic alignment exhibited greater improvement than those with preoperative kyphotic alignment. Furthermore, the choice of surgical approach impacted neurologic recovery among kyphotic patients, with those patients who were approached anteriorly or with a combined approach faring better.

Introduction

Degenerative cervical myelopathy results from extrinsic changes in the cervical spine that lead to both static and dynamic spinal cord compression. The most common 2 etiologies include cervical spondylotic myelopathy (CSM) and ossification of the posterior longitudinal ligament. Spondylotic disease in the former leads to structural compression and the abnormal spinal alignment and the spinal cord excursion leads to dynamic compression and repetitive trauma.1 Nonsurgical management has not demonstrated efficacy for this condition,2, 3 whereas surgical management provides for stabilization and improvement of neurologic disability.4 Indeed, much of the current controversy pertains not to whether surgery should be offered but rather the specific type of surgical management.3, 4, 5 Disease pathoanatomy may guide the surgical decision-making, and preoperative cervical spine global sagittal alignment has been demonstrated recently to be associated with baseline neurologic disability.6 A prospective multicenter series of surgical CSM patients reveals similar neurologic outcomes despite the selected surgical approach,7 although perioperative morbidity may be heightened among patients approached posteriorly.5, 8

It is well established that the preoperative myelopathy score is one of the strongest predictors of postoperative neurologic status in prospective cohorts of patients with CSM.4, 9 Although global sagittal alignment has been associated with the intensity of spinal cord hyperintensity on magnetic resonance (MRI) and the severity of preoperative myelopathy, an important question remains as to the impact of this alignment on the potential for postsurgical neurologic improvement. Indeed, Zhang et al. have suggested that heightened MRI T2 hyperintensity does prognosticate for a lesser degree of postoperative neurologic improvement.3, 10, 11 A secondary question is whether operative correction of sagittal deformity has an impact on the extent of neurologic improvement.

Various surgical techniques can achieve different amounts of sagittal correction, more so for differences between multilevel anterior discectomy and multilevel anterior corpectomy approaches4 and less so for anterior approaches over posterior approaches.12 Experimental models of myelopathy reveal that cervical spine kyphosis is associated with demyelination, atrophy, and neuronal loss of the anterior horn and decreased vascular supply of the anterior spinal cord.13 Tang et al.14 have suggested that efforts to correct cervical spinal alignment may be appropriate and found that postoperative favorable alignment correlates with improved Neck Disability Index (NDI) scores, although this group of patients was heterogeneous for diagnosis.

Our objective was to assess how preoperative cervical sagittal alignment correlates with postoperative neurologic improvement in a prospective series of CSM patients treated at a single, tertiary-care center. Our second objective was to define whether surgical correction of kyphotic alignment independently provided for more substantially improved neurologic disability.

Section snippets

Methods

This study was performed by an ambispective analysis of prospectively collected data of CSM patients operated at a single, tertiary-care neurosurgical center during a period of 5 years (2007–2012) by 3 spinal neurosurgeons. The study population was a surgical cohort with inclusion criteria of patients with age older than 18 years of age who had symptomatic CSM with concordant spinal MRI. Exclusion criteria included patients with ossification of the posterior longitudinal ligament, previous

Results

We performed an analysis of 124 patients with symptomatic CSM, 65% of whom were men, with an average age of 60 ± 10 years and an average body mass index of 28 ± 5. Demographic data are summarized in Table 1, with no differences in age, sex, smoking status, or comorbidity found between patients on the basis of sagittal spinal alignment. Most frequently, the severity of myelopathy was moderate by both mJOA and Nurick grades, as summarized in Table 2, again without any specific differences

Discussion

Nonoperative management of symptomatic CSM generally is associated with disease progression, whereas surgical intervention can provide for neurologic stabilization and improvement in myelopathy. The choice of surgical approaches remains controversial, although mostly include both spinal cord decompression and spinal column stabilization. Patient stratification among those who are likely to achieve postoperative symptomatic improvement is even more elusive. Previous work by Mohanty et al.6 has

Conclusion

In this cohort of surgical CSM patients, the majority of patients exhibited neurologic improvement by the various myelopathy severity scores. Patients with preoperative kyphotic alignment exhibited a lesser degree of postoperative improvement compared with those who had preserved lordosis, and this was independent of whether the alignment was corrected at the time of surgery. Those patients with preoperative kyphosis had lesser improvement and deteriorated more frequently if approached by

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Conflict of interest statement: M.G.F. holds the Halbert Chair in Neural Repair and Regeneration and support from the Dezwirek Foundation.

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