Are Functional Gains Durable After Decompressive Surgery for Cervical Myelopathy?: Commentary on an article by Victor Hin Ting Yick, MBBS, et al.: "Neurological Survivorship Following Surgery for Degenerative Cervical Myelopathy. A Longitudinal Study on 195 Patients".

Abstract

Commentary In degenerative cervical myelopathy, spine surgeons generally accept the concept that patients will show clinically meaningful improvement after spinal cord decompression. At a minimum, the spine literature and common sense support the notion that cord decompression will at least halt ongoing neurological deterioration. Surgeons may debate the best method of decompression (anterior or posterior) and whether decompression with fusion is necessary, but there is little dissension with regard to the need for a surgical procedure in the setting of moderate to severe myelopathy1. The extent to which early neurological improvement after the surgical treatment of degenerative cervical myelopathy is sustained in the long term is unknown. Using the concept of neurological survivorship and Kaplan-Meier curves, Yick et al. demonstrate that, although most patients improve after decompressive surgery, not all of these good early results are durable. The authors found that as many as 17.9% of patients will see a recurrent decline in neurological function by 10 years, and most of these patients who underwent failed treatment (74.3%) underwent a revision surgical procedure. Given the published high reoperation rates in cervical spine surgery, these results in degenerative cervical myelopathy are not particularly surprising. In a recent minimum 10-year follow-up of anterior cervical fusion in 159 patients, Buttermann reported a 31% reoperation rate2. In the current study, Yick et al. confirm what smaller, short-term studies have suggested: improvement after decompression for degenerative cervical myelopathy is fleeting in many patients and reoperation is common. Such knowledge is valuable when counseling patients both before and after the surgical procedure. In addition to describing the neurological survivorship of these patients, Yick et al. drilled down on the risk factors for failure. Some of these significant risk factors are patient-specific and are not controllable by the surgeon. These factors include renal failure and spinal cord signal change on T2-weighted magnetic resonance imaging sequences. A cord signal change, associated with cellular changes in the cord secondary to severe cord compression, is often irreversible3 and, as seen in the current study, is associated with ongoing declines in neurological function. Other significant risk factors are modifiable. Surgeons can use these factors to modify their surgical management of cervical myelopathy and, hopefully, improve future neurological survivorship. First, and most importantly, surgeons should not be performing suture laminoplasty. Patients treated with this technique had the worst neurological survivorship (31.2%) and tended to experience treatment failure early after the surgical procedure. Second, patients with ossification of the posterior longitudinal ligament did best when decompression was combined with fusion. Surgeons should give strong consideration to including fusion in patients with ossification of the posterior longitudinal ligament to improve outcomes. Conversely, surgeons might consider avoidance of fusion in younger patients with cervical compressive myelopathy. The top risk factor for late neurological decline was adjacent-level stenosis, proximal or distal to a fusion construct. In these patients, perhaps a posterior decompression without fusion or a laminoplasty with plating will result in better neurological survivorship. Yick et al. should be commended for their efforts to publish longer-term neurological outcomes for this complex group of patients. The strengths of the study include a large cohort of 195 patients and a mean follow-up of 76 months. The weaknesses of the study include a retrospective design with many patients (49) excluded because of incomplete follow-up. Furthermore, many of the included patients (37) had a follow-up period shorter than 2 years. Nevertheless, Yick et al. identify important predictive factors for neurological survivorship after surgical treatment of degenerative cervical myelopathy and give surgeons specific pearls to help with surgical planning. A long-term prospective study with a minimum 10-year follow-up is still necessary to define optimal surgical approaches for degenerative cervical myelopathy.