The Spine Blog

Friday, March 17, 2017

Is neuromonitoring indicated in routine anterior cervical spine surgery?

Neuromonitoring (NM) is considered the standard of care for deformity correction surgery, however, its role in routine anterior cervical spine surgery for degenerative conditions is less clear. A recent article published in Spine by Ajiboye et al. based on the Pearl Diver database demonstrated a decrease in the rate of NM use during ACDF from over 20% in 2007 to under 5% in 2014.1 This study also reported no differences in the rate of neurological injury between the monitored and unmonitored groups. In the March 15 issue, this group published a follow-up article in which they performed a meta-analysis in an attempt to determine the test characteristics of NM for anterior cervical surgery and whether it decreased the rate of intra-operative neurological injury. They identified 10 studies that evaluated NM use in anterior cervical surgery. Not surprisingly, the included studies were primarily Level IV evidence, with two retrospective cohort studies graded Level III. The studies were also quite heterogeneous in terms of neuromonitoring technique (i.e. SSEPs vs. MEPS vs. both), thresholds for defining a positive intra-operative alarm, and the types of patients (i.e. radiculopathy, myelopathy, trauma, tumor, infection) and procedures (i.e. ACDF, corpectomy or both) included. Only two of the studies compared the rate of neurological injury between the monitored and unmonitored groups. Despite these limitations, the authors combined the data for analysis, which included over 26,000 patients (though a single database study included over 22,000 of these). The overall rate of perioperative neurological injury was 0.19%, with a rate of 0.64% if each study was weighted equally. The studies that included only ACDF had a lower neurological injury rate (0.19%) as compared to those that included corpectomies as well (1%), though the large database study with over 22,000 patients included only ACDF patients and had one of the lowest neurological injury rates (0.12%), which likely pulled down the average for the ACDF-only studies. There were no significant differences in the rate of neurological injury for the monitored vs. non-monitored groups. The overall sensitivity of NM was 71%, and the positive predictive value was only 24%, indicating a false positive rate of 76%.

 

The authors did a nice job combining the available evidence on this topic, despite it being of relatively low quality and of a heterogeneous nature. The strength of a meta-analysis is limited by the quality of the included studies, which is the most significant limitation of the current study. The heterogeneity in terms of NM technique, alarm threshold, and patient and procedure characteristics also make it difficult to interpret the data. Due to the fortunately low rate of intra-operative neurological injury, this is a very difficult topic to study as huge numbers of patients are needed to sufficiently power a study. The large database study included in this meta-analysis represents one way to address the power issue, however, the ability of such a study to capture every case of neurological injury is questionable given that study’s very low rate of neurological injury. Additionally, it is unclear how each study defined neurological injury, so it is not possible to determine the rate of major spinal cord injury or less concerning neurological injuries such as C5 palsy. While this study did not address it, the major question regarding NM use for routine anterior cervical surgery is whether or not it can actually alert the surgeon to a reversible neurological insult. Most of the neurological injuries that occur intra-operatively are probably not reversible, so alerting the surgeon to such a problem intra-operatively does not change the outcome. The current study is probably not definitive in demonstrating the lack of efficacy of neuromonitoring for routine anterior cervical surgery, however, it does support the current trend in the spine surgery community of moving away from NM for these cases.

Please read Dr. Ajiboye’s article in the March 15 issue. Does this change how you view the use of NM in anterior cervical surgery? Let us know by leaving a comment on The Spine Blog.

 

Adam Pearson, MD, MS

Associate Web Editor

 

REFERENCE

1.            Ajiboye RM, D'Oro A, Ashana AO, et al. Routine Use of Intraoperative Neuromonitoring During ACDFs for the Treatment of Spondylotic Myelopathy and Radiculopathy Is Questionable: A Review of 15,395 Cases. Spine (Phila Pa 1976) 2017;42:14-9.