Letter to the Editor Does Spinal Cord Line Influence Choice of Surgical Approach in Multilevel Cervical Spondylotic Myelopathy?

LETTER: to the article by Tong M-J, Hu Y-B, Wang T hisX-Y,isZhuin reference S-P, Tian N-F, Fang M-Q, et al in a recent issue of 1

WORLD NEUROSURGERY. The authors attempted to define a new classification to predict postoperative recovery effect for multilevel cervical spondylotic myelopathy patients using a new spinal cord line based on T2-weighted magnetic resonance imaging (MRI). For defining the starting and end points of the spinal cord (SC) line, the authors took Point A as the posteroinferior point of the SC at C2, while point B was the posterosuperior point of the SC at C7. These points should actually be labeled as the cord adjacent to the posteroinferior end of C2 vertebral body and posterosuperior end of C7 vertebral body because the posteroinferior and superior point of the SC at C2 and C7, respectively, will mean the posterior part of the cord adjoining the lamina in a lordotic spine. Fujiyoshi et al2 developed the K-line connecting the midpoints of the spinal canal at C2 and C7 on neutral lateral radiograph to predict incomplete indirect decompression for the patients with OPLL. The modified K-line was developed to take soft tissue decompressive factors into consideration and was defined by Sun et al3 as a line connecting both anterior points of the SC at the level of the inferior vertebrae endplates of C2 and C7 on sagittal T1-weighted MRI. This is quite similar to the line proposed by the authors in this article, and the need for development of a new MRI-based line to predict prognosis in patients of cervical compressive myelopathy has not been elucidated. The age of the patients in the 2 groups is significantly different. Further, no mention was made of the other comorbidities in the 2 groups. The impact of such a difference needs to be analyzed using a multivariate analysis. The 2 groups have been fairly matched for the T2 signal changes on MRI, but no mention has been made of the T1 signal changes. Uchida et al4 concluded that low-intensity signal on preoperative T1-weighted imaging but not T2-weighted imaging correlated with poor postoperative neurologic outcome. Suri et al5 also concluded that the presence of intramedullary signal changes on T1- and T2-weighted sequences on MRI in patients with cervical spondylotic myelopathy (CSM) indicates a poor prognosis. However, the T2 signal intensity changes reflect a broad spectrum of spinal cord reparative potentials. They further defined the predictors of surgical outcomes as preoperative signal intensity change patterns of the spinal cord and their postoperative persistence/regression on radiologic evaluations, age at the time of surgery, multiplicity of involvement, and chronicity of the disease and surgical approach (anterior/posterior).5

WORLD NEUROSURGERY 105: 1007, SEPTEMBER 2017

Preoperative cervical curvature has not been considered in deciding the surgical approach, which is an important factor in deciding the type of surgery to be performed in such patients.6 Follow-up of 1 year is a relatively shorter time period to determine the recovery rate of patients. Liu et al7 in their systematic review concluded that for multilevel CSM patients, the final follow-up Japanese Orthopedic Association score for the anterior group was significantly higher than for the posterior group (P < 0.05, weighted mean difference 0.83 [0.24, 1.43]) in the follow-up time 5 years’ subgroup but had no significant differences in the follow-up time >5 years’ subgroup (P > 0.05). Liu et al8 in their systematic review concluded that higher rates of surgical complications and complication-related reoperation were associated with multilevel corpectomy, and posterior laminoplasty may be the preferred method of treatment for multilevel cervical myelopathy when the involved surgical segments were 3. The previously mentioned factors need to be considered before the SC line and its classifications can be used to predict postoperative recovery effect in patients with multilevel CSM. Mohit Agrawal, Sachin Anil Borkar, Manoj Phalak, Raghav Singla, Ashok K. Mahapatra All India Institute of Medical Sciences, New Delhi, India To whom correspondence should be addressed: Sachin Anil Borkar, M.D. [E-mail: [email protected]] http://dx.doi.org/10.1016/j.wneu.2017.05.100.

REFERENCES 1. Tong M-J, Hu Y-B, Wang XY, Zhu S-P, Tian N-F, Fang M-Q, et al. The Spinal Cord Line Can Predict Postoperative Recovery for Multilevel Cervical Spondylotic Myelopathy. World Neurosurg. 2017;104:361-366. 2. Fujiyoshi T, Yamazaki M, Kawabe J, Endo T, Furuya T, Koda M, et al. A new concept for making decisions regarding the surgical approach for cervical ossification of the posterior longitudinal ligament: the K-line. Spine (Phila Pa 1976). 2008;33:E990-E993. 3. Sun LQ, Li M, Li YM. Prediction of incomplete decompression after cervical laminoplasty on magnetic resonance imaging: the modified K-line. Clin Neurol Neurosurg. 2016;146:12-17. 4. Uchida K, Nakajima H, Takeura N, Yayama T, Guerrero AR, Yoshida A, et al. Prognostic value of changes in spinal cord signal intensity on magnetic resonance imaging in patients with cervical compressive myelopathy. Spine J. 2014;14: 1601-1610. 5. Suri A, Chabbra RP, Mehta VS, Gaikwad S, Pandey RM. Effect of intramedullary signal changes on the surgical outcome of patients with cervical spondylotic myelopathy. Spine J. 2003;3:33-45. 6. Rhee JM, Basra S. Posterior surgery for cervical myelopathy: laminectomy, laminectomy with fusion, and laminoplasty. Asian Spine J. 2008;2:114-126. 7. Liu T, Xu W, Cheng T, Yang HL. Anterior versus posterior surgery for multilevel cervical myelopathy, which one is better? A systematic review. Eur Spine J. 2011;20: 224-235. 8. Liu X, Min S, Zhang H, Zhou Z, Wang H, Jin A. Anterior corpectomy versus posterior laminoplasty for multilevel cervical myelopathy: a systematic review and meta-analysis. Eur Spine J. 2014;23:362-372.

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Does Spinal Cord Line Influence Choice of Surgical Approach in Multilevel Cervical Spondylotic Myelopathy?

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