Elsevier

World Neurosurgery

Volume 115, July 2018, Pages e152-e159
World Neurosurgery

Original Article
Is the Cervical Anterior Spinal Artery Compromised in Cervical Spondylotic Myelopathy Patients? Dual-Energy Computed Tomography Analysis of Cervical Anterior Spinal Artery

https://doi.org/10.1016/j.wneu.2018.03.217Get rights and content

Highlights

  • Cervical myelopathy is a common acquired cause of spinal cord dysfunction in older patients.

  • A hypoxic–ischemic environment secondary to chronic spinal cord compression plays an important role in the pathogenesis of myelopathy.

  • This study aims to assess the altered blood flow to spinal cord in CSM using dual-energy computed tomography.

  • This study uses DECT to identify anterior spinal artery blood flow in CSM.

Objective

Cervical myelopathy is a common, acquired cause of spinal cord dysfunction in older patients. It is postulated that a hypoxic or ischemic environment secondary to chronic spinal cord compression plays an important role in the pathogenesis of myelopathy. This study aims to use dual-energy computed tomography (DECT) to assess the altered blood flow to the spinal cord in patients with cervical spondylotic myelopathy (CSM). To our knowledge, this study is the first to use DECT in identifying comprised anterior spinal artery blood flow in patients with CSM.

Methods

Fifty patients with single disc level CSM and 10 volunteers without CSM underwent DECT of the cervical spine to analyze and compare the ASA. The neurologic status of each patient was evaluated preoperatively and postoperatively at 5 days, 1 month, and 6 months using the Japanese Orthopedic Association (JOA) score. All the patients with CSM underwent single-level anterior cervical discectomy and fusion, and at postoperative day 5, each patient underwent repeated DECT. The anterior spinal artery before and after surgery was compared in patients with CSM. The blood flow in terms of iodine content at a specific region of interest was measured in the axial CT of the volunteers group and in the preoperative and postoperative axial CT of patients with CSM. Correlations between change in blood flow and clinical improvement at each follow-up point were analyzed statistically.

Results

Iodine content (100 mg/mL) was 14.2800 ± 1.89527 at the C3/C4 disc level, 14.8280 ± 1.83820 at the C4/C5 disc level, and 15.5000 ± 2.41048 at the C5/C6 level. In patients with CSM, the preoperative iodine content (100 mg/mL) measured was 10.2621 ± 2.37396 in C3/C4 disc-level compression, 12.1438 ± 1.63447 in C4/C5 disc-level compression, and 14.0620 ± 2.44390 in C5/C6 disc-level compression. Postoperative iodine content (100 mg/mL) measurement changed to 13.78 ± 2.77 for the C3/C4 disc level, 14.16 ± 1.90 for the C4/C5 disc level, and 15.14 ± 2.62 for the C5/C6 disc level. The JOA score was 13.650 preoperatively, 14.010 at 5 days postoperatively, 14.630 at 1 month postoperatively, and 15.000 at 6 months postoperatively. The 1- and 6-month correlation ratios between the JOA and change in blood flow were statistically significant, with an r value of 0.746 (P < 0.05) and 0.760 (P < 0.05), respectively.

Conclusions

This study provided evidence for the benefit of DECT as a radiographic tool for identifying the compromised cervical anterior spinal artery in patients with CSM. We believe that DECT is the one of the best radiographic tools available to provide an objective screening tool to detect compromised blood flow in patients with CSM.

Introduction

Cervical spondylotic myelopathy (CSM), wherein the spinal cord is compromised within the vertebral canal by degenerative changes, is the most common acquired cause of spinal cord dysfunction among those older than 55 years.1 Teresi et al.2 identified 26% of general subjects older than 64 years old with spinal cord compression on magnetic resonance imaging.2 It has been widely accepted that the pathophysiology of cervical spondylotic myelopathy (CSM) involves static factors, resulting in acquired or developmental stenosis, and dynamic factors that involve repetitive injury to the cervical spinal cord.3, 4

The signs and symptoms are widely dependent on the relative degree to which the posterior, dorsolateral and ventrolateral columns, the ventral horns, and the cervical nerve root of the spinal cord are involved.2 However, there is still a lack of understanding why some patient develops severe symptomatology, whereas others have few or no symptoms despite radiographic evidence confirming similar degrees of compression. Histologic examination of the spinal cord in patients with spondylotic myelopathy revealed flattening of the cord, swelling of myelin and axons, demyelination in the posterolateral and anterolateral columns, neuronal loss in the anterior horns, and gliosis.5 As a basis of reasoning, it was assumed that the chronic degenerative changes can compress major feeding arteries of the cervical spine, resulting in pathologically reduced blood flow and compromised spinal cord perfusion.5 A cadaveric study that supports this theory has demonstrated a curved and stretched anterior spinal artery and branches of lateral pial plexus around the degenerative spondylo-osteophytes.6

In light of ongoing concerns about altered blood flow in cervical spondylotic myelopathy, a radiographic tool to detect compromised blood flow in patients with CSM in a clinical setting would be valuable. Attempts to detect altered anterior spinal artery (ASA) blood flow have been reported previously using the present-day availability of computed tomography (CT) angiography, and they have been unsuccessful.7 The concept of dual-energy CT (DECT) involves the acquisition of 2 datasets using different X-ray energy spectra.8, 9 The potential for material decomposition using a dual-energy method has been known since the late 1970s; however, clinical implementation of this technique was limited on early-generation CT scanners.10, 11

The goal of the present study was to use DECT as a screening tool to identify and compare the blood flow in cervical anterior spinal artery in CSM patients and volunteers without cervical spondylotic myelopathy, to discuss the effect of surgical decompression for cervical spondylotic myelopathy on the cervical ASA, and to acknowledge and highlight the changes in blood flow of cervical anterior spinal artery after surgical treatment with the improvement in the Japanese Orthopedic Association (JOA) score of CSM patients.

Section snippets

Patients with Cervical Spondylotic Myelopathy

Between June 2016 and April 2017, a total of 50 patients were prospectively included in our study. The inclusion criteria for this study was: 1) Patient presented with typical symptom of cervical myelopathy that were not alleviated after at least 6-month conservative treatment; 2) Obvious single disc-level cervical spinal cord compression as shown by magnetic resonance imaging studies; 3) Patient agreed to receive surgical treatment and cooperate with follow-up visits after surgery. These

Results

The study included 50 patients with CSM patients (29 men and 21 women) with an average age (and standard deviation) of 56.24 ± 10.435 years (range, 31–72 years) and 10 volunteers without cervical spondylotic myelopathy (7 men and 3 women) with an average age (and standard deviation) of 53 ± 9.24 years (range, 31–64 years). The average length of symptoms in CSM patients was 10.26 ± 2.44 months. The demographic features and radiologic parameters are shown in Table 1. The JOA scores (Table 1) for

Discussion

Chronic degenerative changes in the cervical spine cause an interruption in the blood supply to the spinal cord that may be a significant component in the initiation and progression of CSM.14 The cadaveric study conducted by Breig et al.6 supports the suggestion of compromised ASA blood flow by degenerative changes in the cervical spine to axonal pathways, including corticospinal tracts. Clinical attempts to identify compromised ASA in patients with CSM have been unsuccessful.7

In this study

References (23)

  • H.K. Genant et al.

    Quantitative bone mineral analysis using dual energy computed tomography

    Invest Radiol

    (1977)
  • Cited by (0)

    Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

    Shiyang Wu, Suraj Chandoo, and Minyu Zhu contributed equally to this work.

    This work was supported by grants from the National Natural Science Foundation of China (81571190, 81771348) and Wenzhou Public Welfare Science and Technology Project (Y20170082).

    View full text