Prevalence and Predictive Factors of Concurrent Cervical Spinal Cord Compression in Adult Spinal Deformity

Takayoshi Shimizu, MD, PhD; Ronald A. Lehman Jr, MD; Suthipas Pongmanee, MD; J. Alex Sielatycki, MD; Eric Leung, BA; K. Daniel Riew, MD; Lawrence G. Lenke, MD

Disclosures

Spine. 2019;44(15):1049-1056. 

In This Article

Discussion

In this study, we report the prevalence of and predictive factors for cervical spinal cord compression based on MRI in patients with ASD undergoing major thoracolumbar reconstruction surgery. Among the patients, 33.8% (41/121) showed significant CSCC (CCI Grade>2). Age, BMI, and PI-LL mismatch independently predicted the severity of CSCC. Clinically, we had noticed a high rate of cervical cord compression findings both by careful physical examination and history in this patient population; and thus began obtaining routine c-spine MRI as a screening for compression. As our results show, there is a high rate of cervical spinal cord compression in thoracolumbar deformity patients.

Simultaneous stenosis of the cervical and lumbar spine has been well known as "tandem stenosis," which was first reported by Dagi et al[9] in 1987. The prevalence of tandem stenosis ranges from 5% to 24% depending on the modality used to diagnose it.[8–12] Lee et al[8] reported that the incidence of tandem stenosis based on sagittal MRI was 23.7%. However, only a few studies focused on the association of cervical stenosis with the extent of thoracolumbar deformity. Schairer et al[2] demonstrated that 31.0% of patients with thoracolumbar deformity had a diagnosis of cervical spondylosis without detailed evaluation on MRI. Our study presented a more reliable, MRI-based prevalence of cervical cord compression in patients with ASD.

In the intraoperative phase of complex ASD surgeries, various factors, such as prolonged positioning of the cervical spine in hyperextension and suboptimal mean blood pressure due to blood loss and anesthetic agents, could increase and/or induce the risk of cervical cord injury at the compressed levels.[1] In addition, fusion of the thoracolumbar spine may postoperatively worsen the cervical symptoms due to spontaneous reciprocal changes in the cervical alignment. Therefore, it is crucial for deformity surgeons to evaluate the cervical spine preoperatively. Physical examination alone is not reliable for detecting cervical myelopathy. In fact, 85.3% of patients with significant CSCC (Grade>2 CCI) were asymptomatic or with myelopathy that is difficult to detect in our series. Rhee et al[13] described that one-fifth of patients with cervical myelopathy were negative for myelopathic signs. In these patients, diagnostic imaging study, most commonly MRI, should be considered a preoperative assessment, in addition to a thorough neurologic examination. Nevertheless, it may not be cost-effective to perform preoperative MRI in all patients undergoing ASD surgery. Our study demonstrated older age, BMI, and PI-LL mismatch as predictive factors for significant CSCC. We suggest performing MRI on these patients prior to thoracolumbar reconstruction. Age and obesity have been shown to significantly influence the presence of disc degeneration in the cervical spine as well as the lumbar spine.[14] Determining the cut-off age to perform preoperative MRI is not easy; however, our results imply that patients aged over 70 years should undergo MRI due to the high prevalence of CSCC in this age group (over 50%). Also, it should be noted that even those patients in their 30s had a 37.5% rate of Grade>2 CCI. Teraguchi et al[15] reported that patients with obesity (BMI > 27 kg/m2) had an odds ratio of 1.60 for the presence of cervical disc degeneration. The data in the present study are not able to provide a pathophysiologic explanation for the association between increased BMI and CSCC, we suspect metabolic derangement or potentially microvascular changes related to diabetes may play a role. Further study would be needed to confirm this association and to explore potential pathophysiologic explanations. The relationship between cervical degeneration and thoracolumbar alignment has rarely been reported. Fujimori et al[3] described that radiographic degeneration score correlated with loss of cervical lordosis in the setting of compensatory hypothoracic kyphosis induced by degenerative flat back (that is, high PI-LL mismatch). These patients were commonly seen in the current series. Conversely, in decompensated thoracolumbar malalignment with high PI-LL mismatch, hyperlordosis of the cervical spine can occur.[16] In either of the two situations, high PI-LL mismatch results in nonphysiologic hyper-/hypo-lordosis, which can accelerate degenerative change of disc and ligaments.

In this series of patients with ASD, four patients (3.3%) underwent cervical decompression and fusion prior to thoracolumbar reconstruction. In patients presenting with apparent myelopathic signs or symptoms, most surgeons would recommend cervical spine surgery before thoracolumbar reconstruction. On the contrary, in the case of an asymptomatic but significant cord compression on MRI (Figure 4A–F), prophylactic decompression prior to thoracolumbar deformity operation may be controversial. On the basis of the current literature, the occurrence of cord injury after minor trauma in patients with asymptomatic cervical cord compression is likely uncommon and even intramedullary T2 hyper-intensity cannot be a pure predictor for myelopathy development.[17,18] However, it is difficult to completely exclude the presence of cervical myelopathy with physical examination alone, especially in patients with significant thoracolumbar deformity. Treating these patients without knowing the presence of coexisting cervical cord compression could theoretically lead to a devastating cord injury. In addition, we recommend intraoperative neuromonitoring with recording from both upper and lower extremities and keeping the neck in gentle neutral position using halo-ring or Gardner–Wells tong traction throughout the operation.

Figure 4.

Typical thoracolumbar deformity patient with significant but asymptomatic cervical cord compression. 67-year-old male with degenerative flat back syndrome undergoing T8-sacrum/pelvis fusion; body mass index (BMI) 27.3 kg/m2 and PI-LL mismatch 41.4°. (A, B) Preoperative coronal and sagittal X-ray. (C, D) Postoperative coronal and sagittal X-ray. (E) MRI sagittal view showing significant cord compression at C3/4 and C4/5. (F) MRI axial view at C3/4 showing Grade 3 CCI (Cord Compression Index, anterior score 3 + posterior score 3).

The segment in which significant CSCC was most frequently observed was the mid-cervical levels (C4/5 and C5/6). In addition, almost half of the patients with significant CSCC showed more than two-level compression. These findings are in agreement with previous findings that demonstrated a high prevalence of degenerative changes of the cervical spine in those segments.[15,19] Surgeons should expect that multiple compressions commonly coexist in those segments in patients with thoracolumbar deformity.

Some limitations of this study should be noted. Due to the nature of the study, some patients referred from other hospitals had already undergone MRI and been diagnosed with cervical stenosis. This might have caused bias to the neurological evaluation at initial visit. Second, cervical radiculopathy was not assessed in this study on every patient unless there was something in the patient's history which prompted a formal upper extremity examination. Concurrent radiculopathy can also be worsened after a long thoracolumbar reconstruction operation. Future studies are planned with prospectively collected data, including postoperative progression of clinical signs and comparison between patients with and without cervical spine surgery prior to thoracolumbar realignment surgery.

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