At levels C1-C2, ASIA grade A–C paralysis occurred in 7 of 12 patients (58.3%). ASIA grade A–B paralysis developed in three patients, all of whom were classified as having ESCC 1b spinal cord compression.
Of the 113 patients with L2-L5 lesions, there were 52 patients (46.0%) who exhibited dural compression without paralysis, which was indicative of ASIA grade E paralysis. There were 18 patients (15.9%) with ASIA grade C paralysis, and there were only 3 patients (2.7%) with ASIA grade B paralysis. Also, three patients with L2-L5 lesions and ESCC grade 3 spinal cord compression did not develop paralysis.
At the S1 level (n = 9), there were five patients (55.6%) with dural compression who did not develop paralysis, which was indicative ASIA grade E. There were no patients with ASIA grade C or worse paralysis.
On the contrary, the incidence of ASIA grade C or worse paralysis was high among the patients with ESCC grade 2 or worse spinal cord compression at the C7-L1 level (Tables 1–4).
ASIA grade D or worse paralysis developed in at least 50% of the patients with ESCC grade 1b or worse spinal cord compression at the C1-T2 level (Tables 1 and 2), whereas it arose in at least 50% of the patients with ESCC grade 1c or worse spinal cord compression at the T3-L5 level (Tables 3 and 4).
Examinations of the Patients Who Suffered Rapidly Progressive Paralysis
There were 19 patients who suffered deterioration of one grade or more to ASIA grade C or worse within the first 3 weeks after MRI (C3-C6, one patient; C7-T2, four patients; T3-T10, eight patients; T11-L1, five patients; and L2-L5, one patient). The primary foci consisted of lung cancer in six patients; liver cancer in three patients; bladder cancer in two patients; and breast cancer, prostate cancer, colorectal cancer, gastric cancer, gallbladder cancer, neuroblastoma, and uterine cancer in one patient each. The nature of the primary focus was unclear in one patient. Of these, rapidly progressive paralysis occurred in at least 30% of the patients who exhibited anterolateral or circumferential ESCC grade 2 or 3 spinal cord compression at the C7-T2, T11-L1, or T3-T10 level on MRI cross-sections (Table 5, Figure 3).
Bilsky et al reported that the ESCC scale, which consists of four grades, is useful for selecting the optimal treatment for spinal cord compression.8 In 2010, they indicated that T2-weighted axial images were more useful than T1-weighted axial images for discriminating between the grades of the ESCC scale.3 In this study, the use of T2-weighted axial MRI for ESCC scale–based evaluations of spinal cord compression resulted in favorable inter- and intraexaminer agreement.
In clinical practice, the MRI findings of spinal cord compression are not always correlated with the severity of paralysis, which depends on the level of the affected spinal cord site. Paralysis often progresses rapidly, leading to severe conditions in many cases. However, no previous studies have reported the grade of spinal cord compression at which neurological symptoms appear or paralysis rapidly progresses.
In addition, few studies have investigated the relationship between the MRI findings of spinal cord compression and the severity or extent of paralysis with respect to the level of the affected spinal cord site. Recently, Oshima et al9 conducted a retrospective study of T2-weighted axial MR images and reported that postoperative gait function could be predicted based on the circumferential ratio of cord compression (CRCC). They also indicated that there was no relationship between the compression site (the direction of the compression) and pretreatment paralysis/post-treatment gait function. In addition, they emphasized that nerve function depended on the grade of circumferential spinal cord compression and that spinal cord compression does not involve a simple mechanical compressive force.
Oshima et al also reported that a CRCC of more than 50% was correlated with poor ambulatory function, suggesting that the CRCC is a useful MRI finding for assessing the risk of metastatic spine tumor–induced paralysis. In our study, circumferential spinal cord compression and spinal deformity were seen in some, but not all, cases of severe paralysis.
In the present study, at least 50% of the patients with ESCC grade 1b or worse spinal cord compression at the C1-T2 level developed ASIA grade D or worse paralysis (Tables 1 and 2). In addition, at least 50% of the patients with ESCC grade 1c or worse spinal cord compression at the T3-L5 level developed ASIA grade D or worse paralysis (Tables 3 and 4). This difference might have been caused by dynamic factors associated with the cervical spine or cervical-thoracic transition area. Neurological symptoms might appear even if the grade of spinal cord compression or entrapment is low.
With respect to patients that are at high risk of the rapid progression of paralysis to a severe condition, it is difficult to predict paralysis based on T2-weighted axial MRI alone unless the relationship between the timing of MRI examinations and the stage of paralysis could be elucidated. In this study, we retrospectively reviewed the cases of patients whose paralysis deteriorated by one grade or more to ASIA grade C or worse within the first 3 weeks after MRI. The frequency of lung cancer patients was high among these patients, but lung cancer did not account for a significant percentage of all subjects. When we examined our T2-weighted axial MRI findings for each same spinal cord level, we found that the patients that exhibited anterolateral or circumferential ESCC grade 2 or 3 spinal cord compression at the C7-T2, T11-L1, or T3-T10 level constituted a high-risk group for the deterioration of paralysis, that is, they demonstrated a paraplegia incidence of at least 30% within the first 3 weeks after MRI (Figure 3). Although MRI results might depend on the timing of MRI with respect to the stage of paralysis, treatment should be started promptly in patients who fall into the abovementioned group.
The limitations of this study were as follows: (1) the craniocaudal direction of the patients’ spinal cord compression was not taken into account, although the examiners exhibited 100% consistency with respect to their ability to identify the level of each paralysis-inducing lesion; (2) no dynamic factors were examined10; and (3) the timing of MRI with respect to the stage of paralysis was unclear.11 Concerning tumor-related mechanical compression, we could not investigate the duration of compression, primary tumor rigidity, or the intraspinal circulation under compression. A prospective study involving these factors should be conducted in future.
Furthermore, some patients with severe paralysis or whose paralysis had deteriorated rapidly at the time of the MRI examination were already operated on within the next 3 weeks. Therefore, the rate of rapidly deteriorating paralysis may increase further.
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Keywords:Copyright © 2018 The Author(s). Published by Wolters Kluwer Health, Inc.
epidural spinal cord compression scale; magnetic resonance imaging; metastatic spinal tumors; paralysis; paraplegia