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Published online before print April 12, 2007, 10.1148/radiol.2433060583
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(Radiology 2007;243:820-827.)
© RSNA, 2007

Neuroradiology

Acute Cervical Traumatic Spinal Cord Injury: MR Imaging Findings Correlated with Neurologic Outcome—Prospective Study with 100 Consecutive Patients1

Firoz Miyanji, MD, Julio C. Furlan, MD, MSc, MBA, PhD, Bizhan Aarabi, MD, Paul M. Arnold, MD, and Michael G. Fehlings, MD, PhD, FRCSC

1 From the Spinal Program, Krembil Neuroscience Centre, Toronto Western Hospital, University Health Network, 399 Bathurst St, West Wing, 4th Floor, Room 449, Toronto, Ontario, Canada M5T 2S8 (F.M., J.C.F., M.G.F.); Department of Surgery, Division of Neurosurgery, University of Toronto, Toronto, Ontario, Canada (F.M., J.C.F., M.G.F.); Department of Neurosurgery, School of Medicine, University of Maryland, Baltimore, Md (B.A.); and Kansas University Neurological Surgery, Kansas City, Mo (P.M.A.). Received April 4, 2006; revision requested May 31; revision received June 30; accepted August 2; final version accepted October 4. M.G.F., P.M.A., B.A. supported by funds from an unrestricted grant to the Spine Trauma Study Group, Minneapolis, Minn. J.C.F. supported by the Lawson Fellow-Neurology from The Toronto General & Western Hospital Foundation. M.G.F. supported by the Krembil Chair in Neural Repair and Regeneration. Address correspondence to M.G.F. (e-mail: michael.fehlings{at}uhn.on.ca).


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 ADVANCES IN KNOWLEDGE
 References
 
Purpose: To prospectively evaluate whether quantitative and qualitative magnetic resonance (MR) imaging assessments after spinal cord injury (SCI) correlate with patient neurologic status and are predictive of outcome at long-term follow-up.

Materials and Methods: The study included 100 patients (79 male, 21 female; mean age, 45 years; age range, 17–96 years) with traumatic cervical SCI. Ethics committee approval and informed consent were obtained. The American Spinal Injury Association (ASIA) motor score was used as the outcome measure at admission and follow-up. The ASIA impairment scale was used to classify patients according to injury severity. Three quantitative (maximum spinal cord compression [MSCC], maximum canal compromise [MCC], and lesion length) and six qualitative (intramedullary hemorrhage, edema, cord swelling, soft-tissue injury [STI], canal stenosis, and disk herniation) imaging parameters were studied. Data were analyzed by using the Fisher exact test, the Mantel-Haenszel {chi}2 test, analysis of variance, analysis of covariance, and stepwise multivariable linear regression.

Results: Patients with complete motor and sensory SCIs had more substantial MCC (P = .005), MSCC (P = .002), and lesion length (P = .005) than did patients with incomplete SCIs and those with no SCIs. Patients with complete SCIs also had higher frequencies of hemorrhage (P < .001), edema (P < .001), cord swelling (P = .001), stenosis (P = .01), and STI (P = .001). MCC (P = .012), MSCC (P = .014), and cord swelling (P < .001) correlated with baseline ASIA motor scores. MSCC (P = .028), hemorrhage (P < .001), and cord swelling (P = .029) were predictive of the neurologic outcome at follow-up. Hemorrhage (P < .001) and cord swelling (P = .002) correlated significantly with follow-up ASIA score after controlling for the baseline neurologic assessment.

Conclusion: MSCC, spinal cord hemorrhage, and cord swelling are associated with a poor prognosis for neurologic recovery. Extent of MSCC is more reliable than presence of canal stenosis for predicting the neurologic outcome after SCI.

© RSNA, 2007


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 ADVANCES IN KNOWLEDGE
 References
 
Extrinsic compression of the spinal cord and the internal architecture of the spinal cord are best visualized with magnetic resonance (MR) imaging. Qualitative findings such as cord hemorrhage, edema, soft-tissue and ligamentous injury, hematoma, and herniated disk have been previously described, and correlations between these findings and degree of neurologic injury, recovery, and eventual outcome have been proposed in patients with acute cervical spinal cord injury (SCI) (1–18). In most studies to date, however, these qualitative parameters have been used to examine the association between imaging parameters and neurologic outcome after SCI. In particular, very few studies have been focused on the quantitative MR imaging examination of patients with acute SCI.

Although previous reports have outlined various computed tomographic (CT) and MR imaging parameters for assessing neurologic damage and the prognosis after acute SCI, only a few reliable quantitative radiologic outcome measures are described in the literature (19). Fehlings et al (20) developed a radiologic method for assessing the spinal canal compromise and cord compression in acute traumatic cervical SCI, and this technique was subsequently tested for intra- and interobserver reliability (21). Further work to develop quantitative approaches that link MR imaging changes to neurologic outcome after cervical SCI is needed (22). Moreover, imaging criteria for objective assessment of the effect(s) of any drug or surgical intervention in SCI clinical trials need to be established. Thus, the purpose of our study was to prospectively evaluate whether quantitative and qualitative MR imaging assessments after SCI correlate with patient neurologic status and are predictive of outcome at long-term follow-up.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 ADVANCES IN KNOWLEDGE
 References
 
Study Population
The research ethics boards and institutional review boards of both participating institutions (Toronto Western Hospital and University of Maryland Medical System [R Adams Cowley Shock Trauma Center]) approved our study, and informed consent was obtained. Health Insurance Portability and Accountability Act compliance was observed for the University of Maryland Medical System. We included all consecutive patients with cervical spine trauma who were admitted to the Toronto Western Hospital or University of Maryland Medical System from March 2000 through March 2005. However, patients with concomitant head injury and a Glasgow coma scale score lower than 15 were excluded from the study. One hundred patients (79 male, 21 female; mean age, 45 years; age range, 17–96 years) were examined. The clinical (demographic, etiologic, and SCI level) data and neurologic assessment findings at both hospital admission and follow-up were recorded.

Outcome Measures
The American Spinal Injury Association (ASIA) motor score was used as the neurologic measurement tool and outcome measure at admission (baseline ASIA motor score) and last clinical visit (follow-up ASIA motor score). The ASIA motor score, which is considered the reference standard for neurologic examination of individuals with SCI, is a validated reliable measurement instrument with discriminative and evaluative values (23–27).

In addition, the ASIA impairment scale was used to classify the severity of SCI by means of assessment of motor and sensory impairments (Table 1) (27). ASIA grade A indicates complete motor and sensory impairment below the level of injury. ASIA grades B, C, and D indicate incomplete SCI, with evidence of sacral sensory sparing. Patients with ASIA grade B status have complete motor impairment, whereas those with ASIA grade C status have motor function below the level of injury, with a muscle grade lower than 3 (on scale of 1–5) on the Medical Research Council scale. Patients with ASIA grade D have motor function below the injury level, with key muscle groups graded 3 or higher on the Medical Research Council scale. ASIA grade E corresponds to no motor or sensory deficit.


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  		Table 1. ASIA Grading for Neurologic and Functional Classification of SCI

 
MR Imaging
MR images were obtained within 24–48 hours (median, 24 hours) after the injury. All MR imaging examinations were performed with a 1.5-T magnet (Signa; GE Medical Systems, Milwaukee, Wis). Standardized MR imaging protocols for the acutely injured spine were used at both centers: For sagittal T1-weighted imaging, a two-dimensional spin-echo sequence was performed by using a conventional imaging option with no phase wrap, 450/minimum (repetition time msec/echo time msec), a receiver bandwidth of 15.63 kHz, a matrix of 512 x 192 (frequency encoding x phase encoding), three acquired signals, and no phase correction. For sagittal T2-weighted imaging, a two-dimensional fast-recovery fast spin-echo (accelerated) sequence was performed by using imaging options that included no phase wrap, an extended dynamic range, tailored radiofrequency, and fast recovery; 6200/114; an echo train length of 33; a receiver bandwidth of 41.67 kHz; a matrix of 512 x 224; four acquired signals; and phase correction. Both the T1-weighted and the T2-weighted examinations were performed in the anteroposterior frequency direction by using an 8CTL12 coil, a section thickness of 3.0 mm, an intersection gap of 0.5 mm, a 24-cm field of view, and no contrast material enhancement.

Image Interpretation: Quantitative and Qualitative Variables
An observer (F.M., a spine fellow board certified in orthopedic surgery with 7 years experience) analyzed the MR images obtained in all patients and collected the data on all quantitative and qualitative parameters. The observer was blinded to the patients' clinical and neurologic data. Quantitative analysis included assessment of three parameters: maximum (bone) canal compromise (MCC), maximum spinal cord compression (MSCC), and lesion length. Midsagittal T1- and T2-weighted MR images were used to determine the MCC and MSCC, respectively, as described by Fehlings et al (20) (Fig 1). In all patients, the lesion length was determined where intramedullary cord signal intensity change was depicted on T2-weighted images. Lesion length was defined as the distance between the most cephalic and the most caudal extent of the cord signal intensity change (Fig 1).


Figure 1A
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  		Figure 1a: Midsagittal (a) T1-weighted (475/10) and (b) T2-weighted (4000/87) MR images obtained in 45-year-old man with acute traumatic C5 through C6 mild (ASIA grade D) SCI after a fall show the distances of the spinal canal and spinal cord at the injury site (Di and di, respectively), one segment below the injury site (Db and db, respectively), and one segment above the injury site (Da and da, respectively) used to (a) estimate the MCC and (b) measure spinal canal compression. (c) Midsagittal T2-weighted image obtained in the same patient shows the distance from the most cephalic extent [(a)] to the most caudal extent [(b)] of the injury, which represents the length of the lesion.

 

Figure 1B
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  		Figure 1b: Midsagittal (a) T1-weighted (475/10) and (b) T2-weighted (4000/87) MR images obtained in 45-year-old man with acute traumatic C5 through C6 mild (ASIA grade D) SCI after a fall show the distances of the spinal canal and spinal cord at the injury site (Di and di, respectively), one segment below the injury site (Db and db, respectively), and one segment above the injury site (Da and da, respectively) used to (a) estimate the MCC and (b) measure spinal canal compression. (c) Midsagittal T2-weighted image obtained in the same patient shows the distance from the most cephalic extent [(a)] to the most caudal extent [(b)] of the injury, which represents the length of the lesion.

 

Figure 1C
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  		Figure 1c: Midsagittal (a) T1-weighted (475/10) and (b) T2-weighted (4000/87) MR images obtained in 45-year-old man with acute traumatic C5 through C6 mild (ASIA grade D) SCI after a fall show the distances of the spinal canal and spinal cord at the injury site (Di and di, respectively), one segment below the injury site (Db and db, respectively), and one segment above the injury site (Da and da, respectively) used to (a) estimate the MCC and (b) measure spinal canal compression. (c) Midsagittal T2-weighted image obtained in the same patient shows the distance from the most cephalic extent [(a)] to the most caudal extent [(b)] of the injury, which represents the length of the lesion.

 
The level of SCI was identified as the level of maximum cord compression depicted on MR images or the level of underlying ligamentous, soft-tissue, or osseous injury in patients without radiologic evidence of cord compression. The presence of cord signal intensity change was also used to help identify the level of SCI.

In addition to quantitative analysis findings, potential prognostic qualitative MR findings, as suggested in the literature, were also documented (1–7,19,20,28). These findings included intramedullary hemorrhage, cord edema, cord swelling (focal widening of cord), soft-tissue injury (STI), preinjury stenosis, and disk herniation. Fat saturation on fast spin-echo T2-weighted images was used to enhance the visualization of ligaments and STIs. Increased signal intensity of the perivertebral tissues on T2-weighted images was operationally considered evidence of the presence of STI (17,18).

Statistical Analyses
Comparisons were made among three groups: patients with complete SCIs (ASIA grade A), patients with incomplete SCIs (ASIA grade B, C, or D), and neurologically healthy subjects (ASIA grade E). Data were analyzed by using univariate and multivariable methods. The qualitative parameters—intramedullary hemorrhage, cord edema, cord swelling, STI, preinjury stenosis, and disk herniation—were independently analyzed as dichotomous variables (ie, findings either present or absent) in a univariate manner. The Fisher exact test was used to compare the frequency of each predefined qualitative variable. The Mantel-Haenszel {chi}2 test was used to evaluate whether there was a trend in terms of the frequency of SCI as compared with the degree of completeness of SCI. Mean follow-up times among the three study groups were compared by using analysis of variance (29). Analysis of covariance with the Tukey post hoc test was used to compare the continuous variables (MCC, MSCC, and lesion length) and the potential covariates (sex and age) among the three study groups (29).

Finally, the best models for predicting neurologic status at admission (baseline ASIA motor score) and for predicting neurologic recovery (follow-up ASIA motor score, unadjusted and adjusted for baseline motor score) were selected from among the analyses of all qualitative and quantitative variables. Stepwise multivariable linear regression was used to identify the models that included only significant variables and the highest R2 regression (30).

The sample size was calculated for multivariable regression analysis, which was the most important statistical method used in our study. Given that at least 10 cases per independent variable are required for multivariable linear regression analysis, we estimated a sample size of 100 patients for data analysis at a power of 80% and a 5% significance level. All data analyses were performed by using SAS, version 8.02 (SAS Institute, Cary, NC), software. Values were reported as means ± standard errors of the mean. For all statistical testing except the post hoc analyses, significance was set at the 5% level.


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 ADVANCES IN KNOWLEDGE
 References
 
The most common mechanism of injury in the 100 patients was motor vehicle accident (Table 2). The C5 through C6 spinal level was the most commonly involved (Table 2). Most (51%) patients had an incomplete SCI at admission (Table 2). The mean follow-up period for all patients was 7.3 months (range, 1–35 months).


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  		Table 2. Characteristics of Patients with Acute Traumatic Cervical SCI

 
Analysis of Qualitative Variables
The frequencies of intramedullary hemorrhage, cord edema, cord swelling, preinjury stenosis, and STI at the site of injury differed significantly among the patients with complete SCIs, the patients with incomplete SCIs, and the neurologically healthy subjects with cervical spine trauma, as observed on T2-weighted MR images. These findings were more common in the complete SCI group (Fisher exact test) (Fig 2). In addition, frequencies of intramedullary hemorrhage, cord edema, cord swelling, and STI were directly correlated with severity of SCI (Mantel-Haenszel {chi}2 test) (Fig 2). However, the frequencies of preinjury stenosis and disk herniation did not differ significantly among the three groups (Fig 2).


Figure 2
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  		Figure 2: Bar graph shows the frequency of each qualitative MR variable (hemorrhage, edema, stenosis, STI, cord swelling, and herniated disk [HD]) in patients with complete SCIs, patients with incomplete SCIs, and patients with spine trauma without SCI. P values were derived by using Fisher exact (top value) and Mantel-Haenszel {chi}2 (bottom value enclosed in brackets) tests.

 
Analysis of Quantitative Variables and Potential Covariates
The mean follow-up period after injury was similar among the patients with complete SCIs (6.25 months ± 0.99), the patients with incomplete SCIs (6.91 months ± 0.79), and the neurologically healthy subjects (9.02 months ± 1.94; P = .299, analysis of variance).

The mean extent of MCC was significantly different between patients with complete SCIs and those with incomplete SCIs (Fig 3). A more substantial degree of MCC was seen in the patients with complete SCIs (R2 = 0.222, P = .005; analysis of covariance with Tukey post hoc test). In addition, the mean extent of MCC for the complete SCI group was more significant among the male patients than among the female patients (P = .011), whereas age was not significantly associated with MCC (P = .195).


Figure 3A
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  		Figure 3a: Graphs show extents of the quantitative MR variables, (a) MSCC and MCC and (b) lesion length, in patients with complete SCIs (white bar), patients with incomplete SCIs (gray bar), and patients with spine trauma without SCI (black bar) at admission.

 

Figure 3B
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  		Figure 3b: Graphs show extents of the quantitative MR variables, (a) MSCC and MCC and (b) lesion length, in patients with complete SCIs (white bar), patients with incomplete SCIs (gray bar), and patients with spine trauma without SCI (black bar) at admission.

 
The extent of MSCC was significantly different between patients with complete and those with incomplete SCIs (Fig 3); more substantial MSCC was seen in the patients with complete SCIs (R2 = 0.171, P = .002; analysis of covariance with Tukey post hoc test). Age correlated with MSCC in the complete SCI group, with the older patients showing more substantial cord compression (P = .026). Sex was not significantly correlated with MSCC (P = .687).

Finally, lesion length was significantly different between patients with complete and those with incomplete SCIs (R2 = 0.343, P = .005; analysis of covariance with Tukey post hoc test) (Fig 3). The lesions in the patients with incomplete SCIs (ASIA grade B, C, or D) or minimal neurologic deficits (ASIA grade E) had a mean length of 20 mm or less, whereas those in the patients with complete injuries had a mean length of 40 mm. Neither age (P = .2) nor sex (P = .875) was significantly associated with lesion length.

Analysis of Potential Predictors of Outcome
By using stepwise multivariable regression, we analyzed all six predefined qualitative variables (intramedullary hemorrhage, cord edema, cord swelling, STI, preinjury stenosis, and disk herniation) and the three quantitative variables (lesion length, MCC, and MSCC) as potential predictors of ASIA motor scores at admission (baseline neurologic assessment) and last follow-up visit (with or without adjustment for baseline ASIA motor scores). The best model for predicting the baseline ASIA motor score included MCC, MSCC, and cord swelling as significant covariates (model 1, Table 3). The best model for predicting unadjusted follow-up neurologic outcome included MSCC, intramedullary hemorrhage, and cord swelling (model 2, Table 3). After controlling for the baseline ASIA motor score, the best model for predicting the follow-up ASIA motor score adjusted for baseline ASIA motor score included only intramedullary hemorrhage and cord swelling (model 3, Table 3).


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  		Table 3. Results of Stepwise Multivariable Regression Analysis of Quantitative and Qualitative Variables as Potential Predictors of Baseline, Unadjusted Follow-up, and Adjusted Follow-up ASIA Motor Scores

 

   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
ADVANCES IN KNOWLEDGE
 References
 
In our study, we determined that the severity of MSCC and the extents of intramedullary hemorrhage and cord swelling were key predictors of neurologic recovery after traumatic cervical SCI. However, after controlling for the baseline neurologic status at multivariable regression analysis, only intramedullary hemorrhage and cord swelling were significantly correlated with neurologic recovery after SCI. We observed lower baseline ASIA motor scores at admission in those patients with more substantial MCC, MSCC, and cord swelling. The patients who had complete SCI had more substantial MCC, MSCC, and lesion length compared with the patients who had incomplete injuries and the neurologically healthy subjects. The patients with complete SCIs were also found to have higher frequencies of intramedullary hemorrhage, cord edema, cord swelling, and STI.

Quantitative MR Imaging Variables
Most published studies are retrospective reviews of data from inhomogeneous cohorts and include descriptions of MR imaging changes in SCI without quantification of the degree of cord compression or canal compromise at the level of injury (1,3–8,19,22,28). In an evidence-based analysis of the literature, Rao and Fehlings (19) reported that there was a lack of studies in which the investigators had sought to quantify the degree of spinal canal compromise or cord compression in acute cervical spinal trauma. Most studies have been focused on other pathologic states: Only 13 of the 37 studies that we identified included patients with cervical SCI. Even fewer reports describe quantitative imaging assessments.

Kang et al (15) attempted to quantify canal compromise by using lateral cervical radiography and noted a smaller anteroposterior diameter of the canal in patients with complete SCIs and in those with incomplete SCIs compared with the diameter of the canal in neurologically healthy subjects. Hayashi et al (16) used MR imaging to assess the degree of cord compression at the level of maximum injury in patients with cervical SCI. Mild cord compression was defined as an anteroposterior cord diameter of more than two-thirds the cord diameter at the C1 spinal level, whereas severe cord compression was defined as an anteroposterior cord diameter of less than two-thirds the cord diameter at this level. The frequency of complete motor paralysis was higher in patients with severe cord compression (30%) compared with that in patients with mild cord compression (20%). Yamazaki et al (31) analyzed the factors affecting outcome after traumatic central cord syndrome and used CT to assess the anteroposterior diameter of the spinal canal. They observed a relatively larger anteroposterior diameter of the canal to be predictive of greater neurologic recovery.

We used an objective quantitative approach to assess the MR images obtained in patients with cervical spine trauma with or without SCI. The quantitative measurements of MSCC and MCC used in our study have been previously reported to be objective, reliable, and standardized, with good inter- and intraobserver reliability (20,21). In our study, there were significant differences between patients with complete SCIs and those with incomplete SCIs in terms of all parameters assessed. In particular, we noted that MCC, MSCC, and lesion length were much greater in patients with complete SCIs.

In our series, age correlated with MSCC in the complete SCI group, with older patients showing more substantial cord compression. The correlation between old age and more substantial cord compression was likely secondary to preexisting degenerative changes and spondylosis, which are commonly observed in older individuals. Although the MCC in the complete SCI group was more substantial among the male patients, this quantitative parameter did not correlate with neurologic outcome.

Qualitative MR Imaging Variables
Previous reports have described the usefulness of MR imaging in the examination of patients with SCI (1,8,12,17,18,32–34). Although initial reports were only descriptive, some investigators have compared MR imaging changes with patient neurologic status (1,8,12,17,18,32–34). Bondurant et al (1) proposed three patterns of abnormality depicted on MR images: The type I abnormality pattern is depicted as a region of decreased signal intensity surrounded by a thin rim of high signal intensity, consistent with intraspinal hemorrhage, on T2-weighted images. The type II pattern is depicted as a region of high signal intensity, representing cord edema, on T2-weighted images. The type III pattern is depicted as a central region of hypointensity mixed with a peripheral region of high signal intensity, consistent with contusion, on T2-weighted images. Bondurant et al (1) subsequently reported that type I lesions represent the most severe form of SCI (ASIA grade A). The type II and type III abnormality patterns were seen in patients with incomplete injuries or in neurologically healthy subjects, and these patients showed neurologic improvement over time. Other investigators similarly found intramedullary hemorrhage exclusively in patients with ASIA grade A injuries, with degrees of cord swelling and cord edema directly proportional to severity of injury (2,6).

Tewari et al (32) also found MR imaging to have diagnostic and prognostic value in the setting of SCI. They found patients with minimal cord changes at MR imaging to have the best outcomes and patients with cord edema to have the next best outcomes. Patients with hemorrhage and contusion had the worst outcomes. Liao et al (34) examined nine preschool-age children who had SCIs without MR imaging abnormalities. They found MR imaging patterns to have substantial prognostic correlations with neurologic outcomes. A normal spinal cord appearance was prognostic of complete recovery, and intramedullary lesions correlated with permanent deficits and functional disability. Similarly, Shimada and Tokioka (8) identified four distinct patterns of MR signal intensity changes that correlated well with severity of spinal cord damage and clinical outcome. Ishida and Tominaga (33) assessed predictors of neurologic recovery in patients with acute central cervical SCI and found absence of MR signal intensity in the spinal cord and good early neurologic improvement to be important predictors of long-term improvement of neurologic function.

We obtained results similar to those in the literature in our qualitative MR imaging assessment. The findings intramedullary hemorrhage, cord edema, and cord swelling were more frequently associated with complete SCI and were directly proportional to the severity of injury. Although intramedullary hemorrhage was not independently predictive of the baseline neurologic status at multivariable analysis—probably owing to a strong correlation with the extent of cord compression—it was also not strongly predictive of neurologic outcome at follow-up. In addition, we found no significant difference in the frequency of preinjury stenosis or disk herniation among the three patient groups (complete SCI, incomplete SCI, and neurologically healthy), as previously reported (2,14,35,36).

Although Flanders et al (2) did not find an association between STI and extent of SCI, we observed a significant difference in our study groups, with complete ASIA grade A injuries involving more associated STI. This finding probably represents the high-energy mechanism routinely seen in patients with complete (ASIA grade A) SCIs.

Clinical Importance of Quantitative and Qualitative MR Variables
Patients with incomplete SCI have some chance of neurologic recovery; the prognosis is far less optimistic for patients with complete injuries (37). It is generally accepted that the level of cord injury at the moment of impact determines the eventual prognosis; however, most SCIs entail an acute insult followed by a variable degree of continuing cord compression concomitant with secondary insults (38,39). The optimal timing of surgical intervention for these patients remains controversial (40). Certainly, objective radiologic criteria for determining the usefulness of such intervention need to be established. In our series, MSCC—in addition to intramedullary hemorrhage and cord swelling—was indicative of a poor prognosis. Therefore, early surgical intervention may be of benefit in some patients. To our knowledge, this was the first study in which qualitative and quantitative MR imaging parameters were combined for the prediction of patient neurologic outcomes determined by using ASIA motor scores.

Limitations
Predicting a perfect correlation between severity of neurologic deficit and the static findings seen on MR images of spinal cord compression remains a challenge. MR images obtained after the moment of impact clearly underrepresent the dynamic component of spinal cord compression at the time of maximal injury. Repeat MR images obtained at final follow-up or 2–3 weeks after the injury may be beneficial in assessing such a correlation. Shimada and Tokioka (8) found that the best times for prognostic MR imaging were the time of injury and 2–3 weeks later.

In addition to the dynamic component of cord compression, the precise location of the injury within the cord is also very important in determining the severity of neurologic injury. In our study, qualitative analysis and SCI lesion length were used to define the signal intensity of the lesion without specifically addressing the precise location of the lesion within the cord. Compared with a larger cord lesion in a less important location, a small lesion in a critical location is more likely to manifest clinically as more substantial functional neurologic deficits. Advanced multiplanar MR imaging techniques may enable such topographic correlations to be better determined.

In addition, spin-echo MR imaging, which has limited pathophysiologic usefulness in the setting of trauma, was used in our study. Advanced imaging techniques such as diffusion imaging and diffusion-tensor imaging, which have been used more recently to evaluate axonal brain injury, have been shown to be more useful in identifying additional shearing injuries that are not visible on conventional MR images. Arfanakis et al (41) found diffusion-tensor MR imaging to be useful in identifying diffuse axonal injury during the first 24 hours after traumatic brain injury. Results of the Huisman study (42) showed that diffusion-weighted imaging depicts additional shearing injuries that are not visible on T2-weighted fluid-attenuated inversion recovery or T2*-weighted images. Evaluating SCIs with a combination of such imaging techniques may yield additional pathophysiologic markers for severity of tissue injury and predictors of the later neurologic outcome. Imaging indexes based on pathophysiologic models may enable more accurate prediction of injury and thereby facilitate better assessment of the prognosis and better application of treatment strategies. Although the mean follow-up period of 6 months in our study has been determined to be a valid clinical end point for SCI, future longer-term follow-up studies may yield additional information (43,44).

In conclusion, our study results showed MR imaging to be a useful tool in prognosticating a patient's potential for neurologic recovery. More substantial MSCC, intramedullary hemorrhage, and/or cord swelling at the time of injury is associated with a poorer prognosis. In addition to validating reports in the existing literature, our study results suggest that extent of direct spinal cord compression—specifically, MSCC—is more reliable than presence of canal stenosis for predicting the neurologic outcome of patients.


   ADVANCES IN KNOWLEDGE
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 ADVANCES IN KNOWLEDGE
References
 


   ACKNOWLEDGMENTS
 
The technical support of David Mikulis, MD, Yuriy Petrenko, MD, and Amy Lem is gratefully acknowledged.


   FOOTNOTES
 

Abbreviations: ASIA = American Spinal Injury Association • MCC = maximum canal compromise • MSCC = maximum spinal cord compression • SCI = spinal cord injury • STI = soft-tissue injury

Authors stated no financial relationship to disclose.

Author contributions: Guarantors of integrity of entire study, J.C.F., M.G.F.; study concepts/study design or data acquisition or data analysis/interpretation, all authors; manuscript drafting or manuscript revision for important intellectual content, all authors; manuscript final version approval, all authors; literature research, F.M., J.C.F., M.G.F.; clinical studies, all authors; statistical analysis, J.C.F., M.G.F.; and manuscript editing, all authors


   References
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 ADVANCES IN KNOWLEDGE
 References
 

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