Short-term predictive potential of quantitative assessment of spinal cord impairment in patients undergoing French-door Laminoplasty for degenerative cervical myelopathy: preliminary results of an exploratory study exploiting intraoperative ultrasound data

Normalizing spinal cord compression measures in degenerative cervical myelopathy

BACKGROUND CONTEXT

Accurate and automatic MRI measurements are relevant for assessing spinal cord compression severity in degenerative cervical myelopathy (DCM) and guiding treatment. The widely-used maximum spinal cord compression (MSCC) index has limitations. Firstly, it normalizes the anteroposterior cord diameter by that above and below the compression but does not account for cord size variation along the superior-inferior axis, making MSCC sensitive to compression level. Secondly, cord shape varies across individuals, making MSCC sensitive to this variability. Thirdly, MSCC is typically calculated by an expert-rater from a single sagittal slice, which is time-consuming and prone to variability.

PURPOSE

This study proposes a fully automatic pipeline to compute MSCC.

DESIGN

We developed a normalization strategy for traditional MSCC (anteroposterior diameter) using a healthy adults database (n = 203) to address cord anatomy variability across individuals and evaluated additional morphometrics (transverse diameter, area, eccentricity, and solidity).

PATIENT SAMPLE

DCM patient cohort of n = 120.

OUTCOME MEASURES

Receiver operating characteristic (ROC) and area under the curve (AUC) were used as evaluation metrics.

METHODS

We validated the method in a mild DCM patient cohort against manually derived morphometrics and predicted the therapeutic decision (operative/conservative) using a stepwise binary logistic regression incorporating demographics and clinical scores.

RESULTS

The automatic and normalized MSCC measures correlated significantly with clinical scores and predicted the therapeutic decision more accurately than manual MSCC. Significant predictors included upper extremity sensory dysfunction, T2w hyperintensity, and the proposed MRI-based measures. The model achieved an area under the curve of 0.80 in receiver operating characteristic analysis.

CONCLUSION

This study introduced an automatic method for computing normalized measures of cord compressions from MRIs, potentially improving therapeutic decisions in DCM patients. The method is open-source and available in Spinal Cord Toolbox v6.0 and above.

A Three-Dimensional Morphological Assessment for Evaluating Pre- and Postsurgery in Cervical Laminoplasty

OBJECTIVE

The efficacy of medical treatments and the changes in radiologic imaging before and after treatment have consistently remained pivotal factors. This is particularly critical for surgical procedures, where precise evaluation of disparities pre and postsurgery or the accuracy of implantation is paramount. Based on three-dimensional morphological interests, we provide an automatic quantification evaluation method that delivers an evident base for assessing the outcomes of a widely employed surgical technique, cervical laminoplasty.

METHODS

The sample study included patients who underwent cervical laminoplasty for cervical spondylotic myelopathy/ossification of the longitudinal ligament. We present a superimposition method that facilitates a unique and precise assessment between pre and postsurgery. The degree of expansion was evaluated by the canal volume increase and canal expansion rate after surgery.

RESULTS

There were 31 patients with 112 vertebral segments measured. The target cervical's pre and postoperative canal areas were 122.63 ± 30.34 and 196.50 ± 37.10 mm2, respectively (P < 0.001). The average cervical canal expansion rate was 64.42%. The expansion effect of C5 cervical laminoplasty was the maximum (71.01%), and the canal volume of other segments expanded by approximately 60%. The functional outcomes demonstrated significant improvements in symptoms.

CONCLUSIONS

The quantification evaluation method can be utilized for any morphology changes before and after laminoplasty, as it does not lead to errors or variations from different inspection machines or human factors. The automatic method delivers an evident base for assessing the outcomes of a widely employed surgical technique.

Preliminarily exploring the intraoperative ultrasonography characteristics of patients with degenerative cervical myelopathy

BACKGROUND

How to quickly read and interpret intraoperative ultrasound (IOUS) images of patients with degenerative cervical myelopathy (DCM) to obtain meaningful information? Few studies have systematically explored this topic.

PURPOSE

To systematically and comprehensively explore the IOUS characteristics of patients with DCM.

MATERIALS AND METHODS

This single-center study retrospectively included patients with DCM who underwent French-door laminoplasty (FDL) with IOUS guidance from October 2019 to March 2022. One-way ANOVA and Pearson's /Spearman's correlation analysis were used to analyze the correlations between the cross-sectional area of the spinal cord (SC) and individual characteristics; the relationships between the morphology, echogenicity, pulsation, decompression statuses, compression types of SC, location of the spinal cord central echo complex (SCCEC) and the disease severity (the preoperative Japanese Orthopedic Association score, preJOA score); the difference of the spinal cord pulsation amplitude(SCPA) and the SCCEC forward movement rate (FMR) between the compressed areas(CAs) and the non-compressed areas (NCAs).

RESULTS

A total of 38 patients were successfully enrolled (30 males and 8 females), and the mean age was 57.05 ± 10.29 (27-75) years. The cross-sectional area of the SC was negatively correlated with age (r = - 0.441, p = 0.006). The preJOA score was significantly lower in the heterogeneous group than in the homogeneous group (P < 0.05, p = 0.005). The hyperechoic area (HEA) was negatively while the SCCEC FMR was positively correlated with the preJOA score (r = - 0.334, p = 0.020; r = 0.286, p = 0.041). The SCCEC FMR and SCPA in CAs were significantly greater than those in NCAs (p < 0.05, p = 0.007; P < 0.001, P = 0.000).

CONCLUSION

The cross-sectional area of the SC decreases with age in adults. More changes in intramedullary echogenicity and less moving forward of the SCCEC often indicate poor SC status, and the SCCEC FMR and SCPA are more pronounced in CAs.

Increased blood flow of spinal cord lesion after decompression improves neurological recovery of degenerative cervical myelopathy: an intraoperative ultrasonography-based prospective cohort study

INTRODUCTION

Surgical decompression is a highly effective therapy for degenerative cervical myelopathy (DCM), but the mechanisms of neurological recovery following decompression remain unclear. This study aimed to evaluate the spinal cord blood flow status after sufficient decompression by intraoperative contrast-enhanced ultrasonography (CEUS) and to analyze the correlation between neurological recovery and postdecompressive spinal cord blood perfusion in DCM.

MATERIALS AND METHODS

Patients with multilevel DCM were treated by ultrasound-guided modified French-door laminoplasty using a self-developed rongeur. Neurological function was evaluated using the modified Japanese Orthopaedic Association (mJOA) score preoperatively and at 12 months postoperatively. Spinal cord compression and cervical canal enlargement before and after surgery were assessed by magnetic resonance imaging and computerized tomography. The decompression status was evaluated in real time by intraoperative ultrasonography, while the spinal cord blood flow after sufficient decompression was assessed by CEUS. Patients were categorized as favourable (≥50%) or unfavourable (<50%) recovery according to the recovery rate of the mJOA score at 12 months postoperatively.

RESULTS

Twenty-nine patients were included in the study. The mJOA scores were significantly improved in all patients from 11.2±2.1 preoperatively to 15.0±1.1 at 12 months postoperatively, with an average recovery rate of 64.9±16.2%. Computerized tomography and intraoperative ultrasonography confirmed adequate enlargement of the cervical canal and sufficient decompression of the spinal cord, respectively. CEUS revealed that patients with favourable neurological recovery had a greater increased blood flow signal in the compressive spinal cord segment after decompression.

CONCLUSIONS

In DCM, intraoperative CEUS can clearly reflect spinal cord blood flow. Patients with increased blood perfusion of the spinal cord lesion immediately after surgical decompression tended to achieve greater neurological recovery.

Technical Aspects of Intra-Operative Ultrasound for Spinal Cord Injury and Myelopathy: A Practical Review

OBJECTIVES

To compile intra-operative techniques, established imaging parameters, available equipment and software, and clinical applications of intraoperative ultrasound imaging (IOUSI) for spinal cord injury (SCI) and myelopathy.

METHODS

PubMed and Google Scholar were searched for relevant articles. The articles were reviewed and selected by 2 independent researchers. After article selection, data were extracted and summarized into research domains. PRISMA systematic review process was followed.

RESULTS

Of the 2477 articles screened, 16 articles met the inclusion criteria. In patients with SCI and myelopathy, common quantitative measurements obtained using IOUSI were noted: 1) ultrasound elastography, 2) midsagittal anteroposterior diameter, 3) transverse, 4) transverse diameter, 5) maximum spinal cord compression, and 6) compression ratioTo ensure adequate decompression and to look for residual compression, the lateral and the craniocaudal margins of the laminectomy site were inspected in both axial and sagittal planes. In instances where quantitative assessment was not possible, cord decompression and degree of residual compression were gauged by inspecting the interface between the ventral border of the spinal cord and any potentially compressive elements, and by searching for symmetric and rhythmic cerebrospinal fluid pulsations. Use of contrast-enhanced ultrasoundand molecular imaging are additional advances in objective assessments for SCI and myelopathy.

CONCLUSIONS

This review outlines the potential of IOUSI in patients presenting with SCI and myelopathy. Moreover, by identifying potential for inter-operator variability in certain subjective measurements, we illustrate the need for further research to quantify and standardize those assessments.

Comparative intra- and inter-observer reliability of two methods for evaluating intraoperative ultrasonography-based spinal cord hyperechogenicity intensity in degenerative cervical myelopathy

Objectives

During French-door laminoplasty, a linear array transducer of IOUS was used to observe and record the spinal cord decompression. To acquire a higher-reliability method, and compare the in-observer and inter-observer reliability of two methods in evaluating the hyperechoic intensity of spinal cord ultrasound in degenerative cervical myelopathy (DCM).

Background

The intensity of spinal cord hyperechogenicity is considered as a potential predictor of neurological recovery in DCM after decompression, but the accuracy of gray value ratio (GVR) is affected by many factors.

Methods

Totally 28 patients (20 males and 8 females) who had been followed up for 12 months were included. Their mean age at surgery was 61.2 ± 10.8 years and the average symptom duration was 23.36 ± 22.11 months. The gray values of circles 1, 2 and 3 were recorded as Gcompression, Gnorml and Gsac, respectively. Circle 1 was drawn with the maximum brightness point within the spinal cord as the center, circle 2 with the same area was plotted on the spinal cord with uniform echogenicity, without compression and at least 1 cm away from the circle 1, and circle 3 was drawn on the dorsal dural sac at the same segment as circle 1. GVR was calculated as follows: GVR-A = G_compression/G_norml (method A), and GVR-B = G_compression/G_sac (method B). The in-observer and inter-observer reliabilities of the two methods were compared. It is generally believed a reliability coefficient < 0.40 and > 0.75 indicate poor and good reliability respectively. The images-based GVR-B using this protocol demonstrates higher inter- and intraobserver reliabilities than GVR-A, and can be used as the basis for prognostic prediction and future studies.

Results

All examination acquisitions were successfully completed. GVR-A averaged 2.043 (0.318–5.56), and GVR-B averaged 0.578(0.06–1.41). GVR-B has better repeatability of gray value measurement, smaller relative standard deviation (RSD%) (0.298 vs. 0.32) and larger inter-group correlation coefficient compared with GVR-A. The mean value (MD) of the GVR difference calculated by GVR-B between the two clinicians was closer to 0.

Conclusions

For DCM patients routinely using ultrasound for real-time cord visualization during spinal cord decompression by French-door laminoplasty, the images-based GVR-B using this protocol demonstrates better inter- and intraobserver reliabilities compared with GVR-A.

Intraoperative ultrasonography in laminectomy for degenerative cervical spondylotic myelopathy: a clinical and radiological evaluation

Background

The incidence of cervical myelopathy due to spinal stenosis is constantly growing in an aging population. Especially in multisegmental disease, dorsal laminectomy is the intervention of choice. Intraoperative imaging with ultrasound might provide additional information about extent and sufficiency of spinal cord decompression.

Methods

In this prospective study, the width of the subarachnoid space was systematically measured by intraoperative ultrasound at predefined sites at the cranial and caudal edge of decompression in axial and sagittal reconstruction. These data were compared with corresponding sites on postoperative T2-weighted MRI imaging. In addition, the functional outcome was assessed by modified Japanese Orthopaedic Association (mJOA) score. A historical patient cohort treated without ultrasound-guided laminectomy served as control group.

Results

Altogether, 29 patients were included. According to mJOA score at last follow-up, 7/29 patients reported stable symptoms and 21/29 patients showed a substantial benefit with no or minor residual neurological deficits. One patient suffered from a new C5 palsy. Intraoperative ultrasound-guided posterior decompression provided excellent overview in all cases. Measurement of the width of the subarachnoid space acquired by intraoperative ultrasound and postoperative MRI images showed a very high correlation, especially at the cranial level (p < 0.001, r = 0.880). Bland–Altman analysis showed that most patients were within the 1.96 × SD limits of agreement throughout all measurements. No ultrasound procedure-related complications were observed. Compared to a historical cohort of 27 patients, no significant differences were found regarding functional outcome (p = 0.711).

Conclusion

Intraoperative sonography visualises the surgically achieved restoration of the subarachnoid space in good correlation with postoperative MRI and might serve as a fast, precise and reliable tool for intraoperative imaging in cervical laminectomy. However, we could not demonstrate a clinical benefit with regard to functional outcome.

Potential of intraoperative ultrasonographic assessment of the spinal cord central echo complex in predicting postoperative neurological recovery of degenerative cervical myelopathy

BACKGROUND AND PURPOSE

The spinal cord central echo complex (SCCEC) is a special ultrasonography-based intramedullary structure, but its clinical significance in degenerative cervical myelopathy (DCM) is undefined. This study aimed to explore the potential of the SCCEC in predicting postoperative neurological recovery in DCM.

METHODS

Thirty-two DCM patients who underwent intraoperative ultrasonography-guided French-door laminoplasty were prospectively enrolled. The modified Japanese Orthopaedic Association (mJOA) score was evaluated preoperatively and 12 months postoperatively. SCCEC width (SCCEC-W), and anteroposterior diameter (APD) and transverse diameter (TD) of the spinal cord were measured on transverse ultrasonographic images, while the tissue widths from anterior and posterior borders of the spinal cord to the SCCEC were measured on sagittal ultrasonographic images. The APD of the spinal cord and occupying rate of the spinal canal were measured on preoperative magnetic resonance imaging (MRI).

RESULTS

All patients achieved improvements in mJOA scores, with an average recovery rate (RR) of 68.69 ± 20.22%. Spearman correlation analysis revealed that SCCEC-W, and ratios between the SCCEC-W and APD/TD based on ultrasonography, correlated moderately with mJOA score RR, with coefficients of -0.527, -0.605 and -0.514, respectively. The ratio between SCCEC-W and ultrasonographic TD correlated moderately with preoperative APD of the spinal cord. The MRI measurements and ultrasonography-based tissue widths showed no significant correlation with mJOA score RR.

CONCLUSIONS

The SCCEC may have predictive potential as an intraoperative indicator of neurological recovery in treating DCM. SCCEC-W may be related to spinal cord compression in DCM.

Inadequate spinal cord expansion in intraoperative ultrasound after decompression may predict neurological recovery of degenerative cervical myelopathy

OBJECTIVE

To compare the neurological recovery between patients with adequate and inadequate immediate spinal cord expansion after sufficient decompression in degenerative cervical myelopathy (DCM).

METHODS

Twenty-seven patients subjected to French-door laminoplasty underwent the guidance of intraoperative ultrasound (IOUS) and were prospectively included. The modified Japanese Orthopedic Association (mJOA) score was evaluated before surgery and at 12 months postoperatively. The maximum spinal cord compression (MSCC) after sufficient decompression was calculated on the IOUS image; patients were divided into adequate (MSCC ≥ 0.95) and inadequate (MSCC < 0.95) expansion groups according to the MSCC. The mJOA score, spinal cord hyperechogenicity, age at surgery, symptom duration, occupational rate of the spinal canal, and the minimum anteroposterior diameter of the spinal cord between the two groups were compared.

RESULTS

Initially, 2 cases showed residual compression on IOUS; after further decompression, all patients acquired sufficient decompression. All patients achieved improvements in mJOA scores with an average recovery rate of 68.6 ± 20.3%. The recovery rate of the mJOA score of the inadequate expansion group was significantly inferior to that of the adequate expansion group (59.2 ± 21.7% versus 76.2 ± 16.2%, p = 0.028). The spinal cord hyperechogenicity was more common in the inadequate expansion group, while the spinal cord anteroposterior diameter of the inadequate expansion group was significantly smaller than that of the adequate expansion group.

CONCLUSIONS

The application of IOUS in French-door laminoplasty could help to confirm sufficient decompression for the treatment of DCM. Inadequate spinal cord expansion after sufficient decompression had the high possibility of predicting less satisfactory neurological recovery of DCM.

KEY POINTS

• The intraoperative ultrasound revealed that not all degenerative cervical myelopathy patients acquired adequate spinal cord expansion after sufficient decompression. • Patients who failed to acquire adequate spinal cord expansion commonly combined with spinal cord hyperechogenicity and trended to achieve less satisfactory neurological recovery after surgical decompression. • Inadequate spinal cord expansion after sufficient decompression had the high possibility of predicting less satisfactory neurological recovery of patients with degenerative cervical myelopathy.

Intensity of Intraoperative Spinal Cord Hyperechogenicity as a Novel Potential Predictive Indicator of Neurological Recovery for Degenerative Cervical Myelopathy

OBJECTIVE

To analyze the correlations between intraoperative ultrasound and MRI metrics of the spinal cord in degenerative cervical myelopathy and identify novel potential predictive ultrasonic indicators of neurological recovery for degenerative cervical myelopathy.

MATERIALS AND METHODS

Twenty-two patients who underwent French-door laminoplasty for multilevel degenerative cervical myelopathy were followed up for 12 months. The Japanese Orthopedic Association (JOA) scores were assessed preoperatively and 12 months postoperatively. Maximum spinal cord compression and compression rates were measured and calculated using both intraoperative ultrasound imaging and preoperative T2-weight (T2W) MRI. Signal change rates of the spinal cord on preoperative T2W MRI and gray value ratios of dorsal and ventral spinal cord hyperechogenicity on intraoperative ultrasound imaging were measured and calculated. Correlations between intraoperative ultrasound metrics, MRI metrics, and the recovery rate JOA scores were analyzed using Spearman correlation analysis.

RESULTS

The postoperative JOA scores improved significantly, with a mean recovery rate of 65.0 ± 20.3% (p < 0.001). No significant correlations were found between the operative ultrasound metrics and MRI metrics. The gray value ratios of the spinal cord hyperechogenicity was negatively correlated with the recovery rate of JOA scores (ρ = -0.638, p = 0.001), while the ventral and dorsal gray value ratios of spinal cord hyperechogenicity were negatively correlated with the recovery rate of JOA-motor scores (ρ = -0.582, p = 0.004) and JOA-sensory scores (ρ = -0.452, p = 0.035), respectively. The dorsal gray value ratio was significantly higher than the ventral gray value ratio (p < 0.001), while the recovery rate of JOA-motor scores was better than that of JOA-sensory scores at 12 months post-surgery (p = 0.028).

CONCLUSION

For degenerative cervical myelopathy, the correlations between intraoperative ultrasound and preoperative T2W MRI metrics were not significant. Gray value ratios of the spinal cord hyperechogenicity and dorsal and ventral spinal cord hyperechogenicity were significantly correlated with neurological recovery at 12 months postoperatively.