Chronic extradural compression of spinal cord leads to syringomyelia in rat model

Treatment of Syringomyelia Characterized by Focal Dilatation of the Central Canal Using Mesenchymal Stem Cells and Neural Stem Cells

BACKGROUND

Syringomyelia is a progressive chronic disease that leads to nerve pain, sensory dissociation, and dyskinesia. Symptoms often do not improve after surgery. Stem cells have been widely explored for the treatment of nervous system diseases due to their immunoregulatory and neural replacement abilities.

METHODS

In this study, we used a rat model of syringomyelia characterized by focal dilatation of the central canal to explore an effective transplantation scheme and evaluate the effect of mesenchymal stem cells and induced neural stem cells for the treatment of syringomyelia.

RESULTS

The results showed that cell transplantation could not only promote syrinx shrinkage but also stimulate the proliferation of ependymal cells, and the effect of this result was related to the transplantation location. These reactions appeared only when the cells were transplanted into the cavity. Additionally, we discovered that cell transplantation transformed activated microglia into the M2 phenotype. IGF1-expressing M2 microglia may play a significant role in the repair of nerve pain.

CONCLUSION

Cell transplantation can promote cavity shrinkage and regulate the local inflammatory environment. Moreover, the proliferation of ependymal cells may indicate the activation of endogenous stem cells, which is important for the regeneration and repair of spinal cord injury.

A Novel Rat Model of Venous Hypertensive Myelopathy Produced by Arteriovenous Bypass Plus Venous Stenosis

BACKGROUND AND OBJECTIVES

Venous hypertensive myelopathy (VHM), mainly induced by the spinal dural arteriovenous fistula, is a congestive spinal cord injury that currently has no appropriate animal model available in preclinical research.

METHODS

Sprague Dawley rats (280-320 g) were used. The rats were divided into 3 groups: (1) Group 1, which underwent renal artery-dorsal spinal venous bypass (AVB group); (2) Group 2, which underwent renal artery-dorsal spinal venous bypass and drainage vein stenosis (AVB/VS group); and (3) Control group, with T13 dorsal vein ligation. The success of the model was assessed using Doppler ultrasound and 7.0-T magnetic resonance imaging. Transmission electron microscopy, histochemistry, proteomics, and western blot analysis were used to evaluate ultrastructural, pathological, and molecular features in the spinal cord and cerebrospinal fluid (CSF).

RESULTS

The success rate of the arteriovenous bypass was 100% at 5 days and 83% at 2 weeks. The locomotor assessment showed decreased lower extremity strength in the AVB/VS group (P = .0067), whereas unremarkable changes were found in the AVB and Control groups. Histochemical staining suggested a 2-fold expansion of the dorsal spinal vein in the AVB/VS group, which was lower than that in the AVB group (P < .05); however, the former displayed greater myelin and neuronal damage (P < .05) and slight dilatation of the central canal (P > .05). Proteomics analysis revealed that the complement and coagulation cascade pathways were upregulated in the CSF of AVB/VS rats, whereas the C3 level was elevated both in the CSF and bilateral spinal cord. Furthermore, overexpression of C3, ITGB2, and CD9 in the spinal cord was confirmed by immunoblotting.

CONCLUSION

These findings suggest that the AVB/VS model can effectively mimic the clinical and molecular characteristics of VHM. Furthermore, they suggest that impaired deep intramedullary venous drainage is the key reason for the VHM.

The Physiological Occlusion of the Central Canal May Be a Prerequisite for Syringomyelia Formation

OBJECTIVE

Syringomyelia is a common central nervous system disease characterized by the dilation of the central canal (CC). Regarding the pathogenesis of syringomyelia, cerebrospinal fluid (CSF) circulation obstruction in the subarachnoid space (SAS) of the spinal cord has been widely accepted. However, clinical and animal studies on obstructing the CSF in SAS failed to form syringomyelia, challenging the theory of SAS obstruction. The precise pathogenesis remains unknown.

METHODS

We utilized an extradural compression rat model to investigate the pathogenesis underlying syringomyelia. Magnetic resonance imaging enabled detection of syringomyelia formation. To assess CSF flow within the SAS, Evans blue was infused into the cisterna magna. Histological analysis allowed morphological examination of the CC. Furthermore, CSF flow through the CC was traced using Ovalbumin Alexa-Flour 647 conjugate (OAF-647). Scanning electron microscopy (SEM) enabled visualization of ependymal cilia.

RESULTS

The findings showed that the dura mater below the compression segment exhibited lighter coloration relative to the region above the compression, indicative of partial obstruction within the SAS. However, the degree of SAS occlusion did not significantly differ between syringomyelia (SM-Y group) and those without (SM-N group). Intriguingly, hematoxylin and eosin staining and CSF tracing revealed occlusion of the CC accompanied by reduced CSF flow in the SM-Y group compared to SM-N and control groups. SEM images uncovered impairment of ependymal cilia inside the syringomyelia.

CONCLUSION

CC occlusion may represent a physiological prerequisite for syringomyelia formation, while SAS obstruction serves to initiate disease onset. The impairment of ependymal cilia appears to facilitate progression of syringomyelia.

Single-cell transcriptomics reveals ependymal subtypes related to cytoskeleton dynamics as the core driver of syringomyelia pathological development

Syringomyelia is a common clinical lesion associated with cerebrospinal fluid flow abnormalities. By a reversible model with chronic extradural compression to mimic human canalicular syringomyelia, we explored the spatiotemporal pathological alterations during syrinx development. The most dynamic alterations were observed in ependymal cells (EPCs), oligodendrocyte lineage, and microglia, as a response to neuroinflammation. Among different cell types, EPC subtypes experienced obvious dynamic alterations, which were accompanied by ultrastructural changes involving the ependymal cytoskeleton, cilia, and dynamic injury in parenchyma primarily around the central canal, corresponding to the single-cell transcripts. After effective decompression, the syrinx resolved with the recovery of pathological damage and overall neurological function, implying that for syringomyelia in the early stage, there was still endogenous repair potential coexisting with immune microenvironment imbalance. Ependymal remodeling and cilia restoration might be important for better resolution of syringomyelia and parenchymal injury recovery.

Suppression of TGFβR-Smad3 pathway alleviates the syrinx induced by syringomyelia

BACKGROUND

Syringomyelia is a cerebrospinal fluid (CSF) disorder resulted in separation of pain and temperature, dilation of central canal and formation of syrinx in central canal. It is unclear about mechanisms of the dilation and syrinx formation. We aimed to investigate roles of ependymal cells lining central canal on the dilation, trying to reduce syrinx formation in central canal.

METHODS

We employed 78 Sprague-Dawley (SD) rats totally with syringomyelia to detect the contribution of ependymal cells to the dilation of central canal. Immunofluorescence was used to examine the activation of ependymal cells in 54 syringomyelia rat models. BrdU was used to indicate the proliferation of ependymal cells through intraperitoneal administration in 6 syringomyelia rat models. 18 rats with syringomyelia were injected with SIS3, an inhibitor of TGFβR-Smad3, and rats injected with DMSO  were used as control. Among the 18 rats, 12 rats were used for observation of syrinx following SIS3 or DMSO administration by using magnetic resonance imaging (MRI) on day 14 and day 30 under syringomyelia without decompression. All the data were expressed as mean ± standard deviation (mean ± SD). Differences between groups were compared using the two-tailed Student's t-test or ANOVA. Differences were considered significant when *p < 0.05.

RESULTS

Our study showed the dilation and protrusions of central canal on day 5 and enlargement from day 14 after syringomyelia induction in rats with activation of ependymal cells lining central canal. Moreover, the ependymal cells contributed to protrusion formation possibly through migration along with central canal. Furthermore, suppression of TGFβR-Smad3 which was crucial for migration reversed the size of syrnix in central canal without treatment of decompression, suggesting TGFβR-Smad3 signal might be key for dilation of central canal and formation of syrinx.

CONCLUSIONS

The size of syrinx was decreased after SIS3 administration without decompression. Our study depicted the mechanisms of syrinx formation and suggested TGFβR-Smad3 signal might be key for dilation of central canal and formation of syrinx.

Post-traumatic syringomyelia resolution following surgical treatment: the moniliform syrinx with a better prognosis

BACKGROUND

Post-traumatic syringomyelia (PTS) presented as a serious delayed complication after spinal cord injury (SCI). In our preliminary pathological investigation of PTS in an animal model, the endogenous repair was activated during the early stage of the central canal expansion. We thought about whether there might be an "early syringomyelia state" with a better outcome.

OBJECTIVE

This study aimed to further understand the pathophysiological basis of PTS's occurrence, development, and outcome.

MATERIALS AND METHODS

A cross-sectional observational study from a single-center syringomyelia database prospectively maintained at China International Neuroscience Institute (CHINA-INI). A consecutive series of 28 PTS patients at our institution for surgical treatment met the inclusion criteria of this study. Their clinical and imaging data in a long-term follow-up were reviewed retrospectively. We compared the surgical outcome between moniliform and distended syringomyelia based on high‑resolution MRI and syringomyelia-related symptoms. American Spinal Injury Association (ASIA) impairment scale (AIS) grade to assess their neurological status.

RESULTS

Through a series of phenotypic comparisons, we found that moniliform-like syrinx belongs to a special morphological state with a shorter natural history. The patients in the moniliform group had a better surgical outcome compared with those in the distended group (P = 0.028): more obvious symptom improvement as shown in Kaplan-Meier analysis (P = 0.033, Chi square = 4.523) and a higher syringomyelia resolution rate (P = 0.024).

CONCLUSION

We consider the delayed post-traumatic syringomyelia with moniliform type with a better surgical outcome and emphasize the importance of timely intervention to restore cerebrospinal fluid circulation.

Relationship Between Syrinx Resolution and Cervical Sagittal Realignment Following Decompression Surgery for Chiari I Malformation Related Syringomyelia Based on Configuration Phenotypes

OBJECTIVE

Combined with different configuration types of syringomyelia, to analyze the correlation between syrinx resolution and changes in cervical sagittal alignment following Foramen magnum and Magendie dredging (FMMD) for syringomyelia associated with Chiari I malformation (CM-I), and to further explore the respective relationship with clinical outcome.

METHODS

A consecutive series of 127 patients with CM-I and syringomyelia who underwent FMMD in our center met the inclusion criteria of this study. Their clinical records and radiologic data were retrospectively reviewed. The Japanese Orthopedic Association (JOA) scoring system and the Chicago Chiari Outcome Scale (CCOS) were used to evaluate the surgical efficacy. The phenotypes of syringomyelia and the clinical characteristics of the patients were analyzed according to grouping by cervical curvature at baseline.

RESULTS

The preoperative straight or kyphotic cervical alignment is more common in the moniliform syrinx. After surgery, the syrinx resolution and cervical sagittal realignment in the moniliform group are more obvious, and the corresponding prognosis is relatively better. Spearman correlation analysis showed that the ΔS/C ratio (the change ratio of syrinx/cord) was positively correlated with the CCOS (p = 0.001, r = 0.897) and ΔC2-7A (the change of lower cervical angle) (p = 0.002, r = 0.560). There was also a correlation between the ΔJOA score (the change rate of the JOA score) and ΔC2-7A (p = 0.012, r = 0.467).

CONCLUSION

After decompression surgery, syrinx resolution may coexist with the changes in the subaxial lordosis angle, especially for syrinx in moniliform type, and the relationship between syrinx resolution and cervical sagittal realignment might be valuable for evaluating the surgical outcome.

Phenotypes and Prognostic Factors of Syringomyelia in Single-Center Patients With Chiari I Malformation: Moniliform Type as a Special Configuration

OBJECTIVE

The specific association between morphometric characteristics of the syrinx and the prognosis of Chiari malformation type I (CM-I) with syringomyelia following surgical procedure seems to have not been fully elaborated. This study focused on the preoperative clinical and radiologic parameters in CM-I patients with syringomyelia to find out the relationship between the patients' clinical status and the phenotypes of the syrinx with surgical outcome.

METHODS

A continuous series of pediatric and adult patients with CM-I and syringomyelia from a prospectively maintained database in a single center were included, and we explored the related factors affecting the prognosis following decompression surgery through retrospective analysis of clinical presentations, imaging characteristics, and the morphological features of syringomyelia, to provide a clinical reference for the treatment of syringomyelia.

RESULTS

There were 28 pediatric patients (13.8%), and 174 adults (86.2%) included in our study. The average Chicago Chiari Outcome Scale score was 14.56 ± 1.78. The overall prognosis after surgery was good in our series, among them 152 cases (75.25%) with a favorable prognosis, and syrinx was resolved effectively in 172 cases (85.15%). According to the univariate and multivariate analyses, the preoperative symptom duration, observation time, and with/without moniliform type were independent factors affecting the prognosis in adults. The most obvious difference between moniliform type and nonmoniliform type lies in the preoperative symptom duration, ventral subarachnoid space at the foramen magnum, and with/without straightened cervical physio-curve.

CONCLUSION

Timely decompression surgery could achieve a better outcome in CM-I patients with syringomyelia. Moniliform syringomyelia may suggest a relatively better prognosis.

A novel classification and its clinical significance in Chiari I malformation with syringomyelia based on high-resolution MRI

BACKGROUND

The existing classification in Chiari I malformation (CM-I) has limited significance for the selection of surgical methods.

OBJECTIVE

The purpose of this study was to investigate the surgery of CM-I with syringomyelia based on the high-resolution MR imaging (HRMRI) findings.

METHODS

Data from 115 patients were collected and retrospectively analyzed. For those with syringomyelia up to the level of C1, HRMRI was performed and according to the communication status between the fourth ventricle and the syringomyelia, patients can be divided into four types, namely Type A: classic communicating; Type B: partial communicating; Type C: non-communicating; Type D: atrophic. All operations were performed with Foramen magnum and Magendie dredging (FMMD), and all intradural factors that may have induced the obstruction of CSF circulation were recorded. The efficiency of operation on syringomyelia was evaluated by mJOA, imaging findings, and complications in the follow-up periods.

RESULTS

The postoperative follow-up period was from 12 to 24 months, with an average of 14.3 months. At 1 year, the mJOA of 115 patients was significantly higher than that before the operations (before surgery 12.1 ± 2.3 vs. after surgery 14. 2 ± 1.4, P < 0.05). In addition, postoperative re-examination showed that the size of the syringomyelia was reduced or completely resolved in patients of Type A, 100% (2/2); Type B, 81% (9/11); Type C, 84% (81/97); and Type D, 20% (1/5).

CONCLUSIONS

According to our new classification based on HRMRI, FMMD is the key to surgical treatment, especially for Type A and Type B patients.

Wireless Epidural Electrical Stimulation in Combination With Serotonin Agonists Improves Intraspinal Metabolism in Spinal Cord Injury Rats

OBJECTIVES

The combination of epidural electrical stimulation (EES) and serotonin agonists (5-HTA) effectively restores rhythmic lower-limb movements and improves intraspinal hemodynamics after spinal cord injury (SCI). Nonetheless, whether EES + 5-HTA improves intraspinal metabolism remains unclear. The present study aimed to evaluate the effects of EES + 5-HTA on intraspinal metabolism in SCI rats.

MATERIALS AND METHODS

Wireless EES (WEES) implantation with complete T8 transection was performed in SCI rats. Electrodes were placed at the T12 and L2 vertebral levels. After rest for a week, the SCI rats received 11 weeks of WEES + 5-HTA treatment and treadmill training. WEES was switched off after each daily training. Locomotor function was evaluated by motion capture at week 12. Positron emission tomography-computed tomography was conducted to evaluate basal metabolism when WEES was switched off and assess task metabolism when WEES was switched on.

RESULTS

With locomotor recovery after training for 11 weeks, WEES + 5-HTA conjointly improved basal metabolism (vs. each intervention alone; p < 0.05) and linearly modulated task metabolism in a frequency-dependent manner (R² = 0.8901). Furthermore, 60 Hz of WEES was identified as the threshold for the extensive activation of the spinal cord's task metabolism below the transection plane (p < 0.05).

CONCLUSIONS

WEES + 5-HTA could conjointly restore basal metabolism to a healthy level and modulate task metabolism by adjusting the stimulation frequency.

Intradural Pathology Causing Cerebrospinal Fluid Obstruction in Syringomyelia and Effectiveness of Foramen Magnum and Foramen of Magendie Dredging Treatment

OBJECTIVE

This article discusses the procedure of foramina magnum and Magendie dredging, summarizing the pathologic changes in the intradural region of the craniocervical junction in patients with syringomyelia and the pathophysiologic mechanism of cerebrospinal fluid (CSF) circulation obstruction.

METHODS

Clinical data from 50 adult patients with syringomyelia treated at Xuanwu Hospital from July 2018 to January 2019 were collected and retrospectively analyzed. All operations were performed with foramina magnum and Magendie dredging, and all intradural factors that may have induced the obstruction of CSF circulation were recorded.

RESULTS

Intradural pathology was found in all patients. The pathologic changes that may have caused obstruction of the CSF circulation include tonsil occupying the foramen magnum and overlying foramen of Magendie in 88% (44/50), intertonsillar arachnoid adhesions in 36% (18/50), tonsil to medulla arachnoid adhesions in 18% (9/50), medialized tonsils in 70% (35/50), vermian branch of posterior inferior cerebellar artery in 22% (11/50), arachnoid veil in 16% (8/50), cisterna magna cyst in 4% (2/50), and tonsil to dura mater arachnoid adhesions in 8% (4/50). Mean duration of follow-up was 13.3 months. The long-term effective rate was 96.0%. Postoperative magnetic resonance imaging revealed that the size of the syringomyelia was reduced or completely resolved in 88% of patients. The mean preoperative Japanese Orthopaedic Association score was 12.9 ± 3.1, which improved to 14.7 ± 3.2 (P < 0.05) at last clinical follow-up.

CONCLUSIONS

Intradural pathology that causes CSF circulation obstruction exists in many forms. Relieving the obstruction of the foramen magnum and foramen of Magendie is key to surgical treatment.