Automatic segmentation of dura for quantitative analysis of lumbar stenosis: A deep learning study with 518 CT myelograms

BACKGROUND

The diagnosis of lumbar spinal stenosis (LSS) can be challenging because radicular pain is not often present in the culprit-level localization. Accurate segmentation and quantitative analysis of the lumbar dura on radiographic images are key to the accurate differential diagnosis of LSS. The aim of this study is to develop an automatic dura-contouring tool for radiographic quantification on computed tomography myelogram (CTM) for patients with LSS.

METHODS

A total of 518 CTM cases with or without lumbar stenosis were included in this study. A deep learning (DL) segmentation algorithm 3-dimensional (3D) U-Net was deployed. A total of 210 labeled cases were used to develop the dura-contouring tool, with the ratio of the training, independent testing, and external validation datasets being 150:30:30. The Dice score (DCS) was the primary measure to evaluate the segmentation performance of the 3D U-Net, which was subsequently developed as the dura-contouring tool to segment another unlabeled 308 CTM cases with LSS. Automatic masks of 446 slices on the stenotic levels were then meticulously reviewed and revised by human experts, and the cross-sectional area (CSA) of the dura was compared.

RESULTS

The mean DCS of the 3D U-Net were 0.905 ± 0.080, 0.933 ± 0.018, and 0.928 ± 0.034 in the five-fold cross-validation, the independent testing, and the external validation datasets, respectively. The segmentation performance of the dura-contouring tool was also comparable to that of the second observer (the human expert). With the dura-contouring tool, only 59.0% (263/446) of the automatic masks of the stenotic slices needed to be revised. In the revised cases, there were no significant differences in the dura CSA between automatic masks and corresponding revised masks (p = 0.652). Additionally, a strong correlation of dura CSA was found between the automatic masks and corresponding revised masks (r = 0.805).

CONCLUSIONS

A dura-contouring tool was developed that could automatically segment the dural sac on CTM, and it demonstrated high accuracy and generalization ability. Additionally, the dura-contouring tool has the potential to be applied in patients with LSS because it facilitates the quantification of the dural CSA on stenotic slices.

Physiological pseudo-thickened cauda equina associated with dural sac dilatation on magnetic resonance imaging

OBJECTIVES

In daily clinical practice, the assessment of the thickness of the cauda equina on lumbar spine magnetic resonance imaging is an important parameter. However, its relevance to the size of the dural sac in non-pathological conditions is unknown. To examine the relationship between the size of the dural sac and the apparent thickness of the cauda equina nerve root using lumbar spine magnetic resonance imaging in non-pathological conditions.

METHODS

We retrospectively measured the dural sac diameter and vertebral body diameter, counted the apparent number, and calculated total cross-sectional area of the cauda equina, dural sac ratio and the area of one apparent nerve root of cauda equina in 100 cases. Spearman's rank correlation coefficient (ρ) was used.

RESULTS

Dural sac ratio and diameter were positively correlated with the area of one apparent nerve root (ρ=0.77, P<0.001; ρ=0.74, P<0.001; respectively) and negatively correlated with the apparent number of cauda equina in a single cross-section (ρ=-0.63, P<0.001; ρ=-0.52, P<0.001; respectively).

CONCLUSIONS

A larger dural sac ratio and diameter was associated with an apparently thicker cauda equina and lower visible number. In a larger dural sac, the physiologically clumped and apparently thicker cauda equina should not be misdiagnosed as pathological.

Association between filum terminale internum length and pain in Cavalier King Charles spaniels with and without syringomyelia

Background

Lumbar syringomyelia (SM), lumbosacral pain, and more caudal spinal cord termination are reported in Cavalier King Charles spaniels (CKCS). Data are lacking on the clinical relevance of alterations in their spinal cord terminal structures.

Objectives

To compare spinal cord termination level and filum terminale internum length (FTIL) with presence of lumbar SM and clinical signs in CKCS.

Animals

Forty‐eight CKCS.

Methods

In this prospective study, pain was quantified using owner and clinician assessments. Vertebral level of spinal cord and dural sac termination, presence of SM, and FTIL were determined from sagittal magnetic resonance imaging (MRI) sequences. Kappa and intraclass correlation (ICC) analyses determined interobserver reliability. The MRI findings were compared to owner and clinician‐reported pain quantification.

Results

Interobserver reliability was good for spinal cord and dural sac termination (kappa = 0.61 and 0.64, respectively) and excellent for FTIL (ICC: 92% agreement). The spinal cord terminated at 6th lumbar vertebra in 1, 7th lumbar vertebra in 31, and the sacrum in 15 dogs, and termination level was associated with lumbar SM (P = .002) but not clinical signs. Mean FTIL was 2.9 ± 1.08 mm; it was associated with owner‐reported pain (P = .033) and spinal palpation scores (P = .023). Painful CKCS without SM had shorter FTIL compared to normal CKCS and painful CKCS with SM (P = .02).

Conclusions

Painful CKCS without SM have decreased distance between the termination of the spinal cord and dural sac, suggesting a shorter FTIL. More caudal spinal cord termination is associated with development of lumbar SM.

Correlation of the lumbar dural sac dimension with the spread of spinal anesthesia in elderly female patients: A prospective observational study

BACKGROUND

To test a hypothesis that the dural sac dimension would be correlated with the spinal block level, we evaluated the correlation between the lumbar dural sac dimension and the spread of spinal anesthesia in elderly women.

METHODS

In 40 women over the age of 65 years, the lumbar dural sac dimensions were measured at the L2-L3, L3-L4, L4-L5, and L5-S1 intervertebral spaces using ultrasonography in the lateral decubitus position, followed by the administration of spinal anesthesia. The correlation coefficients were analyzed for the lumbar dural sac dimension at each intervertebral level, peak sensory block level, peak motor block, time to peak sensory and peak motor blockade, durations of sensory and motor blockade, and patient characteristics. We subsequently analyzed the partial correlations between the lumbar dural sac dimension and the outcomes of spinal anesthesia, while adjusting for age, body mass index, and waist circumference.

RESULTS

Peak sensory block level was inversely correlated with each lumbar sac dimension: L2-L3 (ρ = -0.37, P = .029), L3-L4 (ρ = -0.57, P < .001), L4-L5 (ρ = -0.65, P < .001), and L5-S1 (ρ = -0.49, P = .002) intervertebral spaces. Partial correlation analysis with adjustment for age, body mass index, and waist circumference revealed inverse correlations between the lumbar dural sac dimension at the following intervertebral spaces and peak sensory block level: L3-L4 (r = -.52, P = .003), L4-L5 (r = -.76, P < .001), and L5-S1 (r = -.65, P < .001).

CONCLUSIONS

Outcomes of ultrasonographic investigation revealed an inverse correlation between the lumbar dural sac dimension and peak sensory block level in elderly women.

Variation in the position of the conus medullaris and dural sac in adult dogs

Although it has long been stated that the level of spinal cord termination varies depending on the size of the dog, the evidence for this remains limited. The aim of this study is to investigate the position of the conus medullaris (CM) and dural sac (DS) in a population of dogs of varying size. MRIs of the thoracolumbosacral spine of 101 dogs were included. The location of CM and DS was determined on sagittal T2-weighted images and T1-weighted images, respectively, by three independent observers. The bodyweight and the back length were used as markers of size. Regression analysis showed that the termination point of the CM had a statistically significant relationship with bodyweight (R²=0.23, P<0.05). Although not statistically significant (P=0.058), a similar relationship was found between CM and back length (R²=0.21). No statistically significant relationship was found between the termination point of the DS and bodyweight (P=0.24) or back length (P=0.19). The study confirms the terminal position of the CM is dependent on size, with a more cranial position with increasing size; however, the termination point of DS remains constant irrespective of dog size.

Morphometric analysis of spinal cord termination in Cavalier King Charles Spaniels

BACKGROUND

There is an association between Chiari malformations, syringomyelia (CMSM) and tethered cord syndrome (TCS) in people, suggesting Cavalier King Charles Spaniels (CKCS) with CMSM could also have TCS. Currently there are no data on the position of the caudal spinal cord structures in CKCS.

OBJECTIVE

To describe and compare location of spinal cord termination in CKCS with weight-matched controls and to examine the relationship between SM and spinal cord termination.

ANIMALS

Thirty-nine CKCS and 33 controls with thoracolumbar MRIs; 34 of 39 CKCS also had cervical MRIs.

METHODS

Blinded retrospective study. Spinal cord and dural sac termination were determined from T2-weighted sagittal and transverse images and half-Fourier acquisition single-shot turbo spin echo sequences. Intra-observer reliability was determined using kappa analysis. Presence of SM was compared with location of spinal cord and dural sac termination.

RESULTS

Intra-observer reliability was moderate for identifying spinal cord termination (Kappa = 0.6) and good for dural sac termination (Kappa = 0.8). The spinal cord terminated at lumbar vertebra 6 (L6) in 1, 7 (L7) in 22, and sacrum in 16 CKCS versus 9 at L6, 23 at L7, 1 at sacrum in controls. Spinal cord (P < .001) and dural sac (P = .002) termination were significantly more caudal in CKCS compared to controls. The presence of thoracolumbar SM was associated with more caudal dural sac termination in CKCS (P = .03).

CONCLUSIONS AND CLINICAL IMPORTANCE

The relationship between TL SM and possible spinal cord tethering because of a more caudal dural sac termination should be investigated.

Determining the extent of the dural sac for the performance of caudal epidural blocks in newborns

BACKGROUND

Information regarding the position and relationship of vital structures within the caudal canal is important for anesthesiologists who perform a caudal block. This information can be acquired by anatomical dissection, with ultrasound technology, or radiological studies.

AIMS

The aim of this study was to determine the position of the dural sac in neonates by measuring the distance of the termination of the dural sac from the apex of the sacral hiatus in neonatal cadavers.

METHODS

After careful dissection, the distance from the apex of the sacral hiatus to the dural sac was measured in a sample of neonatal cadavers.

RESULTS

In 39 neonatal cadavers, the mean distance from the apex of the sacral hiatus to the dural sac was 10.45 mm. The range of this distance was between 4.94 and 26.28 mm. The mean distance for females was 9.64 mm (range from 6.66 to 15.09); that for males was 10.90 mm (range between 4.94 and 26.28). Linear regression with the log of this distance as the outcome variable gave an estimated 3.3% increase in the distance for each 1 cm increase in the length of the neonate (95% CI for this proportion was 1.91-4.71).

CONCLUSION

Anesthesiologists should be aware of the short distance between the sacral hiatus and the dural sac when performing caudal blocks, the shortest distance was 4.94 mm. Armed with this knowledge, caudal techniques should be modified to improve the safety and reduce the risk of complications, such as dural puncture.

Relationship between Enlargement of the Cross-Sectional Area of the Dural Sac and Neurological Improvements after Cervical Laminoplasty: Differences between Cervical Spondylotic Myelopathy and Ossification of the Posterior Longitudinal Ligament

Introduction

The purpose of this study was to investigate the relationship between postoperative enlargement of the dural sac cross-sectional area at the symptomatic level and neurological improvements after laminoplasty.

Methods

The cross-sectional areas of the dural sac at the symptomatic level before and after laminoplasty and the expansion ratio (post-/preoperative cross-sectional area) were measured using magnetic resonance imaging in patients with ossification of the posterior longitudinal ligament (OPLL) (n = 25) and patients with cervical spondylotic myelopathy (CSM) (n = 49). The relationships between the expansion ratio and the Japanese Orthopedic Association (JOA) score, JOA Cervical Myelopathy Evaluation Questionnaire (JOACMEQ), and postoperative laminae morphology were investigated.

Results

In the OPLL group, the expansion ratio was significantly positively correlated with the postoperative JOA score (P = 0.025), recovery rate of the JOA score (P = 0.026), and postoperative change in lower extremity sensory function according to the JOA score (P = 0.0375); furthermore, patients whose JOACMEQ responses indicated positive outcomes for lower extremity function had a significantly larger expansion ratio than patients with negative results (P = 0.027). In the CSM group, the expansion ratio showed no correlation with the JOA and JOACMEQ scores. The expansion ratio was significantly positively correlated with the width between bilateral gutters in both CSM (P = 0.025) and OPLL (P = 0.0451). In the OPLL group, the expansion ratio in those with a gutter position of less than 0.8 was significantly smaller than that those with a gutter position of more than 0.8 (P = 0.0156). However, there was no correlation between the gutter position and the recovery rate of the JOA score.

Conclusions

In OPLL, insufficient enlargement of the cross-sectional area of the dural sac at the symptomatic level leads to poor neurological improvements after laminoplasty.

Cadaveric study of movement in the unstable upper cervical spine during emergency management: tracheal intubation and cervical spine immobilisation-a study protocol for a prospective randomised crossover trial

INTRODUCTION

Emergency management of upper cervical spine injuries often requires cervical spine immobilisation and some critical patients also require airway management. The movement of cervical spine created by tracheal intubation and cervical spine immobilisation can potentially exacerbate cervical spinal cord injury. However, the evidence that previous studies have provided remains unclear, due to lack of a direct measurement technique for dural sac's space during dynamic processes. Our study will use myelography method and a wireless human motion tracker to characterise and compare the change of dural sac's space during tracheal intubations and cervical spine immobilisation in the presence of unstable upper cervical spine injury such as atlanto-occipital dislocation or type II odontoid fracture.

METHODS AND ANALYSIS

Perform laryngoscopy and intubation, video laryngoscope intubation, laryngeal tube insertion, fiberoptic intubation and cervical collar application on cadaveric models of unstable upper cervical spine injury such as atlanto-occipital dislocation or type II odontoid fracture. The change of dural sac's space and the motion of unstable cervical segment are recorded by video fluoroscopy with previously performing myelography, which enables us to directly measure dural sac's space. Simultaneously, the whole cervical spine motion is recorded at a wireless human motion tracker. The maximum dural sac compression and the maximum angulation and distraction of the injured segment are measured by reviewing fluoroscopic and myelography images.

ETHICS AND DISSEMINATION

This study protocol has been approved by the Ethics Committee of the State Medical Association Rhineland-Palatinate, Mainz, Germany. The results will be published in relevant emergency journals and presented at relevant conferences.

TRIAL REGISTRATION NUMBER

DRKS00010499.

Vertebral level and measurements of conus medullaris and dural sac termination with special reference to the apex of the sacral hiatus: anatomical and magnetic resonance imaging radiologic study

BACKGROUND

Anatomical orientation of the caudal space and termination level of conus medullaris (CMT) and dural sac (DST) has great significance for anaesthetists and neurosurgeons. This study aimed to explore the anatomical landmarks important to perform save spinal anaesthesia, lumber puncture and caudal analgesia through the correlation between the vertebral level of CMT, DST and sacral hiatus apex (SHA) in human cadavers and by using magnetic resonance imaging (MRI).

MATERIALS AND METHODS

Sixty adult cadavers (40 males, 20 females) and 200 (100 males, 100 females) MR lumbosacral images of 16-69-year-old persons were used in this study. Vertebral level of CMT, DST and SHA and their linear distances were determined in cadavers and MRI. Also, anteroposterior diameter at SHA, length and thickness of sacrococcygeal membrane were measured as well, and correlate these levels and their distances with age and sex.

RESULTS

Mean and highest frequent number of MRI vertebral level of CMT was observed at lower third of L1 in men and L1-2 disc in women, that of DST at upper third of S2 in men and middle third of S2 in women, while SHA was seen at middle third of S4 in both men and women with no significant (p > 0.05) age or gender differences. In 5% of cases, CMT, DST and SHA were seen at vertebral level below L2, below S2-3 and above S3, respectively. However, mean vertebral level of CMT, DST, SHA was observed at L1L, S2M and S4U without sex differen-ce in cadaveric specimens, respectively. All linear distances of men MRI revealed significant difference (p < 0.05) compared with those of women except thickness of sacrococcygeal membrane and anterposterior diameter at SHA.

CONCLUSIONS

Accurate knowledge of vertebral level of CMT, DST and SHA and the distances in-between might decrease the iatrogenic injury of dural sac, spinal cord and cauda equina.

Morphometrical analysis of the thoracolumbar dural sac in sheep using computed assisted myelography

OBJECTIVES

Sheep are frequently used as animal models in experimental spinal injury studies. Therefore, extensive knowledge of ovine spinal dimensions is essential for experimental design and interpretation of results obtained in these trials. This study aimed to obtain quantitative morphometrical data of the thoracolumbar dural sac in sheep and determine the anatomical relationship between the dural sac and the vertebral canal.

METHODS

Computed assisted myelography imaging was carried out in five adult German Black-Headed Mutton sheep under general anaesthesia. Transverse images were acquired with 2 mm slice thickness from the first thoracic to the sixth lumbar vertebrae. Sagittal and transverse diameters and the cross-sectional area of the dural sac and vertebral canal were measured. To determine the anatomical relationship between the dural sac and vertebral canal, the pedicle-dural sac distance (PPSD) and the epidural space as well as the SAC (available space for the dural sac) were calculated.

RESULTS

Sagittal diameters of the dural sac ranged from 5.1 to 12.0 mm. Transverse diameters ranged from 5.6 to 12.2 mm. The dural sac area covered 45.9% and 49.0% of the thoracic and lumbar vertebral canal area. The PDSD in the lumbar vertebrae was up to 15.8% larger than in the thoracic ones. The dural sac area was significantly positively correlated with the transverse diameter and area of the vertebral canal.

CLINICAL SIGNIFICANCE

The lumbar vertebral canal contained more space for the dural sac, which seems to be safer for testing spinal implants.

Progressive growth of arachnoid cysts with cauda equina syndrome after lumbar spine surgery

Intradural arachnoid cysts are a rare cause of spinal cord compression. In symptomatic cases neuropathic pain, gait disturbance, and paraparesis or quadriparesis are often present. Postoperative arachnoid cysts have rarely been reported. We describe a 56-year-old male who developed progressively enlarging arachnoid cysts with cauda equina syndrome and vertebral body erosion after lumbar surgery. The clinical presentation of the patient, the possible mechanisms of cyst formation, and the management of the disease are discussed with regard to previous literature.