The anterior dural (Hofmann) ligaments

The relationship between myodural bridges, hyperplasia of the suboccipital musculature, and intracranial pressure

During mammalian evolution, the Myodural Bridges (MDB) have been shown to be highly conserved anatomical structures. However, the putative physiological function of these structures remains unclear. The MDB functionally connects the suboccipital musculature to the cervical spinal dura mater, while passing through the posterior atlanto-occipital and atlanto-axial interspaces. MDB transmits the tensile forces generated by the suboccipital muscles to the cervical dura mater. Moreover, head movements have been shown to be an important contributor to human CSF circulation. In the present study, a 16-week administration of a Myostatin-specific inhibitor, ACE-031, was injected into the suboccipital musculature of rats to establish an experimental animal model of hyperplasia of the suboccipital musculature. Using an optic fiber pressure measurement instrument, the present authors observed a significant increase in intracranial pressure (ICP) while utilizing the hyperplasia model. In contrast, surgically severing the MDB connections resulted in a significant decrease in intracranial pressure. Thus, these results indicated that muscular activation of the MDB may affect CSF circulation, suggesting a potential functional role of the MDB, and providing a new research perspective on CSF dynamics.

Anterior approach to remove a pre-medullary meningioma in the cervical spine: Technical case report

BACKGROUND

Regarding their relation to the spinal cord (SC), resection of pre-medullary meningiomas may be technically challenging. Anterior approach via corpectomy represents a nice option reducing the need for mobilization of the SC.

CASE DESCRIPTION

We describe the case of a patient presenting with a cervical meningioma, located anterior to the SC and operated on through an anterior approach. Surgery consisted of a 2-levels discectomy and C7 corpectomy, midline opening of the dura and then microsurgical resection of the tumor. After coagulation of the implantation base, the dura was then closed in a watertight fashion. Finally, the anterior column was reconstructed using a titanium mesh-cage and anterior plating.

CONCLUSION

In the case of cervical meningioma located anterior to the SC, anterior approach may be considered as an alternative option to remove the tumor.

Abnormal spinal cord motion at the craniocervical junction in hypermobile Ehlers-Danlos patients

OBJECTIVE

The craniocervical junction (CCJ) is anatomically complex and comprises multiple joints that allow for wide head and neck movements. The thecal sac must adjust to such movements. Accordingly, the thecal sac is not rigidly attached to the bony spinal canal but instead tethered by fibrous suspension ligaments, including myodural bridges (MDBs). The authors hypothesized that pathological spinal cord motion is due to the laxity of such suspension bands in patients with connective tissue disorders, e.g., hypermobile Ehlers-Danlos syndrome (EDS).

METHODS

The ultrastructure of MDBs that were intraoperatively harvested from patients with Chiari malformation was investigated with transmission electron microscopy, and 8 patients with EDS were compared with 8 patients without EDS. MRI was used to exclude patients with EDS and craniocervical instability (CCI). Real-time ultrasound was used to compare the spinal cord at C1-2 of 20 patients with EDS with those of 18 healthy control participants.

RESULTS

The ultrastructural damage of the collagen fibrils of the MDBs was distinct in patients with EDS, indicating a pathological mechanical laxity. In patients with EDS, ultrasound revealed increased cardiac pulsatory motion and irregular displacement of the spinal cord during head movements.

CONCLUSIONS

Laxity of spinal cord suspension ligaments and the associated spinal cord motion disorder are possible pathogenic factors for chronic neck pain and headache in patients with EDS but without radiologically proven CCI.

Anatomy of the posterolateral spinal epidural ligaments

Background

The epidural ligaments (ELs) (of Hofmann) were described as fibrous bands interconnecting the ventrolateral spinal dura and the posterior longitudinal ligament below L1. They are hardly ever discussed in the literature or considered in hypothesis-driven basic science experiments or spine biomechanical models.

Methods

Intraoperative photographs were obtained to illustrate a group of posterolateral spinal ELs. In addition, electronic database searches (PubMed, Ovid Embase, and SCOPUS) were utilized to summarize the anatomy, and relevant clinical and surgical factors impacting these ELs.

Results

ELs attach circumferentially at most spinal levels. They anchor the nerve root sleeves ventrally, and therefore, may play a role in the some idiopathic neurologic deficits (e.g., postoperative radiculopathies, C5 palsies) in patients without radiological compression. The posterolateral ELs originate on the dura dorsal to the nerve root sleeves and insert on the ipsilateral lamina, interlaminar ligament, and facet capsule. They appear to be continuous with the peridural membrane, a fibrovascular sheath that surrounds the thecal sac and serves as a scaffold for the internal vertebral venous plexus of Batson and epidural fat.

Conclusion

The spinal ELs should be divided sharply during surgery to prevent durotomies, especially in patients with advanced spondylosis and facet arthropathy. Disconnecting these ligaments releases the thecal sac laterally and ventrally, allowing for medial mobilization when performing discectomies or for working in the ventral epidural space.

Evaluate the characteristics and clinical significance of "toxic twin-leaf" sign in spinal epidural metastases before percutaneous vertebroplasty

Objective

Our study aimed to analyze morphological features of spinal epidural metastases using magnetic resonance imaging (MRI) and investigate the formation mechanism and clinical significance of the “toxic twin-leaf” sign in spinal epidural metastasis.

Materials and methods

We retrospectively studied 108 patients with spinal epidural metastases who underwent MRI. Patients were divided into “toxic twin-leaf” sign group (group A) and irregular group (group B). Chi-square test was used to analyze data on sex, vertebra location, presence of fracture in the corresponding vertebral body, involvement of the corresponding pedicle, and the primary tumor. Further, group data were analyzed using the rank sum test; p ​< ​0.05 was considered significant.

Results

The “twin-leaf” sign was noted in 88 cases with 136 epidural masses and 20 cases of irregular shape in 108 patients; the “toxic twin-leaf” sign accounted for 87.18% of spinal epidural metastases. A difference between groups in the vertebra location (p ​< ​0.01) was observed, but no differences were found in sex, presence of fractures in the corresponding vertebral body, involvement of the corresponding pedicle, and primary tumor (p ​> ​0.05). Intergroup differences in the rate of spinal stenosis on axial and sagittal images were significant.

Conclusions

MRI axial sequences clearly revealed the morphology of spinal epidural metastases. Detection of the “toxic twin-leaf” sign in spinal epidural metastases was of great clinical significance. Furthermore, determining the degree of spinal stenosis in the axial sequence provided a more accurate evaluation of patients’ condition compared to the sagittal sequence.

Thoracic myelopathy caused by an extremely rare aberrant epidural ligament: A case report

RATIONALE

The meningovertebral ligaments are a group of tissues that connect the dura and the vertebral bone. Abnormal fibrous ligaments in the canal space, which are essentially different from these ligaments, have been identified and their presence very rarely results in spinal disorder.

PATIENT CONCERNS

A 20-year-old Mongolian woman had developed persistent headache at 15 years of age. She then became unable to run fast when she was 19 years old and had progressively declining ability to move. She complained of back pain and unstable gait 6 months prior to presentation. Physical examination revealed exaggerated deep tendon reflexes in the lower extremities and decreased proximal leg muscle strength bilaterally.

DIAGNOSES

Magnetic resonance imaging (MRI) revealed abnormal bands compressing the spinal cord at the T10/11 level, with large epidural lipomatosis dorsal to the dural tube.

INTERVENTION

To decompress the cord, posterior laminectomy for T3-L3 and removal of the heterotopic ligaments were performed with T8-L1 posterior fusion.

OUTCOMES

Sufficient decompression of the cord was noted on postoperative MRI at the affected segments. The patient could subsequently walk without a cane and headache resolved immediately after the operation.

LESSONS

The presence of an aberrant epidural band is a rare pathologic state that often coexists with a surrounding lipomatosis and can lead to spinal cord compression. Removal of the band is a promising treatment for myelopathy caused by the compressive lesion.

The Posterior Lumbar Epidural Space: Three-Dimensional Reconstruction of High-Resolution MRI: Real and Potential Epidural Spaces and Their Content In Vivo

OBJECTIVE

Our aim was to study the posterior lumbar epidural space with 3D reconstructions of magnetic resonance images (MRIs) and to compare and validate the findings with targeted anatomic microdissections.

DESIGN

We performed 3D reconstructions of high-resolution MRIs from seven patients and normal-resolution MRIs commonly used in clinical practice from 196 other random patients. We then dissected and photographed the lumbar spine areas of four fresh cadavers.

RESULTS

From the 3D reconstructions of the MRIs, we verified that the distribution of the posterior fat pad had an irregular shape that resembled a truncated pyramid. It spanned between the superior margin of the lamina of the caudad vertebra and beyond the inferior margin to almost halfway underneath the cephalad lamina of the cranial vertebra, and it was not longitudinally or circumferentially continuous. The 3D reconstructions of the high-definition MRI also consistently revealed a prelaminar fibrous body that was not seen in most of the usually used low-definition MRI reconstructions. Targeted microdissections confirmed the 3D reconstruction findings and also showed the prelaminar tissue body to be fibrous, crossing from side to side anterior to the cephalad half of each lamina, and spanning from the dural sac to the laminae.

CONCLUSIONS

Three-dimensional reconstructions and targeted microdissection revealed the unique appearance of posterior fat pads and a prelaminar fibrous body. The exact consistency, presence, prevalence with age, presence in other regions, and function of this body are unknown and require further research.

Posterior Dural Shifts Following Spinous Process-Splitting Multi-Level Intervertebral Lumbar Laminectomies

Study Design

Retrospective cohort study.

Purpose

The aim of our study is to evaluate the extent of posterior spinal dural shift following spinous process splitting multi-level intervertebral lumbar laminectomies, and determine the relationship between posterior spinal dural shift and preoperative parameters.

Overview of Literature

There are no existing studies on the posterior spinal dural shift after spinous process-splitting multi-leveled lumbar laminectomies.

Methods

We examined 37 patients who underwent spinous process-splitting laminectomies in at least two intervertebral levels, including at the L5/S level. We defined the distance between the vertebral bodies and the anterior edge of the dural sac in the magnetic resonance images at the L5 vertebral level as the anterior dural space (ADS) and detected the difference (d-ADS) between preoperative ADS (pre-ADS) and postoperative ADS (post-ADS). We assessed the relationship between ADS or d-ADS, and preoperative parameters, including age, sex, lumbar lordosis, focal lordosis (FL), and number of decompression levels.

Results

Post-ADS was significantly greater than pre-ADS (p<0.001). Pre-ADS was significantly correlated with FL (p=0.44, p<0.01) and also with post-ADS (p=0.43, p<0.01). d-ADS was negatively correlated with pre-ADS (p=−0.37, p<0.05). A single regression analysis revealed that the relationship between d-ADS and pre-ADS was described as d-ADS=3.67−0.46×pre-ADS. In one of three patients whose d-ADS was above the range of two standard errors, reoperation was performed because of impingement of the nerve root caused by the excessive posterior dural shift.

Conclusions

Posterior dural shifts occur after spinous process-splitting multi-level lumbar laminectomies, including at the L5/S level. FL and pre-ADS are good predictive factors for posterior dural shift. Excessive posterior dural shift may lead to stretching and impingement of nerve roots and thus require attention.

Morphometric study of the posterior longitudinal ligament at the lumbar spine

PURPOSE

There are only two descriptions of posterior longitudinal ligament (PLL) at the lumbar spine level but its morphologic characteristics are different to cervical and thoracic levels.

METHOD

Spine explantation (from Th12 to L5) followed by resection of the neural arch and the dural sheath in 13 fresh cadavers was performed. The PLL was isolated from other epidural structures and its width was measured and compared to the vertebral body width at each vertebral levels. It was conducted at a microanatomic study concerning the PLL and the posterior outer annulus fibrosus.

RESULTS

The PLL width was reduced craniocaudaly significantly, becoming thin from L4. The average width of PLL was 7.8 mm at L1 and 1.9 mm at L5. The width decreased gradually from L1 to L5 or abruptly from L4. The ratio of PLL width compared to the vertebral body width was 21% at L1 and 3% at L5. Microanatomic study confirmed that the PLL is less thick at its annulus fibrosus adhesion at L4-L5 and L5-S1. The relationship between the PLL and other epidural structures are discussed.

CONCLUSIONS

The presence and function of the ilio-lumbar ligaments and the articular process orientation of L5-S1 may be explanations for PLL width decrease at L4-L5 and L5-S1. Furthermore, this aspect may be considered as one factor contributing to the occurrence of disc herniations at these levels, which levels are more frequently involved in this pathology.

Spinal cord compression syndrome caused by intraspinal epidural fibrous cord: Three case reports

RATIONALE

The spinal cord compression caused by intraspinal epidural fibrous cord.

PATIENT CONCERNS

All patients in this study had spinal cord compression syndrome caused by an intraspinal epidural fibrous cord, manifested as abnormally increased epidural adipose tissue by imaging.

DIAGNOSE

These abnormal fibrous connective tissue strips were not identical to the known pathological tissue such as "meningovertebral ligament." Instead, it might be a novel pathogenic cause for the spinal cord compression.

INTERVENTIONS

The intraspinal exploratory operation.

OUTCOMES

the first case has expected effect, the remaining two need further test.

LESSONS SUBSECTIONS

The disease could be easily misdiagnosed as spinal epidural lipoma or lipomatosis before the operation. However, the overt intraoperative finding was the indefinite starting and ending points of the epidural adipose mass in addition to the increased amount of adipose tissue. The obvious compression on the spinal cord could be found as the extraordinarily large and broad hypertrophic fibrous connective tissue strips.Further studies are needed to elucidate whether it is different from, or associated with, lipoma and epidural lipomatosis, which is a serious issue to be considered by both clinicians and radiologists. Therefore, early discovery,diagnosis, and treatment should be the prerequisites to achieve a satisfactory effect.

A Radiographic Measurement of the Anterior Epidural Space at L4-5 Disc Level

To observe the morphology character of the anterior epidural space at the L_4-5 disc level and to provide an anatomical basis for safely and accurately performing a percutaneous endoscopic lumbar discectomy (PELD). Fifty-five cases with L₅ S₁ lumbar disc herniation were included in this study, and cases with L_4-5 disease were excluded. When the puncture needle reached the epidural space at the L₅ S₁ level, iohexol was injected at the pressure of 50 cm H₂ O during the PELD, then C-Arm fluoroscopy was used to obtain standard lumbar frontal and lateral images. The widths of epidural space at the level of the L₄ lower endplate, the L₅ upper endplate, as well as the middle point of the L_4-5 disc were measured from the lumbar lateral X-ray film. Epidural space at the L_4-5 disc plane performs like a trapezium chart with a short side at the head end and a long side at the tail end in the lumbar lateral X-ray radiograph, while the average widths of epidural space were 10.2 ± 2.5, 12.3 ± 2.3, and 13.8 ± 2.6 mm at the upper, middle, and lower level of the L_4-5 disc. Understanding the morphological characteristics of epidural space will contribute to improving the safety of the tranforaminal percutaneous endoscopy technique.

The Epidural Ligaments (of Hofmann): A Comprehensive Review of the Literature

The epidural space contains the internal vertebral venous plexus, adipose, and other connective tissues. In the anatomical literature, there are nonspecific descriptions of varying fibrous connective tissue bands in the epidural space, mainly mentioned in the lumbar region, that tether the dural sac to the posterior longitudinal ligament, the vertebral canal, and the ligamentum flavum. These ligaments have been termed as Hofmann’s ligaments. This review expands on the anatomy and function of Hofmann’s ligaments, increasing the awareness of their presence and serves as an impetus for further study of their histology, innervation, and function. 

Effectiveness of Bilateral Transforaminal Epidural Steroid Injections in Degenerative Lumbar Spinal Stenosis Patients With Neurogenic Claudication: A Case Series

BACKGROUND

As our population ages, neurogenic claudication (NC) from central canal stenosis of the lumbar spine is becoming an increasingly common condition. Studies have been undertaken to assess the efficacy of caudal, interlaminar, or unilateral transforaminal epidural injections, but bilateral transforaminal epidural injections (BTESIs) have not been evaluated to date.

OBJECTIVE

To assess the therapeutic value and long-term effects of fluoroscope-guided BTESIs in patients with NC from degenerative lumbar spinal stenosis (DLSS) of the central spinal canal.

DESIGN

Case series.

SETTING

Single institution spine clinic.

PATIENTS

Twenty-six adults between the ages of 40 and 90 years with a diagnosis of DLSS and a history of subacute or chronic NC.

METHODS/INTERVENTIONS

Patients meeting inclusion criteria received fluoroscope-guided BTESI of local anesthetic and steroid at the level immediately below the most stenotic level. Patient self-reported pain level, activity level, and overall satisfaction were recorded by telephone interview at 1, 3, and 6 months after injection by an independent observer.

MAIN OUTCOME MEASURES

Pain score and Swiss Spinal Stenosis score at baseline, 1, 3, and 6 months.

RESULTS

Of the 22 participants eligible for analysis, 20, 19, and 18 had follow-up data available at 1, 3, and 6 months, respectively. Reduction in numeric pain scale score of at least 50% was noted in 30% of participants at 1 month, 53% at 3 months, and 44% at 6 months. Swiss Spinal Stenosis subscale scores indicated a significant reduction in the proportion of participants reporting the presence of severe pain in the back, buttocks, and legs (particularly the back or buttocks) at 1, 3, and 6 months of follow-up compared with baseline (P < .05). The proportion of participants reporting severe weakness in the legs or feet also decreased after injection and was statistically significant at 3 months of follow-up (P = .04).

CONCLUSIONS

Fluoroscope-guided BTESI was moderately effective in reducing pain, improving function, and achieving patient satisfaction in patients with NC from DLSS at the central spinal canal in this clinical case series.

LEVEL OF EVIDENCE

IV.

Investigation of meningomyovertebral structures within the upper cervical epidural space: a sheet plastination study with clinical implications

BACKGROUND CONTEXT

Over the past two decades, soft-tissue structures communicating with the dura mater within the epidural space have become the focus of many anatomical and histopathologic studies. The relationship between these bridging structures has yet to be evaluated in situ.

PURPOSE

This is the first study that used E12 sheet plastination to investigate the epidural space of the upper cervical spine in situ and its associated bridging structures. Given the complexity of this space, this study may prove useful to clinical anatomists and surgeons who operate within this region.

STUDY DESIGN

Anatomical and microscopic analyses of structures that communicate with the dura mater within the upper cervical region were carried out.

METHODS

Gross dissection in conjunction with microscopy was used to evaluate bridging communications of the upper cervical spine in 10 cadavers. To evaluate the in situ arrangement of these structures, E12 sheet plastination was used on 13 cadavers.

RESULTS

In all 23 specimens, suboccipital fascia coalesced with the dorsal meningovertebral ligament of the atlas, and inserted directly into the posterior surface of the dura as a single but separable laminar layer. At the level of the atlantoaxial interspace, suboccipital fasciae combined and coalesced with the dorsal meningovertebral ligament of the atlas and the axis. These structures inserted into the posterior surface of the dura mater as a single but separable layer. Microscopy validated these findings and E12 sheet plastination revealed the in situ organization of these soft-tissue structures. E12 sheet plastination also provided new information on dural arrangement at the craniocervical junction, which was observed to be composed of periosteum from the occiput but consisted mainly of deep fascia from the rectus capitis posterior minor.

CONCLUSIONS

E12 sheet plastination has provided in situ visualization of bridging structures within the cervical epidural space and offers new insight into these structures, as well as the composition and arrangement of the posterior atlantooccipital membrane and cerebrospinal dura at the craniocervical junction. This study aims to expand on the anatomical understanding of the upper cervical region while defining structures that may reduce neurosurgical complications, and aid in the understanding of the pathophysiology of certain neurogenic disorders.

The posterior epidural ligaments: a cadaveric and histological investigation in the lumbar region

Purpose. Incidental durotomy is a relatively common complication for patients undergoing posterior spinal surgery. Delineating anatomical variants in the posterior lumbar spinal canal is crucial in reducing future rates of incidental durotomy. Materials and Methods. The ligamentous attachments between the dura mater and ligamentum flavum in the lumbar region of 17 soft-fixed cadavers were investigated. The lumbar vertebral columns were removed, and cross-sectional dissection was performed at levels L1-S1. Anterior retraction of the dorsal dura mater identified attachments between the dorsal surface of the dura mater and the ligamentum flavum. Histological staining of the ligamentous attachments was carried out with hematoxylin and eosin (H&E) and elastic van Gieson (EVG). Results. Posterior epidural ligaments were present in 9 (52.9%) cadavers. Nine (9) separate ligaments were identified in these cadavers, with 3 (33.3%) at L3/L4, 5 (55.5%) at L4/L5, and 1 (11.1%) at L5/S1. Histology confirmed the presence of poorly differentiated collagen-based connective tissue, distinct from the normal anatomy. Conclusions. This study confirms the presence of multiple dorsomedial posterior epidural ligaments at the main sites for posterior spinal surgery (L3-S1). An intraoperative awareness of the variability of such connections may be an important step in reducing static rates of incidental durotomy.

Spinal dural attachments to the vertebral column: An anatomic report and review of the literature

BACKGROUND

The spinal dura is anchored within the vertebral canal by connective tissue in the epidural space as well as the spinal roots. Inadvertent disruption of these dural attachments may lead to durotomy and cerebrospinal fluid (CSF) leaks. We observed well-developed connective tissue ligaments connecting the lumbar dura to the spinal column and examined these tissues microscopically.

METHODS

Intraoperative images were obtained during lumbar laminectomy procedures. They demonstrated connective tissue attachments, linking the lumbar dura to the spinal column in the dorsal midline and dorsolaterally. Tissue samples were obtained and examined microscopically. We then conducted a search of the literature to find references to dural attachments to the spinal column.

RESULTS

Histological examination of the samples showed minimal cellular fibrous tissue. To date no references to these attachments have been made in neurosurgical literature. Previous studies, including live, cadaveric, and radiographic examinations, have demonstrated a dorsomedian fold of dura attached to the junction of the ligamentum flavum, and dorsolateral ligaments that divide the dorsal epidural space into an anterior and posterior compartment.

CONCLUSIONS

Epidural fibrous connections or ligaments between the dura and the lumbar spinal column may be of clinical importance to the neurosurgeon. Care should be taken during lumbar procedures not to disrupt or tear these ligaments as this may cause dural tears and CSF leaks. Identifying these ligaments and cutting them sharply may prevent inadvertent durotomies.

Spontaneous spinal epidural haematomas and the prognostic implications of interval to surgical decompression: a report of two cases

Spontaneous spinal epidural haematomas (SSEHs) are rare causes of spinal cord compression. We present 2 cases of thoracic SSEHs with similar magnetic resonance imaging (MRI) features. Patient 1 was on long-term oral anticoagulants and patient 2 had uncontrolled hypertension. Patient 1 presented with a dense motor deficit, whereas patient 2 developed progressive lower limb weakness. Decompression laminectomy and haematoma evacuation was performed 51 hours later for patient 1 and 14 hours later for patient 2. Both had recovered their lower limb power, but neurological recovery was greater for patient 2. In patients with bleeding diatheses or uncontrolled hypertension, acute SSEHs must be suspected when they present with atraumatic back pain and signs of spinal cord compression. The interval to surgical decompression greatly influences the prognosis for neurological recovery.

The posterior longitudinal ligament and peridural (epidural) membrane

The posterior longitudinal ligament (PLL) is described as having deep and superficial layers, though recent studies have suggested that there may be three layers. Additional membranous structures have been reported, although there is no consensus as to their presence or morphology. The vertebral canal and dural sac were opened and the spinal nerve roots and spinal cord removed. The anterior dural ligaments were sectioned at their attachment to the PLL and the dura mater freed from the posterior surface of the vertebral bodies. The borders of the PLL were identified and the superficial and deep layers separated. The PLL is a wide band in the cervical region becoming more denticulate inferiorly, the widest parts being attached to the intervertebral discs (IVD) and adjacent vertebral body where the superficial and deep layers could not be separated. A continuous well developed peridural membrane attaching to the pedicles was present anterior to the deep PLL as well as a separate, thin, incomplete layer in 6 of 18 cadavers, covering the posterior surface of the superficial PLL.