The anatomy of the peridural membrane of the human spine.

A peridural membranous layer exists between the bony wall of the spinal canal and the dura mater, but reports on the anatomy of this structure have been inconsistent. The objective of this study is to give a precise description of the peridural membrane (PDM) and to define it unambiguously as a distinct and unique anatomical entity. Thirty-four cadaveric sections of human thoraco-lumbar spines were dissected. On gross examination, the PDM appears as a smooth hollow tube that covers the bony wall of the spinal canal. An evagination of this tube into the neural foramen contains the exiting spinal nerve. The entire epidural venous plexus, including its extension into the neural foramina, is contained in the body of the PDM. Histological examination of the PDM shows a variable distribution of veins arteries, lymphatics, and nerves embedded in a continuous sheath of fibrous, areolar, and adipose tissue. The posterior longitudinal ligament may be considered a dense condensation of fibrous tissue within the membrane. Thus, the PDM is a unique, continuous, and complete anatomical structure. In the spinal canal, the PDM is adjacent to the periosteum. In the neural foramen, suprapedicular PDM and pedicular periosteum separate anatomically to form a suprapedicular compartment, bounded anteriorly by the intervertebral disc and posteriorly by the facet joint. Trauma or degeneration of the disc or facet joint may lead to inflammation and pain sensitization of PDM. This protective mechanism may be of considerable importance for the functioning of the spine under conditions of strain.

The peridural membrane of the spine has characteristics of synovium.

The peridural membrane (PDM) is a well-defined structure between dura mater and the wall of the spinal canal. The spine may be viewed as a multi-segmented joint, with the epidural cavity and neural foramina as joint spaces and PDM as synovial lining. The objective of this investigation was to determine if PDM has histological characteristics of synovium. Samples of the PDM of the thoraco-lumbar spine were taken from 23 human cadavers and analyzed with conventional light microscopy and confocal microscopy. Results were compared to reports on similar analyses of synovium in the literature. Histological distribution of areolar, fibrous, and adipose connective tissue in PDM was similar to synovium. The PDM has an intima and sub-intima. No basement membrane was identified. CD68, a marker for macrophage-like-synoviocytes, and CD55, a marker for fibroblast-like synoviocytes, were seen in the lining and sub-lining of the PDM. Multifunctional hyaluronan receptor CD44 and hyaluronic acid synthetase 2 marker HAS2 were abundantly present throughout the membrane. Marked presence of CD44, CD55, and HAS2 in the well-developed tunica muscularis of blood vessels and in the body of the PDM suggests a role in the maintenance and lubrication of the epidural cavity and neural foramina. Presence of CD68, CD55, and CD44 suggests a scavenging function and a role in the inflammatory response to noxious stimuli. Thus, the human PDM has histological and immunohistochemical characteristics of synovium. This suggests that the PDM may be important for the homeostasis of the flexible spine and the neural structures it contains.

The Peridural Membrane of the Human Spine is Well Innervated.

There is evidence that low back pain may originate from a peridural membrane (PDM) at the inferior and medial aspect of neural foramen of the lumbar spine. The objective of this investigation was to determine if this membrane contains neural elements suggestive of sensory innervation with nociceptive function. Spines of four embalmed and three non-embalmed human cadavers were dissected using a sagittal approach to the neural foramen. Seventeen samples of the peridural membrane overlying the neural foramen were collected for immunohistochemistry (IHC) examination by light microscopy and transmission electron microscopy (TEM). Chromagin tagged antibodies to protein gene product 9.5 (PGP9.5) and S-100, and fluorescent antibodies to substance P and calcitonin gene related peptide (CGRP) were used to label neural structures in tissue sections cut from paraffin embedded blocks. This approach allows good visualization of all neural elements, small sensory, and nociceptive nerve fibers in particular. Neural elements were found in all samples. Marked presence of small nerve fibers was observed in 12 of 15 samples. IHC and TEM evaluation revealed myelinated as well as unmyelinated fibers in the peridural membrane. CGRP and substance P immunoreactive fibers indicative of nociceptive function were abundant. These findings confirm and expand evidence that the peridural membrane in human is well innervated and contains sensory nociceptive nerve fibers suggestive of a nociceptive function of the membrane.

Treatment of Common Low Back Pain: A New Approach to an Old Problem.

Low back pain is very common, but the pathophysiology is poorly understood. We present a new hypothesis regarding the pathophysiology of common low back pain supported by our flexible endoscopic observations of the epidural cavity (epiduroscopy), anatomic dissection of embalmed and fresh cadavers, and careful review of preexisting information available on the anatomy of the epidural space and neuroforamen. A new approach to the treatment of common low back pain based on the hypothesis was developed and is presented in the case reports of five patients. Treatment focuses on a perichondrium derivative; the peridural membrane, which creates a suprapedicular compartment in the neuroforamen where we hypothesize inflammatory material accumulates. This produces common low back pain by causing inflammation and sensitization of the peridural membrane and periosteum that forms the boundaries of this compartment. Percutaneous Ablation and Curettage and Inferior Foraminotomy (PACIF(sm)) aims to destroy the peridural membrane, denervate sensitive structures, and remove inflammatory tissues from the suprapedicular canal. The proposed mechanism of action and safety of PACIF(sm) is discussed in the context of epidural and neuroforaminal anatomy. As shown by the five case reports, PACIF(sm) appears to be highly effective and safe, warranting further evaluation.

Lumbosacral epiduroscopy findings predict treatment outcome.

OBJECTIVE: The aim of this study was to evaluate the significance of diagnostic markers obtained through epiduroscopy by evaluating the accuracy of outcome prediction after treatment of epidural pathology using epiduroscopy. DESIGN: A prospective observational study of 139 patients was performed. Patients with chronic low back and leg pain were included. Of the 150 patients who underwent epiduroscopy in the year 2008 at a US hospital, 139 were available for evaluation at 1 month. STUDY: Outcome of treatment was predicted based on direct visual information (hyperemia, vascularity, and fibrosis) and mechanical information (pain to touch, contrast spread, and patency) obtained through epiduroscopy. MAIN OUTCOME MEASURES: Outcome of treatment was measured at 1 month. Accuracy of prediction of outcome was calculated using contingency tables and odds ratios. RESULTS: A prediction of outcome was made in 114 of 139 patients (82%). This prediction was correct in 89 of these 114 patients (accuracy of 78%). The sensitivity and specificity of epiduroscopy with respect to the prediction of outcome were 75% and 82%, respectively. These results were statistically significant (P < 0.01). In 25 of the 139 patients (18%), discrete epidural pathology was not observed. Nine of these 25 patients reported good relief after epiduroscopy. The sensitivity and specificity of epiduroscopy in the diagnosis of epidural pathology were 91% and 39%, respectively. These results were not statistically different (P > 0.1). CONCLUSION: Our results show that lumbosacral epiduroscopy predicts outcome of treatment accurately in the majority of patients. This suggests that information obtained through epiduroscopy may carry significant diagnostic and prognostic value.

Diagnosis of the vertebral level from which low back or leg pain originates. A comparison of clinical evaluation, MRI and epiduroscopy.

BACKGROUND: The precise localization of painful structures in the spine of patients with low back pain and/or pain radiating (LBP/RP) to the lower extremities is important for targeted therapeutic intervention. The aim of the study reported here was to determine and compare the spinal segment(s) where pain was elicited via endoscopic evaluation vs. the vertebral level from where the pain was thought to originate as determined by clinical evaluation and by MRI. METHODS: Observational cohort study of 143 patients 19 to 88 years of age undergoing spinal canal endoscopy (epiduroscopy) in a combined academic and private practice setting January 2008 to December 2008. Patients were asked whether pain generated by pressure upon epidural structures with the tip of an endoscope was similar in character and distribution (concordant) to the pain for which patients sought treatment. Notes from clinical evaluation and MRI reports were reviewed, and segmental level determined to be the locus of pathology was tabulated. RESULTS: One hundred twenty-five (87%) patients reported maximal reproducible pain at a specific level during epiduroscopy. The most common level was at L4 to L5 (87 patients). The least common level was L5 to S1 (2 patients). In only 40 patients did the level determined by clinical evaluation correlate with the level at which pain could be reproduced during epiduroscopy. MRI indicated a specific vertebral level that corresponded to the level at which pain could be reproduced during epiduroscopy in 28 of 143 (20%) patients. The results of the 3 diagnostic methods were significantly different (P < 0.01). CONCLUSION: Results of this study indicate that epiduroscopy is more reliable than is either clinical evaluation or MRI for determining the vertebral level where clinically significant spinal pathology occurs in patients with LBP/RP.

The peridural membrane of the spinal canal: a critical review.

There exists substantial evidence that a peridural membrane (PM) is present in the spinal canal of humans and, like the pleura and peritoneum, has one or more physiologic functions. Innervation of the PM suggests that it may become a source of pain if injured. Although debated, the physiology of this structure has important implications with respect to neuraxial distribution of drugs and for back and radiating pain. This review, separated into embryological, anatomic, and physiologic discussions, provides an in-depth summary of the observations of this connective tissue. The discrepancies between accounts are highlighted within each section. Focused research to clearly elucidate the true nature of the PM, especially as related to neuraxial distribution of drugs and back and radiating pain, is warranted.

Incidence and severity of epidural fibrosis after back surgery: an endoscopic study.

BACKGROUND: Epidural fibrosis has been implicated in the etiology of persistent pain after back surgery (Failed Back Surgery Syndrome [FBSS]). Using spinal endoscopy to view the lumbosacral epidural cavity, the incidence, severity, and appearance of epidural fibrosis was evaluated in patients with FBSS. METHODS: A prospective cohort observational study using epidural endoscopy was done involving 78 patients with persistent pain after back surgery. Patients were evaluated prospectively for the presence of epidural fibrosis and fibrosis was rated using a 4-level grading system based on appearance and resistance to epiduroscope advancement. The incidence of fibrosis detected by epiduroscopy vs. the incidence as reported in magnetic resonance imaging (MRI) studies for the same patients were compared. RESULTS: As diagnosed with epiduroscopy, 83.3% of all patients with persistent pain after back surgery had severe (grade 3 or 4) epidural fibrosis, while 91.0% had significant (grade 2, 3, or 4) fibrosis. In patients who had undergone more extensive surgery, severe fibrosis was present in 91.1% and significant fibrosis in 95.6%. Using MRI, epidural fibrosis was diagnosed only in 16.1% of these patients. All patients with severe epidural fibrosis had a filling defect on epidurography. Concordant pain was present in 84.3% of patients and depended on the severity of fibrosis. Results were statistically evaluated using analysis of frequencies and t-test. P < 0.05 was considered statistically significant. CONCLUSIONS: Epiduroscopy demonstrates that the prevalence of severe epidural fibrosis after FBSS is substantially higher than is generally reported in MRI evaluations. Severe epidural fibrosis is an underlying pathology in most patients with FBSS.

Cell types obtained from the epidural space of patients with low back pain/radiculopathy.

BACKGROUND: We investigated if correlations exist between medical history, tissue abnormalities, and cell types retrieved from the epidural space of patients with chronic low back pain (LBP) and chronic radicular pain (RP). METHODS: Approval was obtained from the Institutional Review Board for the Protection of Human Subjects to study 191 patients undergoing epiduroscopy. Visual inspection was performed and abnormal areas were identified. A specimen obtained from the area using a cytology brush was processed by the Thin Prep technique. Patients were divided into four groups based on the presence or absence and intensity of LBP and RP. The gender and age of the patients were recorded, as was any history of prior back surgery. Areas of tissue abnormalities were rated according to changes in vascularity and amount of fat, fibrosis, and inflammation. Stenosis was assessed from magnetic resonance imaging or computerized tomography scan images. Cytologic assessments included notations of the presence or absence of erythrocytes, leukocytes, cell groups, lipocytes, spindled cells, and large round cells. RESULTS: There was a significant difference in the number of patients from whom big round cells were obtained who had a high degree of LBP compared with the number of patients who had a high degree of both LBP and RP. CONCLUSIONS: The findings provide a foundation for future studies of cells obtained from similar patients with the goal of furthering the understanding of the pathogenesis of LBP/RP.

Ultrarapid opiate detoxification: a review.

PURPOSE: This review on ultrarapid detoxification examines the pharmacology, techniques, and efficacy of this potentially promising technique and contrasts it with conventional treatment modalities. SOURCE: The information found here is derived from experiences at the Texas Tech University, government reports, and peer reviewed journals. PRINCIPLE FINDINGS: Incidence and prevalence of heroin use is on the rise. Social and treatment costs suggest that this problem is staggering. Approximately 400,000 patients are enrolled in or are actively seeking methadone therapy. While many of these individuals want to undergo detoxification, traditional techniques, including methadone tapering are usually unsuccessful. The withdrawal syndrome is extremely unpleasant, may be fatal, and deters patients from completing the detoxification process. Ultrarapid detoxification entails general anesthesia in conjunction with large boluses of narcotic antagonists. This combination allows the individual to completely withdraw from the opiate without suffering the discomfort of the withdrawal syndrome. Unless performed properly, this procedure can be dangerous due to the sympathetic outflow. However, with proper support, this danger can be mitigated. CONCLUSION: Ultrarapid opiate detoxification, performed under the proper circumstances, is associated with few adverse events and is relatively comfortable for patients who seek treatment for their addition.