Dural Area Research Articles

Preliminary Clinical and Radiological Outcomes of the "No-Punch" Decompression Techniques for Unilateral Biportal Endoscopic Spine Surgery.

To avoid the most offending surgical instrument for dural tears, we develop a "no-punch" decompression technique for unilateral biportal endoscopic (UBE) spine surgery. This retrospective study enrolled 68 consecutive patients with degenerative lumbar spinal stenosis segments. The treatment results were evaluated using the visual analogue scale (VAS) for low back and leg pain, the Japanese Orthopaedic Association (JOA) scores, and the Oswestry Disability Index (ODI). Radiological outcomes were evaluated using the preoperative and postoperative magnetic resonance imaging. This study included 36 male and 32 female patients who received 109 segments of decompression, with an average age of 68.7 (37-90 years). The average operation time was 52.2 minutes. The average hospital stay was 3.1 days. There were no dural tears but 3 minor surgical complications, all treated conservatively. The VAS for low back and leg pain improved from 4.6 and 7.0 to 0.8 and 1.2. The JOA score improved from 16.2 to 26.8, with an improvement rate of 82.0%. The ODI improved from 50.1 to 18.7. All these improvements were statistically significant. The cross-sectional dural area improved from 61.1 to 151.3 mm2, with an average increase of 90.2 mm2 and 205.3%. 87.1% of the ipsilateral facet joints and 84.7% of the contralateral facet joints were preserved. In 61% of the decompressed segments, the ipsilateral facet joints were preserved better than the contralateral facet joints. The UBE "no-punch" decompression technique effectively avoids the dural tears. It provides effective neural decompression, excellent facet joint preservation, and good treatment outcomes.

Cerebrospinal fluid leakage due to dural thinning after endoscopic pituitary tumor resection.

Sellar reconstruction is important for preventing cerebrospinal fluid (CSF) leakage after transsphenoidal pituitary surgery. This report describes how, despite standard sellar reconstruction, CSF exudation resulted from dural thinning at the anterior skull base, outside the intrasellar area manipulated during pituitary tumor resection. A 76-year-old man underwent endoscopic transsphenoidal surgery for a pituitary tumor extending toward the anterior skull base. After opening the sellar floor, intractable bleeding from the anterior intercavernous sinus occurred during bone removal at the anterior skull base. Pseudocapsule-based extracapsular resection was completed after stopping the bleeding. On the 10th postoperative day, the patient developed CSF rhinorrhea complicated by marked pneumocephalus, and emergency endoscopic repair of the CSF leak was performed. CSF leakage originated from the thinned dura at the anterior skull base located outside the intrasellar area manipulated during tumor resection. The thinned dural area at the anterior skull base coincided with the site of intractable bleeding of the anterior intercavernous sinus during bone removal in tumor resection. The thinned anterior skull base dura was covered with fascia, overlaid with fat, and closed with the nasoseptal flap. Endoscopic CSF leak repair was successful. Severe damage to the anterior intercavernous sinus can cause extensive exposure of the single-layered inner meningeal dura, where thinning might result in CSF exudation. Therefore, use of autologous tissues to cover and reinforce the severely damaged area of the anterior intercavernous sinus might help prevent postoperative CSF exudation.

Risk Factors for Incidence of Postoperative Spinal Epidural Hematoma Following Multilevel Microendoscopic Laminectomy.

Introduction Due to the narrow portal of entry, microendoscopic laminectomy (MEL) is associated with a risk of postoperative spinal epidural hematoma (POSEH). This risk might be higher when performing multiple-level (m-) MEL. The purpose of this study is to clarify the incidence rate of POSEH following single-level (s-) and m-MEL by each interlaminar level and identify the risk factors for POSEH following m-MEL. Methods A total of 379 patients underwent MEL of the lumbar spine (s-MEL, n=141; m-MEL, n=238). We determined the incidence of POSEH following s-MEL and m-MEL by each interlaminar level. For m-MEL, we clarified the correlation between POSEH and possible risk factors, such as operative findings, the sequence of operated interlaminar levels, and the preoperative cross-sectional dural area (CSA) on magnetic resonance imaging. Results The incidence rate at L2/3 was significantly higher than that at L3/4 and L4/5. Patients who underwent L2/3 decompression at the end of the procedure showed a higher incidence of POSEH at the L2/3 level. Preoperative spinal stenosis was associated with POSEH at the L2/3 level, and CSA of 56 mm2 was a predictive factor for POSEH. Logistic regression analysis revealed that both were significant risk factors. Conclusions In patients undergoing m-MEL, the incidence of POSEH is highest at the L2/3 level, and treatment of the L2/3 level at the end of the procedure and the presence of spinal stenosis are risk factors for POSEH.

Surgery for craniovertebral junction pathologies: minimally invasive anterior submandibular retropharyngeal key-hole approach

BackgroundOur objective was to develop a new, minimally invasive surgical technique for the resolution of craniovertebral junction pathologies, which can eliminate the complications of the previous methods, like liquor-leakage, velopharyngeal insufficiency and wound-dehiscence associated with the transoral or lateral approaches.MethodsDuring the first stage of the operation, three patients underwent occipito-cervical dorsal fusion, while the fourth patient received C1–C2 fusion according to Harms. C1–C2 decompressive laminectomy was performed in all four cases. Ventral C1–C2 decompression with microscope assisted minimally invasive anterior submandibular retropharyngeal key-hole approach (MIS ASR) method was performed in the second stage. The MIS ASR—similarly to the traditional anterior retropharyngeal surgery—preserves the hard and soft palates, yet can be performed through a 25 mm wide incision with the use of only one retractor.ResultsThe MIS ASR approach was a success in all four cases, there were no intra- and postoperative complications. This method, compared to the transoral approach, provided on average 23% (4.56 cm2/6.05 cm2) smaller dural decompression area; nonetheless, the entire pathology could be removed in all cases. After the surgery, all patients have shown significant neurological improvement.ConclusionBased on the outcome of these four cases we think that the MIS ASR approach is a safe alternative to the traditional methods while improving patient safety by reducing the risk of complications.

Intermediate-Grade Meningeal Melanocytoma in a 19-Month- Old Child with Difficulties in Differential Diagnosis and Management.

Intermediate-grade meningeal melanocytoma (IGM) is a rare tumor that has not been reported in children so far. It is speculated to have more aggressive clinical behavior with undefined best management options. In this study, we present a 19-month-old girl as the first case with IGM in English literature. Preoperative diagnosis was ambiguous, given the unclear patient history and radiological features resembling a growing skull fracture or a congenital parietal bone agenesis subtype. During surgery, a dark gray-black dural area (5 × 7 cm in size) was found and then excised. However, the surgery was complicated due to brain edema and swelling, warranting a second surgery for reconstruction and dural repair. Of the 16 reported adult patients, 14 showed a high recurrence rate without adjuvant radiotherapy; 2 showed no recurrence with adjuvant radiotherapy. No adjuvant radiotherapy was given to our patient since she was 19 months old at the time of diagnosis and showed no recurrence at 48-month follow-up until now. Close monitoring with radiological imaging is of paramount importance for such cases.

Unilateral biportal endoscopic decompression for degenerative lumbar canal stenosis.

Unilateral biportal endoscopic (UBE) decompression is a minimally invasive (MI) approach to treat degenerative lumbar canal stenosis (DLCS). Decompression can be performed in a clear and magnified surgical field with proper control of normal saline inflow and outflow. Clinical and radiographic data of 81 consecutive patients of DLCS treated between July 2018 and Feb 2019 using UBE techniques were reviewed. They were 38 males and 43 females with an average age of 70.2. Sixty-nine had pure canal stenosis and 12 patients had associated spondylolisthesis. Bilateral decompression via unilateral laminotomy was performed from the side on patients with more severe neurological symptoms. This is a retrospective study from chart review and image analysis. Therefore, we don't have formal ethical information for this study, and it is not mandatory in our hospital. At the final follow-up, the mean VAS for low back pain was improved from 4.3±3.0 to 1.2±1.0 and the VAS for leg symptoms was improved from 7.3±2.2 to 0.9±0.7. The mean JOA score and ODI was significantly improved from 13.3±7.9 to 25.3±5.0 and from 54.6±16.9 to 14.6±12.6, respectively. Modified Macnab criteria were excellent in 47 patients (58.0%), good in 29 (35.8%), fair in 5 (6.2%). The average hospital stay was 3.6±2.4 days. MRI before and after the operation showed the cross-sectional dural area (CSDA) was significantly increased from 71.4±36.5 to 177.3±59.2 mm2, corresponding to a 201.9%±188.0% increase. The percentage of facet joint preservation was 84.2% on the approach side and 92.9% on the contralateral side. Complications included 4 dural tears, 1 transient motor weakness, 1 inadequate decompression, and 1 epidural hematoma. With UBE techniques, decompression for DLCS can be performed safely and effectively. The soft tissue and facet joint destruction are minimized; therefore, it is possible to avoid spinal fusion as well as to preserve the segmental stability.

Non-Trigeminal Nociceptive Innervation of the Posterior Dura: Implications to Occipital Headache.

Current understanding of the origin of occipital headache falls short of distinguishing between cause and effect. Most preclinical studies involving trigeminovascular neurons sample neurons that are responsive to stimulation of dural areas in the anterior 2/3 of the cranium and the periorbital skin. Hypothesizing that occipital headache may involve activation of meningeal nociceptors that innervate the posterior ⅓ of the dura, we sought to map the origin and course of meningeal nociceptors that innervate the posterior dura overlying the cerebellum. Using AAV-GFP tracing and single-unit recording techniques in male rats, we found that neurons in C2-C3 DRGs innervate the dura of the posterior fossa; that nearly half originate in DRG neurons containing CGRP and TRPV1; that nerve bundles traverse suboccipital muscles before entering the cranium through bony canals and large foramens; that central neurons receiving nociceptive information from the posterior dura are located in C2-C4 spinal cord and that their cutaneous and muscle receptive fields are found around the ears, occipital skin and neck muscles; and that administration of inflammatory mediators to their dural receptive field, sensitize their responses to stimulation of the posterior dura, peri-occipital skin and neck muscles. These findings lend rationale for the common practice of attempting to alleviate migraine headaches by targeting the greater and lesser occipital nerves with anesthetics. The findings also raise the possibility that such procedures may be more beneficial for alleviating occipital than non-occipital headaches and that occipital migraines may be associated more closely with cerebellar abnormalities than in non-occipital migraines.SIGNIFICANCE STATEMENT Occipital headaches are common in both migraine and non-migraine headaches. Historically, two distinct scenarios have been proposed for such headaches; the first suggests that the headaches are caused by spasm or tension of scalp, shoulders, and neck muscles inserted in the occipital region, whereas the second suggests that these headaches are initiated by activation of meningeal nociceptors. The current study shows that the posterior dura overlying the cerebellum is innervated by cervicovascular neurons in C2 DRG whose axons reach the posterior dura through multiple intracranial and extracranial pathways, and sensitization of central cervicovascular neurons from the posterior dura can result in hyper-responsiveness to stimulation of neck muscles. The findings suggest that the origin of occipital and frontal migraine may differ.

Stand-alone anterolateral lumbar interbody fusion for degenerative spondylolisthesis

Objective To evaluate the clinical outcome of anterolateral lumbar interbody fusion (ALLIF) for the treatment of degenerative lumbar spondylolisthesis(DLS). Methods All of 53 patients with degenerative spondylolisthesis were enrolled in this study during January 2014 to January 2016. All patients underwent stand-alone ALLIF with self-locked cage, including 15 males and 38 females with an average of 57.4±11.2 years old. The surgical level included L3,4(4 cases), L4,5(33 cases) and L5S1(16 cases). The operative time, bleed loss and complications were recorded. Clinical outcome was measured by visual analogue scale (VAS), Oswestry disability index (ODI) and the health questionnaire (SF-36). Radiological measures were slippage, disc height, lumbar lordosis, sagittal diameter and area of dural canal, foraminal height and area, and fusion rate. All the data were statistically analyzed. Results All patients were followed up for at least 24 months. The mean operation time was 64.2±12.5 minutes, and the mean bleed loss was 72.8±14.3 ml. No serious complications such as vascular or nerve injury occurred during peri operation. VAS for low back pain, VAS for leg pain and ODI were significantly decreased from 6.8±1.5, 5.6±2.4 and 58.5%±18.6% preoperatively to 1.6±1.2, 1.2±1.1 and 18.5%±8.8% at 24 months postoperatively. The SF-36 scores were improved significantly from 56.7±12.8 preoperatively to 79.4±14.3 at 24 months postoperatively. Slippage of patients was reduced significantly from 22.5%±8.3% preoperatively to 5.7%±2.3%. Disc height and lumbar lordosis were significantly increased from 6.2±1.6 mm and 46.4°±9.2° preoperatively to 10.5±1.4 mm and 53.2°±11.2° at 24 months postoperatively. Sagittal diameter and cross-sectional area of thecal sac were significantly increased from 11.7±2.2 mm and 78.4±28.6 mm2 preoperatively to 13.8±1.6 mm and 112.5±23.9 mm2 at 6 months postoperatively. Intervertebral foramina height and area were significantly increased from 15.8±4.3 mm and 136.5±25.6 mm2 preoperatively to 19.2±2.5 mm and 157.6±23.1 mm2 at 6 months postoperatively. At 24 months follow-up, the fusion rate was 100% and the subsidence rate was 10.5%. Conclusion Stand-alone ALLIF could achieve satisfactory clinical results and reduction for DLS. Disc height and lumbar lordosis were restored. Efficient decompression was obtained with significantly increased sagittal diameter and cross-sectional area of thecal sac and intervertebral foramina height and area. Stand-alone ALLIF provides a new surgical strategy for the treatment of DLS. Key words: Lumbar vertebrae; Spondylolysis; Surgical procedures, minimally invasive; Spinal fusion

Histological investigations on the dura mater vascular system of mice

The human dura mater encephali is a well innervated and vascularized membrane. Its vascular system plays a crucial role in disorders and pathological cases like dural hematoma, meningitis, and different headache types. To investigate these diseases mouse models are increasingly being used. However, the literature on the vascular system of the mouse dura mater is sparse and explicit studies concerned exclusively with its vasculature are lacking. Here we present a detailed light and scanning electron microscopic investigation of the supratentorial dura mater of the mouse species, with a focus on the largest part of it, the parietal dura mater. By utilizing different immunohistochemical and classical staining methods, a “cartography” of the vascular system was achieved. Additionally, the different blood vessel types with their mural cells were characterized. In contrast to humans, no arteries were found in the mouse parietal dura mater. Its supply is assured through frontolateral and occipital localized arteriolar branches. These arteriolar vessels exhibit in some specimens arteriolar anastomoses with one another. The venous blood is drained to the superior sagittal and transverse sinus through satellite venules accompanying the arterioles or through solitary venules. In all samples, large ruptured venules were identified in the frontolateral dural area. Scanning electron microscopy revealed that these vessels were ruptured on the dorsal side (skull bones-oriented side) of the dura. Our results contribute to the anatomical data on the mouse species and may set up a basis for fundamental investigation of disorders, for which the role of dural blood vessels is not yet clarified.

A partially ossified falx cerebri.

During a routine faculty prosection of the head and neck region of an adult female cadaver, a partial ossification of the falx cerebri was found. Ossification of other dural areas or regions of the body were not found. In addition, the brain and remaining organs appeared to be grossly normal. Reports of partial ossification of the falx cerebri are still rare and while certain pathologies such as nevoid basal cell carcinoma syndrome typically present with ossification of the falx on radiographs, the causal relationship of such an abnormality remains unclear.

Improved Magnetic Resonance Myelography of the Cervical Spine Using Image Fusion and Volumetry

Discrepancies between symptoms and imaging findings may be significant in spinal diseases. The relative advantages and disadvantages of postmyelographic CT (pmCT) and magnetic resonance myelography (MRM) in measuring cervical cerebrospinal fluid dimensions and volumes are poorly understood. This study investigated the usefulness of an improved MRM approach and compared its findings of dural areas and volumes of normal and pathologic cervical spine levels with those obtained by pmCT. Sixty patients with suspected cervical spinal stenosis underwent myelography, pmCT, and an improved MRM approach using a dedicated heavily T2-weighted magnetic resonance (MR) sequence in combination with image fusion. Cross-sectional areas and volumes of the dural sac from C2-3 to C7-T1 were compared for significance of differences between mean values. Pearson correlations between pmCT and MRM values were analyzed. Then 99% confidence intervals for normal levels and levels with obvious stenosis were calculated. For normal cervical levels we found no significant differences for both dural areas and volumes between pmCT and MRM. For cervical spine levels C3-4 to C6-7 with pathologic alterations, we found significant larger areas and volumes on MRM when compared with pmCT but not for the levels C2-3 and C7-T1. Both dural area and volume of normal and pathologic levels showed strong correlation between pmCT and MRM. We found no overlap between 99% confidence intervals for normal levels and stenotic levels. The optimized MRM approach (i.e., a dedicated MRM sequence in combination with image fusion) and pmCT demonstrated excellent quantitative volumetric agreement. Image fusion with conventional T2 may be used to aid in diagnosis.

Improved magnetic resonance myelography of the lumbar spine using image fusion and volumetry

The goal of this study was to investigate the usefulness and diagnostic potential of an improved MR myelography approach using a dedicated, heavily T2-weighted, 3D MRI sequence in combination with image fusion. A further aim was to compare dural areas and volumes of normal and pathological altered lumbar spine levels, and accuracy in the assessment of the stenoses, with those obtained by postmyelographic CT. Fifty patients underwent myelography, postmyelographic CT, and the improved MR myelography approach using a dedicated, heavily T2-weighted, 3D MRI sequence and image fusion. Dural cross-sectional areas and volumes for normal lumbar levels and levels with stenosis were calculated for postmyelographic CT and MR myelography data. The significant differences and Pearson correlations between dural cross-sectional areas and volumes from L1-2 to L5-S1 of postmyelographic CT and MR myelography were analyzed. The 99% CIs for normal and stenotic levels in patients with claudication distances less than 100 meters were calculated. For both dural areas and volumes in normal lumbar levels, the authors found no significant differences and strong correlations between postmyelographic CT and MR myelography. For the lower lumbar levels (L4-5 and L5-S1) they found significantly larger dural areas on MR myelography compared with postmyelographic CT, but not for the upper levels (L2-3 and L3-4). Dural volume analysis revealed significantly larger volumes for MR myelography at all 4 lumbar levels with stenoses in the cohort (L2-3 to L5-S1). Complete separation with no overlap was found between the 99% CIs for normal levels and stenotic levels. Differences in dural areas and volumes in this study may have been caused by the fact that in the case of a severely compressed thecal sac, the viscosity of the intrathecally applied contrast agent is too high in the framework of myelography. The gravitationally dependent component is thus too low to achieve sufficient fluid contrast. An optimized MR myelography approach-a dedicated 3D MR myelography sequence with high spatial resolution in combination with image fusion-is required to achieve a more reliable diagnosis of lumbar spine stenoses, especially with severe compression, compared with postmyelographic CT. This MR myelography approach may be helpful in preventing overestimation of lumbar spine stenoses. The upper limits of 99% CIs for stenotic levels can be interpreted as an indication for surgical treatment. However, further studies that include postoperative outcomes are required.

Intraoperative Myelography in Minimally Invasive Decompression for Degenerative Lumbar Spinal Stenosis

A retrospective comparative series study. To develop an intraoperative myelography protocol and determine its value on the treatment results in microendoscopic decompressive laminotomy (MEDL) for degenerative lumbar spinal stenosis. The MEDL is a minimally invasive but technically demanding technique for decompressing spinal stenosis. An intraoperatively assessing method for adequate decompression is lacking, but may be helpful and has positive value on the treatment results. Forty consecutive degenerative lumbar spinal stenosis patients receiving MEDL were included in this study. The earlier 20 patients received MEDL without myelography (the traditional group); the later 20 patients received MEDL with the myelography protocol (the myelography group). An additional intraoperative myelography was performed in the myelography group to help localizing the stenosis before decompression and verifying adequate decompression after decompression. Any residual filling defects identified in the postdecompression myelogram were considered signs of inadequate decompression and additional decompression was performed until they resolved. Inadequate decompression was identified in 4 of 20 patients in the myelography group, but none in the traditional group. Both groups had significant improvement after surgery. However, the myelography group had significantly better results with lower 6-month Oswestry Disability Index (ODI) (6 vs. 10, P=0.049), more ODI improvement (44 vs. 28, P=0.009), higher Japanese Orthopedic Association (JOA) scores (27.5 vs. 24, P=0.043), a higher JOA improvement rate (92.8% vs. 73.2%, P=0.013), and greater decompression effect (56.8% vs. 41.4% cross-sectional dural area, P=0.024). The myelography group also had a higher proportion of patients to have "significant ODI improvement," "JOA success," and "JOA good-to-excellent results." There were no myelography-related complications. The intraoperative myelography protocol provides a simple method to precisely localize the stenosis and verifies the adequacy of decompression; hence, improves the treatment result of MEDL.

Comparison of Magnetic Resonance Imaging and Computed Tomogram-Myelography for Evaluation of Cross Sections of Cervical Spinal Morphology

Comparison of magnetic resonance imaging (MRI) and computed tomography-myelography (CTM) for cervical intracanalar dimensions. To compare the capability and reproducibility of MRI and CTM in measuring the cross-sectional morphology of intracanalar lesions of the cervical spine. The relative advantages and disadvantages of MRI and CTM in measuring cervical intracanalar dimensions are poorly understood. MRI and CTM were used to measure cervical disc levels in 45 subjects with various cervical spinal diseases. Measurements included dural area, dural anteroposterior (A-P) diameter, dural right-left (RL) diameter, cord area, cord anteroposterior (A-P) diameter, cord right-left (RL) diameter and cerebrospinal fluid (CSF) space (anterior and posterior). Each section was graded by 2 orthopedic surgeons for degree of stenosis (Grades, 0-3), and the intra- and interobserver reproducibility of these measurements (intraclass correlation coefficients: ICC) was assessed. In both CTM and MRI, intra- and interobserver reproducibility (ICC) ranged from 0.702 to 0.989, suggesting that both imaging methods are reproducible. Importantly, CTM measurements of dural area, dural A-P diameter, dural RL diameter, and CSF space (anterior and posterior) were slightly, but significantly (P < 0.001), larger than MRI measurements. In contrast, MRI measurements of cord area, cord A-P diameter, and cord RL diameter were slightly, but significantly (P < 0.001), larger than CTM measurements. Degree of stenosis was significantly more severe in MRI than in CTM. Both CTM and MRI provided reproducible measurements of cervical intracanalar dimensions. Measurements of dura were slightly larger in CTM, whereas measurements of spinal cord were slightly larger in MRI, making stenosis more severe in MRI than in CTM. The clinical relevance of these slight differences requires further examination.

Comparison of Magnetic Resonance Imaging and Computed Tomography-Myelography for Quantitative Evaluation of Lumbar Intracanalar Cross-Section

PurposeA comparison of MRI and computed tomography-myelography (CTM) for lumbar intracanalar dimensions. To compare the capability and reproducibility of MRI and CTM in measuring the cross-sectional morphology of intracanalar lesions of the lumbar spine.Materials and MethodsMRI and CTM of lumbar disc levels from 61 subjects with various lumbar spinal diseases were studied. Dural area, dural anteroposterior (AP) diameter, dural right-left diameter, and thickness of the ligamentum flavum were measured by two orthopedic surgeons. Each section was graded by degree of stenosis. Absolute value and intra- and inter-observer correlation coefficients (ICC) of these measurements and the associations between MRI and CTM values were determined.ResultsExcept for MRI determination of ligament flavum thickness, CTM and MRI and intra- and ICC suggested sufficient reproducibility. When measurements of dural area, dural AP diameter, and RL diameter were compared, values in CTM were significantly (p = 0.01-0.004) larger than those in MRI (CTM/MRI ratios, 119%, 111%, and 105%, respectively). As spinal stenosis became more severe, discrepancies between CTM and MRI in measurements of the dural sac became larger.ConclusionBoth CTM and MRI provided reproducible measurements of lumbar intracanalar dimensions. However, flavum thickness may be more accurately measured by CTM. Because the differences in the measurements between CTM and MRI are very slight and there is very little data to suggest that the precise degree of stenosis is related to symptoms or treatment outcome, the usefulness of the CTM over MRI needs to be confirmed in future studies.

Postural Changes of the Dural Sac in the Lumbar Spines of Asymptomatic Individuals Using Positional Stand-Up Magnetic Resonance Imaging

Positional magnetic resonance imaging (MRI) study of control subjects. To determine dimensional changes in the lumbar dural sac as a function of posture, and to establish changes between the supine, erect and seated positions. Studies using computerized tomography and MRI were done to determine the mechanical effects on the lumbar spinal canal in the different positions. There has been no consecutive study, however, in which normal individuals were investigated for positional changes of the dural sac, including true standing position. Thirty-two male asymptomatic volunteers were recruited. The examination was performed using a new MRI system. All subjects were examined with sagittal T2 and axial T1-weighted spin-echo images. The subjects were studied in the supine, standing, and sitting positions. The measurements were made using OSIRIS software (Digital Imaging Unit University Hospital of Geneva, Geneva, Switzerland). On axial images, dural sac cross-sectional area and anteroposterior (AP) dural sac diameter were measured at the level of the L3/4, L4/5, and L5/S1 discs. On midsagittal images, AP dural sac diameter and the upper-endplate angles of L1 and S1 were measured. We found a disc degeneration or disc protrusion in 41% (12/29) of the subjects, but there was no obvious compression of the dural sac. Depending on the postures, the mean dural sac cross-sectional area and AP dural sac diameter changed. At all levels, mean dural sac cross-sectional area in the supine position was significantly smaller than in other postures. The dural area decreased most at the L5/S1 level due to positional change from standing to supine. The largest dural area at the L5/S1 level was in sitting extended. AP dural sac diameter on axial and midsagittal images showed a similar tendency. A significant posture-dependent difference of the dural sac cross-sectional area at the level of intervertebral disc in asymptomatic volunteers has been demonstrated. When the posture changed from supine to standing position, lumbar dural sac volume expanded by the increased pressure of cerebrospinal fluid, and the dural sac cross-sectional area increased. The smallest values were found in the supine position.

Osteopontin and bone metabolism in healing cranial defects in rabbits

Non-collagen proteins such as bone sialoprotein and osteopontin (OPN) form 10% of the extracellular bone matrix. In this study, the influence of OPN on bone repair was investigated. Human OPN (Innogenetics ®) was produced by a recombinant technique and bonded onto the surface of hydroxyapatite (Interpore 200 ®). Thirty rabbits were divided into six equal groups. A circular defect (10 mm) was prepared in each parietal bone. In four rabbits of each group the left and right defects were filled with either OPN-coated hydroxyapatite (OPN-HA) or non-coated hydroxyapatite (HA). One sham animal of each group received no implants. The animals were killed after 1, 2, 6, 12, 18 and 30 weeks. The histological sections were scanned and analysed digitally. There were no statistically significant differences in total bone formation between defects filled with OPN-HA and HA. Bone formation at the borders of the healing area was significantly higher in defects filled with OPN-HA than in those filled with HA. Less bone formation was noted in the OPN-HA and HA groups at the centre of the healing area than at the borders of the healing area and the dural area. Although some animals in the sham group showed a high level of bone formation in the dural area, this was not significantly different to that in the dural area of the other groups. There was no sign of infection or tissue rejection of the graft.

Effects of Epidural Saline Injection on Cerebrospinal Fluid Volume and Velocity Waveform

The phenomenon of epidural "top-up" (increased spread of local anesthetic due to epidural fluid injection) is explained partly by an epidural volume effect. This study was designed to investigate the change in cerebrospinal fluid (CSF) volume and velocity waveform induced by epidural saline injection. (1) Lumbar epidural catheters were placed in 28 patients. Magnetic resonance images were obtained for measurements of lumbosacral CSF volume and velocity waveform. Saline was injected into the epidural space through the catheter to three groups of randomly assigned patients: 5-ml saline (n = 10), 10-ml saline (n = 9), and 15-ml saline (n = 9) groups. A repeat image series was performed after epidural injection to compare CSF volume and velocity waveform before and after epidural injection. (2) We also examined the time course of dural sac compression after epidural saline injection in a separate series. Seven axial images at disk levels from T11-T12 to L5-S1 were obtained before injection and 1, 3, 5, 10, 15, 20, 25, and 30 min after 10-ml saline injection to compare each dural area before and after injection. (1) Saline injected through the epidural catheter compressed the dural sac with variability of the extent of compression, resulting in a significantly decreased CSF volume in all patients (P <== 0.001). The mean reductions in CSF volume were 2.0 +/- 1.0 ml in the 5-ml group, 4.4 +/- 1.4 in the 10-ml group, and 7.2 +/- 2.6 in the 15-ml group. There were significant differences among the three groups (P < 0.05 approximately 0.001). After the saline injection, the synchronization between the CSF velocity waveform and the cardiac cycle disappeared in significantly more patients in the 10-ml group (7 of 9 patients) than in the other groups (P < 0.05). However, there was no significant relation between measures of CSF velocity waveform and dural area in any patient. (2) The maximum reduction of the sum of the total of seven disk areas occurred 5 min after epidural saline injection; thereafter, dural compression was gradually restored but did not return to the value before injection for 30 min. These findings indicate that the reduction in CSF volume was injection-volume dependent, dural compression lasted at least 30 min after saline injection, and the changes of the CSF flow dynamics did not correlate with the degree of dural sac compression.

Functional immunohistochemistry of neuropeptides and nitric oxide synthase in the nerve fibers of the supratentorial dura mater in an experimental migraine model.

The supratentorial cerebral dura of the albino rat is equipped with a rich sensory innervation both in the connective tissue and around blood vessels, which includes nociceptive axons and their terminals; these display intense calcitonin gene-related peptide (CGRP) immunoreactivity. Stereotactic electrical stimulation of the trigeminal (Gasserian) ganglion, regarded as an experimental migraine model, caused marked increase and disintegration of club-like perivascular CGRP-immunopositive nerve endings in the dura mater and induced an apparent increase in the lengths of CGRP-immunoreactive axons. Intravenous administration of sumatriptan or eletriptan, prior to electrical stimulation, prevented disintegration of perivascular terminals and induced accumulation of CGRP in terminal and preterminal portions of peripheral sensory axons. Consequently, immunopositive terminals and varicosities increased in size; accumulation of axoplasmic organelles resulted in the "hollow" appearence of numerous varicosities. Since triptans exert their anti-migraine effect by virtue of agonist action on 5-HT(1D/B) receptors, we suggest that these drugs prevent the release of CGRP from perivascular nerve terminals in the dura mater by an action at 5-HT(1D/B) receptors. Nitroglycerine (NitroPOHL), given subcutaneously to rats, induces increased beading of nitric oxide synthase (NOS)-immunoreactive nerve fibers in the supratentorial cerebral dura mater, and an apparent increase in the number of NOS-immunoreactive nerve fibers in the dural areas supplied by the anterior and middle meningeal arteries, and the sinus sagittalis superior. Structural alterations of nitroxidergic axons innervating blood vessels of the dura mater support the idea that nitric oxide (NO) is involved in the induction of headache, a well-known side effect of coronary dilator agents.

A Sequence Stratigraphic Analysis of the Late Permian Succession in the Dural Area, Central Sydney Basin, New South Wales

This paper presents the results of an integrated core, wireline log and seismic sequence stratigraphic analysis, and structural interpretation, of the Late Permian Illawarra Coal Measures, within the central coalfield, Sydney Basin, New South Wales, using data obtained from an AGEX Pty Ltd exploration programme. Five stratigraphic sequences were correlated from the southern coalfield into the central coalfield, using well control, and were then tied into a local grid of reprocessed single-fold, and more recently acquired multi-fold, seismic data. Time-structure form maps within the Illawarra Coal Measures are presented, together with isochron (time-thickness) maps of five sequences recognised within the upper part of that stratigraphic interval. The structural interpretation and trap validity of the previously explored Dural Dome, within the central coalfield of the Sydney Basin, were revisited during this study and the remaining hydrocarbon potential of that feature has been demonstrated to be relatively small.