Functional characterization of the dural sinuses as a neuroimmune interface.

Despite the established dogma of central nervous system (CNS) immune privilege, neuroimmune interactions play an active role in diverse neurological disorders. However, the precise mechanisms underlying CNS immune surveillance remain elusive; particularly, the anatomical sites where peripheral adaptive immunity can sample CNS-derived antigens and the cellular and molecular mediators orchestrating this surveillance. Here, we demonstrate that CNS-derived antigens in the cerebrospinal fluid (CSF) accumulate around the dural sinuses, are captured by local antigen-presenting cells, and are presented to patrolling T cells. This surveillance is enabled by endothelial and mural cells forming the sinus stromal niche. T cell recognition of CSF-derived antigens at this site promoted tissue resident phenotypes and effector functions within the dural meninges. These findings highlight the critical role of dural sinuses as a neuroimmune interface, where brain antigens are surveyed under steady-state conditions, and shed light on age-related dysfunction and neuroinflammatory attack in animal models of multiple sclerosis.

Cranial Suture Regeneration Mitigates Skull and Neurocognitive Defects in Craniosynostosis.

Craniosynostosis results from premature fusion of the cranial suture(s), which contain mesenchymal stem cells (MSCs) that are crucial for calvarial expansion in coordination with brain growth. Infants with craniosynostosis have skull dysmorphology, increased intracranial pressure, and complications such as neurocognitive impairment that compromise quality of life. Animal models recapitulating these phenotypes are lacking, hampering development of urgently needed innovative therapies. Here, we show that Twist1+/- mice with craniosynostosis have increased intracranial pressure and neurocognitive behavioral abnormalities, recapitulating features of human Saethre-Chotzen syndrome. Using a biodegradable material combined with MSCs, we successfully regenerated a functional cranial suture that corrects skull deformity, normalizes intracranial pressure, and rescues neurocognitive behavior deficits. The regenerated suture creates a niche into which endogenous MSCs migrated, sustaining calvarial bone homeostasis and repair. MSC-based cranial suture regeneration offers a paradigm shift in treatment to reverse skull and neurocognitive abnormalities in this devastating disease.

Meningeal γδ T cells regulate anxiety-like behavior via IL-17a signaling in neurons.

Interleukin (IL)-17a has been highly conserved during evolution of the vertebrate immune system and widely studied in contexts of infection and autoimmunity. Studies suggest that IL-17a promotes behavioral changes in experimental models of autism and aggregation behavior in worms. Here, through a cellular and molecular characterization of meningeal γδ17 T cells, we defined the nearest central nervous system-associated source of IL-17a under homeostasis. Meningeal γδ T cells express high levels of the chemokine receptor CXCR6 and seed meninges shortly after birth. Physiological release of IL-17a by these cells was correlated with anxiety-like behavior in mice and was partially dependent on T cell receptor engagement and commensal-derived signals. IL-17a receptor was expressed in cortical glutamatergic neurons under steady state and its genetic deletion decreased anxiety-like behavior in mice. Our findings suggest that IL-17a production by meningeal γδ17 T cells represents an evolutionary bridge between this conserved anti-pathogen molecule and survival behavioral traits in vertebrates.

Meningeal Mechanisms and the Migraine Connection.

Migraine is a complex neurovascular pain disorder linked to the meninges, a border tissue innervated by neuropeptide-containing primary afferent fibers chiefly from the trigeminal nerve. Electrical or mechanical stimulation of this nerve surrounding large blood vessels evokes headache patterns as in migraine, and the brain, blood, and meninges are likely sources of headache triggers. Cerebrospinal fluid may play a significant role in migraine by transferring signals released from the brain to overlying pain-sensitive meningeal tissues, including dura mater. Interactions between trigeminal afferents, neuropeptides, and adjacent meningeal cells and tissues cause neurogenic inflammation, a critical target for current prophylactic and abortive migraine therapies. Here we review the importance of the cranial meninges to migraine headaches, explore the properties of trigeminal meningeal afferents, and briefly review emerging concepts, such as meningeal neuroimmune interactions, that may one day prove therapeutically relevant.

Identification of direct connections between the dura and the brain.

The arachnoid barrier delineates the border between the central nervous system and dura mater. Although the arachnoid barrier creates a partition, communication between the central nervous system and the dura mater is crucial for waste clearance and immune surveillance1,2. How the arachnoid barrier balances separation and communication is poorly understood. Here, using transcriptomic data, we developed transgenic mice to examine specific anatomical structures that function as routes across the arachnoid barrier. Bridging veins create discontinuities where they cross the arachnoid barrier, forming structures that we termed arachnoid cuff exit (ACE) points. The openings that ACE points create allow the exchange of fluids and molecules between the subarachnoid space and the dura, enabling the drainage of cerebrospinal fluid and limited entry of molecules from the dura to the subarachnoid space. In healthy human volunteers, magnetic resonance imaging tracers transit along bridging veins in a similar manner to access the subarachnoid space. Notably, in neuroinflammatory conditions such as experimental autoimmune encephalomyelitis, ACE points also enable cellular trafficking, representing a route for immune cells to directly enter the subarachnoid space from the dura mater. Collectively, our results indicate that ACE points are a critical part of the anatomy of neuroimmune communication in both mice and humans that link the central nervous system with the dura and its immunological diversity and waste clearance systems.

Venous-plexus-associated lymphoid hubs support meningeal humoral immunity.

There is increasing interest in how immune cells in the meninges-the membranes that surround the brain and spinal cord-contribute to homeostasis and disease in the central nervous system1,2. The outer layer of the meninges, the dura mater, has recently been described to contain both innate and adaptive immune cells, and functions as a site for B cell development3-6. Here we identify organized lymphoid structures that protect fenestrated vasculature in the dura mater. The most elaborate of these dural-associated lymphoid tissues (DALT) surrounded the rostral-rhinal confluence of the sinuses and included lymphatic vessels. We termed this structure, which interfaces with the skull bone marrow and a comparable venous plexus at the skull base, the rostral-rhinal venolymphatic hub. Immune aggregates were present in DALT during homeostasis and expanded with age or after challenge with systemic or nasal antigens. DALT contain germinal centre B cells and support the generation of somatically mutated, antibody-producing cells in response to a nasal pathogen challenge. Inhibition of lymphocyte entry into the rostral-rhinal hub at the time of nasal viral challenge abrogated the generation of germinal centre B cells and class-switched plasma cells, as did perturbation of B-T cell interactions. These data demonstrate a lymphoid structure around vasculature in the dura mater that can sample antigens and rapidly support humoral immune responses after local pathogen challenge.

The movers and shapers in immune privilege of the CNS.

Discoveries leading to an improved understanding of immune surveillance of the central nervous system (CNS) have repeatedly provoked dismissal of the existence of immune privilege of the CNS. Recent rediscoveries of lymphatic vessels within the dura mater surrounding the brain, made possible by modern live-cell imaging technologies, have revived this discussion. This review emphasizes the fact that understanding immune privilege of the CNS requires intimate knowledge of its unique anatomy. Endothelial, epithelial and glial brain barriers establish compartments in the CNS that differ strikingly with regard to their accessibility to immune-cell subsets. There is a unique system of lymphatic drainage from the CNS to the peripheral lymph nodes. We summarize current knowledge on the cellular and molecular mechanisms involved in immune-cell trafficking and lymphatic drainage from the CNS, and we take into account differences in rodent and human CNS anatomy.

Bridging anatomical gaps between brain and immune system.

It is increasingly clear that the central nervous system (CNS) relies significantly on both adaptive and innate immune cells for its repair and lifelong maintenance. These interactions hold profound implications for brain aging and neurodegeneration. Recent work by Smyth et al. describes newfound anatomical connections between the brain and dura mater, which they named the arachnoid cuff exit points.

Neonatal IL-4 Over-Exposure is Accompanied by Macrophage Accumulation in Dura Mater After Instant Anti-inflammatory Cytokine Response in CSF.

Multiple studies have shown that clinical events resulting into neonatal IL-4 over-exposure, such as asthma in early life and food allergy, were associated with brain damage and that the neuroinflammation induced by them might lead to cognitive impairments, anxiety-/depressive-like behaviors. IL-4 is the most major elevated cytokine in periphery when these clinical events occur and peripheral IL-4 level positively correlates with the severity of those events. Our previous studies have verified that neonatal IL-4 over-exposure induced a delayed neuroinflammatory damage in rodents, which might have adverse implications for brain development and cognition. Neuroinflammation in brain parenchyma is often accompanied by changes in CSF cytokines levels. However, whether the cytokines levels in CSF change after neonatal IL-4 over-exposure is unknown. Here, we found a delayed pro-inflammatory cytokines response (higher IL-6, IL-1ß and, TNF levels) in both hippocampus and CSF after an instant anti-inflammatory cytokine response in IL-4 over-exposed rats. Moreover, the pro-inflammatory cytokines response appeared earlier in CSF than in hippocampus. The level of each of the pro-inflammatory cytokines in CSF positively correlated with that in hippocampus at the age of postnatal day 42. More microglia numbers/activation and higher M-CSF level in the hippocampus in IL-4 over-exposed rats were also observed. Furthermore, there were more macrophages with inflammatory activation in dural mater of IL-4 over-exposed rats. In sum, neonatal IL-4 over-exposure in rats induces delayed inflammation in CSF, suggesting CSF examination may serve as a potential method in predicting delayed neuroinflammation in brain following neonatal IL-4 over-exposure.

Near-infrared spectroscopy to measure brain oxygenation: A comparison of measurements on the skin, skull and dura mater.

BACKGROUND: The reliability of near-infrared spectroscopy (NIRS) for measuring cerebral oxygenation (ScO2 ) is controversial due to the possible contamination from extracranial tissues. We compared ScO2 measured with the NIRS optode on the forehead, the skull and the dura mater in anaesthetised patients undergoing craniotomy. We hypothesised that ScO2 measured directly on the skull and the dura mater would differ from ScO2 measured on the skin. METHODS: This prospective observational study included 17 adult patients scheduled for elective craniotomy. After induction of general anaesthesia, ScO2 was measured on the forehead skin, as well as on the skull and on the dura mater in the surgical field. The primary comparison was the difference in ScO2 measured on the dura mater and on ScO2 measured on the skin; secondary comparisons were the differences in ScO2 on the skull and ScO2 on the skin and the dura mater, respectively. Data were described with median (5%-95% range) and analysed with the Wilcoxon signed-rank test. RESULTS: ScO2 values on the dura mater were obtained in 11 patients, and median ScO2 (48%, 29%-95%) did not differ significantly from ScO2 on the skin (73%, 49%-92%; p = .052), median difference -25% (-35.6% to -1.2%). ScO2 on the skull (N = 16) was lower than that on the skin (63% [43%-79%] vs. 75% [61%-94%]; p = .0002), median difference -10% (-20.8 to -3.0). CONCLUSION: In adults undergoing craniotomy, NIRS-based ScO2 measured on the dura mater did not reach statistically significantly lower values than ScO2 measured on the skin, whereas values on the skull were lower than on the skin, indicating a contribution from scalp tissue to the signal.

Safety and effectiveness of Evicel® fibrin sealant as an adjunct to sutured dural repair in children undergoing cranial neurosurgery.

PURPOSE: Cerebrospinal fluid (CSF) leakage is a challenging complication of intradural cranial surgery, and children are particularly at risk. The use of dural sealants confers protection in adults, but pediatric studies are scarce. We evaluated the safety and efficacy of Evicel® fibrin sealant as an adjunct to primary dural suturing in children undergoing cranial surgery. METHODS: A multicenter trial prospectively enrolled pediatric subjects (< 18 years) undergoing cranial neurosurgery who, upon completion of primary sutured dural repair, experienced CSF leakage. As agreed by the EMA Evicel® Pediatric Investigation Plan, 40 subjects were intra-operatively randomized 2:1 to Evicel® or additional sutures ('Sutures'). Data analysis was descriptive. The efficacy endpoint was treatment success rate, with success defined as intra-operative watertight closure after provocative Valsalva maneuver (primary endpoint). Safety endpoints were postoperative CSF leakage (incisional CSF leakage, pseudomeningocele or both) and surgical site complications (secondary endpoints). RESULTS: Forty subjects (0.6-17 years) were randomized to Evicel® (N = 25) or Sutures (N = 15) (intention-to-treat). Intracranial tumor was the most common indication and procedures were mostly supratentorial craniotomies. Success rates were 92.0% for Evicel® and 33.3% for Sutures, with a 2.76 estimated ratio of success rates (Farrington-Manning 95% CI [1.53, 6.16]). Sensitivity analyses in per-protocol and safety sets showed similar results. Despite a higher rescue treatment rate, the frequencies of postoperative CSF leakage and wound complications were higher for Sutures than for Evicel®. CONCLUSION: This small-scale prospective study shows Evicel® treatment to be safe and effective as an adjunct to primary sutured dura mater closure in a pediatric population. Compared to additional sutures, Evicel® was associated with reduced postoperative CSF leakage and surgical site complications. (Trial registration: The trial was registered as NCT02309645 and EudraCT 2013-003558-26).

Duraplasty with autologous cervical fascia in pediatric posterior fossa tumor surgery: a single-center experience with 214 cases.

PURPOSE: Posterior fossa surgeries for pediatric tumors pose challenges in achieving optimal dural repair and duraplasty is usually required. Autografts, allografts, xenografts, and synthetic substitutes can be used for duraplasty. Autologous cervical fascia can be a safe and reliable graft option for duraplasty after posterior fossa surgeries. This study aims to investigate the outcomes of duraplasty with autologous cervical fascial graft in children after posterior fossa surgery for pediatric brain tumors. METHODS: Pediatric patients with posterior fossa tumor who underwent surgery between March 2001 and August 2022 were retrospectively reviewed. Data on demographics, preoperative symptoms, diagnosis, tumor characteristics, hydrocephalus history, and postoperative complications, including cerebrospinal fluid (CSF) leakage, pseudomeningocele, and meningitis were collected. Logistic regression analysis was performed to explore risk factors for postoperative complications. RESULTS: Patient cohort included 214 patients. Autologous cervical fascia was used in all patients for duraplasty. Mean age was 7.9 ± 5.3 years. Fifty-seven patients (26.6%) had preoperative hydrocephalus and 14 patients (6.5%) received VPS or EVD perioperatively. Postoperative hydrocephalus was present in 31 patients (14.5%). Rates of CSF leak, pseudomeningocele, and meningitis were 4.2%, 2.8%, and 4.2% respectively. Logistic regression analysis revealed that postoperative EVD and VPS placement were the factors associated with postoperative complications. CONCLUSION: Autologous cervical fascia is a safe and reliable option for duraplasty with minimal risk of postoperative complications. The straightforward surgical technique and with no additional cost for harvesting the graft renders autologous cervical fascia a favorable alternative for resource-limited countries or surgical settings.

Post-craniotomy leptomeningeal cyst: a new presentation of an old problem.

Leptomeningeal cyst (LMC) is a known complication of pediatric head injury but has not been described following a craniotomy other than for craniosynostosis. We present the case of a 20-month-old boy who underwent craniotomy for a traumatic epidural hematoma. There was an inadvertent tear of the dura which was repaired with a pericranial patch and dural sealant. The patient presented with a progressive surgical site swelling 5 months post-surgery and a CT scan revealed an LMC with elevation of the bone flap. He underwent re-exploration with watertight repair of the dural defect and rigid fixation of the bone flap. This iatrogenic LMC provides an opportunity to compare and confirm the pathogenesis vis a vis the more common spontaneous post-traumatic LMC. Our report highlights the importance of proper dural closure and bone fixation after craniotomy in children whose skulls are still growing.

"The novel dura substitute: a revolutionary advancement in neurosurgery".

This Article provides a concise summary of the comprehensive exploration into the dura mater, dural tears, and the groundbreaking medical device, ArtiFascia® Dura Substitute. The neuroanatomy of the dura mater is elucidated, emphasizing its resilience and susceptibility to tears during spinal surgery. Dural repair methods are scrutinized, with research findings revealing the efficacy of primary closure with or without a patch.The introduction of ArtiFascia®, a nanofiber-based resorbable dural repair graft, represents a pivotal moment in neurosurgery. Obtaining 510(k) clearance from the FDA, ArtiFascia® demonstrates exceptional biological benefits, including enhanced cellular adhesion and tissue regeneration. The device's safety is affirmed through chemical analysis and toxicological risk assessment.The NEOART study, a randomized clinical trial involving 85 subjects across prominent European medical centers, validates ArtiFascia®'s superiority over existing dural substitutes. Noteworthy findings include exceptional graft strength, durability, and its ability to withstand physiological pressures.In conclusion, ArtiFascia® marks a revolutionary era in neurosurgery, promising safer and more effective solutions. This innovative device has the potential to elevate standards of care, offering both patients and surgeons an improved experience in navigating the complexities of neurosurgical procedures. The abstract encapsulates the key elements of the research, emphasizing the transformative impact of ArtiFascia® in the field.

Oral bacterial genic expression detection in aneurysm wall of a French population sample - preliminary monocentric study.

INTRODUCTION: The etiology of brain aneurysms remains poorly understood. Finnish research suggests that oral bacteria might contribute to the development and rupture of brain aneurysms. Previous studies by our team have not confirmed these findings, likely due to methodological differences. We aimed to replicate the Finnish study with a French population, using the same primers and comparing the results to internal controls. METHODS: We used RT-qPCR to retrospectively analyze the expression of oral bacterial genes in eight patients. During surgical procedures, four tissue types were consistently sampled from each patient: the aneurysmal wall, the superficial temporal artery (STA), the middle meningeal artery (MMA), and the dura mater (DM). Results were expressed as fold differences employing the 2-∆∆Ct method, and statistical analyses were performed accordingly. RESULTS: Our cohort included eight patients, evenly split into ruptured and unruptured groups. The sex distribution was balanced (4 females, 4 males). We observed DNA expression from oral bacteria in all sampled tissues; however, there were no significant differences between the ruptured and unruptured groups. CONCLUSION: We detected oral bacterial gene expression in the aneurysmal wall, STA, MMA, and DM in a sample of French patients. Although limited by the small sample size, our results suggest a potential role for bacterial involvement in vascular invasiveness related to bacteremia. These findings do not definitively link oral bacteria to the pathogenesis of aneurysm development and rupture.

Dural arteriovenous fistulas in the falx cerebri: case series and literature review.

Dural arteriovenous fistulas (DAVFs) within the falx cerebri are infrequently documented and may be linked with the falcine sinus/venous plexus. The falcine sinus/venous plexus, often regarded as a normal venous structure, can exhibit pathological characteristics, differing from the persistent fetal falcine sinus. A retrospective analysis was conducted at a single center to identify all cases of DAVFs within the falx cerebri spanning from 2002 to 2022. Demographic data, fistula features, treatment modalities, clinical outcomes, and fistula closure were collected and analyzed. Additionally, relevant literature on DAVFs in this location was reviewed. Ten cases were identified at our center, supplemented by 13 cases reported in the literature. In our cohort, patients had an average age of 49.4 ± 8.1 years, with a male predominance of 90%. Trans-arterial embolization (TAE) alone achieved immediate complete occlusion in eight cases, while conservative treatment was pursued in two cases. No treatment-related complications or fistula recurrences were observed. In the literature, seven patients underwent direct surgery, three underwent TAE, and one underwent both direct surgery and radiosurgery for complete fistula closure. No instances of fistula recurrence or treatment complications were reported. Dural arteriovenous fistulas within the falx cerebri are rare, with limited literature available. They typically present as aggressive lesions. Treatment options include direct surgery or TAE. However, due to a lack of long-term DSA follow-up, the cure and recurrence rates are unknown for endovasdcular therapy. Further investigation is warranted to elucidate the involvement of the falcine sinus/venous plexus in falx cerebri DAVFs.

"Curtain-fall" technique for cerebrospinal fluid leak prevention after removal of intradural drainage. Technical note: application in chronic subdural hematoma surgery.

OBJECTIVE: Chronic subdural hematoma (CSDH) is frequently met in neurosurgical practice and often need urgent surgical treatment in case of neurological deterioration. Different surgical approaches to evacuate CSDH are described in the literature. In our experience, an external drainage system is crucial in order to avoid recurrences. We recently encountered a case of subcutaneous CSF collection after drainage removal. Thus, we developed a simple surgical technique to prevent postoperative CSF leak after subdural drainage system removal. METHOD: We have developed a technique in which the periosteum is harvested during the surgery prior to the evacuation of the hemorrhage and fixed with sutures on the uncut dura mater opposite and laterally to the exit of the catheter exiting the dural hole caused by the passage of the Jackson-Pratt subdural drainage system. When the drainage catheter is removed, the flap, partially held by the sutures, falls over the hole avoiding CSF leakage. By using this technique, the small dural hole will be covered with the periosteum allowing for natural closure and wound healing hence preventing CSF leakage. RESULTS: This technique was successfully employed in 21 patients who didn't develop postoperative CSF leakage following CSDH evacuation and removal of subdural drainage system. CONCLUSION: In this technical note, we describe a safe dura closure technique that we developed to help reduce the risk of postoperative CSF leakage following subdural drainage removal, which can, however, also be applied in all surgeries in which a catheter is placed in the subdural space.

Quantitative measurement of dural ectasia: associations with clinical and genetic characteristics in Marfan syndrome.

PURPOSE: Dural ectasia (DE) may significantly impact Marfan syndrome (MFS) patients' quality of life due to chronic lower back pain, postural headache and urinary disorders. We aimed to evaluate the association of quantitative measurements of DE, and their evolution over time, with demographic, clinical and genetic characteristics in a cohort of MFS patients. METHODS: We retrospectively included 88 consecutive patients (39% females, mean age 37.1 ± 14.2 years) with genetically confirmed MFS who underwent at least one MRI or CT examination of the lumbosacral spine. Vertebral scalloping (VS) and dural sac ratio (DSR) were calculated from L3 to S3. Likely pathogenic or pathogenic FBN1 variants were categorized as either protein-truncating or in-frame. The latter were further classified according to their impact on the cysteine content of fibrillin-1. RESULTS: Higher values of the systemic score (revised Ghent criteria) were associated with greater DSR at lumbar (p < 0.001) and sacral (p = 0.021) levels. Patients with protein-truncating variants exhibited a greater annual increase in lumbar (p = 0.039) and sacral (p = 0.048) DSR. Mutations affecting fibrillin-1 cysteine content were linked to higher VS (p = 0.009) and DSR (p = 0.038) at S1, along with a faster increase in VS (p = 0.032) and DSR (p = 0.001) in the lumbar region. CONCLUSION: Our study shed further light on the relationship between genotype, dural pathology, and the overall clinical spectrum of MFS. The identification of protein-truncating variants and those impacting cysteine content may therefore suggest closer patient monitoring, in order to address potential complications associated with DE.

Enhanced technique of dural closure using autologous fat graft and Gelfoam for effective management of dural tear following interlaminar endoscopic lumbar spine surgery.

BACKGROUND: Incidental dural tears are common complications in lumbar spine surgery, particularly in endoscopic procedures where primary closure via suturing is challenging. The absence of a standardized approach for dural closure in endoscopic spine surgery necessitates exploring alternative techniques. OBJECTIVE: This study introduces a surgical technique for dural closure utilizing fat graft and Gelfoam, offering an effective alternative to standard approaches in endoscopic spine surgery. METHODS: Surgical data from patients who underwent interlaminar endoscopic discectomy or stenosis decompression at Lerdsin Hospital from October 2014 to October 2021 were analyzed. RESULTS: Among 393 cases, dural tears occurred in 2% (8 patients). Our technique achieved successful closure in all these cases, with no incidents of cerebrospinal fluid leakage or wound complications. The majority of patients showed favorable clinical outcomes, except for one case involving concomitant nerve root injury. CONCLUSION: This study demonstrates that using fat graft and Gelfoam for dural closure is a simple, reliable, and safe technique, particularly effective for challenging-to-repair areas in interlaminar endoscopic lumbar spine surgery.

Dural Sac Cross-sectional area change from preoperatively and up to 2 years after decompressive surgery for central lumbar spinal stenosis: investigation of operated levels, data from the NORDSTEN study.

PURPOSE: The aim of the present study was to investigate how canal area size changed from before surgery and up to 2 years after decompressive lumbar surgery lumbar spinal stenosis. Further, to investigate if an area change postoperatively (between 3 months to 2 years) was associated with any preoperative demographic, clinical or MRI variables or surgical method used. METHODS: The present study is analysis of data from the NORDSTEN- SST trial where 437 patients were randomized to one of three mini-invasive surgical methods for lumbar spinal stenosis. The patients underwent MRI examination of the lumbar spine before surgery, and 3 and 24 months after surgery. For all operated segments the dural sac cross-sectional area (DSCA) was measured in mm2. Baseline factors collected included age, gender, BMI and smoking habits. Furthermore, surgical method, index level, number of levels operated, all levels operated on and baseline Schizas grade were also included in the analysis. RESULTS: 437 patients were enrolled in the NORDSTEN-SST trial, whereof 310 (71%) had MRI at 3 months and 2 years. Mean DSCA at index level was 52.0 mm2 (SD 21.2) at baseline, at 3 months it increased to 117.2 mm2 (SD 43.0) and after 2 years the area was 127.7 mm2 (SD 52.5). Surgical method, level operated on or Schizas did not influence change in DSCA from 3 to 24 months follow-up. CONCLUSION: The spinal canal area after lumbar decompressive surgery for lumbar spinal stenosis increased from baseline to 3 months after surgery and remained thereafter unchanged 2 years postoperatively.