Lumbar disc herniation (LDH) remains a leading cause of radicular pain and disability worldwide. 1Despite the familiarity of this condition in clinical practice, persistent challenges continue to affect patient management: variable symptom severity despite similar imaging findings, unpredictable rates of spontaneous resorption, and heterogeneous outcomes following both conservative and surgical treatments. 2 Current clinical approaches still rely primarily on history, physical examination, and magnetic resonance imaging evidence of neural compression.However, these methods alone often fail to fully explain prognosis or guide optimal timing for intervention. 3,4As a result, the field is increasingly moving toward integrated and predictive models of care, combining morphology with biological, biomechanical, psychosocial, and technological insights.This Special Issue addresses these challenges by integrating evidence across several complementary domains: Natural history and spontaneous resorption: Improved understanding of when and how disc herniation resorption occurs provides a biological rationale for conservative management in selected patients and highlights imaging and inflammatory mechanisms underlying disc regression. Biomechanics and mechanobiology: Advances in the biomechanical characterization of disc injury are clarifying how mechanical loading, tissue failure patterns, and cellular responses interact to drive herniation, degeneration, and regenerative potential. Risk stratification and recurrence prediction: Systematic evidence on preoperative clinical and radiographic risk factors offers critical insight into predictors of recurrent LDH, supporting more informed surgical decision-making and follow-up strategies. Emerging molecular biomarkers: Circulating inflammatory and molecular signatures are opening new avenues for patient stratification, outcome prediction, and the future development of biologically informed therapies. Microbiome and the gut-spine axis: Growing evidence suggests that gut microbiota may influence systemic inflammation, pain modulation, and disc degeneration, introducing a novel biological dimension to LDH pathophysiology. Optimization of surgical techniques: Comparative analyses of surgical approaches, including the expanding role of endoscopic discectomy, reflect the ongoing evolution toward Neurospine

ObjectiveTo evaluate the clinical significance of a negative K-line in the neck flexion position (FK-line [-]), which indicates that cervical ossification of the posterior longitudinal ligament (OPLL) crosses the K-line during flexion, and to compare surgical outcomes between laminoplasty (LP) and laminectomy with fusion (LF) for multilevel FK-line (-) cervical OPLL.MethodsA total of 349 patients with multiple cervical OPLL who underwent posterior decompression surgery (LP or LF) with a minimum of 2 years of follow-up were stratified by FK-line status. Clinical and radiological parameters were compared between the FK-line (+) and FK-line (-) groups. Subgroup analysis of FK-line (-) patients evaluated the efficacy of LP versus LF. Multivariate regression identified predictors of neurological recovery.ResultsPatients with FK-line (-) OPLL exhibited a smaller FK-line distance, more kyphotic alignment, greater cervical flexion, and lower recovery ratios compared to those with FK-line (+). In the FK-line (-) subgroup, LF achieved a significantly greater increase in FK-line distance, better correction of the flexion angle, and more neurological recovery than LP. Multivariate analyses identified postoperative FK-line distance, C2–7 flexion angle, and preoperative dynamic extension reserve as independent predictors of neurological outcomes.ConclusionFK-line status reflects the sagittal cord position and predicts surgical outcomes in cervical OPLL. In FK-line (-) patients, LF provides better neurological recovery and more effective posterior cord shift and kyphotic alignment correction than LP. Incorporating FK-line assessment to guide surgical planning could improve individualized treatment outcomes for multilevel OPLL.

A Commentary on “Magnetic Resonance Spectroscopy Lipids Peak May Serve as a Potential Biomarker for Back Pain in Intervertebral Disc Degeneration: An Integrative Metabolomics and Proteomics Study Investigating the Role of the Lipid Droplets-Interleukin-17 Inflammatory Axis”

ObjectiveTo elucidate the clinical outcomes of craniocervical realignment surgery in patients with craniovertebral junction (CVJ) kyphosis accompanied by negative sagittal imbalance, and to identify radiological predictors associated with favorable outcomes.MethodsA retrospective analysis was performed on 28 patients who underwent craniocervical realignment between 2014 and 2022 for CVJ kyphosis with accompanying negative sagittal imbalance. Clinical outcomes were evaluated using the Neck Disability Index (NDI), visual analogue scale for neck pain, and the Japanese Orthopaedic Association (JOA) score. Radiographic parameters included the C0–2 angle and the C2–7 sagittal vertical axis (SVA). Favorable outcomes were defined as an improvement of more than 20 points in the NDI and a JOA recovery rate exceeding 50%. Multiple linear regression and receiver operating characteristic (ROC) curve analyses were conducted to identify independent predictors and to determine optimal threshold values.ResultsSignificant improvements in both clinical outcomes and radiographic alignment were observed in association with craniocervical realignment surgery. Patients who achieved favorable outcomes exhibited greater postoperative changes in the C0–2 angle and the C2–7 SVA. Multivariate analysis identified changesm in the C0–2 angle (p=0.019) and C2–7 SVA (p=0.010) as independent predictors of NDI improvement, while age (p=0.033) and C2–7 SVA change (p=0.037) were independently associated with the JOA recovery rate. ROC curve analysis determined optimal cutoff values of ≥10.65° for C0–2 angle change and ≥19.2 mm for C2–7 SVA change, with corresponding area under the curve values of 0.872 and 0.802, respectively.ConclusionCraniocervical realignment appears to be a viable surgical option for patients with CVJ kyphosis and negative sagittal imbalance. Postoperative changes in C0–2 angle and C2–7 SVA were found to be associated with favorable clinical and functional outcomes, suggesting their potential role as prognostic factors.

ObjectiveMotor-evoked potential (MEP) loss during intramedullary (IM) spinal cord tumor surgery impairs the ability to monitor further neural injury. Direct wave (D-wave) monitoring may allow continued assessment of corticospinal tract integrity after MEP loss. This study evaluates the role of D-wave-guided surgery in preserving function and enabling safe resection after MEP loss.MethodsA retrospective study was conducted in adult patients with ependymoma (EPN), cavernous angioma (CA) or subependymoma who experienced MEP loss during IM tumor resection between January 2012 and May 2025. Patients who underwent continued resection under D-wave guidance after MEP loss were compared with those who did not.ResultsAmong 37 eligible patients, 9 underwent D-wave-guided surgery and 28 did not. Functional improvement at the last follow-up was more frequent in the D-wave-guided surgery group (66.7% vs. 17.9%, p=0.011). This trend remained significant in EPN patients (74.4% vs. 9.1%, p=0.003), but not in CA patients. Immediate postoperative motor grade ≤3 was more common in the D-wave-guided surgery group (66.7% vs. 39.3%), although this difference was not statistically significant (p=0.251). By last follow-up, the proportions of patients self-ambulatory without external aids (88.9% vs. 89.3%, p=1.000) were similar between groups. Extent of resection, complications, and recurrence rates showed no significant differences.ConclusionD-wave-guided surgery may enable safe continuation of tumor resection after MEP loss without increasing morbidity. It offers a viable intraoperative strategy to preserve long-term motor function by extending monitoring beyond MEP limitations.

The craniovertebral junction (CVJ) is anatomically complex, protecting important neural and vascular structures while providing a high degree of multidirectional motion. 1 This region is not only prone to age-related changes, but also susceptible to spinal tumors, vascular malformations, and pathologies associated with congenital anomalies.Advances in preoperative imaging evaluation, surgical techniques, and intraoperative support devices have made it possible to perform safer and more sophisticated surgery, but there is still a risk of life-threatening complications.Therefore, surgery in this region requires more highquality treatment strategy considering the pathophysiology of the disease as well as the unique anatomy and biomechanical properties.This special issue "CVJ Challenges" focuses on complicated neurospinal surgery in the CVJ which still remains relatively unknown and controversial in terms of appropriate management.Five articles in this special issue demonstrate an update on the current status of surgery in the CVJ, incorporating cutting-edge techniques and equipment for intractable lesions.These articles provide useful information featuring advanced approaches to intramedullary spinal cord tumors and spinal neoplasms occurring at the CVJ, updated surgical indications for Chiari malformations, and strategies for kyphotic deformities in this region, alongside a historical overview and evolution of spinal fixation techniques.For intramedullary cavernous angiomas with laterality, it has been reported that even in high cervical lesions, the posterolateral sulcus approach is a rational and safe method that aims for complete resection. 2However, challenges remain in the removal of ventrally located angiomas.While motor evoked potentials serve as an important prognostic tool in spinal surgery, they do not necessarily reflect actual motor function with precision in cases of intramedullary tumors. 3This highlights the importance of balancing the results of intraoperative neurophysiological monitoring with the microscopic findings of the spinal cord parenchyma. 2Regarding vertebral body tumors extending from the clivus to C2, transnasal surgical techniques have become increasingly established. 4Appropriate patient selection based on anatomical landmarks is crucial, and improved endoscopic visualization and surgical proficiency have enabled favorable resection outcomes. 5This anterior approach is considered optimal, particularly in minimizing postoperative airway and swallowing dysfunction.In the treatment of Chiari malformation type I, posterior fossa decompression remains the standard procedure.However, surgical strategies based on a novel classification that incorporates posterior fossa volume, hindbrain configuration, and stability in the CVJ Neurospine