Neuropathic Pain after Spinal Surgery

Designing Enhanced Recovery After Surgery Protocols in Neurosurgery: A Contemporary Narrative Review

Enhanced Recovery After Surgery (ERAS) protocols have revolutionized the approach to perioperative care in various surgical specialties. They reduce complications, improve patient outcomes, and shorten hospital lengths of stay. Implementation of ERAS protocols for neurosurgical procedures has been relatively underexplored and underutilized due to the unique challenges and complexities of neurosurgery. This narrative review explores the barriers to, and pioneering strategies of, standardized procedure-specific ERAS protocols, and the importance of multidisciplinary collaboration in neurosurgery and neuroanesthsia, patient-centered approaches, and continuous quality improvement initiatives, to achieve better patient outcomes. It also discusses initiatives to guide future clinical practice, research, and guideline creation, to foster the development of tailored ERAS protocols in neurosurgery.

Annulus Fibrosus Injury Induces Acute Neuroinflammation and Chronic Glial Response in Dorsal Root Ganglion and Spinal Cord-An In Vivo Rat Discogenic Pain Model

Chronic painful intervertebral disc (IVD) degeneration (i.e., discogenic pain) is a major source of global disability needing improved knowledge on multiple-tissue interactions and how they progress in order improve treatment strategies. This study used an in vivo rat annulus fibrosus (AF) injury-driven discogenic pain model to investigate the acute and chronic changes in IVD degeneration and spinal inflammation, as well as sensitization, inflammation, and remodeling in dorsal root ganglion (DRG) and spinal cord (SC) dorsal horn. AF injury induced moderate IVD degeneration with acute and broad spinal inflammation that progressed to DRG to SC changes within days and weeks, respectively. Specifically, AF injury elevated macrophages in the spine (CD68) and DRGs (Iba1) that peaked at 3 days post-injury, and increased microglia (Iba1) in SC that peaked at 2 weeks post-injury. AF injury also triggered glial responses with elevated GFAP in DRGs and SC at least 8 weeks post-injury. Spinal CD68 and SC neuropeptide Substance P both remained elevated at 8 weeks, suggesting that slow and incomplete IVD healing provides a chronic source of inflammation with continued SC sensitization. We conclude that AF injury-driven IVD degeneration induces acute spinal, DRG, and SC inflammatory crosstalk with sustained glial responses in both DRGs and SC, leading to chronic SC sensitization and neural plasticity. The known association of these markers with neuropathic pain suggests that therapeutic strategies for discogenic pain need to target both spinal and nervous systems, with early strategies managing acute inflammatory processes, and late strategies targeting chronic IVD inflammation, SC sensitization, and remodeling.

Failed Back Surgery Syndrome: No Longer a Surgeon's Defeat-A Narrative Review

The introduction of the term Persistent Spinal Pain Syndrome (PSPS-T1/2), replacing the older term Failed Back Surgery Syndrome (FBSS), has significantly influenced our approach to diagnosing and treating post-surgical spinal pain. This comprehensive review discusses this change and its effects on patient care. Various diagnostic methods are employed to elucidate the underlying causes of back pain, and this information is critical in guiding treatment decisions. The management of PSPS-T1/2 involves both causative treatments, which directly address the root cause of pain, and symptomatic treatments, which focus on managing the symptoms of pain and improving overall function. The importance of a multidisciplinary and holistic approach is emphasized in the treatment of PSPS-T1/2. This approach is patient-centered and treatment plans are customized to individual patient needs and circumstances. The review concludes with a reflection on the impact of the new PSPS nomenclature on the perception and management of post-surgical spinal pain.

Physiotherapy interventions for pain relief in individuals with peripheral neuropathic pain: A systematic review and meta-analyses of randomized controlled trials

OBJECTIVE

To evaluate the effectiveness of physiotherapy interventions on peripheral neuropathic pain (pNeP) due to any underlying cause.

METHODS

Multiple databases were searched from database inception until Dec 2021. Studies on physiotherapy interventions for pain relief assessed using the visual analogue scale among individuals with pNeP of any underlying cause were included. Methodological quality was assessed using the PEDro scale and the quality of the evidence using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) tool.

RESULTS

The searches yielded 1498 articles. Seventeen studies met the inclusion criteria and were included in the review. Meta-analysis revealed a significant benefit for laser therapy compared to sham laser on pNeP (weighted mean difference [WMD] -1.27; 95% CI: -2.29 to -0.25; p = 0.01) in people with carpal tunnel syndrome. The pooled analyses revealed a significant effect of spinal cord stimulation compared to control for failed back syndrome (standardised mean difference [SMD; Hedges'g] -0.73; 95% CI: -1.17 to -0.30; p = 0.001) and diabetic neuropathy (SMD -1.63; 95% CI -2.06--1.21; p < 0.001). The effect of acupuncture on chemotherapy-induced pain (SMD - 2.09; 95% CI: -4.27-0.09; p = 0.06) and electromagnetic stimulation on diabetic neuropathic pain (Hedges' g - 0.77; 95% CI: -1.82-0.27; p = 0.15) were insignificant.

CONCLUSION

Evidence supports the use of spinal cord stimulation for the treatment of pNeP secondary to failed back surgery syndrome and diabetic neuropathy. Laser therapy was more effective than sham laser for alleviating pain due to carpal tunnel syndrome. The efficacy of acupuncture and electromagnetic therapy for chemotherapy-induced pain and diabetic neuropathy, respectively remains inconclusive.

The post spinal surgery syndrome: A review

Post spinal surgery syndrome(PSSS) has always been considered only for the pain it causes. However, many other neurological deficits do happen after lower back surgery. The aim of this review is to look into the various other neurological deficits that could happen after a spinal surgery. Using the keywords, foot drop, cauda equina syndrome, epidural hematoma, nerve and dural injury in spine surgery, the literature was searched. Out of the 189 articles obtained, the most important were analyzed. The problems associated with spine surgery have been published in the literature but are much more than the failed back surgery syndrome and cause more discomfort to the patients. To bring about a more sustained and collective awareness and understanding of these complications following spinal surgery, we encompassed all these complications under the heading of PSSS.

A Comparison between Pre-Incisional and Intraoperative Lidocaine Infiltration on Post-Incisional Surgical Pain in Microdiscectomy Surgery: A Randomized Clinical Trial Study

Objectives

Effective postoperative pain control in microdiscectomy surgery is crucial to managing the disease and improving the patient's quality of life. Therefore, this study aimed to assess the potential effectiveness of 2% lidocaine in reducing pain immediately after discectomy surgery.

Methods

A total of 60 patients who underwent microdiscectomy surgery were enrolled in this randomized clinical trial study. They were randomly assigned to three groups: one group received lidocaine just before the incision, another group received lidocaine just before closing the incision, and the third group served as the control. Pain scores were measured at 1, 2, 3, 4, 8, and 12 h after the surgery using a Visual Analogue Scale.

Results

The demographic and clinical characteristics of the study population, including age, weight, length of surgery, gender, and history of diabetes, hypertension, and previous surgery, were comparable across all three groups (P>0.05). There was a significant reduction in pain scores over time in the groups that received lidocaine before (P<0.001) and during surgery (P=0.002). Moreover, there were significant differences in pain scores at all time points among the three groups. Both groups receiving lidocaine showed significantly lower pain scores than the control group (Pbefore surgery=0.005 and Pduring surgery<0.001). However, no significant difference was observed between the groups receiving lidocaine (P=0.080).

Conclusion

These findings highlight the effectiveness of a local injection of 2% lidocaine either before or during the surgery in managing post-incisional surgical pain after discectomy.

Effectiveness of two extended-release buprenorphine formulations during postoperative period in neonatal rats

Information on the effectiveness of a new long-lasting buprenorphine formulation, extended-release buprenorphine, in the neonatal rat is very limited. This study compares whether a high dose of extended-release buprenorphine (XR-Hi) attenuates thermal hypersensitivity for a longer period than a low dose of extended-release buprenorphine (XR-Lo) in a neonatal rat incisional pain model. Two experiments were performed. Experiment one: Male and female postnatal day-5 rat pups (n = 38) were randomly assigned to 1 of 4 treatment groups and received a subcutaneous administration of one of the following: 1) 0.9%NaCl (Saline), 0.1 mL; 2) sustained release buprenorphine (Bup-SR), 1 mg/kg; 3) XR-Lo, 0.65 mg/kg; and 4) XR-Hi, 1.3 mg/kg. Pups were anesthetized with sevoflurane in 100% O₂ and a 5 mm long skin incision was made over the left lateral thigh and underlying muscle dissected. The skin was closed with surgical tissue glue. Thermal hypersensitivity testing (using a laser diode) and clinical observations were conducted 1 hour (h) prior to surgery and subsequently after 1, 4, 8, 24, 48, 72 h of treatment. Experiment two: The plasma buprenorphine concentration level was evaluated at 1, 4, 8, 24, 48, 72 h on five-day-old rat pups. Plasma buprenorphine concentration for all treatment groups remained above the clinically effective concentration of 1 ng/mL for at least 4 h in the Bup-SR group, 8 h in XR-Lo and 24 h in XR-Hi group with no abnormal clinical observations. This study demonstrates that XR-Hi did not attenuate postoperative thermal hypersensitivity for a longer period than XR-Lo in 5-day-old rats; XR-Hi attenuated postoperative thermal hypersensitivity for up to 4 h while Bup-SR and XR-Lo for at least 8 h in this model.

Management of Complications of Posterior Lumber Spine Fixation for Spondylolithesis

This study was aiming at identifying the varieties, causes, treatment and prevention of post lumbar instrumental fixation complications, which was done on a study population of 50 cases, without stratification on bases of sex or age, excluding the patients with known chronic debilitating diseases. Regarding the patients’ population, our demographics shows a clear role of obesity in the pathogenesis of spondylolisthesis in general, regardless of age or sex, the mean BMI was above 30, and this does indeed agree with most studies as mentioned before. Analyzing our results, we found the most affected levels to be L4-5, and L5-S1, which coincides with other studies discussed before, we also found significant dominance of back pain as a presenting complaint, while neurological deficits were rare, by analyzing the etiologies of pathological findings in our patients we found isthmic lythesis followed by spondylolisthesis as the most common etiologies respectively among the studied population.Regarding the positive finding requiring further management in our study, the most common finding was failed prosthesis, and adjacent segment failure, other less frequent findings include Sacroiliac dysfunction, posterior cage migration, screw malpostioning, infection, Dural tear, CSF leak, pseudarthrosis, and one patient with pseudo-meningocele.32 patients (64%) were managed surgically, while the other 18 patients (36%) were managed conservatively, 40 patients had improved complaints, while 10 cases didn’t improve, our results should be seen in the light that our sample size was small, which can be a great limiting factor.

Metformin attenuates post-epidural fibrosis by inhibiting the TGF-β1/Smad3 and HMGB1/TLR4 signaling pathways

Excessive post‐epidural fibrosis is a common cause of recurrent back pain after spinal surgery. Though various treatment methods have been conducted, the safe and effective drug for alleviating post‐epidural fibrosis remains largely unknown. Metformin, a medicine used in the treatment of type 2 diabetes, has been noted to relieve fibrosis in various organs. In the present study, we aimed to explore the roles and mechanisms of metformin in scar formation in a mouse model of laminectomy. Post‐epidural fibrosis developed in a mouse model of laminectomy by spinous process and the T12‐L2 vertebral plate with a rongeur. With the administration of metformin, post‐epidural fibrosis was reduced, accompanied with decreased collagen and fibronectin in the scar tissues. Mechanistically, metformin decreased fibronectin and collagen deposition in fibroblast cells, and this effect was dependent on the HMGB1/TLR4 and TGF‐β1/Smad3 signalling pathways. In addition, metformin influenced the metabolomics of the fibroblast cells. Taken together, our study suggests that metformin may be a potential option to mitigate epidural fibrosis after laminectomy.

Effectiveness of Duloxetine for Postsurgical Chronic Neuropathic Disorders after Spine and Spinal Cord Surgery

Study Design

This is a retrospective observational study with an outpatient setting.

Purpose

This study aimed to describe the effects of duloxetine (DLX) administration for postsurgical chronic neuropathic disorders (both pain and numbness) following spinal surgery in patients without depression.

Overview of Literature

Although several reports indicated the potential of DLX to effectively treat postoperative symptoms as a perioperative intervention, there have been no reports of its positive effect on postsurgical chronic neuropathic disorders.

Methods

A total of 24 patients with postsurgical chronic pain and/or numbness Numeric Rating Scale (NRS) scores of ≥4 were enrolled. All patients underwent spine or spinal cord surgery at Keio University Hospital and received daily administration of DLX for more than 3 months. The mean postoperative period before the first administration of DLX was 35.5±57.0 months. DLX was administered for more than 3 months at a dose of 20, 40, or 60 mg/day, and the degree of pain and numbness was evaluated using the NRS before administration and 3 months after administration. Effectiveness was defined as more than a 2-point decrease in the NRS score following administration.

Results

In terms of the type of symptoms, 15 patients experienced only numbness, eight experienced both pain and numbness, and one experienced only pain. Of the 24 patients, 19 achieved effective relief with DLX. DLX was effective for all patients with postsurgical chronic pain (n=9), and it reduced postsurgical chronic numbness in 18 of 23 patients. No significant difference was observed in background spinal disorders. DLX was not effective for five patients who complained only of postsurgical chronic numbness.

Conclusions

This study reports the effectiveness of DLX for postsurgical chronic neuropathic disorders. Although DLX reduced postsurgical chronic pain (efficacy rate=100%) and numbness (78.3%) in certain patients, further investigation is needed to determine its optimal use.

Perioperative intravenous lignocaine infusion for postoperative pain control in patients undergoing surgery of the spine: protocol for a systematic review and meta-analysis

INTRODUCTION

Intravenous lignocaine is an amide local anaesthetic known for its analgesic, antihyperalgesic and anti-inflammatory properties. Administration of intravenous lignocaine has been shown to enhance perioperative recovery parameters. This is the protocol for a systematic review which intends to summarise the evidence base for perioperative intravenous lignocaine administration in patients undergoing spinal surgery.

METHODS AND ANALYSIS

Our primary outcomes include: postoperative pain scores at rest and movement at predefined early, intermediate and late time points and adverse events. Other outcomes of interest include perioperative opioid consumption, composite morbidity, surgical complications and hospital length of stay. We will include randomised controlled trials, which compared intravenous lignocaine infusion vs standard treatment for perioperative analgesia. We will search electronic databases from inception to present; MEDLINE, EMBASE and Cochrane Library (Cochrane Database of Systematic Reviews and CENTRAL). Two team members will independently screen all citations, full-text articles and abstract data. The individual study risk of bias will be appraised using the Cochrane risk of bias tool. We will obtain a risk ratio or mean difference (MD) from the intervention and control group event rates based on the nature of data. We will correct for the variable measurement tools by using the standardised MD (SMD). We will use a random-effects model to synthesise data. We will conduct five subgroup analysis: major versus minor surgery, emergency versus elective surgery, patients with chronic pain conditions versus patients without, duration of lignocaine infusion and adult versus paediatric. Confidence in cumulative evidence for will be classified according to the Grading of Recommendations, Assessment, Development and Evaluation system. We will construct summary of findings tables supported detailed evidence profile tables for predefined outcomes.

ETHICS AND DISSEMINATION

Formal ethical approval is not required as primary data will not be collected. The results will be disseminated through a peer-reviewed publication.

PROSPERO REGISTRATION NUMBER

CRD420201963314.

Risk Factors for Postsurgical Foot Complaints One Year Following Degenerative Lumbar Spinal Surgery

MINI: Postsurgical foot complaints occurred frequently in 853 degenerative lumbar surgeries (prevalence, 20.6%; n = 176). Risk factor analysis showed that the incidence of postsurgical foot complaint was significantly higher in patients with preoperative foot symptoms (adjusted odds ratio, 5.532) and in those with preoperative sensory deficits on the leg (adjusted odds ratio, 1.904).

STUDY DESIGN

Retrospective.

OBJECTIVE

To investigate the prevalence and risk factors of postsurgical foot complaints (PFCs) following spinal surgery by using a modified pain drawing (PD) instrument.

SUMMARY OF BACKGROUND DATA

Although many patients report nonspecific foot symptoms with various clinical presentation, there is not a well defined diagnostic criterion. PDs are essential for measuring spinal surgery outcomes. We created a modified patient-physician communication-based PD instrument to overcome the limitations of the previous system.

METHODS

We included 853 consecutive patients who underwent decompression with or without fusion. PFCs were defined as sensory foot symptoms, including ambiguous sensations that were not clearly due to spinal pathology. Patients who complained of postoperative foot symptoms at more than two consecutive visits were assigned to the PFC group. The remaining patients were assigned to the asymptomatic group. We collected medical records using our PD instrument and compared variables between the two groups.

RESULTS

In total, 176 (20.6%) of the 853 patients had PFCs. The duration of preoperative leg pain was significantly longer in the PFC group than in the asymptomatic group (2.8 vs. 2.2 years; P = 0.048). The proportions of preoperative foot symptoms (82.9% vs. 43.3%) and sensory deficits on the leg (48.6% vs. 27%) were significantly greater in the PFC group than in the asymptomatic group (P < 0.001). Multivariable logistic regression analysis revealed two independent risk factors: the presence of preoperative foot symptoms (adjusted odds ratio, 5.532) and preoperative sensory deficits on the leg (adjusted odds ratio, 1.904).

CONCLUSION

PFCs occurred frequently after degenerative lumbar spinal surgery (prevalence, 20.6%). Based on our data using PD instrument, it can help reduce the incidence of PFCs if patients are informed and educated that preoperatively existing foot symptom and sensory deficits on the leg are significant risk factors for PFC development.

LEVEL OF EVIDENCE

4.

Effectiveness of and Factors Associated with Balloon Adhesiolysis in Patients with Lumbar Post-Laminectomy Syndrome: A Retrospective Study

Post-laminectomy syndrome (PLS) is characterized by chronic pain and complex pathological entity after back surgery. An epidural adhesiolysis is considered an effective treatment option for lumbar PLS. In this study, we retrospectively analyzed the outcome and evaluated the predictive factors of combined epidural adhesiolysis and balloon decompression using inflatable balloon catheters in lumbar PLS cases. One hundred and forty-seven subjects were retrospectively assessed and analyzed. The percentages of patients who exhibited treatment response were 32.0%, 24.5%, and 22.4% of the study population at 1, 3, and 6 months, respectively. In multivariate logistic regression analysis, the pain duration was independently associated with the treatment response six months after combined epidural adhesiolysis and balloon decompression (odds ratio = 0.985, 95% confidence interval = 0.971-0.999; p = 0.038). In addition, the receiver operating characteristic curve analysis showed that the area under the curve of pain duration after lumbar surgery was 0.680 (95% confidence interval = 0.597-0.754, p = 0.002), with an optimal cut-off value of ≤14 months, sensitivity of 51.5%, and specificity of 81.4% Our results suggest that an early intervention using combined epidural adhesiolysis and balloon decompression in lumbar PLS patients may be associated with a favorable outcome, even though it has limited effectiveness.

Support for a Three-Item Questionnaire Prior to Spinal Surgery: A Health-Related Quality of Life Outcome Study

Objective  Elective lumbar and cervical operations are becoming more common in the United States. Additionally, there is a movement in the literature and clinical practice to discover short versions of longer measures as a way to anticipate an outcome. This study aims to provide neurosurgeons in practice with a three-item questionnaire that can guide referrals to psychological services presurgery. Ultimately, results could lead to an improvement in health-related quality of life (HRQoL) postspinal surgery.

Methods  This quantitative-descriptive, survey-based design with a retrospective chart review component followed 47 patients at baseline ( N = 47), 3 months ( N = 20), 6 months ( N = 31), and 1 year ( N = 19). A single item from the Coping Strategies Questionnaire, the Survey of Pain Attitudes, and the Tampa Scale of Kinesiophobia were utilized in the three-item questionnaire as a baseline measure. Patient-Reported Outcomes Measurement Information System Global Health measured HRQoL outcome at all time points. A linear regression model was conducted to predict mental health QoL postspinal surgery.

Results  This measure can predict mental health QoL outcomes up to 3-month postsurgery. Six-month and 1-year follow-ups are statistically inconclusive.

Conclusion  Individuals who are undergoing spinal surgery show lower mental health QoL outcome at baseline and 3-month postsurgery when responses on a three-item questionnaire are elevated. Limitations and future directions are discussed.

Therapeutic Approaches for Peripheral and Central Neuropathic Pain

Neuropathic pain is a chronic secondary pain condition, which is a consequence of peripheral or central nervous (somatosensory) system lesions or diseases. It is a devastating condition, which affects around 7% of the general population. Numerous etiological factors contribute to the development of chronic neuropathic pain. It can originate from the peripheral part of the nervous system such as in the case of trigeminal or postherpetic neuralgia, peripheral nerve injury, painful polyneuropathies, or radiculopathies. Central chronic neuropathic pain can develop as a result of spinal cord or brain injury, stroke, or multiple sclerosis. As first-line pharmacological treatment options, tricyclic antidepressants, serotonin-norepinephrine reuptake inhibitors, and gabapentinoids are recommended. In trigeminal neuralgia, carbamazepine and oxcarbazepine are the first-choice drugs. In drug-refractory cases, interventional, physical, and psychological therapies are available. This review was structured based on a PubMed search of papers published in the field from 2010 until May 2019.

Association Between Spinal Cord Stimulation and Top-Down Nociceptive Inhibition in People With Failed Back Surgery Syndrome: A Cohort Study

BACKGROUND

Descending nociceptive inhibitory pathways often malfunction in people with chronic pain. Conditioned pain modulation (CPM) is an experimental evaluation tool for assessing the functioning of these pathways. Spinal cord stimulation (SCS), a well-known treatment option for people with failed back surgery syndrome (FBSS), probably exerts its pain-relieving effect through a complex interplay of segmental and higher-order structures.

OBJECTIVE

To the best of our knowledge, no clinical studies have thoroughly investigated the associations between SCS and CPM.

DESIGN

This was a prospective cohort study in people with FBSS.

METHODS

Seventeen people who had FBSS and were scheduled for SCS were enrolled in this study. The CPM model was evaluated at both sural nerves and was induced by electrical stimulation as the test stimulus and the cold pressor test as the conditioning stimulus.

RESULTS

Before SCS, less than 30% of the participants with FBSS showed a CPM effect. Significant increases in the electrical detection threshold on the symptomatic side and the nonsymptomatic side were found. On the symptomatic side, no differences in the numbers of CPM responders before and after SCS could be found. On the nonsymptomatic side, more participants showed a CPM effect during SCS. Additionally, there were significant differences for CPM activation and SCS treatment.

LIMITATIONS

Limitations were the small sample size and the subjective outcome parameters in the CPM model.

CONCLUSIONS

This study revealed a bilateral effect of SCS that suggests the involvement of higher-order structures, such as the periaqueductal gray matter and rostroventromedial medulla (key regions in the descending pathways), as previously suggested by animal research.

Effect of HDAC2/Inpp5f on neuropathic pain and cognitive function through regulating PI3K/Akt/GSK-3β signal pathway in rats with neuropathic pain

The effect of histone deacetylase (HDAC)2/Inositol polyphosphate-5-phosphatase F (Inpp5f) on neuropathic pain and cognitive dysfunction through regulating PI3K/Akt/GSK-3β signal pathway in rats with neuropathic pain was investigated. A total of 80 SPF mature male SD rats were averagely randomized into the sham operation group, the model group, the HDAC2 intervention group (group A) and the Inpp5f intervention group (group B). The rat models of neuropathic pain were established in the model group, and groups A and B. At the 15th day after modeling, rats in group A were transfected with the interference vector of HDAC2, and rats in group B were transfected with the overexpression vector of Inpp5f. Rats in the four groups were observed before modeling, after modeling/before intervention and 3 days after intervention in terms of paw thermal withdrawal latency (PWL), paw withdrawal mechanical threshold (PWT) and changes in cognitive function (Morris water maze and passive avoidance task). Then the rats were sacrificed. RT-qPCR and western blot analysis were used to detect the levels of HDAC2 mRNA, Inpp5f mRNA, phosphorylated PI3K (p-PI3K), phosphorylated AKT (p-AKT), phosphorylated GSK-3β (p-GSK-3β) in rat brain tissue. Correlation of HDAC2 mRNA with Inpp5f mRNA expression levels was detected by Pearsons correlation analysis. Compared with the sham operation group, PWL was significantly lower while PWT was higher in the other 3 groups (P<0.05). Three days after intervention, PWL was significantly higher while PWT was significantly lower (P<0.05). Inhibiting the expression of HDAC2 or promoting the expression of Inpp5f can effectively improve cognitive function in rats (P<0.05). After intervention, compared with the sham operation group, rats in the other 3 groups had higher HDAC2 mRNA level and lower Inpp5f mRNA level (P<0.05). In conclusion, neuropathic pain can cause an increase in HDAC2 expression level and a decrease in Inpp5f expression level, and activate the PI3K/Akt/GSK-3β signal pathway. Inhibition of HDAC2 expression can inhibit the activation of PI3K/Akt/GSK-3β signal pathway through increasing Inpp5f expression, thus improving the condition and cognitive disorder of rats with neuropathic pain.

Pirfenidone inhibits epidural scar fibroblast proliferation and differentiation by regulating TGF-β1-induced Smad-dependent and -independent pathways

Epidural fibrosis causes serious complications in patients who have undergone laminectomy. Pirfenidone is an effective antifibrotic agent but its effect on epidural fibrosis remains unclear. In this study, we aimed to investigate the effect of pirfenidone on epidural fibrosis and to evaluate its mechanism of action on human epidural scar fibroblasts. In a rat model of laminectomy, the degree of epidural fibrosis was quantified via Rydell standard classification, histological analysis, and collagen density analyses. In cultured human epidural scar fibroblasts, cell proliferation was measured using a Cell Counting Kit-8 and EdU assay. Cell apoptosis was detected using Annexin V/propidium iodide staining, and cytotoxicity was evaluated via lactate dehydrogenase assay. Relative mRNA levels of α-smooth muscle actin (α-SMA) and collagen type I were analyzed using quantitative polymerase chain reaction. The protein expression of α-SMA and collagen type I and the phosphorylation status of Smad2, Smad3, protein kinase B (Akt), and p38 were determined via western blotting. Pirfenidone reduced epidural fibrosis by inhibiting fibroblast proliferation and suppressing collagen formation in rats. It also inhibited human epidural scar fibroblast proliferation with no cytotoxic or apoptotic effects. Pirfenidone inhibited fibroblast differentiation by decreasing TGF-β1-induced transcriptional and translational expression of α-SMA. It inhibited TGF-β1-induced phosphorylation of Smad2, Smad3, Akt, and p38. This study suggests that topical application of pirfenidone could reduce epidural scar adhesion after laminectomy, and that its mechanism of action may be the inhibition of TGF-β1-induced epidural scar fibroblast proliferation and differentiation into myofibroblasts through the attenuation of TGF-β1-induced Smad-dependent and -independent pathways.

Narcotic Addiction in Failed Back Surgery Syndrome

Back pain is a common health problem that reduces the quality of life for human beings worldwide. Several treatment modalities have been reported as effective for pain relief. Generally, patients often undergo surgical interventions as pain becomes intractable, after conservative treatment. With advances in surgical techniques, those choosing spinal surgery as an option have increased over time, and instrumentation is more popular than it was years ago. However, some patients still have back pain after spinal operations. The number of patients classified as having failed back surgery syndrome (FBSS) has increased over time as has the requirement for patients receiving long-term analgesics. Because pain relief is regarded as a human right, narcotics were prescribed more frequently than before. Narcotic addiction in patients with FBSS has become an important issue. Here, we review the prevalence of FBSS, the mechanism of narcotic addiction, and their correlations. Additionally, several potentially effective strategies for the prevention and treatment of narcotic addiction in FBSS patients are evaluated and discussed.