The diagnostic workup of patients with neuropathic pain

Effect and underlying mechanisms of spirocyclopiperazinium salt compound DXL-A-24 in rats following spinal nerve ligation

PURPOSE

Neuropathic pain represents a significant public health problem and its effective management remains a challenge. The present study is designed to evaluate the analgesic effect of the spirocyclopiperazinium salt compound DXL-A-24 in spinal nerve ligation (SNL) model, and further to explore the possible molecular mechanisms.

METHODS

SNL model was established on rats, and mechanical allodynia and thermal hyperalgesia were estimated with the von Frey and hot plate tests; the expression of CaMKIIα, CREB, JAK2, STAT3 and c-fos was determined by western blotting; the protein level of TNF-α was analysed by ELISA; the mRNA expression of TNF-α and c-fos was detected using qRT-PCR analysis and the receptor blocking test was used for target searching.

RESULTS

Administration of DXL-A-24 (1, 0.5, 0.25 mg/kg, i.g.) obviously relieved SNL-induced mechanical allodynia and thermal hyperalgesia in rats (P < 0.01), with the percentage of pain threshold elevation (PTE%) was 103 %, 68 % and 47 %, respectively, in mechanical allodynia; the percentage of maximal possible effect (MPE%) was 56 %, 34 % and 21 %, respectively, in thermal hyperalgesia on day 7 after SNL. Pretreatment with peripheral α7 nicotinic or M4 muscarinic receptor antagonist, the effect of DXL-A-24 was completely blocked (P > 0.05). DXL-A-24 significantly reduced the upregulated pCaMKIIα, pCREB, pJAK2, pSTAT3 and TNF-α protein (P < 0.01), which could be blocked by α7 nicotinic receptor or M4 muscarinic receptor antagonist. In addition, administration of DXL-A-24 attenuated the mRNA and protein expression of c-fos and TNF-α mRNA in DRG of SNL rat. We did not observe significant acute toxicity and chronic hepatorenal impairment at effective dose and high dose.

CONCLUSIONS

We report firstly that administration of DXL-A-24 displays obvious antineuropathic pain effects in SNL rats. The underlying mechanism may involve the reduction of the CaMKIIα/CREB and JAK2/STAT3 signalling pathways, and the suppression of TNF-α and c-fos expression, which may be mediated by activating peripheral α7 nicotinic and M4 muscarinic receptors. This study may provide a new perspective for developing new antineuralgic drug.

The Silent Period for Small Fiber Sensory Neuropathy Assessment in a Mixed Cohort of Transthyretin-Mediated Amyloidosis

Background: Transthyretin-mediated amyloidosis (ATTR) is a rare multisystemic disease involving the peripheral nervous system and heart. Autonomic and small fiber involvement is one of the hallmarks of ATTR, and many tools have been proposed to assess this aspect. Aim: The aim of this study was to investigate cutaneous and mixed nerve silent periods (CSP and MnSP) as instruments for small fiber assessment. Methods: A total of 21 ATTR patients, 20 healthy controls, and 18 asymptomatic carriers underwent a sensory conduction study from the right sural and non-dominant ulnar nerves. A motor conduction study from the right deep peroneal and non-dominant ulnar nerves, with their F waves, CSPs, and MnSPs, was performed. Results: The amplitudes of the sural and ulnar sensory nerves and of the peroneal and ulnar motor nerves were reduced in ATTR patients compared to the other groups. F waves from the ulnar and peroneal nerves showed no differences between the three groups. The CSP and MnSP latency, but not amplitude, were increased in both the ulnar and peroneal nerves of ATTR patients. Conclusions: ATTR patients showed axonal involvement of large sensory and motor nerve fibers and demyelinating features of small sensory fibers.

Lumbar Disc Herniation, the Association Between Quantitative Sensorial Test and Magnetic Resonance Imaging Findings

OBJECTIVE

Quantitative sensorial tests (QST) are used for evaluating specific sensorial nerve function. In this study, QST and magnetic resonance imaging (MRI) findings are compared in lumbar disc herniation patients, and the accuracy of QST data was investigated.

MATERIAL AND METHODS

Sixty-four patients between 18 and 70 years of age suffering from radicular pain with positive Lasegue's test were included in this study. Specific criteria included complaints due to L5 discopathy. MRI findings were classified according to the Pfirmann grading system, and QST was applied to the L5 dermatoma of both symptomatic and nonsymptomatic legs of all patients. Vibration detection threshold, heat detection threshold, cold detection threshold, and heat pain detection threshold values were obtained, and MRI findings were classified according to the Pfirmann grading system.

RESULTS

When we compared the symptomatic and nonsymptomatic legs of participants, there were significant differences by means of all QST parameters (0 = 0.00). In a comparison of the QST and MRI Pfirmann grading systems, there is also a strong parallel statistical correlation between the Pfirmann grade and QST parameters (P < 0.05).

CONCLUSIONS

According to the results of our study, QST has an additive effect to MRI for nerve root compression evaluation in the clinical basis, which might enable more sensitive diagnosis and treatment protocol. QST can also be an alternative method for evaluation of nerve root compression in patients who have contraindications for MRI.

Effectiveness of pregabalin as monotherapy or combination therapy for neuropathic pain in patients unresponsive to previous treatments in a Spanish primary care setting

Background and Objective

Patients from a previous study of neuropathic pain (NP) in the Spanish primary care setting still had symptoms despite treatment. Subsequently, patients were treated as prescribed by their physician and followed up for 3 months. Since pregabalin has been shown to be effective in NP, including refractory cases, the objective of this study was to assess the effectiveness of pregabalin therapy in patients with NP refractory to previous treatments.

Methods

This was a post hoc analysis of pregabalin-naïve NP patients treated with pregabalin in a 3-month follow-up observational multicenter study to assess symptoms and satisfaction with treatment. Patients were evaluated with the Douleur Neuropathique en 4 questions (DN4), the Brief Pain Inventory (BPI) and the Treatment Satisfaction for Medication Questionnaire (SATMED-Q) overall satisfaction domain.

Results

1,670 patients (mean age 58 years, 59 % women), previously untreated or treated with ≥1 drug other than pregabalin, were treated with pregabalin (37 % on monotherapy). At 3 months, pain intensity and its interference with activities decreased by half (p < 0.0001), while the number of days with no or mild pain increased by a mean of 4.5 days (p < 0.0001). Treatment satisfaction increased twofold (p < 0.0001). Patients with a shorter history of pain and those with neuralgia and peripheral nerve compression syndrome (PCS) as etiologies had the highest proportion on monotherapy and showed the greatest improvements in pain-related parameters in their respective group categories.

Conclusion

Treatment with pregabalin (as monotherapy or combination therapy) provides benefits in pain and treatment satisfaction in patients with NP, including refractory cases. Shorter disease progression and neuralgia and PCS etiologies are favorable factors for pregabalin treatment response.

Paroxysmal neuropathic pain in an adolescent female with syringomyelia: a review of literature

Paroxysmal neuropathic pain is an uncommon complaint among pediatric patients visiting the emergency department. It is a rare presentation in children with syringomyelia. Patients with syringomyelia may present with a variety of pain symptoms. It is the site and extension of the syrinx, which determines the character of pain. We report an adolescent with Chiari malformation type 1 with syringomyelia who presented with neuropathic pain, dysesthesia, and absent triceps (C7) reflex. The pertinent literature is reviewed.

Translation of drug effects from experimental models of neuropathic pain and analgesia to humans

Neuropathic pain research remains a challenging undertaking owing to: (i) the lack of understanding about the underlying disease processes; and (ii) poor predictive validity of the current models of evoked pain used for the screening of novel compounds. Common consensus is that experimental models replicate symptoms (i.e. have face validity but no construct validity). Another issue that requires attention is the sensitivity of endpoints to discriminate drug effects that are relevant to the disease in humans. In this paper we provide an overview of the pre-clinical models that can be used in conjunction with a model-based approach to facilitate the prediction of drug effects in humans. Our review strongly suggests that evidence of the concentration-effect relationship is necessary for translational purposes.

Post hoc analysis of pregabalin vs. non-pregabalin treatment in patients with cancer-related neuropathic pain: better pain relief, sleep and physical health

BACKGROUND AND PURPOSE

A previous study of cancer-related neuropathic pain (NP) found that a 10-fold increase in pregabalin (PGB) use increased patients' satisfaction with treatment. Further research of PGB vs. non-pregabalin (non-PGB) treatment was carried out to assess if the use of more specific NP-targeting drugs, such as PGB, in combined therapy, in patients with cancer-related NP, provides better health outcomes.

PATIENTS AND METHODS

Post hoc analysis of PGB- vs. non- PGB-treated patients in a 2-month epidemiological, prospective, multicentre study to assess NP prevalence and management in cancer pain patients visiting radiotherapy oncologic units. Patients undertook the Brief Pain Inventory (BPI), Hospital Anxiety and Depression Scale (HADS), the Medical Outcomes Sleep Scale (MOS-Sleep) and the short form (SF-12) Health Survey.

RESULTS

A total of 273 patients with no previous PGB treatment: 162 were treated with PGB polytherapy and 111 with other treatments. At 8 weeks, satisfaction with treatment was 92.6% (PGB) vs. 78.9% (non-PGB), p=0.0024, and benzodiazepine use 37.8% (non-PGB) vs. 19.8% (PGB), p=0.0009. The decreases in BPI total pain intensity and total interference with activities and in MOS overall sleep problems index were significantly larger in the PGB group.

CONCLUSIONS

The addition of more specific NP-targeting drugs to usual treatment, such as PGB, in NP cancer patients provides more satisfaction with treatment and better outcomes in terms of pain intensity, interference with activities and sleep than treatments without specific NP-targeting drugs. Anxiolytic profile of PGB could allow for less use of benzodiazepines.

[Prevalence of neuropathic pain according to the NP4 test in primary care]

BACKGROUND

Primary Care Physicians are usually the first to see patients with neuropathic pain. The aim of this study is to assess the prevalence of neuropathic pain, its therapeutic management, and to clinically characterize these patients.

MATERIAL AND METHODS

An epidemiological, observational, cross-sectional study was carried out in Spanish Primary Care settings. The first 25 patients older than 18 years with any type of pain (a total of 16,115) were registered, and the first 5 with a high neuropathic pain component according to the NP4 test, and was clinically confirmed (n= 3,836) were included in the study. Pain intensity and impact on daily activities, as well as overall satisfaction with treatment were assessed.

RESULTS

A total of 45.7% of patients had neuropathic pain according to NP4 test. The median age was 59 years, and 60% were women. Patients took a mean of 2.4 drugs, with NSAIDs (53%) and non-opioid analgesics (51%) being the most common. The scores for Pain intensity and interference in daily activities were both 6.2. The overall opinion of the SATMED-Q test was 47.3/100, which was 1.4 points lower than the standardised score according to Spanish population.

CONCLUSIONS

Neuropathic pain according to NP4 test is highly prevalent in Spanish Primary Care settings. The management of these patients with NSAIDs and non-opioid analgesics is not appropriate, as they are not recommended for this kind of pain. Although they were being treated with more than 2 analgesics, they still referred to high pain intensity, interference in daily activities, and a low general opinion of the treatment.

Management of Fabry disease

A Fabry-kór a lizoszomális tárolási betegségek csoportjába tartozó, X-kromoszómához kötötten, recesszív módon öröklődő betegség, amely a globotriaozilceramid felhalmozódásához vezet a szervezet legkülönbözőbb szöveteiben. A betegség első tünetei többnyire gyermekkorban jelentkeznek, a progresszió során a betegek súlyos szervi károsodásokkal és korai halálozással számolhatnak. Elsősorban férfiak érintettek, azonban a betegség tüneteit heterozigóta nők esetében is megfigyelhetjük, de náluk a kórkép súlyossága változó, általában enyhébb lefolyású. Az enzimpótló kezelések megjelenése szükségessé tette, hogy részletes diagnosztikus és terápiás protokollt dolgozzunk ki. A jelen dolgozatban megjelenő ajánlásokat egy, a magyarországi Fabry-kóros betegek kezelésében részt vevő orvosokból, a diagnosztika területén dolgozó biológosukból és egyéb szakemberekből álló multidiszciplináris munkacsoport foglalta össze. A munkacsoport áttekintette a korábbi klinikai tanulmányokat, a publikált vizsgálatokat és a közelmúltban megjelent nemzetközi és nemzeti útmutatókat.

Mutation patterns in human α-galactosidase A

A way to study the mutation pattern is to convert a 20-letter protein sequence into a scalar protein sequence, because the 20-letter protein sequence is neither vector nor scalar while a promising way to study patterns is in numerical domain. In this study, we use the amino-acid pair predictability to convert α-galactosidase A with its 137 mutations into scalar sequences, and analyse which amino-acid pairs are more sensitive to mutation. Our results show that the unpredictable amino-acid pairs are more sensitive to mutation, and the mutation trend is to narrow the difference between predicted and actual frequency of amino-acid pairs.

Pain: basics and relevance in dermatology

Scientific progress in pathophysiology and differentiation of pain, functional diagnostic of pain and emerging treatments highlight this subject. Basics of development of pain, as well as differentiation of nociceptive and neuropathic pain are depicted; the latter is illustrated with the example of postherpetic neuralgia. Complex regional pain syndromes are described as a third pain complex. Principles of differentiated pain management are given. Substance groups from the WHO scheme including antipyretic analgesics, non-steroidal antiinflammatory drugs (NSAIDs) and opioids are discussed. Recommendations of the Drug Commission of the German Medical Association concerning NSAIDs and of the International Association for the Study of Pain (IASP) concerning new treatment options for cancer pain are cited. Overviews amongst others from the Cochrane library for local anesthetics, opioids and for the treatment of postherpetic neuralgia are included. Tables are provided to simplify use in daily practice. The goal of this overview is a conceptual development of pain diagnosis and therapy in dermatology.

[Linguistic adaptation into Spanish and psychometric validation of the ID-Pain questionnaire for the screening of neuropathic pain]

BACKGROUND AND OBJECTIVE

To achieve a linguistic adaptation and psychometric validation into Spanish of the ID-Pain questionnaire for the screening of differential diagnosis of pain with a neuropathic component.

MATERIAL AND METHOD

Cross-sectional validation study carried out in 2 phases (cultural adaptation into Spanish language and validation study to test psychometric properties of the scale) in men and women > 18 years, with neuropathic (NP) and nociceptive (NNP) chronic pain for more than 6 months. Feasibility and reliability were explored. Criterion and convergent validity were studied by means of ID-Pain association with reference diagnosis and LANNS (Leeds Assessment of Neuropathic Symptoms and Signs) scale scores. Factor and ROC curves analysis, agreement with reference diagnosis and sensitivity and specificity values were assessed.

RESULTS

A total of 283 subjects -64.4% women; mean age (standard deviation): 59.1 (14.9) years-, 145 (51.2%) with NP and 138 (48.8%) with NNP were included in the study. Administration time was 4.2 (3.0) min. Only 15% of participants required help for test completion. Factor analysis indicated a unifactorial solution accounting for 35.5% of the variance. The instrument was time-stable (test-retest r-Pearson = 0.98; p < 0.0005). Mean score differentiated NP from NNP patients; 3.5 (1.2) vs. 1.2 (1.4) (p < 0.0005). Optimum cut-off value was > or = 3 points, showing an area under the curve = 0.89; p < 0.0005, sensitivity value of 0.81, specificity of 0.84 and kappa coefficient of agreement with reference clinical diagnosis of 0.65. The scale also showed good concurrent validity with LANSS classification of subjects (kappa = 0.61; p < 0.0005).

CONCLUSIONS

The Spanish version of the ID-Pain questionnaire is feasible, reliable and appropriated as a self-administered screening tool for pain with a neuropathic component.

Fabry disease

Fabry disease, an X-linked disorder of glycosphingolipids that is caused by the deficiency of alpha-galactosidase A, is associated with dysfunction of many cell types and includes a systemic vasculopathy. As a result, patients have a markedly increased risk of developing small-fiber peripheral neuropathy, stroke, myriad cardiac manifestations and chronic renal disease. Virtually all complications of Fabry disease are non-specific in nature and clinically indistinguishable from similar abnormalities that occur in the context of more common disorders in the general population. Although Fabry disease was originally thought to be very rare, recent studies have found a much higher incidence of mutations of the GLA gene, suggesting that this disorder is under-diagnosed. Although the etiology of Fabry disease has been known for many years, the mechanism by which the accumulating alpha-D-galactosyl moieties cause this multi-organ disorder has only recently been studied and is yet to be completely elucidated. Specific therapy for Fabry disease has been developed in the last few years but its role in the management of the disorder is still being investigated. Fortunately, standard 'non-specific' medical and surgical therapy is effective in slowing deterioration or compensating for organ failure in patients with Fabry disease. All these aspects are discussed in detail in the present review.

Post-surgical neuropathic pain

Surgeons and anaesthetists are involved in Pain Medicine, as they have a responsibility to contribute to postoperative pain management and are often consulted about longer-term pain problems as well. A large component of persistent pain after surgery can be defined as neuropathic pain (NP). Nerves are injured during surgery and pain can persist after the surgical wound has healed. NP is because of a primary lesion or dysfunction of the peripheral or central nervous system. Prevalence estimates indicate that 2-3% of the population in the developed world experience NP. Persistent post-surgical NP is a mostly unrecognized clinical problem. The chronicity and persistence of post-surgical NP is often severely debilitating and impinges on the psychosocial, physical, economic and emotional well-being of patients. Options for treatment of any neuropathic factors are based on understanding the pain mechanisms involved. The current understandings of the mechanisms involved are presented. There is reasonable evidence for the efficacy of pharmacological management for NP. The aim of this article was to appraise the prevention, diagnostic work-up, the physical and particularly the pharmacological management of post-surgical NP and to provide a glimpse of advances in the field. It is a practical approach to post-surgical NP for all surgeons and anaesthetists. The take-home message is that prevention is better than waiting for post-surgical NP to become persistent.

The diagnostic criteria for small fibre neuropathy: from symptoms to neuropathology

Small fibre neuropathy (SFN), a condition dominated by neuropathic pain, is frequently encountered in clinical practise either as prevalent manifestation of more diffuse neuropathy or distinct nosologic entity. Aetiology of SFN includes pre-diabetes status and immune-mediated diseases, though it remains frequently unknown. Due to their physiologic characteristics, small nerve fibres cannot be investigated by routine electrophysiological tests, making the diagnosis particularly difficult. Quantitative sensory testing (QST) to assess the psychophysical thresholds for cold and warm sensations and skin biopsy with quantification of somatic intraepidermal nerve fibres (IENF) have been used to determine the damage to small nerve fibres. Nevertheless, the diagnostic criteria for SFN have not been defined yet and a 'gold standard' for clinical practise and research is not available. We screened 486 patients referred to our institutions and collected 124 patients with sensory neuropathy. Among them, we identified 67 patients with pure SFN using a new diagnostic 'gold standard', based on the presence of at least two abnormal results at clinical, QST and skin biopsy examination. The diagnosis of SFN was achieved by abnormal clinical and skin biopsy findings in 43.3% of patients, abnormal skin biopsy and QST findings in 37.3% of patients, abnormal clinical and QST findings in 11.9% of patients, whereas 7.5% patients had abnormal results at all the examinations. Skin biopsy showed a diagnostic efficiency of 88.4%, clinical examination of 54.6% and QST of 46.9%. Receiver operating characteristic curve analysis confirmed the significantly higher performance of skin biopsy comparing with QST. However, we found a significant inverse correlation between IENF density and both cold and warm thresholds at the leg. Clinical examination revealed pinprick and thermal hypoesthesia in about 50% patients, and signs of peripheral vascular autonomic dysfunction in about 70% of patients. Spontaneous pain dominated the clinical picture in most SFN patients. Neuropathic pain intensity was more severe in patients with SFN than in patients with large or mixed fibre neuropathy, but there was no significant correlation with IENF density. The aetiology of SFN was initially unknown in 41.8% of patients and at 2-year follow-up a potential cause could be determined in 25% of them. Over the same period, 13% of SFN patients showed the involvement of large nerve fibres, whereas in 45.6% of them the clinical picture did not change. Spontaneous remission of neuropathic pain occurred in 10.9% of SFN patients, while it worsened in 30.4% of them.