Measuring Therapy-Induced Peripheral Neuropathy: Preliminary Development and Validation of the Treatment-Induced Neuropathy Assessment Scale

The impact of scrambler therapy on pain and quality of life for chemotherapy-induced peripheral neuropathy: A pilot study

BACKGROUND

Chemotherapy-induced peripheral neuropathy (CIPN) is a debilitating disturbance among patients who received chemotherapy, with no effective treatment available. Scrambler therapy (ST) is a noninvasive treatment capable of improving multiple quality-of-life symptoms beyond pain. We aimed to evaluate the efficacy of ST for pain and nonpain symptoms related to CIPN.

METHODS

Ten patients with moderate to severe CIPN symptoms for >3 months were enrolled in a single-arm trial of ST for 10 daily sessions. CIPN-related symptoms were measured throughout the treatment period and up to 6 months thereafter.

RESULTS

The worst pain was reduced by 6 months (p = 0.0039). QST demonstrated the greatest improvement in pressure of 60 g (p = 0.308, Cohen's d = 0.42) and cold temperature threshold of 2.5°C (p = 0.9375, Cohen's d = 0.51) in the gastrocnemius area. Symptoms of numbness, tingling, trouble walking, and disturbed sleep had significant improvements at 6 months. Pain medication use decreased by 70% at the end of treatment and by 42% at 6 months. Patient satisfaction was high (82%) and no adverse events with ST treatment were reported.

CONCLUSIONS

The results of this pilot trial support the use of ST by demonstrating improvement in multiple domains of quality of life for CIPN patients during an extended follow-up of 6 months. However, further large-scale studies are needed to confirm our findings.

Chemotherapy-induced peripheral neurotoxicity: single-centre prospective study

OBJECTIVE

Chemotherapy-induced peripheral neurotoxicity (CIPN) ranges from simple paresthesia to paralysis, which may be transient or irreversible. The aim of our study was to detect CINP in our patients undergoing chemotherapy and to study the cumulative neurotoxic doses for the different drugs.

METHODS

This is a cross-sectional prospective study carried out in the medical oncology department of the Habib Bourguiba University Hospital in Sfax. A survey was conducted to detect and explore possible chemo-induced peripheral neuropathy in patients undergoing known potentially neurotoxic anti-cancer treatments.

RESULTS

Seventy-three patients were included in the study. The average age was 51.8 years (13-80 years). The prevalence of CIPN was 52.1%. CIPN was classified as grade I in 24 (63.2%) cases and grade II in 14 (36.8%) cases. No grade III or IV peripheral neuropathy was detected in our patients. Paclitaxel was the drug with the highest incidence of CIPN (76.9%). The chemotherapy (CT) protocols most prone to chemotherapy-induced peripheral neurotoxicity (CIPN) were based on taxanes (47.3%) and oxaliplatin (59%). Paclitaxel was the drug most likely to cause CIPN (76.9%) (p=0.031). Paclitaxel single dose per cycle of 175 mg/m2 (66.67%) was more associated with the occurrence of CIPN than 80 mg/m2 (40%), but without significant difference (p=0.437). The average cumulative dose was estimated at 315 mg/m2 for docetaxel, 474 mg/m2 for oxaliplatin and 579 mg/m2 for paclitaxel (p=0.16).

CONCLUSION

The prevalence of NPCI was 51.1% in our series. Oxaliplatin and taxanes were the main contributors to this complication with cumulative dose over than 300 mg/m2.

Development and validation of the chemotherapy-induced peripheral neuropathy integrated assessment - oxaliplatin subscale: a prospective cohort study

BACKGROUND

Current chemotherapy-induced peripheral neuropathy (CIPN) assessment tools mostly have poor sensitivity and weak anti-interference, so that it is sometimes difficult to provide substantive guidance for clinical intervention. This study aimed to develop an assessment tool dedicated for oxaliplatin to address these limitations.

METHODS

This study screened 445 OIPN-related literatures for producing a symptom list, and developed the questionnaire module through expert supplement, item generation, content correlation analysis, pre-testing, and item improvement. The validation phase used a Chinese population-based prospective cohort study from June 2021 to July 2022. Patients were requested to complete the tested questionnaire, QLQ-CIPN20 and the CTCAE grading one day before cycles 2-6 of chemotherapy. Cronbach's α coefficient and intraclass correlation coefficient (ICC) were calculated for the internal consistency and stability analysis, respectively. Exploratory factor analysis was conducted to investigate the construct validity. The correlations among the tested questionnaire, QLQ-CIPN20 and CTCAE were compared for the criterion validity analysis. Wilcoxon signed-rank sum test was utilized to compare the sensitivity between the tested questionnaire and QLQ-CIPN20.

RESULT

A 20-item CIPN assessment tool named chemotherapy-induced peripheral neuropathy integrated assessment - oxaliplatin subscale (CIPNIA-OS) was developed. The validation phase included 186 patients. Cronbach's α coefficient of CIPNIA-OS was 0.764 (> 0.7), and ICC was 0.997 (between 0.9 and 1). The structure of CIPNIA-OS containing seven factors was examined. The correlation coefficient between CIPNIA-OS and CTCAE was 0.661 (95%CI 0.623 to 0.695), which was significantly higher than that between QLQ-CIPN20 and CTCAE (0.417, 95%CI 0.363 to 0.469, p < 0.01). Besides, the total score of CIPNIA-OS was mostly higher than QLQ-CIPN20, with an average difference of 2.189 (CI 95% 2.056 to 2.322), and the difference gradually expanded with the progress of chemotherapy (p < 0.05).

CONCLUSION

This study developed an original CIPN questionnaire which was dedicated for OIPN assessment. It was a comprehensive tool that covered acute OIPN symptoms and integrated features from several proven CIPN assessment tools. The validation results supported that CIPNIA-OS had satisfactory reliability, stability, construct, criterion validity, and was more accuracy and sensitive than QLQ-CIPN20 in the evaluation of OIPN.

Studies to Assess the Utility of Serum Neurofilament Light Chain as a Biomarker in Chemotherapy-Induced Peripheral Neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) is one of the most common and disabling dose-limiting toxicities of chemotherapy. We report here the results of two separate non-interventional studies (49 patients), which evaluated blood neurofilament light chain (NfL) as a biomarker of CIPN in breast cancer patients treated with paclitaxel. All patients underwent a standard treatment protocol that was established independently of the present studies. NfL was measured in serum using an ultrasensitive single-molecule array and compared with the self-administered European Organization for Research and Treatment of Cancer Quality of Life Questionnaire-CIPN twenty-item scale (CIPN20) and Total Neuropathy Score clinical version (TNSc), a clinician-reported measure of neuropathy progression. The TNSc increased with cumulative dose compared with baseline, and the NfL concentrations were also strongly associated with the cumulative dose of chemotherapy. The analysis showed a correlation between TNSc and NfL. Both TNSc and NfL showed weak to moderate associations with CIPN20 subscores, with a better association for the CIPN20 sensory compared with motor and autonomic subscores. Data from the two studies provide evidence that serum NfL has the potential to be used as a biomarker to monitor and mitigate CIPN. However, studies with additional patients planned in the ongoing clinical trial will determine the universal application of NfL as a biomarker in CIPN.

Overview of radiotherapy-induced chronic pain in childhood cancer survivors: A narrative review

Radiotherapy is an important aspect of oncological treatment in several childhood cancers. However, radiotherapy is known to have numerous side effects, including detrimental effects on growth, neurocognitive impairment, and the development of secondary malignancies. One less studied long-term side effect of pediatric radiotherapy treatment is chronic pain. While the short-term toxicities of radiotherapy resolve over a few weeks to months, the chronic pain caused by radiotherapy-induced tissue damage can significantly affect children's quality of life. As long-term childhood cancer survivors age into adulthood, they are typically followed up by a wide variety of doctors, not all of whom may be familiar with radiotherapy-induced chronic pain and its management. The aim of this review is to discuss the various common manifestations of radiotherapy-related pain in children, as well as ways to identify and manage these. Common radiotherapy-related side effects leading to chronic pain symptoms include radiation fibrosis, enteritis, dermatitis, lymphedema, neuropathic pain, and effects on bone development. The pathophysiology, evaluation and management of these are briefly summarized in this review. This is followed by an overview of radiotherapy techniques that allow greater sparing of normal tissue, minimizing future painful side effects. Finally, the assessment of pain in children is described, as well as strategies for management, and red flag symptoms that should prompt urgent specialist referral. In conclusion, a good understanding of the long-term side effects of radiotherapy treatment in children is essential for the various medical professionals that follow-up the child in the years after treatment. For young children, the evaluation of pain is in itself a challenge, and effects on growth, development, and learning are crucial. For older children, social and psychological factors become increasingly important. As radiation therapy techniques continue to advance, the spectrum and incidence of chronic pain syndromes may change over time.

Assessing chemotherapy-induced peripheral neuropathy with patient reported outcome measures: a systematic review of measurement properties and considerations for future use

PURPOSE

Chemotherapy-induced peripheral neuropathy (CIPN) is a common toxicity of cancer treatment, with potential to significantly impact cancer survivors' long-term quality of life. Patient reported outcome measures (PROMs) are increasingly utilised to evaluate CIPN. However, guidance remains lacking on how to identify fit for purpose PROMs with considerations necessarily differing when used in various research and in-clinic contexts. This study aimed to evaluate evidence about CIPN PROMs measurement properties and propose considerations to optimize CIPN PROM selection for each purpose.

METHODS

A systematic review was conducted to identify literature assessing measurement properties of CIPN PROMs. These were evaluated against Consensus-based Standards for the selection of health Measurement Instruments (COSMIN) criteria and International Society for Quality of Life minimum standards. Risk of Bias (RoB) was assessed using the COSMIN RoB checklist.

RESULTS

Thirty-nine papers evaluating measurement properties of 13 PROMs were included. The European Organization for Research and Treatment of Cancer Quality of Life Chemotherapy-Induced Peripheral Neuropathy Questionnaire (QLQ-CIPN20) and Functional Assessment of Cancer Therapy/Gynecologic Oncology Group-Neurotoxicity (FACT/GOG-Ntx) were the most commonly investigated PROMs and had the most measurement properties meeting established criteria.

CONCLUSION

The use of the QLQ-CIPN20 and FACT/GOG-Ntx to assess CIPN in research settings has the most supporting evidence. However other considerations including study aims, endpoints and target population also factor into PROM selection and need to be considered more often when determining the most suitable outcome measure. Evidence of CIPN PROMs use in clinical practice is limited and their adoption to individual-patient level management requires more evaluation.

Chemotherapy-Induced Peripheral Neuropathy: Epidemiology, Pathomechanisms and Treatment

PURPOSE

This review provides an update on the current clinical, epidemiological and pathophysiological evidence alongside the diagnostic, prevention and treatment approach to chemotherapy-induced peripheral neuropathy (CIPN).

FINDINGS

The incidence of cancer and long-term survival after treatment is increasing. CIPN affects sensory, motor and autonomic nerves and is one of the most common adverse events caused by chemotherapeutic agents, which in severe cases leads to dose reduction or treatment cessation, with increased mortality. The primary classes of chemotherapeutic agents associated with CIPN are platinum-based drugs, taxanes, vinca alkaloids, bortezomib and thalidomide. Platinum agents are the most neurotoxic, with oxaliplatin causing the highest prevalence of CIPN. CIPN can progress from acute to chronic, may deteriorate even after treatment cessation (a phenomenon known as coasting) or only partially attenuate. Different chemotherapeutic agents share both similarities and key differences in pathophysiology and clinical presentation. The diagnosis of CIPN relies heavily on identifying symptoms, with limited objective diagnostic approaches targeting the class of affected nerve fibres. Studies have consistently failed to identify at-risk cohorts, and there are no proven strategies or interventions to prevent or limit the development of CIPN. Furthermore, multiple treatments developed to relieve symptoms and to modify the underlying disease in CIPN have failed.

IMPLICATIONS

The increasing prevalence of CIPN demands an objective approach to identify at-risk patients in order to prevent or limit progression and effectively alleviate the symptoms associated with CIPN. An evidence base for novel targets and both pharmacological and non-pharmacological treatments is beginning to emerge and has been recognised recently in publications by the American Society of Clinical Oncology and analgesic trial design expert groups such as ACTTION.

Clinical and biochemical markers in CIPN: A reappraisal

The increased survival of cancer patients has raised growing public health concern on associated long-term consequences of antineoplastic treatment. Chemotherapy-induced peripheral neuropathy (CIPN) is a primarily sensory polyneuropathy, which may be accompanied by pain, autonomic disturbances, and motor deficit. About 70% of treated cancer patients might develop CIPN during or after the completion of chemotherapy, and in most of them such complication persists after six months from the treatment. The definition of the potential risk of development and resolution of CIPN according to a clinical and biochemical profile would be certainly fundamental to tailor chemotherapy regimen and dosage on individual susceptibility. In recent years, patient-reported and clinician-related tools along with quality of life instruments have been featured as primary outcomes in clinical setting and randomized trials. New studies on metabolomics markers are further pursuing accurate and easily accessible indicators of peripheral nerve damage. The aim of this review is to outline the strengths and pitfalls of current knowledge on CIPN, and to provide a framework for future potential developments of standardized protocols involving clinical and biochemical markers for CIPN assessment and monitoring.

New Developments in the Use of Patient-Reported Outcomes in Cancer Patients Undergoing Immunotherapies

In a previous chapter, how best to measure symptoms was discussed, the desirable properties of a psychometrically valid symptom assessment tool were listed, available symptom assessment tools were reviewed, methods to assist in the interpretation of patient-reported outcomes (PRO) data were provided, and the current use of PROs in immunotherapy was described. Two areas for further research were also identified. These two areas were (1) deciding on the frequency of administration of symptom assessment and (2) determining the adequacy of the chosen symptom list to cover both known and unknown effects of immunotherapy. This brief update provides new developments on these two critical issues that are of significant concerns to researchers and clinicians who are investigating the use of immunotherapies either singly or in combination in cancer patients.

Overview and critical revision of clinical assessment tools in chemotherapy-induced peripheral neurotoxicity

Chemotherapy-induced peripheral neurotoxicity (CIPN) is a major toxicity of cancer treatment, leading to dose reduction and premature treatment cessation, potentially affecting patient function, and quality of life. The development of accurate and sensitive assessment tools for CIPN is essential to enable clinical monitoring during treatment, follow-up of long-term outcomes and measurement of toxicity in clinical trials. This review examines CIPN clinical assessment scales incorporating clinician-based, composite, and patient-reported outcomes (PROs), providing a systematic review of their properties and an updated critical analysis of recommendations on current evidence for their use. This systematic review of CIPN assessment tools identified 50 papers containing 41 assessment tools, across 4 categories (common toxicity criteria; composite neurological scale; PROs; pain scale). The majority of these tools were PROs, underscoring the importance of patient-based assessment of symptoms. While there has been considerable work in the field over the past 10 years, this review highlights significant gaps, including a lack of evaluation of responsiveness and problematic neuropathic pain evaluation. There remains a need for consensus on the best available tool and the need to modify existing instruments to improve utility.

The Treatment-induced Neuropathy Assessment Scale (TNAS): a psychometric update following qualitative enrichment

BACKGROUND

The validation of the Treatment-induced Neuropathy Assessment Scale (TNAS v2.0), a patient-reported outcome measure of symptoms associated with cancer treatment-induced peripheral neuropathy (TIPN), was previously reported. Further patient input (qualitative interviewing, cognitive debriefing) suggested that the measure should be modified to better reflect the TIPN experience. We report the performance of a revised version (TNAS v3.0) for assessing TIPN across cancer treatments. This TNAS version incorporates extensive patient input, in accordance with FDA guidance on the development of patient-reported outcomes measures. Patients with multiple myeloma, colorectal cancer, or gynecological cancer treated with bortezomib, oxaliplatin, or taxane-platinum combination therapy, respectively, completed the TNAS v3.0, European Organization for Research and Treatment of Cancer Chemotherapy-Induced Peripheral Neuropathy (EORTC-CIPN20), and a cognitive debriefing survey during a scheduled clinic visit. Patients also participated in in-depth qualitative interviews about their TIPN symptoms. The psychometric properties of the TNAS v3.0 were evaluated.

RESULTS

Cognitive debriefing survey results were summarized and showed that most patients found the items easy to complete, comprehensible, acceptable, and not redundant. A notable change from TNAS v2.0 was the separation of "numbness" from "tingling," although these 2 items remained the most severe, followed by a new "pain" item. The Cronbach coefficient alphas for the 9-item TNAS were 0.88 and 0.90 at the first and second administrations, respectively, indicating good reliability. The test-retest reliability of the TNAS was 0.97. The correlation coefficients for the 9-item TNAS and the EORTC-CIPN20 were 0.69 for the sensory subscale, 0.70 for the motor subscale, and 0.32 for the autonomic subscale, indicating good validity.

CONCLUSION

This psychometric evaluation showed that the TNAS v3.0 is valid and reliable. Further research is needed to determine clinically meaningful differences in TNAS v3.0 scores and demonstrate its responsiveness over time.

Mechanisms, Predictors, and Challenges in Assessing and Managing Painful Chemotherapy-Induced Peripheral Neuropathy

OBJECTIVE

To describe the known predictors and pathophysiological mechanisms of chronic painful chemotherapy-induced peripheral neuropathy (CIPN) in cancer survivors and the challenges in assessing and managing it.

DATA SOURCES

PubMed/Medline, CINAHL, Scopus, and PsycINFO.

CONCLUSION

The research on chronic painful CIPN is limited. Additional research is needed to identify the predictors and pathophysiological mechanisms of chronic painful CIPN to inform the development of assessment tools and management options for this painful and possibly debilitating condition.

IMPLICATIONS FOR NURSING PRACTICE

Recognition of the predictors of chronic painful CIPN and proactive CIPN assessment and palliative management are important steps in reducing its impact on physical function and quality of life.

Concept domain validation and item generation for the Treatment-Induced Neuropathy Assessment Scale (TNAS)

PURPOSE

Treatment-induced peripheral neuropathy (TIPN) is a difficult problem experienced by patients with cancer that can interfere with their ability to receive optimal therapy. The Treatment-Induced Peripheral Neuropathy Scale (TNAS) is a patient-reported outcome (PRO) measure developed to assess TIPN symptom burden. However, PRO validation is an ongoing process. The aim of this qualitative study was to define the conceptual model, establish content domain validity, and refine items for the TNAS based on patient input.

METHODS

Patients who received bortezomib, oxaliplatin, or platinum-taxane combination therapy reported their experience of TIPN in single qualitative audiotaped interviews. Themes of the TIPN experience were identified by descriptive analysis of the transcribed interviews.

RESULTS

Three groups of 10 patients each who had received bortezomib, oxaliplatin, or platinum-taxane combination therapy, for a total of 30 patients, reported their experiences. Two themes reported by patients were TIPN sensations and functional interference. Five sensations (numbness, tingling, pain, heat or burning, and coldness) and five functional impacts (using hands, walking, maintaining balance or falling, wearing shoes, and sleeping) were reported by at least 20% of patients and were selected for inclusion in the TNAS v3.0 for additional psychometric testing.

CONCLUSIONS

The assessment of TIPN must be convenient, reliable, and practical for patients, who are the most reliable source of information about symptoms. The TNAS, developed with direct patient input, provides an easily administered and conceptually valid method of patient report of TIPN burden for use in research and practice.

Neuropatia periférica em pessoas com mieloma múltiplo

Resumo Objetivo Investigar a prevalência e incidência de neuropatia periférica relacionada ao tratamento com antineoplásicos de pessoas com mieloma múltiplo bem como a associação entre os esquemas quimioterápicos e a neuropatia periférica após o tratamento. Método Estudo documental, correlacional, realizado em dois locais de referência para tratamento oncológico, localizados nos estados do Ceará e Minas Gerais, com análise de pacientes atendidos entre janeiro/2013 e janeiro/2016. Os dados foram analisados utilizando-se análise descritiva e inferencial a partir dos testes qui-quadrado e exato de fisher. Resultados Foram avaliados 100 prontuários de pessoas com mieloma múltiplo com média de idade de 62,7 anos, maioria de homens (64%). O esquema quimioterápico mais utilizado (60%) foi o bortezomibe, dexametasona e ciclofosfamida; 20% dos pacientes apresentavam neuropatia periférica antes do tratamento, 68% desenvolveram durante o tratamento e 56% ao finalizar o tratamento. Não houve associação entre os esquemas quimioterápicos e a neuropatia periférica após o tratamento. Conclusão O presente estudo mostrou um aumento da incidência de NP em indivíduos em tratamento para o MM, 80% apresentaram sintomas de neuropatia antes e/ou durante e/ou após o tratamento com esquemas quimioterápicos. A predominância foi de homens idosos aposentados. O esquema quimioterápico mais utilizado foi o VDC e não foi identificada associação entre os esquemas utilizados e a NP após término o tratamento. As implicações dessas observações recaem sobre a necessidade de avaliação contínua da NP em pessoas com MM, além da monitorização rigorosa desse evento no decorrer do tratamento e após o mesmo, bem como o manejo dos eventos adversos e alterações relacionadas a doença. Não houve associação entre os esquemas quimioterápicos e a neuropatia periférica após o tratamento. Espera-se que os resultados obtidos auxiliem na organização de um registro de dados sobre NP em pacientes com câncer, com o objetivo principal de determinar alvos de intervenção, tornando o cuidado mais eficiente e integral.

Cold Pressor Pain Response in Children With Cancer

OBJECTIVE

The goal of this study was to examine pain responses in pediatric patients with cancer.

METHOD

Children (ages 6 to 18) undergoing treatment for cancer (N=68) completed the cold pressor task.

RESULTS

Average pain tolerance was 118.22 seconds (SD=101.18) and 40% of the children kept their hand in the water the entire 4-minute ceiling. On a 0 to 10 numeric rating scale, children reported a pain severity of 5.07 (SD=3.47) at their first report of pain, a pain severity of 5.94 (SD=3.54) at their maximum report of pain, and a pain severity of 5.33 (SD=3.72) at the time they reached pain tolerance. Children receiving chemotherapy agents (N=56) with possible neuropathic effects exhibited higher pain tolerance compared with children not receiving such treatments (N=10), β=0.84, SE=0.38, Wald χ1=4.88, P=0.027, hazard ratio=2.33, 95% confidence interval (1.10-4.92).

CONCLUSIONS

This study provides data on experimental pain responses in a sample of children undergoing cancer treatment and suggests that pain experience may be moderated by cancer treatment type.

Initial Development and Validation of a Patient-Reported Symptom Survey for Small-Fiber Polyneuropathy

Small-fiber polyneuropathy (SFPN) affects unmyelinated and thinly myelinated peripheral axons. Several questionnaires have been developed to assess polyneuropathy from diabetes or chemotherapy, but none for SFPN from other or unknown causes. A comprehensive survey could help clinicians diagnose and assess treatment responses, define prevalence natural history and cures, and identify research subjects. Thus, we developed the 1-page Small-Fiber Symptom Survey, using input from patients and 21 medical/scientific experts. Participants comprised consenting consecutive patients evaluated for SFPN at the Massachusetts General Hospital plus normal control subjects. Participants SFPN status was stratified on the basis of the results of their objective diagnostic tests (distal leg skin biopsy and autonomic function testing). We measured internal consistency, test retest reliability, convergent validity, and performed a receiver operating curve analysis. The 179 participants averaged 46.6 ± 15.6 years old; they were 73.2% female and 92.2% Caucasian. Eighty-five had confirmed SFPN, mostly idiopathic. Principal component analysis revealed 5 symptom clusters. The questionnaire had good internal consistency (Cronbach α = .893), excellent test retest reliability (r = .927, P < .001) and good to fair convergent validity. Participants with confirmed SFPN had more severe symptoms than others (P = .009). The Small-Fiber Symptom Survey has satisfactory psychometric properties, indicating potential future utility for surveying patient-reported symptoms of SFPN regardless of its cause.

PERSPECTIVE

This article reports the initial development and early psychometric validation of a new patient-reported outcome measure intended to capture the wide range of multisystem symptoms of SFPN. When further developed, it could potentially help clinicians diagnose and monitor patients, and help advance research.

Behavioral and electromyographic assessment of oxaliplatin-induced motor dysfunctions: Evidence for a therapeutic effect of allopregnanolone

The antineoplastic oxaliplatin (OXAL) is pivotal for metastatic cancer treatments. However, OXAL evokes sensory and motor side-effects including pain, muscle weakness, motor nerve fiber dysfunctions/neuropathies that significantly impact patients' lives. Therefore, preclinical investigations are struggling to characterize effective analgesics against OXAL-induced painful/sensory symptoms but surprisingly, OXAL-evoked motor dysfunctions received little attention although these neurological symptoms are also disabling for patients. Here, we validated a rat model of OXAL-induced motor neuropathy by using (i) behavioral methods as the wire suspension and balance beam tests to assess muscle weakness and (ii) electrophysiological techniques to record the gastrocnemius electromyography (EMG). The conductance velocity of motor fibers was reduced and compound muscle action potential (CMAP) duration increased in OXAL-treated rats, leading to CMAP dispersion with no modification of the area under the curve, reflecting a heterogeneous demyelination of motor fibers. Functional motor unit analysis revealed a 50 % decrease of their estimated number which was compensated by a motor unit size increase. OXAL-induced motor weakness appeared as a combined consequence of motor fiber demyelination and motor axonopathy. Because we previously observed that allopregnanolone (AP) counteracted OXAL-evoked painful/sensory symptoms, we evaluated its action against OXAL-induced motor neurological dysfunctions. AP treatment successfully corrected motor behaviors, conductance velocity, CMAP duration, motor unit number (MUN) and motor unit size altered by OXAL-chemotherapy. These results, which are the first to show that AP efficiently rescues OXAL-induced motor neuropathy, consolidate the idea that AP-based therapy may be relevant for the treatment of both sensory and motor peripheral neuropathies.

Managing treatment-related peripheral neuropathy in patients with multiple myeloma

Peripheral neuropathy is one of the most important complications of multiple myeloma treatment. Neurological damage can be observed at the onset of the disease, due to the effect of monoclonal protein or radicular compression, but more often is treatment related. Vinca alkaloids in the past era, and more recently, thalidomide and bortezomib are mainly responsible. Degeneration of dorsal root ganglion is common, prevalently related to angiogenesis inhibition and cytokine modulation in the case of thalidomide and inhibition of the ubiquitin proteasome system in the case of bortezomib. Sensory neuropathy and neuropathic pain are more common; motor neuropathy and autonomic damage are less frequently observed. Neurotoxicity often affects patient's quality of life and requires dose modification or withdrawal of therapy, with a possible effect on the overall response. A prompt recognition of predisposing factors (such as diabetes mellitus, alcohol abuse, vitamin deficiencies, or viral infections) and appearance of signs and symptoms, through a periodic neurological assessment with appropriate scales, is extremely important. Effective management of treatment at the emergence of peripheral neuropathy can minimize the incidence and severity of this complication and preserve therapeutic efficacy. Dose adjustment could be necessary during treatment; moreover, gabapentin or pregabalin, tricyclic antidepressants, serotonin and norepinephrine reuptake inhibitors, carbamazepine, and opioid-type analgesics are suggested according to the pain severity. Some authors reported that patients who develop peripheral neuropathy during their multiple myeloma treatments presented a particular gene expression profile; therefore, future studies could be helpful for a better understanding of possible biological pathways underlying neurotoxicity.