Early recognition of hereditary motor and sensory neuropathy type 1 can avoid life-threatening vincristine neurotoxicity

Toxic medications in Charcot-Marie-Tooth patients: A systematic review

BACKGROUND AND AIMS

Several widely used medications, with a relevant efficacy profile, are toxic to the peripheral nervous system and an even larger number of agents are suspected to be neurotoxic. There are concerns about the use of these drugs in patients with Charcot-Marie-Tooth disease (CMT), a hereditary motor and sensory neuropathy. This review provides evidence-based updated recommendations on this clinically relevant topic.

METHODS

A systematic review of the available studies/reports written in English was performed from July to September 2022 including in the search string all reported putative neurotoxic drugs.

RESULTS

The results of our systematic review provide evidence-based support for the statement that use of vincristine, and possibly paclitaxel, can occasionally induce an atypical, and more severe, course of drug-related peripheral neurotoxicity in CMT patients. It is therefore reasonable to recommend caution in the use of these compounds in CMT patients. However, no convincing evidence for a similar recommendation could be found for all other drugs.

INTERPRETATION

It is important that patients with CMT are not denied effective treatments that may prolong life expectancy for cancer or improve their health status if affected by non-oncological diseases. Accurate monitoring of peripheral nerve function in CMT patients treated with any neurotoxic agent remains mandatory to detect the earliest signs of neuropathy worsening and atypical clinical courses. Neurologists monitoring CMT patients as part of their normal care package or for natural history studies should keep detailed records of exposures to neurotoxic medications and support reporting of accelerated neuropathy progression if observed.

Effective treatment of advanced Hodgkin lymphoma with a modified BEACOPP regimen for a patient with demyelinating hereditary motor and sensory neuropathy type 1 (HMSN1)

Treatment for Hodgkin lymphoma (HL) in adults comprises substantial risk of chemotherapy‐induced peripheral neurotoxicity. Here, we describe the case of patient with Charcot–Marie–Tooth disease or HSMN1 and advanced Hodgkin lymphoma undergoing treatment with modified BEACOPP achieving complete remission without major aggravation of neurological symptoms.

Genetic risk factors for VIPN in childhood acute lymphoblastic leukemia patients identified using whole-exome sequencing

AIM

To identify genetic markers associated with vincristine-induced peripheral neuropathy (VIPN) in childhood acute lymphoblastic leukemia.

PATIENTS & METHODS

Whole-exome sequencing data were combined with exome-wide association study to identify predicted-functional germline variants associated with high-grade VIPN. Genotyping was then performed for top-ranked signals (n = 237), followed by validation in independent replication group (n = 405).

RESULTS

Minor alleles of rs2781377/SYNE2 (p = 0.01) and rs10513762/MRPL47 (p = 0.01) showed increased risk, whereas that of rs3803357/BAHD1 had a protective effect (p = 0.007). Using a genetic model based on weighted genetic risk scores, an additive effect of combining these loci was observed (p = 0.003). The addition of rs1135989/ACTG1 further enhanced model performance (p = 0.0001).

CONCLUSION

Variants in SYNE2, MRPL47 and BAHD1 genes are putative new risk factors for VIPN in childhood acute lymphoblastic leukemia.

Peripheral neuropathy in children and adolescents treated for cancer

Peripheral neuropathy is a well recognised treatment-related toxicity in children with cancer, associated with exposure to neurotoxic chemotherapy agents. Acute damage can occur in sensory, motor, or autonomic neurons, with symptoms that are rarely life threatening, but often severe enough to interfere with function during therapy and after treatment ends. The type of neuropathy and specific symptoms are associated with multiple factors including age at time of therapy, genetic predisposition, chemotherapy type and cumulative dose, and exposure to other agents during therapy. In this Review, we describe the peripheral neuropathy phenotype in children during cancer therapy and among survivors who have completed therapy, to summarise genetic and treatment-related risk factors for neuropathy, and to outline strategies to monitor and detect neuropathy during and after therapy. Additionally, we outline strategies for medical management of neuropathy during treatment and potential rehabilitation interventions to prevent or remediate functional loss.

Antineoplastic agents exacerbating Charcot Marie Tooth disease: red flags to avoid permanent disability

BACKGROUND

Charcot Marie Tooth (CMT) disease is the most common form of hereditary neuropathy. Due to the high prevalence of mild and undiagnosed forms, patients with CMT disease may be exposed to severe neurotoxicity following the administration of neurotoxic chemotherapies. The aim of this report is to alert oncologists to the potential to precipitate severe irreversible peripheral neuropathies when administering neurotoxic compounds to undiagnosed CMT patients.

MATERIAL AND METHODS

A retrospective research in the OncoNeuroTox database was performed (2010-2016), searching for patients with the diagnosis of chemotherapy-induced peripheral neuropathy (CIPN) and CMT disease. A comprehensive literature review for previously published cases was performed using the Pubmed and Cochrane databases (1972-2017).

RESULTS

Among 428 patients with CIPN, we identified eight patients with concomitant CMT disease. Seven patients out of the eight had no previous diagnosis of CMT disease, although accurate familial history disclosed mild signs of peripheral neuropathy in five cases. Patients themselves had minor stigmata of long-standing peripheral damage. Patients received chemotherapy regimens based on vinca alkaloids, taxanes or a combination of vinca alkaloids and platinum compounds. In two cases, cumulative doses were below or equal to the expected neurotoxic threshold. Following chemotherapy administration, patients developed severe length-dependent sensory-motor deficits. Despite early drug discontinuation, most patients remained severely disabled.

CONCLUSION

A brief checklist to disclose long-standing signs of peripheral neuropathy could be helpful to detect patients with undiagnosed hereditary neuropathies who could be at risk of developing severe irreversible neurotoxicity following the administration of neurotoxic agents.

Long-Term Effects, Pathophysiological Mechanisms, and Risk Factors of Chemotherapy-Induced Peripheral Neuropathies: A Comprehensive Literature Review

Neurotoxic anticancer drugs, such as platinum-based anticancer drugs, taxanes, vinca alkaloids, and proteasome/angiogenesis inhibitors are responsible for chemotherapy-induced peripheral neuropathy (CIPN). The health consequences of CIPN remain worrying as it is associated with several comorbidities and affects a specific population of patients already impacted by cancer, a strong driver for declines in older adults. The purpose of this review is to present a comprehensive overview of the long-term effects of CIPN in cancer patients and survivors. Pathophysiological mechanisms and risk factors are also presented. Neurotoxic mechanisms leading to CIPNs are not yet fully understood but involve neuronopathy and/or axonopathy, mainly associated with DNA damage, oxidative stress, mitochondria toxicity, and ion channel remodeling in the neurons of the peripheral nervous system. Classical symptoms of CIPNs are peripheral neuropathy with a “stocking and glove” distribution characterized by sensory loss, paresthesia, dysesthesia and numbness, sometimes associated with neuropathic pain in the most serious cases. Several risk factors can promote CIPN as a function of the anticancer drug considered, such as cumulative dose, treatment duration, history of neuropathy, combination of therapies and genetic polymorphisms. CIPNs are frequent in cancer patients with an overall incidence of approximately 38% (possibly up to 90% of patients treated with oxaliplatin). Finally, the long-term reversibility of these CIPNs remain questionable, notably in the case of platinum-based anticancer drugs and taxanes, for which CIPN may last several years after the end of anticancer chemotherapies. These long-term effects are associated with comorbidities such as depression, insomnia, falls and decreases of health-related quality of life in cancer patients and survivors. However, it is noteworthy that these long-term effects remain poorly studied, and only limited data are available such as in the case of bortezomib and thalidomide-induced peripheral neuropathy.

An asymptomatic mutation complicating severe chemotherapy-induced peripheral neuropathy (CIPN): a case for personalised medicine and a zebrafish model of CIPN

Targeted next-generation sequencing (NGS) identified a novel loss of function mutation in GARS, a gene linked to Charcot-Marie-Tooth disease (CMT), in a paediatric acute lymphoblastic leukaemia patient with severe chemotherapy-induced peripheral neuropathy (CIPN) due to vincristine. The patient was clinically asymptomatic, and lacked a family history of neuropathy. The effect of the mutation was modelled in a zebrafish knockdown system that recapitulated the symptoms of the patient both prior to and after treatment with vincristine. Confocal microscopy of pre- and post-synaptic markers revealed that the GARS knockdown results in changes to peripheral motor neurons, acetylcholine receptors and their co-localisation in neuromuscular junctions (NMJs), whereas a sensitive and reproducible stimulus-response assay demonstrated that the changes correlating with the GARS mutation in themselves fail to produce peripheral neuropathy symptoms. However, with vincristine treatment the GARS knockdown exacerbates decreased stimulus response and NMJ lesions. We propose that there is substantial benefit in the use of a targeted NGS screen of cancer patients who are to be treated with microtubule targeting agents for deleterious mutations in CMT linked genes, and for the screening in zebrafish of reagents that might inhibit CIPN.

Sequencing of Charcot-Marie-Tooth disease genes in a toxic polyneuropathy

OBJECTIVE

Mutations in Charcot-Marie-Tooth disease (CMT) genes are the cause of rare familial forms of polyneuropathy. Whether allelic variability in CMT genes is also associated with common forms of polyneuropathy-considered "acquired" in medical parlance-is unknown. Chemotherapy-induced peripheral neuropathy (CIPN) occurs commonly in cancer patients and is individually unpredictable. We used CIPN as a clinical model to investigate the association of non-CMT polyneuropathy with CMT genes.

METHODS

A total of 269 neurologically asymptomatic cancer patients were enrolled in the clinical trial Alliance N08C1 to receive the neurotoxic drug paclitaxel, while undergoing prospective assessments for polyneuropathy. Forty-nine CMT genes were analyzed by targeted massively parallel sequencing of genomic DNA from patient blood.

RESULTS

A total of 119 (of 269) patients were identified from the 2 ends of the polyneuropathy phenotype distribution: patients that were most and least susceptible to paclitaxel polyneuropathy. The CMT gene PRX was found to be deleteriously mutated in patients who were susceptible to CIPN but not in controls (p = 8 × 10(-3)). Genetic variation in another CMT gene, ARHGEF10, was highly significantly associated with CIPN (p = 5 × 10(-4)). Three nonsynonymous recurrent single nucleotide variants contributed to the ARHGEF10 signal: rs9657362, rs2294039, and rs17683288. Of these, rs9657362 had the strongest effect (odds ratio = 4.8, p = 4 × 10(-4)).

INTERPRETATION

The results reveal an association of CMT gene allelic variability with susceptibility to CIPN. The findings raise the possibility that other acquired polyneuropathies may also be codetermined by genetic etiological factors, of which some may be related to genes already known to cause the phenotypically related Mendelian disorders of CMT.

Chemotherapy-induced peripheral neurotoxicity: a critical analysis

With a 3-fold increase in the number of cancer survivors noted since the 1970s, there are now over 28 million cancer survivors worldwide. Accordingly, there is a heightened awareness of long-term toxicities and the impact on quality of life following treatment in cancer survivors. This review will address the increasing importance and challenge of chemotherapy-induced neurotoxicity, with a focus on neuropathy associated with the treatment of breast cancer, colorectal cancer, testicular cancer, and hematological cancers. An overview of the diagnosis, symptomatology, and pathophysiology of chemotherapy-induced peripheral neuropathy will be provided, with a critical analysis of assessment strategies, neuroprotective approaches, and potential treatments. The review will concentrate on neuropathy associated with taxanes, platinum compounds, vinca alkaloids, thalidomide, and bortezomib, providing clinical information specific to these chemotherapies.

The clinical application of array CGH for the detection of chromosomal defects in 20,126 unselected newborns

Background

Array comparative genomic hybridization (CGH) is a powerful tool for detecting unbalanced chromosomal alterations. To validate the usefulness of array CGH in newborn screening, we examined 20,126 unselected infants. In addition, the number of newborns analyzed with array CGH is the largest one ever reported.

Findings

A total of 20,126 unselected newborns were investigated with array CGH and cytogenetic analyses. The analyses revealed 87 cases with chromosome abnormalities. Of these, 53 cases had significant chromosome aneuploidies, including trisomy 13, trisomy 21, 47,XXY or 45,X, and the other 34 cases presented partial chromosomal deletions or duplications.

Conclusions

In this study, we show that array CGH is an appropriate tool for the screening of chromosomal abnormalities in newborns, especially for the infants without distinct clinical features.

Administration of vincristine in a patient with Machado-Joseph disease

Chemotherapy-induced peripheral neurotoxicity is a major problem because it represents the dose-limiting side effect of a significant number of antineoplastic drugs, such as vinca alkaloids. Hereditary neuropathies usually predispose to severe vincristine neurotoxicity. Here, we report the case of a 56-year-old man with Machado-Joseph disease, also known as spinocerebellar ataxia type 3, treated with a vinca alkaloid without exacerbation of neurological symptoms.

Vincristine-induced peripheral neuropathy in a neonate with congenital acute lymphoblastic leukemia

We report the case of a 46-day-old boy with a fulminant vincristine-induced peripheral neuropathy after treatment for congenital acute lymphoblastic leukemia. Flaccid paralysis developed at the end of the first phase of induction, requiring intubation and ventilation for 51 days. Treatment was initiated with levocarnitine, N-acetylcysteine, and pyridoxine and progressive reversal of the neuropathy occurred over the next 4 months. Potential differences in pathogenesis and presentation of vincristine neurotoxicity and Guillian-Barre syndrome in the neonate are discussed.

Vincristine: Can its therapeutic index be enhanced?

Vincristine is one of the most widely used and more effective drugs in paediatric oncology. The dose-limiting toxicity of neuropathy, lack of proven neuroprotective measures and an incomplete understanding of the pharmacokinetics and pharmacogenetics of vincristine have limited its therapeutic potential. Recent advances in the understanding of vincristine pharmacokinetics and pharmacogenetics, and potential methods of preventing neurotoxicity are reviewed which could enable dose escalation and dose individualisation in order to enhance the therapeutic index.

Low dose vincristine-induced severe polyneuropathy in a Hodgkin lymphoma patient: a case report (vincristine-induced severe polyneuropathy)

Chemotherapeutic drugs are the most common toxic agents for peripheral nerves. Vincristine is a vinca alkaloid drug that is used for the treatment of several malignancies in combination with other chemotherapeutic agents. Treatment with intravenous (IV) vincristine at doses above 5 mg leads to a dose-dependent neuropathy with sensory symptoms but higher cumulative doses at around 30 to 50 mg are needed for the development of motor symptoms. The standard maximum adult IV vincristine dose is 2 mg IV per dose given at weekly intervals. However, administration of a single 2-mg dose IV vincristine may rarely result in the development of peripheral neuropathy. Few case reports have been presented on vincristine-associated severe paralysis in patients with preexisting hereditary neuropathy like Charcot-Marie Tooth (CMT) disease, who received doses even lower than 2 mg. Herein, we reported a Hodgkin lymphoma patient who developed severe polyneuropathy after receiving 2 mg vincristine treatment and was subsequently found to carry the CMT1A duplication responsible for CMT disease.

Charcot-Marie-Tooth disease

Charcot-Marie-Tooth (CMT) disease is a heterogeneous group of genetic disorders presenting with the phenotype of a chronic progressive neuropathy affecting both the motor and sensory nerves. During the last decade over two dozen genes have been identified in which mutations cause CMT. The disease illustrates a multitude of genetic principles, including diverse mutational mechanisms from point mutations to copy number variation (CNV), allelic heterogeneity, age-dependent penetrance and variable expressivity. Population based studies have determined the contributions of the various genes to disease burden enabling evidence-based approaches to genetic testing.

Uneventful administration of vincristine in Charcot-Marie-Tooth disease type 1X

Charcot-Marie-Tooth (CMT) disease is the most common inherited peripheral neuropathy. Administration of vinca alkaloids is considered contraindicated in CMT because of the risk of life threatening acute neuropathy. We describe a 5-year-old patient with a family history of X-linked CMT1 who presented with Wilms tumour. Despite confirmation of a connexin 32 point mutation, the patient was treated with 40.5 mg/m(2) of vincristine with no clinical evidence of drug-related neuropathy. This case describes vincristine being safely administered to a patient with molecularly proven type CMT 1X, but in type 1A CMT vincristine is still contraindicated. An extensive literature review revealed no other series of cases in which vincristine administration in molecularly proven CMT 1X had been described. CMT should be excluded in any patient who develops a profound, acute neuropathy following vincristine, as many patients in the cases reviewed were asymptomatic prior to treatment.

Molecular diagnostics of Charcot-Marie-Tooth disease and related peripheral neuropathies

DNA diagnostics plays an important role in the characterization and management of patients manifesting inherited peripheral neuropathies. We describe the clinical integration of molecular diagnostics with medical history, physical examination, and electrophysiological studies. Molecular testing can help establish a secure diagnosis, enable genetic counseling regarding recurrence risk, potentially provide prognostic information, and in the near future may be important for the choice of therapies.

Heterozygous P0 deficiency protects mice from vincristine-induced polyneuropathy

Patients with hereditary neuropathies are more susceptible to vincristine (VIN)-induced neuropathy than patients without this comorbidity. The heterozygous P0(+/-) mouse is an animal model of a distinct form of inherited neuropathies. These mice produce only 50% of the major myelin protein protein zero (P0) and display signs of demyelination in motor nerves at 4 months of age. Here we investigated the development of neuropathic signs in P0(+/-) and wild-type (wt) mice after VIN treatment. Neuropathy was induced by daily intraperitoneal injections of VIN (0.5 mg/kg body weight) over 10 days. Behavioral and electrophysiological tests were performed at regular time points. Wt mice developed significant hypersensitivity to heat and mechanical stimuli between days 7 and 38 after the first VIN injection. Surprisingly, P0(+/-) mice did not show sensory or motor signs of neuropathy over the whole testing period. Immunohistochemical analysis showed an increase in macrophage numbers in sciatic nerve sections of wt mice after VIN, whereas P0(+/-) mice had higher baseline levels of macrophages without changes after VIN treatment. Semithin sections revealed a decrease in the number of small-diameter myelinated fibers in the sciatic nerves of wt mice after VIN application, whereas P0(+/-) mice had higher baseline values of this fiber subtype that did not change under treatment. Dorsal root ganglion neurons of both genotypes showed an up-regulation of voltage-gated sodium channel immunoreactivity after VIN application without differences between the genotypes. Thus, the P0(+/-) phenotype seems to be protected against VIN-induced neuropathy. The mechanism of this neuroprotection remains elusive.

Medication-induced exacerbation of neuropathy in Charcot Marie Tooth Disease

Toxin or medication-induced worsening of preexisting peripheral neuropathy is a generally accepted but not well-studied phenomenon in humans. Drug-induced exacerbation of Charcot Marie Tooth disease (CMT) neuropathy is a common concern; a list of potential drugs to avoid is maintained by the CMT Association but with limited direct evidence or advice on relative risk. An extensive literature search for reported cases of drug effects in CMT patients found the vast majority concerned excessive vincristine toxicity in patients with undiagnosed demyelinating forms of CMT, many after 1 or 2 doses. The CMT North American database was also queried for all drug-related effects. All but one drug cited as worsening neuropathy was present on a compiled inclusive list. These results and other available evidence were used to develop a revised risk stratified list for CMT patients and clinicians to consult prior to discussing risk to benefit ratios and making treatment decisions.

Charcot-Marie-Tooth disease and related hereditary polyneuropathies: molecular diagnostics determine aspects of medical management

PURPOSE

An evidence-based approach was used to determine the frequency distribution of genes contributing to the Charcot-Marie-Tooth (CMT) disease phenotype.

METHODS

We performed a combined analysis of 11 population-based studies from various ethnic backgrounds to generate an evidence-based testing scheme. To estimate the relative frequencies of the responsible genes for which population-based studies are not available, we used our cohort of clinically classified patients with CMT and related neuropathies collected before the availability of genetic testing.

RESULTS

Similar mutation frequencies were detected in the various studies, revealing a uniform distribution of pathogenic mutations. In CMT1 70% of patients harbor the CMT1A duplication, followed by GJB1 mutations at 8.8%. MPZ and PMP22 mutations are less common, identified on average in 2.9% and 1.5% of patients, respectively. Other genes not tested in population-based studies contribute to less than 1% of disease individually. In CMT2 MFN2 mutations are the most common, although population-based studies are not yet available.

CONCLUSION

CMT represents a heterogeneous group of disorders at the molecular level. Nevertheless, testing for the CMT1A duplication (i.e., duplication of PMP22) alone yields an accurate molecular diagnosis in approximately half of all patients. If one further specifies the clinical type (demyelinating vs. axonal), the yield of detecting a molecular defect increases to 75% to 80% in the demyelinating or CMT1 group with a screening test that evaluates for CMT1A duplication/hereditary neuropathy with liability to pressure palsies deletion and GJB1 point mutations.

Itraconazole-related increased vincristine neurotoxicity: case report and review of literature

Itraconazole is particularly attractive in fungal prophylaxis for cancer patients due to its broad spectrum, including Candida and Aspergillus. It is generally well tolerated. However, its efficacy in preventing invasive aspergillosis could not be demonstrated. A 3-year-old boy diagnosed with acute lymphoblastic leukemia received induction chemotherapy. On day 14, itraconazole solution at a dose of 5 mg/kg was begun. Ten days after itraconazole was started, he developed paralytic ileus, neurogenic bladder, mild left ptosis, and absence of deep reflexes, with severe paralysis of the lower extremities and mild weakness of the upper extremities. Itraconazole withdrawal was followed by rapid improvement, with neurologic examination returning to normal within 6 weeks. Nineteen cases of unusual enhanced vincristine neurotoxicity related to itraconazole have been reported in children. Although the manifestations are the same as those usually associated with the use of vincristine, in these cases the severity appears remarkable. The authors suggest that in the absence of any proven benefit of itraconazole prophylaxis, and given the interaction of this drug with vincristine leading to severe and even potentially fatal toxicities, the combination use of these drugs should be avoided.

Improved testing for CMT1A and HNPP using multiplex ligation-dependent probe amplification (MLPA) with rapid DNA preparations: comparison with the interphase FISH method

Charcot-Marie-Tooth disease type 1A (CMT1A) and hereditary neuropathy with liability to pressure palsies (HNPP) are the two most common peripheral neuropathies, with incidences of about 1 in 2,500. Several techniques can be used to detect the typical 1.5-Mb duplication or deletion associated with these respective conditions, but none combines simplicity with high sensitivity. MLPA is a new technique for measuring sequence dosage. We have assessed its performance for the detection of the specific 1.5-Mb duplication/deletion by prospectively testing 50 patients referred with differential diagnoses of CMT or HNPP. Probes were designed to evaluate the TEKT3, PMP22, and COX10 genes within the CMT1A/HNPP region. We have compared the results with our existing fluorescence in situ hybridization (FISH) assay, which was performed in parallel. There was concordance of results for 49 patients. Of note, one patient showed an intermediate multiplex ligation-dependent probe amplification (MLPA) result with an abnormal FISH result, which is consistent with mosaicism. The assay works equally well with either purified DNA or rapid DNA preparations made by direct cell lysis. The use of the latter significantly reduces the cost of the assay. MLPA is a sensitive, specific, robust, and cost-effective technique suitable for fast, high-throughput testing and offers distinct advantages over other testing methods.

Neurotoxic complications of chemotherapy in patients with cancer: clinical signs and optimal management

Neurotoxic side effects of chemotherapy occur frequently and are often a reason to limit the dose of chemotherapy. Since bone marrow toxicity, as the major limiting factor in most chemotherapeutic regimens, can be overcome with growth factors or bone marrow transplantation, the use of higher doses of chemotherapy is possible, which increases the risk of neurotoxicity. Chemotherapy may cause both peripheral neurotoxicity, consisting mainly of a peripheral neuropathy, and central neurotoxicity, ranging from minor cognitive deficits to encephalopathy with dementia or even coma. In this article we describe the neurological adverse effects of the most commonly used chemotherapeutic agents. The vinca-alkaloids, cisplatin and the taxanes are amongst the most important drugs inducing peripheral neurotoxicity. These drugs are widely used for various malignancies such as ovarian and breast cancer, and haematological cancers. Chemotherapy-induced neuropathy is clearly related to cumulative dose or dose-intensities. Patients who already have neuropathic symptoms due to diabetes mellitus, hereditary neuropathies or earlier treatment with neurotoxic chemotherapy are thought to be more vulnerable for the development of chemotherapy-induced peripheral neuropathy. Methotrexate, cytarabine (cytosine arabinoside) and ifosfamide are primarily known for their central neurotoxic side effects. Central neurotoxicity ranges from acute toxicity such as aseptic meningitis, to delayed toxicities comprising cognitive deficits, hemiparesis, aphasia and progressive dementia. Risk factors are high doses, frequent administration and radiotherapy preceding methotrexate chemotherapy, which appears to be more neurotoxic than methotrexate as single modality. Data on management and neuroprotective agents are discussed. Management mainly consists of cumulative dose-reduction or lower dose-intensities, especially in patients who are at higher risk to develop neurotoxic side effects. None of the neuroprotective agents described in this article can be recommended for standard use in daily practise at this moment, and further studies are needed to confirm some of the beneficial effects described.

Sexual dimorphism for protein kinase c epsilon signaling in a rat model of vincristine-induced painful peripheral neuropathy

Painful peripheral neuropathy is a major dose-limiting adverse effect of many cancer chemotherapeutic agents, such as the vinca alkaloids and taxanes. Recent studies demonstrate sexual dimorphism in second-messenger signaling for primary afferent nociceptor sensitization, and a role of second messengers in the models of metabolic and toxic painful peripheral neuropathies. This study tested the hypothesis that sexual dimorphism alters the severity and second-messenger signaling pathways for enhanced nociception in an animal model of vincristine-induced painful peripheral neuropathy.I.V. injection of vincristine induced mechanical hyperalgesia that was greater in female rats. Gonadectomy in the females but not the males abolished the sex-dependent difference in mechanical hyperalgesia; this effect of gonadectomy in females was reversed by estrogen replacement. Inhibition of protein kinase C epsilon (PKC epsilon ) attenuated vincristine-induced hyperalgesia in males and ovariectomized females, but not in normal females or in estrogen-replaced ovariectomized females. Inhibitors of protein kinase A, protein kinase G, p42 / p44-mitogen activated protein kinase and nitric oxide synthase also attenuated vincristine-induced hyperalgesia, but to a similar degree in both sexes. These data demonstrate an estrogen-dependent sexual dimorphism in vincristine-induced hyperalgesia (female>male) and an unexpected opposite sexual dimorphism in the contribution of PKC epsilon to the severity of this hyperalgesia (male>female).

Molecular Mechanisms, Diagnosis, and Rational Approaches to Management of and Therapy for Charcot-Marie-Tooth Disease and Related Peripheral Neuropathies

During the last decade, 18 genes and 11 additional loci harboring candidate genes have been associated with Charcot-Marie-Tooth disease (CMT) and related peripheral neuropathies. Ten of these 18 genes have been identified in the last 2 years. This phenomenal pace of CMT gene discovery has fomented an unprecedented explosion of information regarding peripheral nerve biology and its pathologic manifestations in CMT. This review integrates molecular genetics with the clinical phenotypes and provides a flowchart for molecular-based diagnostics. In addition, we discuss rational approaches to molecular therapeutics, including novel biologic molecules (eg, small interfering ribonucleic acid [siRNA], antisense RNA, and ribozymes) that potentially could be used as drugs in the future. These may be applicable in attempts to normalize gene expression in cases of CMT type 1A, wherein a 1.5 Mb genomic duplication causes an increase in gene dosage that is associated with the majority of CMT cases. Aggresome formation by the PMP22 gene product, the disease-associated gene in the duplication cases, could thus be avoided. We also discuss alternative therapeutics, in light of other neurodegenerative disorders, to disrupt such aggresomes. Finally, we review rational therapeutic approaches, including the use of antioxidants such as vitamin E, coenzyme Q10, or lipoic acid to relax potential oxidative stress in peripheral nerves, for CMT management.

Neuromuscular complications of cancer

Neuromuscular complications of cancer are common and can affect any component of the peripheral nervous system from peripheral nerve cell body to muscle. Perhaps the most common complication is a length-dependent symmetric axonal polyneuropathy that is often multifactorial in etiology, resulting from metabolic and treatment effects of the primary malignancy. However, neuromuscular disorders may also be the presenting complaint in many conditions, including disorders caused by malignant infiltration of nerve and disorders cause by paraneoplastic syndromes. Although many of the paraneoplastic conditions are poorly responsive to treatment, not all are, and one hopes that prompt diagnosis of the underlying malignancy will lead to improved patient outcome. Recognition of iatrogenic neuromuscular complications is also important to modify treatment protocols when possible and thus decrease the risk of long-term neurologic disability.

Neurologic complications of cancer therapy

Neurologic complications of chemotherapy are relatively common. The diagnosis of chemotherapy-associated neurotoxicity remains a clinical one, and is largely based on the exclusion of other possible causes. The goal of this review is to describe the neurotoxicity associated with established chemothrerapeutic agents and with some of the newer biologic agents, monoclonal antibodies and targeted molecular therapies used in the treatment of cancer.