Acute deterioration of Charcot-Marie-Tooth disease IA (CMT IA) following 2 mg of vincristine chemotherapy

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.

Effect of pyridoxine plus pyridostigmine treatment on vincristine-induced peripheral neuropathy in pediatric patients with acute lymphoblastic leukemia: a single-center experience

BACKGROUND

Vincristine (VCR), which is a key component of chemotherapy, is important for survival. VCR is associated with a well-known side effect, including neurotoxicity.

AIMS

The aim of this study was to evaluate the features of vincristine-induced peripheral neuropathy (VIPN) and the effectiveness of pyridoxine plus pyridostigmine therapy in children with acute lymphoblastic leukemia.

METHODS

The WHO and NCI CTCAE neurotoxicity scorings were used to evaluate VIPN at diagnosis, in the first month, and after the third month of the treatment. The clinical features of 23 patients having acute lymphoblastic leukemia with VIPN during the period of July 2013-February 2016 were prospectively evaluated.

RESULTS

The mean age was 72.8 ± 51.6 months, and 26.1%, 56.5%, and 17.4% were in standard, moderate, and high-risk groups, respectively. Neuropathy frequently occurred at induction (82.6%) and reinduction (17.4%) of the protocol. Drop foot (82.6%), leg pain (82.6%), and difficulty in walking (82.6%) were observed. The mean total cumulative dose of neuropathy occurrence was 5.6 ± 2.03 mg/m². Our study showed that both the WHO and NCI CTCAE scorings were significantly improved via pyridoxine plus pyridostigmine therapy.

CONCLUSION

The WHO and NCI CTCAE scorings may be used for evaluating neuropathy at diagnosis and follow-up of neurotoxicity with treatment. Pyridoxine plus pyridostigmine therapy may be an effective option in the treatment of VIPN.

Rate of Changes in CMT Neuropathy and Examination Scores in Japanese Adult CMT1A Patients

Introduction: We aimed to clarify when adult patients with Charcot-Marie-Tooth disease type 1A (CMT1A), especially those diagnosed at middle or advanced ages, first showed symptoms and whether the rate of disease progression is accelerated by aging.

Methods: Medical records of CMT1A outpatients between 2012 and 2019 were reviewed. The age at diagnosis, age when symptoms first appeared, and rate of disease progression, assessed based on clinical outcome measures including the CMT Neuropathy Score (CMTNS), Rasch-modified CMTNS (CMTNS-R), CMT Examination Score (CMTES), and Rasch-modified CMTES (CMTES-R) were analyzed.

Results: Among 45 adult CMT1A patients, 42% had been diagnosed after 50 years of age, whereas 91% of all patients had exhibited some CMT-related symptoms before 20 years of age. The annual increase of all clinical outcome measures did not differ between patients under and over 50 years. Even when limited to patients whose initial CMTES-R showed mild to moderate severity, the rate of change in CMTES-R did not differ between the two age groups (the annual mean ± standard deviation, under 50 years: 1.1 ± 1.0, and over 50 years: 0.9 ± 1.1, p = 0.68). To determine whether patients with disabilities at a young age have a higher deterioration rate, they were classified into three groups according to their current age and age at diagnosis: patients under 50 years of age, patients over 50 years of age but diagnosed before 50, and patients diagnosed after 50 years of age. The mean annual increase of all clinical outcome measures, however, did not differ among these groups (CMTES-R: 1.03 ± 1.01 vs. 0.94 ± 1.57 vs. 0.81 ± 0.88, respectively, p = 0.87).

Discussion: CMT1A patients develop symptoms in childhood and adolescence even if such symptoms are not noticeable until reaching an advanced age. Deterioration rates of clinical outcome measures are constant irrespective of the age in their adulthood, although we cannot rule out the limitation that the difference did not reach significance because of the small number of patients. Being aware of the existence of a considerable number of undiagnosed CMT patients will help promote the avoidance of inadequate medication.

Cancer Rehabilitation: Acute and Chronic Issues, Nerve Injury, Radiation Sequelae, Surgical and Chemo-Related, Part 1

Individuals with cancer commonly experience functional impairments. Symptoms may present immediately or years to decades following their treatment. These impairments may include fatigue, pain, neuropathy, lymphedema, or radiation fibrosis syndrome and have the potential to deleteriously impact their function and quality of life. Cancer rehabilitation is a comprehensive resource that facilitates maximizing and maintaining cancer survivors' physical, social, psychological, and vocational functioning. This article covers the common functional impairments experienced by cancer survivors and the treatment strategies used in cancer rehabilitation. Application of these services can enhance the ongoing care for cancer survivors.

Peripheral nervous system involvement in lymphomas

The peripheral nervous system may be involved at any stage in the course of lymphoproliferative diseases. The different underlying mechanisms include neurotoxicity secondary to chemotherapy, direct nerve infiltration (neurolymphomatosis), infections, immune-mediated, paraneoplastic or metabolic processes and nutritional deficiencies. Accordingly, the clinical features are heterogeneous and depend on the localization of the damage (ganglia, roots, plexi, and peripheral nerves) and on the involved structures (myelin, axon, and cell body). Some clinical findings, such a focal or diffuse involvement, symmetric or asymmetric pattern, presence of pain may point to the correct diagnosis. Besides a thorough medical history and neurological examination, neurophysiological studies, cerebrospinal fluid analysis, nerve biopsy (in selected patients with suspected lymphomatous infiltration) and neuroimaging techniques (magnetic resonance neurography and nerve ultrasound) may be crucial for a proper diagnostic workup.

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.

Charcot-Marie-Tooth hereditary neuropathy revealed after administration of docetaxel in advanced breast cancer

Charcot-Marie-Tooth (CMT) neuropathy is the most common hereditary cause of neuropathy. Diagnosis is usually not made during the childhood but in adolescence or late adulthood. It is reported in the literature that some neurotoxic chemotherapeutical agents can reveal an asymptomatic CMT IA hereditary neuropathy. To our knowledge, we report here the first case of CMT IA revealed in a 55-year-old woman after the administration of docetaxel/trastuzumab/pertuzumab for metastatic breast cancer. This case stresses again the necessity to obtain a complete personal and familial anamnesis and to perform a neurologic examination before the administration of neurotoxic chemotherapeutical agents to prevent the clinical expression of these hereditary neuropathies.

Towards a functional pathology of hereditary neuropathies

A growing number of hereditary neuropathies have been assigned to causative gene defects in recent years. The study of human nerve biopsy samples has contributed substantially to the discovery of many of these neuropathy genes. Genotype-phenotype correlations based on peripheral nerve pathology have provided a comprehensive picture of the consequences of these mutations. Intriguingly, several gene defects lead to distinguishable lesion patterns that can be studied in nerve biopsies. These characteristic features include the loss of certain nerve fiber populations and a large spectrum of distinct structural changes of axons, Schwann cells and other components of peripheral nerves. In several instances the lesion patterns are directly or indirectly linked to the known functions of the mutated gene. The present review is designed to provide an overview on these characteristic patterns. It also considers other aspects important for the manifestation and pathology of hereditary neuropathies including the role of inflammation, effects of chemotherapeutic agents and alterations detectable in skin biopsies.

Clinical genomics: from a truly personal genome viewpoint

The path to Clinical Genomics is punctuated by our understanding of what types of DNA structural and sequence variation contribute to disease, the many technical challenges to detect such variation genome-wide, and the initial struggles to interpret personal genome variation in the context of disease. This review describes one perspective of the development of clinical genomics; whereas the experimental challenges, and hurdles to overcoming them, might be deemed readily apparent, the non-technical issues for clinical implementation may be less obvious. Some of these latter challenges, including: (1) informed consent, (2) privacy, (3) what constitutes potentially pathogenic variation contributing to disease, (4) disease penetrance in populations, and (5) the genetic architecture of disease, and the struggles sometimes faced for solutions, are highlighted using illustrative examples.

Successful Treatment of Amyloid Light-chain Amyloidosis in a Charcot-Marie-Tooth Disease Patient with Lenalidomide, Cyclophosphamide, and Dexamethasone

A 70-year-old woman with Charcot-Marie-Tooth disease (CMT) suffered from nephrotic syndrome and a renal biopsy revealed non-AA amyloid depositions that contained immunoglobulin light chain λ. Her serum λ free LC was elevated to 80.8 mg/L and she was diagnosed with primary amyloid light-chain (AL) amyloidosis. She was subsequently treated with lenalidomide, cyclophosphamide, and dexamethasone (RCD). After 14 cycles of RCD, she achieved complete remission. Her serum albumin levels gradually normalized to 3.1 g/dL. No exacerbation of neurologic symptoms related to CMT was observed. Thus, RCD may be a well-tolerated and effective regimen for treating AL amyloidosis in patients with CMT disease.

Exacerbation of Charcot-Marie-Tooth type 2E neuropathy following traumatic nerve injury

Charcot-Marie-Tooth disease (CMT) is the most commonly inherited peripheral neuropathy. CMT disease signs include distal limb neuropathy, abnormal gait, sensory defects, and deafness. We generated a novel line of CMT2E mice expressing hNF-L(E397K), which displayed muscle atrophy of the lower limbs without denervation, proximal reduction in large caliber axons, and decreased nerve conduction velocity. In this study, we challenged wild type, hNF-L and hNF-L(E397K) mice with crush injury to the sciatic nerve. We analyzed functional recovery by measuring toe spread and analyzed gait using the Catwalk system. hNF-L(E397K) mice demonstrated reduced recovery from nerve injury consistent with increased susceptibility to neuropathy observed in CMT patients. In addition, hNF-L(E397K) developed a permanent reduction in their ability to weight bear, increased mechanical allodynia, and premature gait shift in the injured limb, which led to increasingly disrupted interlimb coordination in hNF-L(E397K). Exacerbation of neuropathy after injury and identification of gait alterations in combination with previously described pathology suggests that hNF-L(E397K) mice recapitulate many of clinical signs associated with CMT2. Therefore, hNF-L(E397K) mice provide a model for determining the efficacy of novel therapies.

PMP22 related neuropathies: Charcot-Marie-Tooth disease type 1A and Hereditary Neuropathy with liability to Pressure Palsies

PMP22 related neuropathies comprise (1) PMP22 duplications leading to Charcot-Marie-Tooth disease type 1A (CMT1A), (2) PMP22 deletions, leading to Hereditary Neuropathy with liability to Pressure Palsies (HNPP), and (3) PMP22 point mutations, causing both phenotypes. Overall prevalence of CMT is usually reported as 1:2,500, epidemiological studies show that 20-64% of CMT patients carry the PMP22 duplication. The prevalence of HNPP is not well known. CMT1A usually presents in the first two decades with difficulty walking or running. Distal symmetrical muscle weakness and wasting and sensory loss is present, legs more frequently and more severely affected than arms. HNPP typically leads to episodic, painless, recurrent, focal motor and sensory peripheral neuropathy, preceded by minor compression on the affected nerve. Electrophysiological evaluation is needed to determine whether the polyneuropathy is demyelinating. Sonography of the nerves can be useful. Diagnosis is confirmed by finding respectively a PMP22 duplication, deletion or point mutation. Differential diagnosis includes other inherited neuropathies, and acquired polyneuropathies. The mode of inheritance is autosomal dominant and de novo mutations occur. Offspring of patients have a chance of 50% to inherit the mutation from their affected parent. Prenatal testing is possible; requests for prenatal testing are not common. Treatment is currently symptomatic and may include management by a rehabilitation physician, physiotherapist, occupational therapist and orthopaedic surgeon. Adult CMT1A patients show slow clinical progression of disease, which seems to reflect a process of normal ageing. Life expectancy is normal.

Vincristine-related neuropathy versus acute inflammatory demyelinating polyradiculoneuropathy in children with acute lymphoblastic leukemia

The objective of this study was to evaluate whether electroneurography could help in differentiating between vincristine-induced neuropathy and acute inflammatory demyelinating polyradiculoneuropathy. We performed electroneurography in 7 children from September 2006 to March 2009 admitted to receive chemotherapy including vincristine for acute lymphoblastic leukemia, in whom severe acute limb weakness developed, suggesting vincristine-induced neuropathy. Three of 7 patients had electroneurography, suggesting acute inflammatory demyelinating polyradiculoneuropathy. They received intravenous immunoglobulins without discontinuing chemotherapy, and within 10 days their electroclinical conditions improved. Although electroneurography showed only absent F waves, preventing us from reaching a definitive neurophysiological diagnosis of acute inflammatory demyelinating polyradiculoneuropathy, children's presenting clinical manifestations, their disease course, and rapid and complete recovery after intravenous immunoglobulins argued strongly in its favor. A prompt, correct differential diagnosis of vincristine neuropathy and acute inflammatory demyelinating polyradiculoneuropathy in patients with acute lymphoblastic leukemia receiving vincristine is essential to improve disease outcome and prolong life expectancy.

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.

Processing of nerve biopsies: a practical guide for neuropathologists

Nerve biopsy is a valuable tool in the diagnostic work-up of peripheral neuropathies. Currently, major indications include interstitial pathologies such as suspected vasculitis and amyloidosis, atypical cases of inflammatory neuropathy and the differential diagnosis of hereditary neuropathies that cannot be specified otherwise. However, surgical removal of a piece of nerve causes a sensory deficit and – in some cases – chronic pain. Therefore, a nerve biopsy is usually performed only when other clinical, laboratory and electrophysiological methods have failed to clarify the cause of disease. The neuropathological work-up should include at least paraffin and resin semithin histology using a panel of conventional and immunohistochemical stains. Cryostat section staining, teased fiber preparations, electron microscopy and molecular genetic analyses are potentially useful additional methods in a subset of cases. Being performed, processed and read by experienced physicians and technicians nerve biopsies can provide important information relevant for clinical management.

[Pharmacologically-induced neurocatastrophes]

Drug-induced adverse reactions represent a significant health problem in developed countries. These events cause 5% of hospital admissions and are one of the main causes of mortality. Neurological manifestations are among the most frequent. This article reviews catastrophic cerebrovascular situations and confusional syndromes, as well as epilepsy, structural encephalopathy, neuromuscular disorders, catastrophic movement disorders and infections, all of which can be drug-induced.

Peripheral neuropathy in survivors of childhood acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is the most common form of cancer in children. Recent advances in treatment have led to dramatically improved survival rates. Standard ALL treatment includes multiple administrations of the chemotherapeutic drug vincristine, which is a known neurotoxic agent. Although peripheral neuropathy is a well-known toxicity among children receiving vincristine acutely, the long-term effects on the peripheral nervous system in these children are not clear. The objective of this study was to determine the prevalence of neuropathy and its impact on motor function and quality of life (QOL) among children who survived ALL. Thirty-seven survivors of childhood ALL aged 8-18 underwent evaluation for neuropathy through self-reported symptoms, standardized examinations, and nerve conduction studies (NCS). Functional impact of neuropathy was assessed using the Bruininks-Oseretsky test of Motor Proficiency (BOT-2). QOL was assessed using the PedsQL. Nerve conduction study abnormalities were seen in 29.7% of children who were longer than 2 years off therapy for ALL. Most children with an abnormal examination or NCS did not have subjective symptoms. Although overall motor function was below population norms on the BOT-2, presence of neuropathy did not significantly correlate with motor functional status or QOL.

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.

The pathophysiology of the chronic pain cycle

The diagnosis and treatment of chronic pain is an area in which the field of medicine is failing to offer the best possible care to patients. This article presents a clinically driven view of the condition with an emphasis on active recognition and intervention. Defining aspects of chronic pain, including the emotional and psychologic components, are introduced with regard to recognition and diagnosis. The pathophysiologic mechanisms that underlie the transition from acute pain to chronic pain are reviewed from the standpoint of treatment intervention. Finally, specific chronic pain states that affect the lower extremities are considered.

Chemotherapy-induced neuropathy

Neurotoxic side effects of cancer therapy are second in frequency to hematological toxicity. Unlike hematological side effects that can be treated with hematopoietic growth factors, neuropathies cannot be treated and protective treatment strategies have not been effective. For the neurologist, the diagnosis of a toxic neuropathy is primarily based on the case history, the clinical and electrophysiological findings, and knowledge of the pattern of neuropathy associated with specific agents. In most cases, toxic neuropathies are length-dependent, sensory, or sensorimotor neuropathies often associated with pain. The platinum compounds are unique in producing a sensory ganglionopathy. Neurotoxicity is usually dependent on cumulative dose. Severity of neuropathy increases with duration of treatment and progression stops once drug treatment is completed. The platinum compounds are an exception where sensory loss may progress for several months after cessation of treatment ("coasting"). As more effective multiple drug combinations are used, patients will be treated with several neurotoxic drugs. Synergistic neurotoxicity has not been extensively investigated. Pre-existent neuropathy may influence the development of a toxic neuropathy. Underlying inherited or inflammatory neuropathies may predispose patients to developing very severe toxic neuropathies. Other factors such as focal radiotherapy or intrathecal administration may enhance neurotoxicity. The neurologist managing the cancer patient who develops neuropathy must answer a series of important questions as follows: (1) Are the symptoms due to peripheral neuropathy? (2) Is the neuropathy due to the underlying disease or the treatment? (3) Should treatment be modified or stopped because of the neuropathy? (4) What is the best supportive care in terms of pain management or physical therapy for each patient? Prevention of toxic neuropathies is most important. In patients with neuropathy, restorative approaches have not been well established. Symptomatic and other management are necessary to maintain and improve quality of life.

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.

Peripheral nervous system involvement in patients with cancer

Involvement of the peripheral nervous system (PNS) is common in patients with cancer and any part, including motor neurons, sensory ganglia, nerve roots, plexuses, cranial and peripheral nerves, and neuromuscular junctions, can be affected. Different mechanisms can initiate damage associated with cancer-related PNS disorders. These include tumour infiltration, toxicity of treatments, metabolic and nutritional perturbations, cachexia, virus infections, and paraneoplastic neurological syndromes. The type of cancer, lymphoma, or solid tumour is a further determinant of a PNS disorder. In this Review we discuss the different causes and mechanisms of disorders of the PNS in patients with cancer and we will focus on their assessment and diagnosis.

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.

Chemotherapy-induced peripheral neuropathy: pathogenesis and emerging therapies

Peripheral neuropathy is a major dose-limiting side effect of many chemotherapeutic agents. The type and degree of neuropathy depend on the chemotherapy drug, dose-intensity, and cumulative dose. Disabling peripheral neuropathy has a significant negative impact on quality of life. Accordingly, a reliable assessment of chemotherapy-induced peripheral neurotoxicity is necessary, especially if potential neuroprotective agents are to be investigated. Chemoprotectants are agents that have been developed to ameliorate the toxicity associated with cytotoxic drugs. They aim to provide site-specific protection for normal tissues, without compromising antitumor efficacy. Several chemoprotectant compounds have been studied in recent clinical trials. These trials must include sufficient dose-limiting events for study and assessment of both toxicity and antitumor effect. A future avenue of investigation includes the identification of patients at higher risk for the development of peripheral neuropathy based on their genotype. Identification of these higher-risk patients may enable us to devise prevention strategies prior to the onset of this potentially debilitating complication.

Vincristine neuropathy: neurophysiological and genetic studies in a case of Wilms tumor

We report a 10-year-old female with Wilms tumor (WT) who developed severe neuropathy after the fifth weekly dose of vincristine. The girl was previously asymptomatic and the family history was negative for inherited neuropathies. Neurophysiological studies and electrodiagnostic findings were suggestive of a axonal neuropathy with greater motor than sensory characteristics not typical of Charcot-Marie-Tooth (CMT) Type 1A. Genetic studies were performed in view of the degree of neurotoxicity. Duplication of 17p11.2 was found that supported the diagnosis of CMT Type 1A. The patient is alive without disease and with minimal weakness of the lower extremities after 42 months. Neurophysiological studies, repeated at 8 and 24 months, were negative. Although the association of asymptomatic CMT and vincristine neuropathy has been previously reported, the present case is of note because the reversible neuropathy occurred after five doses of vincristine, suggesting that possible more people suffering vincristine neurotoxicity may have underlying and asymptomatic CMT.

Chemotherapy-induced peripheral neuropathy

While cancer remains an important public health concern, novel and enhanced treatment modalities have increased the length of survival of individuals diagnosed with the disease. The treatment of most cancers requires the use of chemotherapeutic agents to affect cure, maintain control of the disease, or provide palliation of symptoms. Although the use of chemotherapeutic agents can serve to prolong life, such agents are associated with significant side effects. Increasing clinical evidence suggests treatment of cancer with neurotoxic agents results in some degree of peripheral neuropathy. Specific drug categories implicated in the development of peripheral neuropathy are the plant alkaloids, interferons, antimitotics, taxanes, and platinum-based compounds. Drug-induced peripheral neuropathy is sensory, dose-related and cumulative and is usually delayed, appearing weeks after initiation of therapy. The number of individuals at risk for the development of chemotherapy-induced neuropathy is expected to increase proportionately with clinical protocols utilizing higher or more frequent dosing. As advanced cancer treatments and clinical trials can result in extending the lives of individuals affected by cancer, long-term functional deficits resulting from life-saving treatments must now be addressed. As such, peripheral neuropathy has emerged as an important consequence of cancer therapy.

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.