Effect of pain in pediatric inherited neuropathies

Charcot-Marie-Tooth disease: from historical landmarks in Brazil to current care perspectives

Hereditary motor and sensory neuropathy, also known as Charcot-Marie-Tooth disease (CMT), traditionally refers to a group of genetic disorders in which neuropathy is the main or sole feature. Its prevalence varies according to different populations studied, with an estimate between 1:2,500 to 1:10,000. Since the identification of PMP22 gene duplication on chromosome 17 by Vance et al., in 1989, more than 100 genes have been related to this group of disorders, and we have seen advances in the care of patients, with identification of associated conditions and better supportive treatments, including clinical and surgical interventions. Also, with discoveries in the field of genetics, including RNA interference and gene editing techniques, new treatment perspectives begin to emerge. In the present work, we report the most import landmarks regarding CMT research in Brazil and provide a comprehensive review on topics such as frequency of different genes associated with CMT in our population, prevalence of pain, impact on pregnancy, respiratory features, and development of new therapies.

Review of general and head and neck/oral and maxillofacial features of Charcot-Marie-Tooth disease and dental management considerations

Charcot-Marie-Tooth disease (CMTD) is an uncommon progressive neuromuscular disorder of the peripheral nervous system and primarily leads to distal extremity weakness and sensory deficits. Frequently, affected patients manifest pes cavus, drop foot, and digit contractures that may pose significant challenges in ambulation and grasping objects. Although there are numerous articles of this syndrome in the medical literature, there is a limited number of dental publications. The objective of this article is to review the general and head and neck/oral and maxillofacial features of CMTD. General guidelines for dental management are also provided.

Challenges in Treating Charcot-Marie-Tooth Disease and Related Neuropathies: Current Management and Future Perspectives

There is still no effective drug treatment available for Charcot-Marie-Tooth neuropathies (CMT). Current management relies on rehabilitation therapy, surgery for skeletal deformities, and symptomatic treatment of pain; fatigue and cramps are frequent complaints that are difficult to treat. The challenge is to find disease-modifying therapies. Several approaches, including gene silencing, to counteract the PMP22 gene overexpression in the most frequent CMT1A type are under investigation. PXT3003 is the compound in the most advanced phase for CMT1A, as a second-phase III trial is ongoing. Gene therapy to substitute defective genes or insert novel ones and compounds acting on pathways important for different CMT types are being developed and tested in animal models. Modulation of the Neuregulin pathway determining myelin thickness is promising for both hypo-demyelinating and hypermyelinating neuropathies; intervention on Unfolded Protein Response seems effective for rescuing misfolded myelin proteins such as P0 in CMT1B. HDAC6 inhibitors improved axonal transport and ameliorated phenotypes in different CMT models. Other potential therapeutic strategies include targeting macrophages, lipid metabolism, and Nav1.8 sodium channel in demyelinating CMT and the P2X7 receptor, which regulates calcium influx into Schwann cells, in CMT1A. Further approaches are aimed at correcting metabolic abnormalities, including the accumulation of sorbitol caused by biallelic mutations in the sorbitol dehydrogenase (SORD) gene and of neurotoxic glycosphingolipids in HSN1.

Pain Phenotypes in Rare Musculoskeletal and Neuromuscular Diseases

For patients diagnosed with a rare musculoskeletal or neuromuscular disease, pain may transition from acute to chronic; the latter yielding additional challenges for both patients and care providers. We assessed the present understanding of pain across a set of ten rare, noninfectious, noncancerous disorders; Osteogenesis Imperfecta, Ehlers-Danlos Syndrome, Achondroplasia, Fibrodysplasia Ossificans Progressiva, Fibrous Dysplasia/McCune-Albright Syndrome, Complex Regional Pain Syndrome, Duchenne Muscular Dystrophy, Infantile- and Late-Onset Pompe disease, Charcot-Marie-Tooth Disease, and Amyotrophic Lateral Sclerosis. Through the integration of natural history, cross-sectional, retrospective, clinical trials, & case studies we described pathologic and genetic factors, pain sources, phenotypes, and lastly, existing therapeutic approaches. We highlight that while rare diseases possess distinct core pathologic features, there are a number of shared pain phenotypes and mechanisms that may be prospectively examined and therapeutically targeted in a parallel manner. Finally, we describe clinical and research approaches that may facilitate more accurate diagnosis, monitoring, and treatment of pain as well as elucidation of the evolving nature of pain phenotypes in rare musculoskeletal or neuromuscular illnesses.

Quality of Life in Painful Peripheral Neuropathies: A Systematic Review

Objective

Neuropathic pain is a common presenting complaint of patients with peripheral neuropathy (PN) and is considered one of the most disabling neuropathic symptoms, with detrimental effects on patients' quality of life (QoL). The aim of this review was to overview the current literature that focuses on QoL in painful PN of various aetiologies. We sought to clarify the direct effect of pain and its treatment on patients' QoL.

Methodology

A systematic computer-based literature search was conducted using the PubMed database to search for papers on QoL in painful PN. Information was extracted regarding prevalence, demographics, and response to treatment where relevant.

Results

We identified 66 articles eligible for inclusion. The vast majority of studies (n=47) focused on patients with diabetic PN. Other aetiologies of painful PN where QoL has been studied to date include gluten, immune-mediated, HIV, chemotherapy-induced, and chronic idiopathic axonal polyneuropathy. Pharmacological treatment is the mainstay in managing pain and has a direct positive and independent effect on the overall QoL. Other nonpharmacological approaches can also be of benefit, either alone or as adjuvant treatments, and are discussed.

Conclusion

The findings demonstrate that QoL is impaired in painful PN and should not be neglected in clinical practice. Patients' pain management and subsequent impact on QoL should routinely be assessed and monitored.

Do Commonly Used Measures of Pain Intensity Only Reflect Pain Intensity in Youths With Bothersome Pain and a Physical Disability?

The objective of this cross-sectional study was to evaluate the extent to which non-pain intensity factors influence the ratings of pain intensity on two commonly used measures: the Wong-Baker Faces pain rating scale (FACES) and the Verbal Rating Scale (VRS) in a sample of youths with physical disabilities and bothersome pain. Study participants came from a convenience sample of 115 youths (age: X ¯ = 14.4 years; SD = 3.3), who participated in a survey on the impact of pain in young people with a physical disability. They were administered measures of pain intensity, pain catastrophizing, depressive symptoms, pain interference, and pain control beliefs. Zero-order correlation analyses were used to examine the associations among the pain intensity scores, while regression analyses were used to test the influence of the non-pain intensity factors on the pain intensity scores. Although pain intensity scores from all scales were significantly associated with one another, the correlations were moderate. Regression analyses showed that the FACES and VRS also reflect pain interference, in addition to pain intensity. The fact that the FACES and VRS ratings reflect more than pain intensity should be considered when selecting a pain measure. The results of this study also provide information to help interpret results after treatment.

Charcot-Marie-Tooth Disease and Other Genetic Polyneuropathies

PURPOSE OF REVIEW

Genetic polyneuropathies are rare and clinically heterogeneous. This article provides an overview of the clinical features, neurologic and electrodiagnostic findings, and management strategies for Charcot-Marie-Tooth disease and other genetic polyneuropathies as well as an algorithm for genetic testing.

RECENT FINDINGS

In the past 10 years, many of the mutations causing genetic polyneuropathies have been identified. International collaborations have led to the development of consortiums that are undertaking careful genotype-phenotype correlations to facilitate the development of targeted therapies and validation of outcome measures for future clinical trials. Clinical trials are currently under way for some genetic polyneuropathies.

SUMMARY

Readers are provided a framework to recognize common presentations of various genetic polyneuropathies and a rationale for current diagnostic testing and management strategies in genetic polyneuropathies.

Pain in Charcot-Marie-Tooth disease: an update

ABSTRACT Charcot-Marie-Tooth (CMT) disease, the most common inherited peripheral neuropathy, has pain as one of its clinical features, yet it remains underdiagnosed and undertreated. This literature review assessed data related to pain from CMT to determine its prevalence, type and importance as a symptom, which, unlike other symptoms, is likely to be treated. The research encompassed 2007 to 2017 and included five articles that addressed pain from CMT. All of the papers concurred that pain is frequently present in CMT patients, yet its classification remains undefined as there has been no consensus in the literature about the mechanisms that cause it.

Diseases of the peripheral nerves

This chapter reviews the diseases of the peripheral nerves from a neuropathologic point of view, with a special focus on specific morphologic changes, and includes a summary of the histopathologic methods available for their diagnosis. As the rate of obesity and the prevalence of type 2 diabetes increase, diabetic neuropathy is the most common cause of peripheral neuropathy. Many systemic disorders with metabolic origin, like amyloidosis, hepatic failure, vitamin deficiencies, uremia, lipid metabolism disorders, and others, can also cause axonal or myelin alterations in the peripheral nervous system. The most notable causes of toxic neuropathies are chemotherapeutic agents, alcohol consumption, and exposure to heavy metals and other environmental or biologic toxins. Inflammatory neuropathies cover infectious neuropathies (Lyme disease, human immunodeficiency virus, leprosy, hepatitis) and neuropathies of autoimmune origin (sarcoidosis, Guillain-Barré syndrome/acute inflammatory demyelinating polyneuropathy, chronic inflammatory demyelinating polyneuropathy, and diverse forms of vasculitis. The increasing number of known diseases causing gene mutations in hereditary peripheral neuropathies requires precise characterization, which includes histopathology.

Update on Charcot-Marie-Tooth disease

PURPOSE OF REVIEW

Charcot-Marie-Tooth disease (CMT) is the common terminology used to describe the hereditary neuropathies. This update reviews advances in the past year in our understanding of these diseases, including some important earlier references.

RECENT FINDINGS

In the past year, advances in next-generation sequencing continued to increase the number of genes associated with CMT. The connection between genotype and phenotype has become more complicated. New insights into the pathogenesis of the diseases are reviewed. Treatment and clinical trial updates coming from these new insights, as well as use of high-throughput screening to match potential treatments with targets, are moving the field forward. There is a discussion of potential next steps, including the use of patient-derived induced pluripotent stem cells, to enhance our understanding of individual genotypes and phenotypes.

SUMMARY

The use of high-throughput screens, and techniques such as RNAi and induced pluripotent stem cell continue to push forward other therapies for specific genetic forms of CMT and are potentially more generalizable to peripheral neuropathies. These developments, along with the development of improved outcome measures and longitudinal natural history data, advance CMT, making the future for finding treatments and/or cures closer than it has ever been.

The genetics of Charcot-Marie-Tooth disease: current trends and future implications for diagnosis and management

Charcot–Marie–Tooth (CMT) disease is the most common hereditary polyneuropathy and is classically associated with an insidious onset of distal predominant motor and sensory loss, muscle wasting, and pes cavus. Other forms of hereditary neuropathy, including sensory predominant or motor predominant forms, are sometimes included in the general classification of CMT, but for the purpose of this review, we will focus primarily on the forms associated with both sensory and motor deficits. CMT has a great deal of genetic heterogeneity, leading to diagnostic considerations that are still rapidly evolving for this disorder. Clinical features, inheritance pattern, gene mutation frequencies, and electrodiagnostic features all are helpful in formulating targeted testing algorithms in practical clinical settings, but these still have shortcomings. Next-generation sequencing (NGS), combined with multigene testing panels, is increasing the sensitivity and efficiency of genetic testing and is quickly overtaking targeted testing strategies. Currently, multigene panel testing and NGS can be considered first-line in many circumstances, although obtaining initial targeted testing for the PMP22 duplication in CMT patients with demyelinating conduction velocities is still a reasonable strategy. As technology improves and cost continues to fall, targeted testing will be completely replaced by multigene NGS panels that can detect the full spectrum of CMT mutations. Nevertheless, clinical acumen is still necessary given the variants of uncertain significance encountered with NGS. Despite the current limitations, the genetic diagnosis of CMT is critical for accurate prognostication, genetic counseling, and in the future, specific targeted therapies. Although whole exome and whole genome sequencing strategies have the power to further elucidate the genetics of CMT, continued technological advances are needed.

Validity of three rating scales for measuring pain intensity in youths with physical disabilities

BACKGROUND

There is growing evidence confirming that youths with physical disabilities are at risk for chronic pain. Although many scales for assessing pain intensity exist, it is unclear whether they are all equally suitable for youths. The aim of this study was to address this knowledge gap by comparing the validity of the Numerical Rating Scale (NRS-11), the Wong Baker FACES Pain Rating Scale (FACES), and a 6-point categorical Verbal Rating Scale (VRS-6) for assessing pain intensity among youths (aged 8-20) with physical disabilities.

METHODS

One hundred and thirteen youths (mean age = 14.19 years; SD = 2.9) were interviewed and asked to rate their current pain intensity and recalled (in the past week) worst, least, and average pain with the NRS-11 and the FACES. Participants were also asked to rate their average pain intensity during the past 4 weeks using a VRS-6, and were administered measures assessing pain interference, disability and psychological functioning.

RESULTS

Analyses showed that all of the pain intensity measures were associated positively with each other. Nevertheless, the NRS-11 appeared to out-perform both the VRS-6 and in particular the FACES scale with respect to: (1) the associations with the validity criterion (i.e. pain interference, disability and psychological functioning) and (2) a lack of any moderating effect of age on the association between the measure and the criterion variables.

CONCLUSIONS

The findings support the validity of the NRS-11 for assessing pain intensity in youths with physical disabilities between the ages of 8 and 20 years.

A brief review of recent Charcot-Marie-Tooth research and priorities

This brief review of current research progress on Charcot-Marie-Tooth (CMT) disease is a summary of discussions initiated at the Hereditary Neuropathy Foundation (HNF) scientific advisory board meeting on November 7, 2014. It covers recent published and unpublished in vitro and in vivo research. We discuss recent promising preclinical work for CMT1A, the development of new biomarkers, the characterization of different animal models, and the analysis of the frequency of gene mutations in patients with CMT. We also describe how progress in related fields may benefit CMT therapeutic development, including the potential of gene therapy and stem cell research. We also discuss the potential to assess and improve the quality of life of CMT patients. This summary of CMT research identifies some of the gaps which may have an impact on upcoming clinical trials. We provide some priorities for CMT research and areas which HNF can support. The goal of this review is to inform the scientific community about ongoing research and to avoid unnecessary overlap, while also highlighting areas ripe for further investigation. The general collaborative approach we have taken may be useful for other rare neurological diseases.

Small nerve fiber involvement in CMT1A

OBJECTIVE

To assess the involvement of small nerve fibers in Charcot-Marie-Tooth type 1A (CMT1A).

METHODS

We used indirect immunofluorescence and confocal microscopy on punch biopsies from glabrous (fingertip) and hairy (thigh and leg) skin of 20 unrelated patients with CMT1A to quantify somatic and autonomic nerve fibers. In particular, we quantified epidermal nerve fibers (ENF), Meissner corpuscles (MC), intrapapillary myelinated endings (IME), and sudomotor nerves. We correlated morphologic data with findings from quantitative sensory testing, sudomotor output, sympathetic skin response, and cardiovascular reflexes. A control population of healthy age- and sex-matched controls was included with a matching ratio of 1:2.

RESULTS

We found a length-dependent loss of ENFs that worsened with aging. We also observed a loss of MCs, IMEs, and sudomotor nerves. The loss of ENF at distal leg correlated with the increase in heat-pain thresholds (p < 0.05) and with tactile thresholds (p < 0.05). Sudomotor nerve fiber loss correlated with ENF density (p < 0.05) and sweating output (p < 0.001).

CONCLUSIONS

We demonstrated through morphologic, physical, and psychophysical testing that small somatic and autonomic fibers are abnormal and cause symptoms in patients with CMT1A. Awareness of such symptoms by the clinician could lead to better treatment.