Detection of hereditary motor sensory neuropathy type I in childhood

Detection of surface-EMG activity from the extensor digitorum brevis muscle in healthy children walking

OBJECTIVE

The purpose of the study was the assessment of activation patterns of the extensor digitorum brevis (EDB) muscle in healthy children, during walking at self-selected speed and cadence.

APPROACH

To this end, statistical gait analysis was performed on surface electromyographic (sEMG) signals of the EDB, in a large number (hundreds) of strides per subject. sEMG data from the tibialis anterior (TA) and gastrocnemius lateralis (GL) were also investigated for comparative purposes.

MAIN RESULTS

Results from 23 healthy children showed a large variability in the number of muscle activations, occurrence frequency, and onset-offset instants across considered strides. The assessment of different modalities of muscle activation allowed the identification of a single activity pattern, common to all the modalities and we were able to characterize the behavior of the EDB during the gait of healthy children. The pattern of EDB activity centered in two main regions of the gait cycle: in the second half of the stance phase (detected in 100% of subjects) and in the final swing phase (50%). Comparison with the TA and GL regions of activity suggested that the EDB and TA worked mainly as antagonist muscles for the ankle joint, while the EDB and GL did not oppose each other in action, but acted in synergy for the control of the ankle joint during walking.

SIGNIFICANCE

The 'Normality' pattern for the EDB activity reported here represents the first attempt to develop a reference for dynamic sEMG of the EDB in healthy children, enabling us to include the physiological variability of the phenomenon. Present results could be useful for discriminating physiological and pathological behavior in children and for deepening the maturation of the gait.

Clinical correlates of Charcot-Marie-Tooth disease in patients with pes cavus deformities

INTRODUCTION

Given its association with Charcot-Marie-Tooth disease (CMT), pes cavus is a common reason for referral to a neurologist. We investigated clinical features that may predict CMT in children with pes cavus.

METHODS

In this study we retrospectively reviewed pes cavus patients referred to Boston Children's Hospital in the past 20 years. Patients were categorized as idiopathic or CMT, based on EMG/genetic testing, and their clinical features were compared.

RESULTS

Of the 70 patients studied, 33 had idiopathic pes cavus, and 37 had genetically confirmed CMT. Symptoms of weakness, unsteady gait, family history of pes cavus and CMT, and signs of sensory deficits, distal atrophy and weakness, absent ankle jerks, and gait abnormalities were associated with CMT.

CONCLUSIONS

In children with pes cavus, certain clinical features can predict CMT and assist in selection of patients for further, potentially uncomfortable (EMG) and expensive (genetic) confirmatory investigations.

Painful pes planovalgus: an uncommon pediatric orthopedic presentation of Charcot-Marie-Tooth disease

Charcot-Marie-Tooth (CMT) disease is an inherited progressive neurologic disorder often diagnosed by the characteristic cavovarus feet. In the pediatric population, the presentation is often more variable and age dependent. Pediatric orthopedic surgeons may be referred patients for the evaluation of musculoskeletal symptoms that may be consistent with early CMT, but because of the lack of the surgeon's familiarity, the diagnosis may be delayed or missed. We present three patients with pes planovalgus who were found to have CMT and review the recent literature relevant to the pediatric orthopedic surgeon. The clinical summary is given for three patients who presented to the orthopedic surgery department for lower extremity symptoms and were eventually diagnosed with CMT. A literature search was performed and information valuable for a pediatric orthopedic surgeon to consider is summarized. Foot morphology in most young children with CMT initially is pes planovalgus, with the minority being pes cavovarus. As the child grows, the proportion changes to become nearly entirely cavus or cavovarus, with very few remaining planovalgus or planus. Unexplained regional pain may also be suggestive of CMT. Whereas CMT often presents initially in adolescent or adult patients with cavovarus feet, thin calves, or a high-stepping gait, pediatric presentation is not so consistent. Young children with CMT often have pes planovalgus. There are even some variants of CMT where patients still may present with severe pes planovalgus into late adolescence. We recommend that pediatric orthopedic surgeons consider CMT even in patients who do not have cavus or cavovarus feet, especially in the context of unexplained regional pain of the lower extremities. Patients should be referred to a pediatric neurologist for definitive diagnosis and management, with the orthopedic surgeon remaining involved for specific procedures.

Charcot-Marie-Tooth type 1a in a child with Long QT syndrome

Charcot-Marie-Tooth disease (CMTD) is a hereditary demyelinating peripheral neuropathy clinically presenting with sensory and motor defects, but rarely affecting cardiac function. Long QT syndrome (LQTS) is a congenital or acquired cardiovascular disorder characterized by ventricular depolarization defect. No studies reported CMTD in association with LQTS. We describe a child and his family who had both CMT1A and LQTS.

Congenital pes cavus in a Charcot-Marie-tooth disease type 1A newborn

A 3-year-old female infant with Charcot-Marie-Tooth disease type 1A had congenital pes cavus, normal motor development, and duplication of the peripheral myelin protein 22 gene, PMP22. Her father, carrying the same gene duplication, developed neuropathy, tremor, and auditory impairment beginning in early adulthood. This is a case of congenital pes cavus in a Charcot-Marie-Tooth disease type 1A patient. The infant had pes cavus caused by the hereditary sensorimotor neuropathy; the family provides a clear example of clinical anticipation.

Neurophysiologic abnormalities in children with Charcot-Marie-Tooth disease type 1A

Although Charcot-Marie-Tooth disease type 1A (CMT1A) initially manifests in the first decade, there are no large studies describing its neurophysiologic features in childhood. We report neurophysiologic findings in 80 children aged 2-16 years with CMT1A who underwent median motor and sensory nerve conduction studies. Neurophysiologic abnormalities were present in all children. Median motor nerve conduction velocity was invariably less than 33 m/s (mean 18.7 m/s, range 9.0-32.9 m/s), with conduction velocities significantly slower in children aged 7-16 years compared with children aged 6 years and below. All children had prolonged distal motor latencies (mean 7.3 ms, range 4.0-12.3 ms). The compound muscle action potential (CMAP) amplitude was reduced from an early age (mean 7.1 mV, range 2.1-13.5 mV), and its normal increase with age was attenuated. Median sensory responses were present in only seven children, all aged less than 9 years and with slowed sensory conduction. Neurophysiologic abnormalities are present in all children with CMT1A from the age of 2 years. Motor conduction slowing progresses through the first 6 years of life and thereafter remains stable. CMAP amplitude is reduced from an early age, and the normal physiologic increase with age is attenuated. Median sensory responses may be recorded in younger children, and their presence does not exclude the diagnosis of CMT1A.

Prevalence of Charcot-Marie-Tooth disease in patients who have bilateral cavovarus feet

It is not uncommon to see a patient with bilateral cavovarus feet in the outpatient setting. A large percentage of these patients are subsequently diagnosed with an associated condition, such as Charcot-Marie-Tooth disease. The purpose of the present report was to determine the prevalence of Charcot-Marie-Tooth disease in children who have bilateral cavovarus feet. A chart review of children with bilateral cavovarus feet was done. Patients were excluded if they had an existing medical problem known to be associated with bilateral cavovarus feet. Charcot-Marie-Tooth disease was diagnosed after a clinical assessment by an orthopaedic surgeon and a neurologist. The diagnosis was confirmed by either standard nerve conduction velocity studies and/or the CMT DNA Duplication Detection Test (Athena Diagnostics Inc, Worchester, MA). A positive family history was noted only if the diagnosis had been confirmed by a nerve conduction velocity study and/or CMT DNA Duplication Detection Test. One hundred forty-eight patients met the study criteria. The probability of a patient with bilateral cavovarus feet being diagnosed with Charcot-Marie-Tooth disease, regardless of family history, was 78% (116 patients). A family history of Charcot-Marie-Tooth disease increased the probability to 91%. It is recommended that all patients with bilateral cavovarus feet, especially with a known family history, be investigated for Charcot-Marie-Tooth disease.

Clinical and electrophysiological aspects of Charcot-Marie-Tooth disease

Charcot-Marie-Tooth disease (CMT) is a genetically heterogeneous group of disorders sharing the same clinical phenotype, characterized by distal limb muscle wasting and weakness, usually with skeletal deformities, distal sensory loss, and abnormalities of deep tendon reflexes. Mutations of genes involved in different functions eventually lead to a length-dependent axonal degeneration, which is the likely basis of the distal predominance of the CMT phenotype. Nerve conduction studies are important for classification, diagnosis, and understanding of pathophysiology. The subdivision into demyelinating CMT1 and axonal CMT2 types was a milestone and is still valid for the majority of patients. However, exceptions to this partition are increasing. Intermediate conduction velocities are often found in males with X-linked CMT (CMTX), and different intermediate CMT types have been identified. Moreover, for some genes, different mutations may result either in demyelinating CMT with slow conduction, or in axonal CMT. Nerve conduction slowing is uniform and diffuse in the most common CMT1A associated with the 17p12 duplication, whereas it is often asymmetric and nonhomogeneous in CMTX, sometimes rendering difficult the differential diagnosis with acquired inflammatory neuropathies. The demyelinating recessive forms, termed CMT4, usually have early onset and run a more severe course than the dominant types. Pure motor CMT types are now classified as distal hereditary motor neuronopathy. The diagnostic approach to the identification of the CMT subtype is complex and cannot be based on the clinical phenotype alone, as different forms are often clinically indistinguishable. However, there are features that may be of help in addressing molecular investigation in a single patient. Late onset, prominent or peculiar sensory manifestations, autonomic nervous system dysfunction, cranial nerve involvement, upper limb predominance, subclinical central nervous system abnormalities, severe scoliosis, early-onset glaucoma, neutropenia are findings helpful for diagnosis.

Foot deformities in children with hereditary motor and sensory neuropathy

The authors reviewed 104 feet from 52 consecutive children with hereditary motor and sensory neuropathy (HMSN) seen for the first time in clinics in two pediatric institutions between 1996 and 2003. Sixty-nine feet had a cavovarus deformity, 23 feet had a planovalgus deformity, and 12 feet had no significant deformity. All cases with deformity had bilateral involvement, and of those with deformity, only 45% had symmetric involvement. In HMSN I, III, IV, V, and X-linked HMSN, cavovarus was the most common deformity. However, in HMSN II, 55% of feet had a planovalgus deformity, 36% had a cavovarus deformity, and 9% had no deformity. In all, 43 feet underwent surgery of some type. Surgery, and in particularly combined bony and soft tissue procedures, was performed much more frequently on feet with cavovarus than planovalgus deformities. Soft tissue surgery alone was performed at an earlier age than combined bony and soft tissue surgery.

Initial semeiology in children with Charcot-Marie-Tooth disease 1A duplication

The aim of this study was to describe the initial signs and symptoms in Charcot-Marie-Tooth disease type 1A (CMT-1A). Twelve secondary cases with CMT-1A were serially evaluated. Ages at initial clinical examination ranged between 1 month and 5 years (mean, 2 years) and final ages between 6 and 23 years (mean, 13 years). First signs of the disease were detected at initial or upon serial examinations in all 12 patients at ages ranging between 1 and 10 years (median, 4 years). The most frequent signs were lower limb areflexia in 12, difficulty in heel walking in 8, nerve enlargement in 6, atrophy of intrinsic foot muscles in 6, clawing of toes in 5, pes cavus or cavus varus in 4, shortening of Achilles tendon in 3, peroneal weakness in 1, and stocking hypoesthesia in 1. Only three patients were symptomatic at the initial evaluation. We conclude that initial CMT-1A signs usually appear in early childhood, although they may be quite subtle and require serial examinations for detection. Lower limb areflexia is the only constant early sign.

Clinico-electrophysiological correlation of extensor digitorum brevis muscle atrophy in children with charcot-marie-tooth disease 1A duplication

The purpose of the study is to describe the electrophysiologic abnormalities accounting for the appearance and progression of extensor digitorum brevis (EDB) muscle atrophy in Charcot-Marie-Tooth-disease type 1A (CMT-1A) children. Twelve children with CMT-1A duplication were serially evaluated. Initial ages of clinico-electrophysiological exams ranged from 1 month to 4 years (mean: 2 years) and final ages from 6 to 23 years (mean: 13). All subjects had two or more electrophysiological studies of the peroneal nerve. EDB atrophy was observed in two out of 12 (17%) patients by the age of 5, in eight out of ten (80%) examined between 5 and 9 years, and in all eight (100%) patients who had reached the second decade at the end. Nerve conduction maturation was systematically abnormal, but by age of 5 the mean values of nerve conduction parameters of peroneal nerve did not significantly differ from those in older patients. Compound muscle action potential (CMAP) amplitudes of EDB were reduced in 42% of cases initially and 100% upon last exam. Furthermore, a constant finding throughout the study was progressive attenuation of CMAPs, these becoming unobtainable in four cases. EDB muscle atrophy in CMT-1A children is an age-dependent sign which is accounted for by gradual reduction of the distal peroneal nerve CMAP amplitudes.