New insights into the pathophysiology of pes cavus in Charcot–Marie–Tooth disease type 1A duplication

Vibration perception among children and adolescents with Charcot-Marie-tooth disease and implications for foot posture

BACKGROUND

Alterations in vibration perception among children and adolescents with Charcot-Marie-Tooth disease might explain observed changes in foot posture. Therefore, this cross-sectional study compared the vibration perception of the lower limbs in youths with and without Charcot-Marie-Tooth disease and verified the cut-off value of the distal vibration perception for the Charcot-Marie-Tooth group. In addition, associations between dynamic plantar pressure, vibration perception and isometric muscle strength were investigated.

METHODS

Participants aged 9-18 (Charcot-Marie-Tooth group n = 32; Typical group n = 32) had vibration perception measured by a 128-Hz graduated tuning fork. The static and dynamic foot posture were evaluated by the Foot Posture Index and pressure distribution measuring system, respectively. For the Charcot-Marie-Tooth group, a hand-held dynamometer evaluated the isometric muscle strength of the lower limbs.

FINDINGS

Children with Charcot-Marie-Tooth disease presented impaired vibration perception at the distal phalanx of the hallux and head of the first metatarsal compared to their typically developing peers, while adolescents with Charcot-Marie-Tooth disease showed impairment in all the tested regions compared to their typically developing peers. The cut-off value for vibration perception for participants with Charcot-Marie-Tooth disease was 5.7, considering the original grade of the tuning-fork 128 Hz. Among the associations established for the Charcot-Marie-Tooth group, a greater vibration perception at the distal phalanx of the hallux was associated with a longer rearfoot contact time (β = 31.02, p = 0.04).

INTERPRETATION

These new findings may guide the clinical evaluation and rehabilitation treatment for children and adolescents with Charcot-Marie-Tooth disease.

The variability of isokinetic ankle strength is different in healthy older men and women

CONTEXT

In the elderly, weak lower limb muscles impair functional tasks' performance.

OBJECTIVE

To evaluate the healthy elderly's ankle dorsiflexion and plantarflexion maximum torque and its variability in two sets of 5 RM isokinetics evaluation.

METHOD

50 women (68.0 ± 4.6 years old) and 50 men (72.7 ± 8.5 years old) did two sets of ankle plantar flexor and dorsiflexor isokinetic tests at 30°/s. Peak torque, total work, and coefficient of variation were analyzed.

RESULTS

Men did the strongest plantarflexion torque (p < 0.05) and dorsiflexion torque (p < 0.05); their highest peak torque occurred at set 2 (p < 0.05), while the largest plantarflexion torque variability (p < 0.05), dorsiflexion torque variability (p < 0.05), and the largest plantarflexion torque variability occurred at set 1 (p < 0.05). Men did the highest plantarflexion and dorsiflexion total work (p < 0.05) at set 2 (p < 0.05).

CONCLUSION

Older men are stronger than older women. The torque variability, in men, was higher during the first set, suggesting an adaptation to the isokinetics evaluation. Clinicians and researchers should consider that different muscles might need different numbers of sets and trials to measure their maximal muscle strength.

LRSAM1 and the RING domain: Charcot-Marie-Tooth disease and beyond

In the past decade, mutations in LRSAM1 were identified as the genetic cause of both dominant and recessive forms of axonal CMT type 2P (CMT2P). Despite demonstrating different inheritance patterns, dominant CMT2P is usually characterized by relatively mild, slowly progressive axonal neuropathy, mainly involving lower limbs, with age of onset between the second and fifth decades of life. Asymptomatic individuals were identified in several pedigrees exemplifying the strong phenotypic variability of these patients requiring serial clinical evaluation to establish correct diagnosis; in this respect, magnetic resonance imaging of lower-limb musculature showing fatty atrophy might be helpful in detecting subclinical gene mutation carriers. LRSAM1 is a universally expressed RING-type E3 ubiquitin protein ligase catalysing the final step in the ubiquitination cascade. Strikingly, TSG101 remains the only known ubiquitination target hampering our mechanistic understanding of the role of LRSAM1 in the cell. The recessive CMT mutations lead to complete loss of LRSAM1, contrary to the heterozygous dominant variants. These tightly cluster in the C-terminal RING domain highlighting its importance in governing the CMT disease. The domain is crucial for the ubiquitination function of LRSAM1 and CMT mutations disrupt its function, however it remains unknown how this leads to the peripheral neuropathy. Additionally, recent studies have linked LRSAM1 with other neurodegenerative diseases of peripheral and central nervous systems. In this review we share our experience with the challenging clinical diagnosis of CMT2P and summarize the mechanistic insights about the LRSAM1 dysfunction that might be helpful for the neurodegenerative field at large.

Physical function and performance measures of children and adolescents with Charcot-Marie-Tooth disease

This study aimed to verify whether there are differences in foot type, physical function, and performance between children and adolescents with Charcot-Marie-Tooth disease (CMT) and their healthy counterparts, and whether an interval of 6 months, from the initial assessment, reveals any significant changes on physical performance and other specific physical measures of the lower limbs. Subjects and Methods: Participants between 6 and 17 years of age, with CMT (CMT group n = 40), were compared to healthy participants (Control group, n = 49). Twenty participants with CMT completed the follow-up. We collected anthropometric, goniometric (ankle and knee), and dynamometric (inversion, eversion, plantar flexors, dorsiflexors, knee, hip extensors) measures, agonist/antagonist ratios, feet alignment (Foot Posture Index - FPI), muscle power (Long Jump), Pediatric Balance Scale (PBS), and 10-meter walk test (10MWT). Results: Compared to Control, CMT showed reduced passive range of motion (ROM), weakness in all evaluated muscles, increased agonist/antagonist ratios, predominance of varus and lower performance (PBS and Long Jump). After 6 months, CMT measures did not change. Conclusion: The cross-sectional analysis showed reduced ROM, strength, power, and distal muscle imbalance, as well as secondary limitations (PBS and 10MWT) in children and adolescents with CMT. These biomechanical and functional alterations did not change at the 6-month follow-up.

Is there a relationship between the occurrence of frenular ligaments and the type of fibularis longus tendon insertion?

PURPOSE

The fibularis longus muscle (FLM) is located in the lateral compartment of the leg. Although the FLM presents high morphological variability, particularly the tendon, little is known of its insertion. Similarly, little information exists regarding the great diversity of the Frenular ligament. The main aim of the study was hence to characterize the morphology of the fibularis longus tendon (FLT) and its accessory bands, to classify it and to determine the incidence of frenular ligaments. I hypothesize that the presence of anterior/posterior frenular ligament can be closely correlated with a given type of fibularis longus tendon insertion.

METHODS

Classical anatomical dissection was performed on 100 lower limbs (50 female, 50 male) fixed in 10% formalin solution. The morphology of the insertion of the FLT and of the frenular ligaments was evaluated.

RESULTS

The FLM was present in all specimens. Three types of insertion were observed, the most common being Type I (49%): a single distal attachment in which the tendon inserts into the lateral tubercle of the base of the I metatarsal bone. The second most common type was Type II (40%): bifurcated distal attachment, the main tendon inserts into the lateral tubercle of the base of the I metatarsal bone. This group was divided into three subtypes (A-C), subtype (A) - the accessory band inserts into the medial cuneiform bone; subtype (B) - a strong, accessory band inserts into both the base of the I metatarsal bone and the medial cuneiform bone, including the first metatarsal-cuneiform joint; subtype (C) - the accessory band inserts into the first interosseus dorsalis muscle. The rarest type was Type III (9%), characterized by a single distal tendon, which fuses with other adjacent muscle tendons before insertion. The main tendon inserts into the lateral tubercle of the base of the I metatarsal bone; this group was divided into two subtypes (IIIA - fusion with the tibialis posterior tendon and IIIB - fusion with the adductor hallucis longus). The anterior frenular ligament was present in 49% of specimens, whereas the posterior frenular ligament joined the FLT to the long calcaneo-cuboid ligament and was present in 9%.

CONCLUSION

Both the fibularis longus tendon and frenular ligament present high morphological variability. The anterior frenular ligament is closely correlated with Type I of the proposed classification, while the posterior frenular ligament is associated with Type II b. Knowledge of particular types of insertion is essential for both clinicians and anatomists.

LEVEL OF EVIDENCE

- II basic science research.

The adult cavus foot

Cavovarus deformity can be classified by the severity of malalignment ranging from a subtle and flexible to a severe and fixed cavovarus deformity of the foot.In the mild cavovarus foot, careful clinical assessment is required to identify the deformity.Weight-bearing radiographs are necessary to indicate the apex of the deformity and quantify the correction required.Surgery is performed when conservative measures fail and various surgical procedures have been described, including a combination of soft-tissue releases, tendon transfers and osteotomies, all with the aim of achieving a plantigrade and balanced foot.Joint-sparing surgery is the best option in flexible cavovarus foot even in Charcot-Marie-Tooth (CMT) disease (peroneal muscular atrophy).Arthrodesis is indicated in severe rigid cavus foot or in degenerative cases. Cite this article: EFORT Open Rev 2017;2. DOI: 10.1302/2058-5241.2.160077. Originally published online at www.efortopenreviews.org.

Rehabilitation in Charcot-Marie-Tooth disease type 1

Charcot-Marie-Tooth disease is the most common inherited peripheral neuropathy with a prevalence of approximately 1 in 2,500 [1]. The most common subtype is the autosomal dominant type 1A, which is caused by an intrachromosomal duplication on chromosome 17p11.2 [2,3]. A consecutive primary loss of the myelin sheath leads to secondary axonal degeneration. Characteristic clinical findings include distally pronounced muscle wasting, secondary skeletal deformities, sensory loss, and reduced deep tendon reflexes [4,5]. The individual clinical phenotypes vary, even among monozygotic twins [6]. They range from sub-clinical manifestations to rare cases of wheelchair-bound patients. Overall, the quality of life is significantly impaired [7]. Despite ongoing research, no curative treatments are currently available [8]. A recently published ascorbic acid trial showed no significant effect on the clinical phenotype of CMT1A patients [9,32,36]. Nevertheless, physical therapy and moderate exercises are proven to be positively disease-modifying. While a cure lies beyond the scope of physical therapy, it may prevent the rapid aggravation of the clinical phenotype [10,11,17]. Recent studies suggest that CMT patients experience physical as well as mental benefits from rehabilitation programmes, but they also perceive that the performed exercises were not specifically designed to their needs [11]. In fact, there is little evidence-based data and no common consensus on rehabilitation in patients suffering from Charcot-Marie-Tooth disease.

Evolution of Charcot-Marie-Tooth disease type 1A duplication: a 2-year clinico-electrophysiological and lower-limb muscle MRI longitudinal study

The objective of this study was to analyze Charcot-Marie-Tooth disease type 1A (CMT1A) evolution. We conducted a 2-year longitudinal study in 14 CMT1A patients and 14 age- and sex-matched controls. In the patients, we performed neurological examination with hand-held dynamometry, electrophysiology, and lower-limb muscle MRI, both at baseline and 2 years later, while controls were examined at baseline only. Patients' ages ranged from 12 to 51 years. Outstanding manifestations on initial evaluation included pes cavus, areflexia, lower-limb weakness, and foot hypopallesthesia. In evaluating muscle power, good correlation was observed between manual testing and dynamometry. Compared to controls, Lunge, 10-Meter-Walking, and 9-Hole-Peg tests were impaired. Their CMT neuropathy score and functional disability scale showed that patients exhibited mild phenotype and at most slight walking difficulty. Electrophysiology revealed marked nerve conduction slowing and variable compound muscle action potential amplitude reduction. On lower-limb muscle MRI, there was distally accentuated fatty infiltration accompanied by edema in calf muscles. All these clinico-electrophysiological and imaging findings remained almost unaltered during monitoring. Using multivariate analysis, no significant predictors of progression associated to the disease were obtained. We conclude that in the 2-year period of study, CMT1A patients showed mild progression with good concordance between clinico-electrophysiological and imaging findings.

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.