Charcot-Marie-Tooth Disease with Myelin Protein Zero Mutation Presenting as Painful, Predominant Small-Fiber Neuropathy.

Charcot-Marie-Tooth disease (CMT) rarely presents with painful symptoms, which mainly occur in association with myelin protein zero (MPZ) gene mutations. We aimed to further characterize the features of painful neuropathic phenotypes in MPZ-related CMT. We report on a 58-year-old woman with a longstanding history of intermittent migrant pain and dysesthesias. Examination showed minimal clinical signs of neuropathy along with mild changes upon electroneurographic examination, consistent with an intermediate pattern, and small-fiber loss upon skin biopsy. Genetic testing identified the heterozygous variant p.Trp101Ter in MPZ. We identified another 20 CMT patients in the literature who presented with neuropathic pain as a main feature in association with MPZ mutations, mostly in the extracellular MPZ domain; the majority of these patients showed late onset (14/20), with motor-nerve-conduction velocities predominantly in the intermediate range (12/20). It is hypothesized that some MPZ mutations could manifest with, or predispose to, neuropathic pain. However, the mechanisms linking MPZ mutations and pain-generating nerve changes are unclear, as are the possible role of modifier factors. This peculiar CMT presentation may be diagnostically misleading, as it is suggestive of an acquired pain syndrome rather than of an inherited neuropathy.

Are novel outcome measures for Charcot-Marie-Tooth disease sensitive to change? The 6-minute walk test and StepWatch™ Activity Monitor in a 12-month longitudinal study.

Charcot-Marie-Tooth (CMT) is the most common inherited neuropathy, yet has no available pharmacological therapy. Past pharmacotherapy trials failed to provide positive results, possibly due to a poor choice of outcome measures. We previously performed a study in which we validated the 6-minute walk test and StepWatch™ Activity Monitor in CMT. The aim of the current study was to determine if these outcome measures are sensitive to change over a 12-month period. In this longitudinal multicenter study, 149 out of 169 initially enrolled patients were re-evaluated after 12 months using the 6-minute walk test, StepWatch™ Activity Monitor and other outcome measures commonly adopted in CMT disease. Statistical analysis showed a worsening of the CMT-Neuropathy Score (p < 0.05), strength of distal muscles measured by myometry (p < 0.05) and StepWatch™ Activity Monitor outputs (p < 0.05). The 10 meter walking test (p > 0.05), muscular strength as detected by clinical evaluation (p > 0.05), 6-minute walk test (p > 0.05), pain (p > 0.05) and quality of life (p > 0.05) showed no change. In the current study, patients showed clinical worsening over 12 months, confirmed by a reduction of activity as detected by StepWatch™ Activity Monitor. The 6-minute walk test failed to detect change.

Selected items from the Charcot-Marie-Tooth (CMT) Neuropathy Score and secondary clinical outcome measures serve as sensitive clinical markers of disease severity in CMT1A patients.

This study evaluates primary and secondary clinical outcome measures in Charcot-Marie-Tooth disease type 1A (CMT1A) with regard to their contribution towards discrimination of disease severity. The nine components of the composite Charcot-Marie-Tooth disease Neuropathy Score and six additional secondary clinical outcome measures were assessed in 479 adult patients with genetically proven CMT1A and 126 healthy controls. Using hierarchical clustering, we identified four significant clusters of patients according to clinical severity. We then tested the impact of each of the CMTNS components and of the secondary clinical parameters with regard to their power to differentiate these four clusters. The CMTNS components ulnar sensory nerve action potential (SNAP), pin sensibility, vibration and strength of arms did not increase the discriminant value of the remaining five CMTNS components (Ulnar compound motor action potential [CMAP], leg motor symptoms, arm motor symptoms, leg strength and sensory symptoms). However, three of the six additional clinical outcome measures - the 10m-timed walking test (T10MW), 9 hole-peg test (9HPT), and foot dorsal flexion dynamometry - further improved discrimination between severely and mildly affected patients. From these findings, we identified three different composite measures as score hypotheses and compared their discriminant power with that of the CMTNS. A composite of eight components CMAP, Motor symptoms legs, Motor symptoms arms, Strength of Legs, Sensory symptoms), displayed the strongest power to discriminate between the clusters. As a conclusion, five items from the CMTNS and three secondary clinical outcome measures improve the clinical assessment of patients with CMT1A significantly and are beneficial for upcoming clinical and therapeutic trials.

Ascorbic acid in Charcot-Marie-Tooth disease type 1A (CMT-TRIAAL and CMT-TRAUK): a double-blind randomised trial.

BACKGROUND: Ascorbic acid reduced the severity of neuropathy in transgenic mice overexpressing peripheral myelin protein 22 (PMP22), a model of Charcot-Marie-Tooth disease type 1A (CMT1A) associated with the PMP22 duplication. However, in three 1-year trials, ascorbic acid had no benefit in human beings. We did a multicentre 2-year trial to test the efficacy and tolerability of ascorbic acid in patients with CMT1A. METHODS: Adult patients (aged 18-70 years) with symptomatic CMT1A were enrolled from nine centres in Italy and the UK, and were randomly assigned (1:1 ratio) to receive 1·5 g/day oral ascorbic acid or matching placebo for 24 months. The randomisation sequence was computer generated by block randomisation, stratified by centre and disease severity, and patients were allocated to treatment by telephone. The primary outcome was change in the CMT neuropathy score (CMTNS) at 24 months. Secondary outcomes were timed 10 m walk test, nine-hole peg test, overall neuropathy limitations scale, distal maximal voluntary isometric contraction, visual analogue scales for pain and fatigue, 36-item short-form questionnaire, and electrophysiological measurements. Patients, treating physicians, and physicians assessing outcome measures were masked to treatment allocation. Analysis of the primary outcome was done on all randomised patients who received at least one dose of study drug. This study is registered, numbers ISRCTN61074476 (CMT-TRAUK) and EudraCT 2006-000032-27 (CMT-TRIAAL). FINDINGS: We enrolled and randomly assigned 277 patients, of whom six (four assigned to receive ascorbic acid) withdrew consent before receiving treatment; 138 receiving ascorbic acid and 133 receiving placebo were eligible for analysis. Treatment was well tolerated: 241 of 271 patients (89% in each group) completed the study; 20 patients (nine receiving ascorbic acid) dropped out because of adverse events. Mean CMTNS at baseline with missing data imputed was 14·7 (SD 4·8) in the ascorbic acid group and 13·9 (4·2) in the placebo group. Mean worsening of CMTNS was 0·2 (SD 2·8, 95% CI -0·3 to 0·7) in the ascorbic acid group and 0·2 (2·7, -0·2 to 0·7) in the placebo group (mean difference 0·0, 95% CI -0·6 to 0·7; p=0·93). We recorded no differences between the groups for the secondary outcomes at 24 months. 21 serious adverse events occurred in 20 patients, eight in the ascorbic acid group and 13 in the placebo group. INTERPRETATION: Ascorbic acid supplementation had no significant effect on neuropathy compared with placebo after 2 years, suggesting that no evidence is available to support treatment with ascorbic acid in adults with CMT1A. FUNDING: Telethon-UILDM and AIFA (Italian Medicines Agency) for CMT-TRIAAL, and Muscular Dystrophy Campaign for CMT-TRAUK.

A multicenter, randomized, double-blind, placebo-controlled trial of long-term ascorbic acid treatment in Charcot-Marie-Tooth disease type 1A (CMT-TRIAAL): the study protocol [EudraCT no.: 2006-000032-27].

There is no treatment for Charcot-Marie-Tooth disease 1A (CMT1A), but ascorbic acid (AA) is efficacious in the transgenic mouse model. Thus, a clinical trial of AA in CMT1A is warranted. The CMT-TRIAAL is a phase III randomized, double-blind, placebo-controlled study involving 222 CMT1A adults from eight Italian centers. Eligible for the study are symptomatic adults with genetically confirmed CMT1A. Treatment consists of 2-year oral AA (1500mg/day) or placebo. The primary trial endpoint is an improvement in CMT Neuropathy Score. Secondary efficacy endpoints are changes in distal arm and leg maximum voluntary isometric contraction; 10m timed walking; 9-hole-peg test; overall neuropathy limitations scale; pain and fatigue visual analog scales; health-related quality of life (SF-36); and electrophysiology. Clinical-electrophysiological assessments are performed at baseline and every 6 months thereafter. In consenting patients from three centers, skin biopsy is performed to evaluate PMP22 expression. The study will last 34 months, starting from March 2006.

Sensory manifestations in Charcot-Marie-Tooth disease.

Involvement of sensory nerves in Charcot-Marie-Tooth (CMT) disease is well known, however, sensory symptoms are usually overlooked. To assess the frequency and features of sensory symptoms in a cohort of patients with CMT, we investigated in a prospective study 52 consecutive CMT patients, diagnosed on the basis of clinical, neurophysiological, and genetic features and classified in CMT type 1 (CMT1) (20 patients, including 14 with CMT1A) and CMT type 2 (CMT2) (32 patients). Positive sensory symptoms were reported by 28 patients (54%), including neuropathic pain in 6 patients. Pain, either neuropathic or nociceptive, was present in 29 patients (56%) and in 15 patients as a main symptom. Positive sensory symptoms were present in 24 of 32 CMT2 patients (75%) and in 4 of 20 CMT1 patients (20%) (p < 0.001); there was a presenting manifestation in 11/32 CMT2 patients vs. 1/20 in CMT1 patients (p = 0.018), and one of the main features in 6/32 CMT2 patients vs. 1/20 CMT1 patients. Frequency of positive sensory symptoms in CMT1A patients was similar to that of the entire CMT1 group. Within the CMT2 group, patients with positive sensory symptoms as a main or onset feature (11 patients) had significantly later onset (median 57 vs. 25 years; p = 0.042) and less severely impaired motor action potentials than CMT2 patients without positive sensory symptoms (8 patients). Nociceptive pain was especially frequent in CMT1A patients (10/14, 71%). Sensory manifestations in CMT seem more frequent than previously thought, especially in CMT2; however, their frequency may be different in the genetic subtypes of the disease and/or an expression of phenotypic variability. Sensory symptoms, and in particular pain, may represent an important issue in the management of CMT patients, especially in a physical medicine approach.