Characterizing Ventilatory Muscle Dysfunction in Inclusion Body Myositis.

OBJECTIVE: Investigation of the frequency and progression of ventilatory muscle dysfunction in patients with inclusion body myositis, the most common myopathy after age of 50 yrs. Prior research is limited to case series and cross-section studies. DESIGN: This is a retrospective review of pulmonary function tests, respiratory symptoms, and muscle strength testing. RESULTS: Of the 54 patients reviewed (mean age: 65 ± 9 yrs and disease duration: 7 ± 7 yrs), the majority ( n = 32, 59%) had restrictive forced vital capacity deficits at initial visit. Patients with reduced forced vital capacity showed higher prevalence of respiratory symptoms; but age, body mass index, and limb strength were similar when compared with patients without restrictive forced vital capacity. Mean rate of forced vital capacity decline of 0.108 l/yr in inclusion body myositis patients. Lower baseline limb strength correlated with longer disease duration and future forced vital capacity decline (eg, weaker patients experienced faster decline). CONCLUSIONS: Based on forced vital capacity, there is a high frequency of ventilatory pump muscle weakness in inclusion body myositis, which is associated with a higher burden of respiratory symptoms. Baseline strength may indicate risk of respiratory decline and need for vigilant screening. Importantly, ventilatory and limb muscle decline may not progress in a corresponding manner, highlighting the importance of pulmonary function surveillance.

Spinal Muscular Atrophy in the Treatment Era.

Spinal muscular atrophy is an autosomal-recessive degenerative neuromuscular disease that has historically been categorized into 5 types based on the individual's best functional ability. Two rather remarkable treatments have recently been approved for commercial use, and both have markedly changed the natural history of this disease. Here the authors report several cases of individuals, ranging from infants to adults, to highlight diagnostic considerations, along with initial and long-term treatment considerations in these individuals who now have the potential for stabilization to significant improvement in functional outcomes.

Pregnancy and delivery in women with spinal muscular atrophy.

OBJECTIVES: To expand the limited available knowledge about pregnancy and delivery in women with spinal muscular atrophy (SMA) using a cohort of genetically proven SMA patients from USA. METHODS: This was a cross-sectional questionnaire-based study. We mailed questionnaires to 58 women with confirmed SMA. RESULTS: Thirty-two women responded, reporting 35 pregnancies, including 19 women with at least one pregnancy. In this cohort, preterm labor and delivery by cesarean section were more common in mothers with SMA particularly SMA type 2. Seventy-four percent of mothers reported increased weakness during pregnancy that persisted after delivery in 42%. SMA mothers generally had a positive experience and good outcomes and elected to have more than one pregnancy. CONCLUSION: This information regarding pregnancy in women with genetically confirmed 5q SMA will prove useful in guiding future research and in providing counseling to women with SMA.

A randomized controlled trial of methotrexate for patients with generalized myasthenia gravis.

OBJECTIVE: To determine the steroid-sparing effect of methotrexate (MTX) in patients with symptomatic generalized myasthenia gravis (MG). METHODS: We performed a 12-month multicenter, randomized, double-blind, placebo-controlled trial of MTX 20 mg orally every week vs placebo in 50 acetylcholine receptor antibody-positive patients with MG between April 2009 and August 2014. The primary outcome measure was the prednisone area under the dose-time curve (AUDTC) from months 4 to 12. Secondary outcome measures included 12-month changes of the Quantitative Myasthenia Gravis Score, the Myasthenia Gravis Composite Score, Manual Muscle Testing, the Myasthenia Gravis Quality of Life, and the Myasthenia Gravis Activities of Daily Living. RESULTS: Fifty-eight patients were screened and 50 enrolled. MTX did not reduce the month 4-12 prednisone AUDTC when compared to placebo (difference MTX - placebo: -488.0 mg, 95% confidence interval -2,443.4 to 1,467.3, p = 0.26); however, the average daily prednisone dose decreased in both groups. MTX did not improve secondary measures of MG compared to placebo over 12 months. Eight participants withdrew during the course of the study (1 MTX, 7 placebo). There were no serious MTX-related adverse events. The most common adverse event was nonspecific pain (19%). CONCLUSIONS: We found no steroid-sparing benefit of MTX in MG over 12 months of treatment, despite being well-tolerated. This study demonstrates the challenges of conducting clinical trials in MG, including difficulties with recruitment, participants improving on prednisone alone, and the need for a better understanding of outcome measure variability for future clinical trials. CLASSIFICATION OF EVIDENCE: This study provides Class I evidence that for patients with generalized MG MTX does not significantly reduce the prednisone AUDTC over 12 months of therapy.

Spinal Muscular Atrophy Biomarker Measurements from Blood Samples in a Clinical Trial of Valproic Acid in Ambulatory Adults.

BACKGROUND: Clinical trials of therapies for spinal muscular atrophy (SMA) that are designed to increase the expression the SMN protein ideally include careful assessment of relevant SMN biomarkers. OBJECTIVE: In the SMA VALIANT trial, a recent double-blind placebo-controlled crossover study of valproic acid (VPA) in ambulatory adult subjects with SMA, we investigated relevant pharmacodynamic biomarkers in blood samples from SMA subjects by direct longitudinal measurement of histone acetylation and SMN mRNA and protein levels in the presence and absence of VPA treatment. METHODS: Thirty-three subjects were randomized to either VPA or placebo for the first 6 months followed by crossover to the opposite arm for an additional 6 months. Outcome measures were compared between the two treatments (VPA and placebo) using a standard crossover analysis. RESULTS: A significant increase in histone H4 acetylation was observed with VPA treatment (p = 0.005). There was insufficient evidence to suggest a treatment effect with either full length or truncated SMN mRNA transcript levels or SMN protein levels. CONCLUSIONS: These measures were consistent with the observed lack of change in the primary clinical outcome measure in the VALIANT trial. These results also highlight the added benefit of molecular and pharmacodynamic biomarker measurements in the interpretation of clinical trial outcomes.

Entrapment neuropathies.

Compression neuropathy includes a heterogeneous group of focal neuropathy syndromes related to peripheral nerve compression. Although acute or chronic compression-related injury may occur in essentially any peripheral nerve, certain anatomic considerations may predispose certain nerves to intrinsic or extrinsic compression-related injury. The clinical presentations of specific compression or entrapment syndromes depend on factors such as chronicity, location, severity, and mechanism of involvement of a particular nerve. In this article the diagnosis and management strategies of the more common and well-established entrapment and compression-related neuropathy syndromes are addressed.