Ted M. Burns

CLINICAL FINDINGS IN MUSK-ANTIBODY POSITIVE MYASTHENIA GRAVIS: A U.S. EXPERIENCE

We performed a retrospective chart review on 53 muscle‐specific kinase antibody (MuSK‐Ab)‐positive myasthenia gravis (MG) patients at nine university‐based centers in the U.S. Of these, 66% were Caucasian, 85% were women, and age of onset was 9–79 years. Twenty‐seven patients were nonresponsive to anticholinesterase therapy. Myasthenia Gravis Foundation of America improvement status was achieved in 53% patients on corticosteroids, 51% with plasma exchange, and in 20% on intravenous immunoglobulin (IVIG). Thymectomy was beneficial in 7/18 patients at 3 years. Long‐term (≥3 years) outcome was very favorable in 58% of patients who achieved remission and/or minimal manifestation status. Overall, 73% improved. There was one MG‐related death. This survey reinforces several cardinal features of MuSK‐Ab‐positive MG, including prominent bulbar involvement and anticholinesterase nonresponsiveness. Facial or tongue atrophy was rare. Most patients respond favorably to immunotherapy. The best clinical response was to corticosteroids and plasma exchange, and the poorest response was to IVIG. Long‐term outcome is favorable in about 60% of cases. Muscle Nerve, 2009

The MG Composite: A valid and reliable outcome measure for myasthenia gravis.

Objective: To study the concurrent and construct validity and test-retest reliability in the practice setting of an outcome measure for myasthenia gravis (MG). Methods: Eleven centers participated in the validation study of the Myasthenia Gravis Composite (MGC) scale. Patients with MG were evaluated at 2 consecutive visits. Concurrent and construct validities of the MGC were assessed by evaluating MGC scores in the context of other MG-specific outcome measures. We used numerous potential indicators of clinical improvement to assess the sensitivity and specificity of the MGC for detecting clinical improvement. Test-retest reliability was performed on patients at the University of Virginia. Results: A total of 175 patients with MG were enrolled at 11 sites from July 1, 2008, to January 31, 2009. A total of 151 patients were seen in follow-up. Total MGC scores showed excellent concurrent validity with other MG-specific scales. Analyses of sensitivities and specificities of the MGC revealed that a 3-point improvement in total MGC score was optimal for signifying clinical improvement. A 3-point improvement in the MGC also appears to represent a meaningful improvement to most patients, as indicated by improved 15-item myasthenia gravis quality of life scale (MG-QOL15) scores. The psychometric properties were no better for an individualized subscore made up of the 2 functional domains that the patient identified as most important to treat. The test-retest reliability coefficient of the MGC was 98%, with a lower 95% confidence interval of 97%, indicating excellent test-retest reliability. Conclusions: The Myasthenia Gravis Composite is a reliable and valid instrument for measuring clinical status of patients with myasthenia gravis in the practice setting and in clinical trials.

Multipoint incremental motor unit number estimation as an outcome measure in ALS

Background: Improved outcome measures are necessary to reduce sample size and increase power in amyotrophic lateral sclerosis (ALS) clinical trials. Motor unit number estimation (MUNE) is a potentially attractive tool. MUNE methods previously employed in multicenter trials exhibited excessive variability and were prone to artifact. Objective: To evaluate a modification of standard incremental MUNE in a multicenter natural history study of subjects with ALS. Methods: Fifty healthy subjects were evaluated twice and 71 subjects with ALS were studied repeatedly for up to 500 days. Side and nerve studied was based on clinical examination findings. Nerves were stimulated at 3 specified locations and 3 increments were obtained at each location. Average single motor unit action potential (SMUP) amplitude was calculated by adding the amplitude of the third increment at each location and dividing by 9; SMUP was divided into maximum CMAP amplitude to determine the MUNE. Results: Test-retest variability was 9% in normal subjects. Average MUNE for normal subjects was 225 (±87), and was 41.9 (±39) among subjects with ALS at baseline. Subjects with ALS showed clear decrements over time, with an overage rate of decline of approximately 9% per month. SMUP amplitude increased with time in a fashion consistent with the known pathophysiology of ALS. Conclusion: Multipoint incremental MUNE has a number of attributes that make it attractive as an outcome measure in ALS and other diseases characterized by motor unit loss. It can be rapidly performed on any EMG machine and has repeatability and rates of decline that favorably compare to other previously described methods.

Less is more, or almost as much: A 15‐item quality‐of‐life instrument for myasthenia gravis

We describe the process whereby a recently developed myasthenia gravis (MG)‐specific quality‐of‐life (QOL) instrument was reduced from 60 items to 15 items while maintaining potential usefulness in the clinic and in prospective treatment trials. In data from a recently completed prospective trial of mycophenolate mofetil (MMF) in MG, the MG‐QOL15 correlated as highly as the 60‐item MG‐QOL for physical and social domains of the 36‐item health survey of the Medical Outcomes Study Short Form (SF‐36). Correlation coefficients for the MG‐QOL15 were similar to the 60‐item MG‐QOL for the Quantitative Myasthenia Gravis (QMG), MG‐specific Manual Muscle Testing (MG‐MMT), and the MG‐specific Activities of Daily Living (MG‐ADL) scores at week 0 and for change in scores from week 0 to week 12 in the MMF trial. Using the physician global impression at week 12 of the trial as the “gold standard,” the MG‐QOL15 demonstrated high sensitivity. Because the MG‐QOL15 instrument can be quickly and easily administered and interpreted, it is a potential QOL measure for treatment trials and the clinical evaluation of patients with MG. Muscle Nerve, 2008

Electrical impedance myography as a biomarker to assess ALS progression

Abstract Electrical impedance myography (EIM), a non-invasive, electrophysiological technique, has preliminarily shown value as an ALS biomarker. Here we perform a multicenter study to further assess EIM’s potential for tracking ALS. ALS patients were enrolled across eight sites. Each subject underwent EIM, handheld dynamometry (HHD), and the ALS Functional Rating Scale-revised (ALSFRS-R) regularly. Techniques were compared by assessing the coefficient of variation (CoV) in the rate of decline and each technique’s correlation to survival. Results showed that in the 60 patients followed for one year, EIM phase measured from the most rapidly progressing muscle in each patient had a CoV in the rate of decline of 0.62, compared to HHD (0.82) and the ALSFRS-R (0.74). Restricting the measurements to the first six months gave a CoV of 0.55 for EIM, 0.93 for HHD, and 0.84 for ALSFRS-R. For both time-periods, all three measures correlated with survival. Based on these data, a six-month clinical trial designed to detect a 20% treatment effect with 80% power using EIM would require only 95 patients/arm compared to the ALSFRS-R, which would require 220 subjects/arm. In conclusion, EIM can serve as a useful ALS biomarker that offers the prospect of greatly accelerating phase 2 clinical trials.

Construction of an efficient evaluative instrument for Myasthenia Gravis: The MG composite

We assessed the performance of items from the Quantitative Myasthenia Gravis (QMG), MMT (Manual Muscle Test), and MG‐ADL (Myasthenia Gravis – Activities of Daily Living) scales, using data from two recently completed treatment trials of generalized MG. Items were selected that were relevant to manifestations of MG, meaningful to both the physician and the patient, and responsive to clinical change. After the 10 items were chosen, they were weighted based on input from MG experts from around the world, considering factors such as quality of life, disease severity, risk, prognosis, validity, and reliability. The MG Composite is easy to administer, takes less than 5 minutes to complete, and requires no equipment. Weighting of the response options of the 10 items should result in ordinal scores that better represent MG status and are more responsive to meaningful clinical change. To better determine its suitability for clinical use and for treatment trials, the MG Composite will be tested prospectively at several academic medical centers and will be used as a secondary measure of efficacy in pending clinical trials of MG. Muscle Nerve 38: 1553–1562, 2008

Quality of life and measures of quality of life in patients with neuromuscular disorders.

In this review we present an overview of quality of life (QOL) and QOL measures in neuromuscular disorders. We discuss the characteristics of QOL measures used in neuromuscular research, highlighting differences between generic versus disease‐specific and global versus health‐related QOL instruments. The phenomenon of response shift is reviewed. Commonly used QOL instruments are reviewed for amyotrophic lateral sclerosis, muscle diseases, myasthenia gravis, and polyneuropathy. We also review some of what is known about QOL for patients with these neuromuscular disorders. Muscle Nerve 46: 9–25, 2012

Inflammation and neuropathic attacks in hereditary brachial plexus neuropathy

Objective: To study the role of mechanical, infectious, and inflammatory factors inducing neuropathic attacks in hereditary brachial plexus neuropathy (HBPN), an autosomal dominant disorder characterised by attacks of pain and weakness, atrophy, and sensory alterations of the shoulder girdle and upper limb muscles. Methods: Four patients from separate kindreds with HBPN were evaluated. Upper extremity nerve biopsies were obtained during attacks from a person of each kindred. In situ hybridisation for common viruses in nerve tissue and genetic testing for a hereditary tendency to pressure palsies (HNPP; tomaculous neuropathy) were undertaken. Two patients treated with intravenous methyl prednisolone had serial clinical and electrophysiological examinations. One patient was followed prospectively through pregnancy and during the development of a stereotypic attack after elective caesarean delivery. Results: Upper extremity nerve biopsies in two patients showed prominent perivascular inflammatory infiltrates with vessel wall disruption. Nerve in situ hybridisation for viruses was negative. There were no tomaculous nerve changes. In two patients intravenous methyl prednisolone ameliorated symptoms (largely pain), but with tapering of steroid dose, signs and symptoms worsened. Elective caesarean delivery did not prevent a typical postpartum attack. Conclusions: Inflammation, probably immune, appears pathogenic for some if not all attacks of HBPN. Immune modulation may be useful in preventing or reducing the neuropathic attacks, although controlled trials are needed to establish efficacy, as correction of the mutant gene is still not possible. The genes involved in immune regulation may be candidates for causing HBPN disorders.

Mycophenolate mofetil in AChR‐antibody‐positive myasthenia gravis: Outcomes in 102 patients

Two recent randomized, controlled trials failed to demonstrate a benefit of mycophenolate mofetil (MMF) over prednisone in the treatment of myasthenia gravis (MG). We reviewed our experience with MMF in MG to determine whether these trials may have been unsuccessful because of their short duration and the unpredicted benefit of prednisone. We reviewed outcomes and prednisone dosage for all our acetylcholine‐receptor (AChR)‐antibody positive MG patients treated with MMF alone or with prednisone for at least 3 months. The percentage of patients with a desirable outcome (MG‐specific Manual Muscle Test score <4 or Myasthenia Gravis Foundation of America post‐invention status of minimal manifestations or better) began to increase after 6 months; 80% of those followed for >24 months had a desirable outcome. Prednisone dose decreased after 12 months; after 25 months, 54.5% of patients took no prednisone and 75% took <7.5 mg/day. This retrospective analysis provides class IV evidence that MMF begins to improve AChR‐positive MG after 6 months, both with prednisone and as monotherapy. Muscle Nerve 41: 593–598, 2010

Guillain-Barré syndrome.

Guillain-Barré syndrome (GBS) is an acute-onset, monophasic, immune-mediated polyneuropathy that often follows an antecedent infection. The diagnosis relies heavily on the clinical impression obtained from the history and examination, although cerebrospinal fluid analysis and electrodiagnostic testing usually provide evidence supportive of the diagnosis. The clinician must also be familiar with mimics and variants to promptly and efficiently reach an accurate diagnosis. Intravenous immunoglobulin and plasma exchange are efficacious treatments. Supportive care during and following hospitalization is also crucial.