Hans D. Katzberg

Immune-mediated necrotizing myopathy associated with statins.

We report patients from two neuromuscular centers who were evaluated between the years 2000 and 2008 and met the following criteria: (1) proximal muscle weakness occurring during or after treatment with statins; (2) elevated serum creatine kinase (CK); (3) persistence of weakness and elevated CK despite discontinuation of the statin; (4) improvement with immunosuppressive agents; and (5) muscle biopsy showing necrotizing myopathy without significant inflammation. Twenty‐five patients fulfilled our inclusion criteria. Twenty‐four patients required multiple immunosuppressive agents. Fifteen patients relapsed after being tapered off immunosuppressive therapy. Exposure to statins prior to onset was significantly higher in patients with necrotizing myopathy (82%) as compared to those with dermatomyositis (18%), polymyositis (24%), and inclusion‐body myositis (38%) seen in the same time period. The lack of improvement following discontinuation of statins, the need for immunosuppressive therapy, and frequent relapse when treatment was tapered suggest an immune‐mediated etiology for this rare, statin‐associated necrotizing myopathy. Muscle Nerve, 2010

Evidence-based guideline: Intravenous immunoglobulin in the treatment of neuromuscular disorders: Report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology

Objective: To assess the evidence for the efficacy of IV immunoglobulin (IVIg) to treat neuromuscular disorders. Methods: The MEDLINE, Web of Science, and EMBASE databases were searched (1966–2009). Selected articles were rated according to the American Academy of Neurologys therapeutic classification of evidence scheme; recommendations were based on the evidence level. Results and Recommendations: IVIg is as efficacious as plasmapheresis and should be offered for treating Guillain-Barré syndrome (GBS) in adults (Level A). IVIg is effective and should be offered in the long-term treatment of chronic inflammatory demyelinating polyneuropathy (Level A). IVIg is probably effective and should be considered for treating moderate to severe myasthenia gravis and multifocal motor neuropathy (Level B). IVIg is possibly effective and may be considered for treating nonresponsive dermatomyositis in adults and Lambert-Eaton myasthenic syndrome (Level C). Evidence is insufficient to support or refute use of IVIg in the treatment of immunoglobulin M paraprotein–associated neuropathy, inclusion body myositis, polymyositis, diabetic radiculoplexoneuropathy, or Miller Fisher syndrome, or in the routine treatment of postpolio syndrome or in children with GBS (Level U). IVIg combined with plasmapheresis should not be considered for treating GBS (Level B). More data are needed regarding IVIg efficacy as compared with other treatments/treatment combinations. Most studies concluded IVIg-related serious adverse effects were rare. Given the variable nature of these diseases, individualized treatments depending on patient need and physician judgment are important.

Assessment: Symptomatic treatment for muscle cramps (an evidence-based review) Report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology

Background: A Food and Drug Administration advisory in 2006 warned against the off-label use of quinine sulfate and its derivatives in the treatment of muscle cramps. Physicians are faced with a difficult scenario in choosing a treatment regimen for patients with muscle cramps. This American Academy of Neurology assessment systematically reviews the available evidence on the symptomatic treatment of muscle cramps. Methods: A total of 563 potential articles were reviewed, of which 24 met the inclusion criteria of prospective trials evaluating the efficacy of a particular treatment on muscle cramps as a primary or secondary outcome. Results: There are Class I studies showing the efficacy of quinine derivatives for treatment of muscle cramps. However, the benefit is modest and there are adverse effects from published prospective trials as well as case reports. There is one Class II study each to support the use of Naftidrofuryl, vitamin B complex, lidocaine, and diltiazem in the treatment of muscle cramps. Recommendations: Although likely effective (Level A), quinine derivatives should be avoided for routine use in the management of muscle cramps because of the potential of toxicity, but in select patients they can be considered for an individual therapeutic trial once potential side effects are taken into account. Vitamin B complex, Naftidrofuryl, and calcium channel blockers such as diltiazem are possibly effective and may be considered in the management of muscle cramps (Level C). Further studies are needed to identify agents that are effective and safe for the treatment of muscle cramps.

Changing outcome in inflammatory neuropathies Rasch–comparative responsiveness

Objectives: We performed responsiveness comparison between the patient-reported Inflammatory Rasch-built Overall Disability Scale (I-RODS) and the widely used clinician-reported Inflammatory Neuropathy Cause and Treatment–Overall Neuropathy Limitation Scale (INCAT-ONLS) in patients with Guillain-Barré syndrome (GBS), chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), and immunoglobulin M–monoclonal gammopathy of undetermined significance related polyneuropathy (IgM-MGUSP). Methods: One hundred thirty-seven patients (GBS: 55, CIDP: 59, IgM-MGUSP: 23) with a new diagnosis or clinical relapse assessed both scales. Patients with GBS/CIDP were examined at 0, 1, 3, 6, and 12 months; patients with IgM-MGUSP at 0, 3, and 12. We subjected all data to Rasch analyses, and calculated for each patient the magnitude of change on both scales using the minimal clinically important difference (MCID) related to the individual standard errors (SEs). A responder was defined as having an MCID-SE ≥1.96. Individual scores on both measures were correlated with the EuroQoL thermometer (heuristic responsiveness). Results: The I-RODS showed a significantly higher proportion of meaningful improvement compared with the INCAT-ONLS findings in GBS/CIDP. For IgM-MGUSP, the lack of responsiveness during the 1-year study did not allow a clear separation. Heuristic responsiveness was consistently higher with the I-RODS. Conclusion: The I-RODS more often captures clinically meaningful changes over time, with a greater magnitude of change, compared with the INCAT-ONLS disability scale in patients with GBS and CIDP. The I-RODS offers promise for being a more sensitive measure and its use is therefore suggested in future trials involving patients with GBS and CIDP.

ELECTROPHYSIOLOGIC CORRELATIONS WITH CLINICAL OUTCOMES IN CIDP

Data are lacking on correlations between changes in nerve conduction (NC) studies and treatment response in chronic inflammatory demyelinating polyneuropathy (CIDP). This report examined data from a randomized, double‐blind trial of immune globulin intravenous, 10% caprylate/chromatography purified (IGIV‐C [Gamunex]; n = 59) versus placebo (n = 58) every 3 weeks for up to 24 weeks in CIDP. Motor NC results and clinical measures were assessed at baseline and endpoint/week 24. Improvement from baseline in adjusted inflammatory neuropathy cause and treatment score correlated with improvement in proximally evoked compound muscle action potential (CMAP) amplitudes (r = −0.53; P < 0.001) of all nerves tested and with improvement in CMAP amplitude of the most severely affected motor nerve (r = −0.36; P < 0.001). Correlations were observed between improvement in averaged CMAP amplitudes and dominant‐hand grip strength (r = 0.44; P < 0.001) and Medical Research Council sum score (r = 0.38; P < 0.001). Overall, the change in electrophysiologic measures of NC in CIDP correlated with clinical response to treatment. Muscle Nerve, 2010

Electrophysiology in chronic inflammatory demyelinating polyneuropathy with IGIV

Patients with chronic inflammatory demyelinating polyneuropathy (CIDP) received immune globulin intravenous, 10% caprylate/chromatography purified (IGIV‐C, Gamunex; n = 59) or placebo (n = 58) every 3 weeks for up to 24 weeks (first period) in a randomized, double‐blind, parallel‐group, response‐conditional, crossover study. Motor and sensory nerves were assessed at baseline and endpoint/week 24. A nonsignificant trend toward improvement in the proximal amplitude of the most severely affected motor nerve was observed with IGIV‐C (0.69 ± 1.86 mV) versus placebo (0.47 ± 2.29 mV), and a greater improvement of 1.08 ± 2.15 mV with IGIV‐C versus 0.46 ± 2.03 mV with placebo (P = 0.089) was observed with exclusion of data from Erbs point stimulation. Greater improvements from baseline favoring IGIV‐C were observed for 127/142 electrophysiologic parameters. The averaged motor amplitudes from all motor nerves significantly improved with IGIV‐C versus placebo [treatment difference, 0.62 mV; 95% confidence interval (CI), 0.05, 1.20; P = 0.035], and conduction block decreased significantly (treatment difference, −5.54%; 95% CI, −10.43, −0.64; P = 0.027), particularly in the lower limbs. Overall, the data suggest that IGIV‐C improves electrophysiologic parameters in CIDP. Muscle Nerve, 2009

The quantitative myasthenia gravis score: comparison with clinical, electrophysiological, and laboratory markers.

Objective: To determine whether the quantitative myasthenia gravis score (QMGS) accurately represents disease severity in patients with myasthenia gravis (MG). Methods: One hundred thirty-five patients with MG from 2 previous randomized studies were included. QMGS correlation with the Myasthenia Gravis Foundation of America (MGFA) score, quality of life scale, acetylcholine receptor antibodies (AChRAbs), and electrophysiological parameters was studied. Results: The QMGS showed a good correlation with the MGFA scale (r2 = 0.54, P < 0.0001), jitter (rs = 0.40, P < 0.0001), and 15-item quality of life scale (rs = 0.41, P = 0.007) and was less well correlated with the 60-item myasthenia gravis–specific quality of life survey and other electrophysiological markers. No correlation was demonstrated with AchRAb titers, but AchRAb-positive patients had higher QMGS (14.2 ± 4.5) than AchRAb-negative patients (12.0 ± 3.7, P = 0.008). Conclusions: These results demonstrate that the QMGS is a valid marker for disease severity as shown by the MGFA scale, quality of life scale, and jitter, supporting the use of the QMGS as a primary outcome measure in clinical trials of MG.

Conduction Slowing in Diabetic Sensorimotor Polyneuropathy

OBJECTIVE Mild demyelination may contribute more to the pathophysiology of nerve fiber injury in diabetic sensorimotor polyneuropathy (DSP) than previously thought. We investigated the clinical and electrodiagnostic classifications of nerve injury in diabetic patients to detect evidence of conduction slowing in DSP. RESEARCH DESIGN AND METHODS Type 1 diabetic subjects (n = 62) and type 2 diabetic subjects (n = 111) with a broad spectrum of DSP underwent clinical examination and nerve conduction studies (NCS). Patients were classified as having axonal (group A), conduction slowing (group D), or combined (group C) DSP based on electrodiagnostic criteria. Patients with chronic immune-mediated neuropathies were not included. The groups were compared using ANOVA, contingency tables, and Kruskal-Wallis analyses. RESULTS Of the 173 type 1 and type 2 diabetic subjects with a mean age of 59.1 ± 13.6 years and hemoglobin A1c (HbA1c) of 8.0 ± 1.8% (64 ± 19.7 mmol/mol), 46% were in group A, 32% were in group D, and 22% were in group C. The severity of DSP increased across groups A, D, and C, respectively, based on clinical and NCS parameters. The mean HbA1c for group D subjects (8.9 ± 2.3% [74 ± 25.1 mmol/mol]) was higher than for group A and group C subjects (7.7 ± 1.4% [61 ± 15.3 mmol/mol] and 7.5 ± 1.3% [58 ± 14.2 mmol/mol]; P = 0.003), and this difference was observed in those with type 1 diabetes. CONCLUSIONS The presence of conduction slowing in patients with suboptimally controlled type 1 diabetes indicates the possibility that this stage of DSP may be amenable to intervention via improved glycemic control.

Epidemiology of myasthenia gravis in Ontario, Canada.

Incidence and prevalence estimates in myasthenia gravis have varied widely. Recent studies based on administrative health data have large sample sizes but lack rigorous validation of MG cases, and have not examined the North American population. Our aim was to explore trends in MG incidence and prevalence for the years 1996-2013 in the province of Ontario, Canada (population 13.5 million). We employed a previously validated algorithm to identify MG cases. Linking with census data allowed for the calculation of crude- and age/sex-standardized incidence and prevalence rates for the years 1996-2013. The regional distribution of MG cases throughout the province was examined. Mean age at the first myasthenia gravis encounter was 60.2 ± 17.1 years. In 2013, there were 3611 prevalent cases in Ontario, and the crude prevalence rate was 32.0/100,000 population. Age- and sex-standardized prevalence rates rose consistently over time from 16.3/100,000 (15.4-17.1) in 1996 to 26.3/100,000 (25.4-27.3) in 2013. Standardized incidence rates remained stable between 1996 (2.7/100,000; 95% CL 2.3-3.0) and 2013 (2.3/100,000; 2.1-2.6). Incidence was highest in younger women and older men, and geographic variation was evident throughout the province. In conclusion, this large epidemiological study shows rising myasthenia gravis prevalence with stable incidence over time, which is likely reflective of patients living longer, possibly due to improved disease treatment. Our findings provide accurate information on the Canadian epidemiology of myasthenia gravis and burden for health care resources planning for the province, respectively.

A comparison of electrodiagnostic tests in ocular myasthenia gravis.

Objectives: We aimed to determine whether the diagnostic yield of single-fiber electromyography (SFEMG) in different grades of ocular myasthenia gravis (OMG) is enhanced by repetitive nerve stimulation studies (RNS). Methods: One hundred twenty-one patients with a diagnosis of mild, moderate, or severe OMG based on clinical criteria had SFEMG of the frontalis muscle and RNS of the facial nerve. Tests results were compared by contingency table analysis. Results: In these patients, 19% had abnormal RNS and 95% had abnormal SFEMG. SFEMG was abnormal in 93%, 96%, and 100% with mild, moderate, and severe OMG, respectively. One patient with abnormal RNS had normal SFEMG, but the SFEMG study was incomplete. Conclusion: Like in generalized MG, SFEMG is more sensitive than RNS for all grades of OMG. Furthermore, if a complete SFEMG study is normal, addition of RNS does not improve the diagnostic yield.