Muscle & nerve
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Case Reports
Increased sensitivity to a nondepolarizing muscle relaxant in a patient with acquired neuromyotonia.
Neuromyotonia is a disorder of hyperexcitability of the peripheral nerve. It has electromyographic features of spontaneous, continuous, irregularly occurring doublets, or multiplets of motor unit potential discharges. Neuromyotonia is characterized by both myokymic and neuromyotonic discharges. ⋯ The patient showed increased sensitivity to the neuromuscular effects of rocuronium. This increase in sensitivity may be explained by downregulation of acetylcholine receptors in response to chronic high agonist (acetylcholine) concentrations. If patients with neuromyotonia receive anesthesia, we recommend that smaller doses of a nondepolarizing muscle relaxant be administered, accompanied by monitoring of neuromuscular function, so as to provide optimal muscle relaxation while avoiding overdose and prolonged postoperative recovery.
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Randomized Controlled Trial
Corticosteroid iontophoresis to treat carpal tunnel syndrome: a double-blind randomized controlled trial.
Even though injection of corticosteroids into the carpal tunnel alleviates the symptoms of mild to moderately severe carpal tunnel syndrome (CTS), it has not gained universal popularity due to its invasiveness. This study was designed to investigate the effectiveness of dexamethasone iontophoresis as a noninvasive method of treating CTS. We carried out a double-blind randomized controlled trial comparing six sessions of iontophoresis with 0.4% dexamethasone sodium phosphate with distilled water in 17 patients. ⋯ Although there was subjective improvement of symptom severity scores in the treatment group as quantified by the Levine Self-Assessment Questionnaire, similar improvement was also observed in the control group (P < 0.05). Although corticosteroid iontophoresis is feasible in clinical settings and is well-tolerated by patients, iontophoresis of 0.4% dexamethasone was not effective in the treatment of mild to moderate CTS. Muscle Nerve 39: 627-633, 2009.
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Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), multifocal motor neuropathy (MMN), and anti-myelin-associated glycoprotein (anti-MAG) neuropathy are three demyelinating acquired neuropathies, with distinct responses to immunotherapy. In placebo-controlled, double-blind, randomized trials, intravenous immunoglobulin (IVIg) has been effective for CIDP and MMN, and plasmapheresis has been effective for CIDP. ⋯ This review examines the use and toxicity associated with these immunotherapy medications in treating patients with chronic immune-mediated demyelinating neuropathies. Muscle Nerve, 2009.
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Previous studies have documented the presence of rimmed vacuoles, atrophic fibers, and increased lysosomal cathepsin activity in skeletal muscle from animal models of chloroquine-induced myopathy, suggesting that muscle fibers in this type of myopathy may be degraded via the lysosomal-proteolysis pathway. Given recent evidence of abnormal ubiquitin accumulation in rimmed vacuoles, in this study we chose to examine the significance of the ubiquitin-proteasome proteolytic system in the process of muscle fiber destruction in experimental chloroquine myopathy. Expression of ubiquitin, 26S proteasome proteins, and ubiquitin ligases, such as muscle-specific RING finger-1 (MuRF-1) and atrogin-1/muscle atrophy F-box protein (MAFbx), was analyzed in innervated and denervated rat soleus muscles after treatment with either saline or chloroquine. ⋯ Ubiquitin and proteasome immunostaining, and ubiquitin, MuRF-1, and atrogin-1/MAFbx mRNAs were significantly increased in denervated soleus muscles from saline- and chloroquine-treated rats when compared with contralateral innervated muscles. Further, ubiquitin and ubiquitin ligase mRNA levels were higher in denervated muscles from chloroquine-treated rats when compared with saline-treated rats. These data demonstrate increased proteasomes and ubiquitin in denervated muscles from chloroquine-treated rats and suggest that the ubiquitin-proteasome proteolysis pathway as well as the lysosomal-proteolysis pathway mediate muscle fiber destruction in experimental chloroquine myopathy.
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Case Reports
Myotonic dystrophy type 2 with focal asymmetric muscle weakness and no electrical myotonia.
Genetically proven myotonic dystrophy type 2 (DM2) was found in a 61-year-old woman with creatine kinase (CK) elevation and only isolated weakness of one triceps. There was no clinical or electrical myotonia. ⋯ Muscle biopsy showed nonspecific myopathic features and highly atrophic fibers with nuclear clumps. DM2 should be considered in patients with focal proximal weakness and abnormal EMG without myotonic discharges.