Muscle & nerve
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Although neuropathies of the infrapatellar nerve (infrapatellar branch of the saphenous nerve, IPBSN) have been reported clinically, no electrophysiological method has been defined to evaluate IPBSN conduction. We therefore studied a total of 60 saphenous nerves and 60 IPBSNs from 36 volunteers. ⋯ Sensory nerve action potentials were obtained from each subject; mean latency of the first positive peak was 8.1 +/- 0.9 ms, conduction velocity was 54 +/- 4.4 m/s, and response amplitude was 1.3 +/- 1.1 microV. The method that we describe may be an easy and useful electrophysiological test for neuropathies of the IPBSN.
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Randomized Controlled Trial
Measures of dyspnea in patients with amyotrophic lateral sclerosis.
Respiratory symptoms are not well characterized in amyotrophic lateral sclerosis (ALS). The baseline dyspnea index (BDI) and transition dyspnea index (TDI) are indices designed to measure change in dyspnea over time. They are easy to administer and do not inquire about specific physical tasks. ⋯ The TDI detected worsening dyspnea by 4 weeks and declined significantly more over the subsequent 8 weeks. The TDI was significantly associated with changes in forced vital capacity and appeared more sensitive to changes in dyspnea than the ALS functional rating scale-respiratory subscale (ALS-FRS R) and a visual analog scale of breathlessness. The BDI and TDI thus appear to be useful measures in ALS and may have both clinical and research applications.
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Denervation induces muscle fiber atrophy and changes in the gene expression rates of skeletal muscle. Electrical stimulation (ES) is a procedure generally used to treat denervated muscles in humans. This study evaluated the effect of ES based on chronaxie and rheobase on the expression of the myoD and atrogin-1 genes in denervated tibialis anterior (TA) muscle of Wistar rats. ⋯ However, ES did not prevent muscle-fiber atrophy after denervation. Thus, ES based on chronaxie values and applied to denervated muscles using surface electrodes, as normally used in human rehabilitation, was able to reduce the myoD and atrogin-1 gene expressions, which are related to muscular growth and atrophy, respectively. The results of this study provide new information for the treatment of denervated skeletal muscle using surface ES.
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Stiff-person syndrome (SPS) is a disorder characterized by progressive muscle rigidity with superimposed painful muscle spasms and gait impairment due to continuous motor activity. Evidence has accumulated in favor of SPS representing an autoimmune, predominantly encephalomyelopathic disorder resulting from B-cell-mediated clonal production of autoantibodies against presynaptic inhibitory epitopes on the enzyme glutamic acid decarboxylase (GAD) and the synaptic membrane protein amphiphysin. ⋯ The scarcity of neuropathological correlates stand in sharp contrast with the severity of the disability in affected individuals and suggests that functional impairment of inhibitory circuits without structural damage is sufficient to develop the full clinical spectrum of SPS. The rarity of this condition limits the feasibility of controlled clinical trials in the treatment of SPS, but the available evidence suggest that drugs that increase cortical and spinal inhibition such as benzodiazepines and drugs that provide immune modulation such as intravenous immunoglobulin, plasmapheresis, and prednisone are effective treatments.
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Conventional local anesthetics such as bupivacaine cause considerable myotoxicity and neurotoxicity, whereas tetrodotoxin (TTX) does not. Tetrodotoxin combined with bupivacaine or vasoconstrictors produces long-duration nerve blockade. To assess whether these prolonged blocks can be produced without increased myotoxicity, Sprague-Dawley rats were injected with bupivacaine, TTX, and both, or TTX plus epinephrine. ⋯ Similarly, in differentiated cells from a myoblast cell line (C2C12), TTX caused either no or minimal worsening of cell viability from bupivacaine at 2 or 7 days. Epinephrine did not worsen TTX's relatively minimal cytotoxicity. Tetrodotoxin may thus be useful in producing prolonged nerve block with minimal myotoxicity and perhaps neurotoxicity.