Muscle & nerve
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Predictors of response to neuropathic pain treatment in patients with painful distal sensory neuropathies are lacking. The 5% lidocaine patch is believed to exert its effects on neuropathic pain via a local stabilizing effect on cutaneous sensory afferents. As such, it provides a model to assess whether the status of epidermal innervation as determined by skin biopsy or quantitative sensory testing (QST) of small- and large-diameter sensory afferents might serve as predictors of response to topical, locally active treatment. ⋯ Similarly we observed no consistent association between treatment response and QST for vibration, cooling, warm, heat-pain, and cold-pain thresholds, or distal sensory NCS. Thus, distal-leg skin biopsy, QST, and sensory NCS cannot be used to identify patients with painful polyneuropathy likely to respond to a lidocaine patch in clinical practice. Further studies are required to clarify precisely the mechanism and site of action of the lidocaine patch in patients with peripheral neuropathic pain.
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Comparative Study Clinical Trial
Predictors of noninvasive ventilation tolerance in patients with amyotrophic lateral sclerosis.
Noninvasive ventilation (NIV) appears to improve survival and quality of life in patients with amyotrophic lateral sclerosis (ALS), but little is known about predictors of NIV tolerance. NIV use was assessed and clinical predictors of tolerance were investigated, using predictive modeling, in ALS patients diagnosed and followed in our clinic until death over a 4-year time period. Patients were prescribed NIV based on current practice parameters when respiratory symptoms were present or forced vital capacity was less than 50%. ⋯ Tolerance was six times more likely in limb-onset than bulbar-onset ALS patients, with a trend toward reduced tolerance in those with lower forced vital capacity at NIV initiation. Age, gender, and duration of disease were not predictors of NIV tolerance. We conclude that a majority of ALS patients who are prescribed NIV can successfully become tolerant to its use.
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A quick-acting, quick-reversing method for blocking action potentials in peripheral nerves could be used in the treatment of muscle spasticity and pain. A high-frequency alternating-current (HFAC) sinusoidal waveform is one possible means for providing this type of block. HFAC was used to block peripheral motor nerve activity in an in vivo mammalian model. ⋯ HFAC block has three phases: an onset response; a period of asynchronous firing; and a steady state of complete or partial block. The onset response and the asynchronous firing can be minimized by using an optimal frequency-amplitude combination. In general, the onset response was lowest for the combination of 30 kHZ and 10 V.
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The aim of this study was to determine whether pulmonary function tests have a role in predicting the need for ventilation support in myasthenia gravis. Medical records were reviewed for 42 patients with severe myasthenia gravis who required 55 admissions to the intensive care unit. ⋯ Hypercapnia was frequent and was more common in patients who required mechanical ventilation. Worsening of these pulmonary function and blood gas values in patients with myasthenia gravis may guide decisions about intubation and ventilatory support.