Muscle & nerve
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Case Reports
Reversible nitrous oxide-induced myeloneuropathy with pernicious anemia: case report and literature review.
A previously healthy 27-year-old woman developed a subacute myeloneuropathy after receiving nitrous oxide anesthesia for dental procedures. Neurologic evaluation revealed that she was vitamin B(12) deficient due to underlying pernicious anemia. Discontinuation of nitrous oxide and supplementation with vitamin B(12) resulted in dramatic clinical improvement, with near-complete normalization of her neurologic examination. This case and published reports reviewed here emphasize that favorable outcomes are possible following prompt recognition and treatment of vitamin B(12) deficiency.
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Catalase is a major antioxidant enzyme. Increasing catalase expression represents a promising avenue to improve muscle function in certain physiological conditions and in some muscle diseases. We hypothesized that catalase overexpression should not impair normal muscle contraction. ⋯ Furthermore, EDL fatigue response was not altered. Taken together, we have developed a novel AAV vector to enhance catalase expression. Lack of apparent toxicity in normal muscle strongly supports further exploration of this vector to reduce oxidative stress-induced muscle damage.
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Transient decrease in the excitability of a reflex circuit following its activation by appropriate stimuli is a well-recognized phenomenon, but it is unclear how this applies to thermoalgesic stimuli during quantitative sensory testing (QST). We examined the effects induced by a thermoalgesic (conditioning) stimulus on the response to a subsequent (test) stimulus of the same characteristics. All tests were done using a Peltier thermode with a surface area of 12.5 cm(2) using ramp rates of 2 degrees C/s and variable interstimulus intervals (ISIs) ranging from 10 to 60 s. ⋯ However, latency of warm perception was significantly delayed and pain perception intensity was significantly reduced with respect to conditioning stimuli at ISIs below 60 s. Our results indicate a transient saturation of warm and heat pain perception systems after a thermoalgesic stimulus. We therefore recommend that time intervals of >1 min be used between two consecutive thermoalgesic stimuli when examining QST.
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Measurements of T2 relaxation times in tissues have provided a unique, noninvasive method to investigate the microenvironment of water molecules in vivo. As more clinical imaging is performed at higher field strengths, tissue relaxation times need to be reassessed in order to optimize tissue contrast. The purpose of this study was to investigate the water proton T2 relaxation time in human median nerve at 7 T. ⋯ The T2 relaxation time of the median nerve was 18.3 +/- 1.9 ms, which is significantly shorter than the T2 measured in previous studies performed at 1.5 T and 3 T. Further, the T2 relaxation time of the median nerve is shorter than the T2 relaxation time of other tissues, such as brain tissue, at the same field strength. Since the T2 relaxation time of water protons is sensitive to the water microenvironment, relaxation measurements and, in general, a more quantitative magnetic resonance imaging approach might help in detecting and investigating diseases of peripheral nervous system, such as compressive and inflammatory neuropathies, in humans.
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Case Reports
Cervical myelopathy caused by retrograde intraneural dissection of anesthetic solution.
Brachial plexus block is a generally safe procedure for postoperative analgesia following shoulder surgery. This report describes brachial plexus block complicated by intraneural dissection of anesthetic solution, resulting in severe damage to the upper spinal cord. Other investigators have hypothesized that this rare complication is caused by accidental needle placement within the substance of the cord. This case demonstrates that the complication can occur despite a peripherally located needle.