Muscle & nerve
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The time- and dose-dependent effects of acute high-dose corticosteroids on the diaphragm muscle are poorly defined. This study aimed to examine in rabbits the temporal relationships and dose-response effects of acute high-dose methylprednisolone succinate on diaphragmatic contractile and structural properties. Animals were assigned to groups receiving: (1) 80 mg/kg/day methylprednisolone (MP80) intramuscularly for 1, 2, and 3 days; (2) 10 mg/kg/day methylprednisolone (MP10, pulse-dose) for 3 days; or (3) saline (placebo) for 3 days; and (4) a control group. ⋯ Significant myofibrillar disarray was also observed in both MP groups. The decline in Po was significantly associated with the increased volume density of abnormal myofibrils. Thus, very high-dose methylprednisolone (MP80) can produce rapid reductions in diaphragmatic function, whereas pulse-dose methylprednisolone (MP10) produces only modest functional loss.
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We report on two children presenting at birth with respiratory failure, bilateral diaphragmatic eventration, and floppiness. Electrodiagnostic studies of the limbs, and biochemical and DNA studies excluded generalized neuromuscular diseases. ⋯ Diaphragm muscle biopsy showed a paucity of muscle fibers. Isolated hypoplasia of the diaphragm is a rare cause of neonatal respiratory failure, which may have a favorable outcome with long-term ventilatory support.