Neurosurgery
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In an attempt to answer questions regarding nerve injection injuries, we injected 11 agents in current use and commonly administered by intramuscular injection into the sciatic nerves of adult Wistar rats. Equal volumes of normal saline were used as control. We harvested the sciatic nerves at various times after injection and examined them by both light and electron microscopy. ⋯ Large, heavily myelinated fibers were more susceptible to injection injury than smaller, thinly myelinated nerve fibers. The effect of the injected drug seemed to be related to injury of the nerve fiber unit--both the axon and the Schwann cell with its myelin sheath. Regeneration in damaged nerves was a constant finding; even the most severely injured nerves, with total axonal degeneration, underwent subsequent regeneration.
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The syndrome of inappropriate antidiuretic hormone secretion (SIADH) developed approximately 7 days after a spontaneous subarachnoid hemorrhage in a 63-year-old woman with an anterior cerebral artery aneurysm. The hyponatremia associated with this syndrome resulted in a deterioration of the patient's clinical condition and focal neurological signs, which simulated the clinical deterioration after spontaneous subarachnoid hemorrhage that is often caused by other intracranial pathological conditions. ⋯ Prompt recognition and treatment of the SIADH resulted in prompt improvement, and we were then able to proceed with the planned craniotomy for the aneurysm. The syndrome and its importance are discussed.