Neurosurgery
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Electric spinal cord stimulation (SCS) is widely used as a treatment modality for ischemic pain in peripheral arterial insufficiency. The background for the therapeutic effect may be a temporary inhibition of sympathetically maintained peripheral vasoconstriction. In this series of experiments, the involvement of different types of cholinergic and adrenergic receptor subclasses in the vasodilatory effect was explored in anesthetized rats. ⋯ The vasodilatory effect of SCS in the animal model used here seems to a large extent to be mediated by an inhibitory effect on peripheral vasoconstriction maintained via efferent sympathetic activity involving nicotinic transmission in the ganglia and the postganglionic alpha 1-adrenoreceptors. The involvement of beta-receptors seems to be different in skin and muscle, beta 1 being more important for the changes in the skin and beta 2 being more important for those in muscle. The high-intensity antidromic response, earlier believed to explain how SCS exerted its vasodilatory effect, was resistant to cholinergic and adrenergic manipulations and seems to depend on entirely different mechanisms.
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Most shunt-dependent hydrocephalic patients present with predictable symptoms of headache and mental status changes when their cerebrospinal fluid shunts malfunction. Their intracranial pressure (ICP) is usually high, and they usually respond to routine shunt revision. This report describes 12 shunted patients who were admitted with the full-blown hydrocephalic syndrome but with low to low-normal ICP. ⋯ All 11 were subsequently treated successfully with a new medium- or low-pressure shunt. One patient was treated successfully with prolonged shunt pumping. We postulate that: 1) the development of this low-pressure hydrocephalic state is related to alteration of the viscoelastic modulus of the brain, secondary to expulsion of extracellular water from the brain parenchyma, and to structural changes in brain tissues due to prolonged overstretching; 2) certain patients are susceptible to developing low-pressure hydrocephalic state because of an innate low brain elasticity due to bioatrophic changes; 3) low-pressure hydrocephalic state symptoms are due not to pressure changes but to brain tissue distortion and cortical ischemia secondary to severe ventricular distortion and elevated radial compressive stresses within the brain; and 4) treatment must be directed toward allowing the entry of water into the brain parenchyma and the restoration of baseline brain viscoelasticity.
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The techniques for the treatment of intracranial arteriovenous fistulae include angiographic balloon occlusion of the fistula as well as direct surgical attack. Regardless of the method, the occurrence of severe hyperemia caused by a lack of autoregulation after obliteration of the fistula remains a significant concern. ⋯ Single photon emission computed tomography and transcranial Doppler studies confirmed the lack of hyperemia during the test occlusion, allowing consideration of treatment plans involving acute fistula occlusion without the difficulty imposed by gradual occlusion and permitting a more accurate evaluation of risk. The purpose of this report is to illustrate how clinical evaluation of intracranial hemodynamics can contribute significantly to treatment decisions.
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Biography Historical Article
Historical perspective. David Ferrier (1843-1928).
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A meta-analysis of published randomized studies comparing prophylactic antibiotics to placebo in craniotomies was performed. Ten studies were examined; eight met criteria for inclusion into the meta-analysis. The analysis showed an advantage of antibiotics over placebo at the P < 10-8 level. ⋯ Cumulative meta-analyses showed that this conclusion could have been confidently drawn by 1988, after only four of the eight eligible trials had been published. Trials published since that time have reinforced these conclusions but have not significantly altered them. Future studies should compare proposed new antibiotic regimens with one of those already demonstrated to be effective, not with a placebo.