RESUMO
With the progress of image-guided localization, body immobilization system, and computerized delivery of intensity-modulated radiation delivery, it became possible to perform spine radiosurgery. The next question is how to translate the high technology treatment to the clinical application. Clinical trials have been performed to demonstrate the feasibility of spine radiosurgery and efficacy of the treatment in the setting of spine metastasis, leading to the randomized trials by a cooperative group. Radiosurgery has also demonstrated its efficacy to decompress the spinal cord compression in selected group of patients. The experience indicates that spine radiosurgery has a potential to change the clinical practice in the management of spine metastasis and spinal cord compression.
RESUMO
The traditional theory of communicating hydrocephalus has implicated the bulk flow component of CSF motion; that is, hydrocephalus is generally understood as an imbalance between CSF formation and absorption. The theory that the cause of communicating hydrocephalus is malabsorption of CSF at the arachnoid villi is not substantiated by experimental evidence or by physical reasoning. Flow-sensitive MRI has shown that nearly all CSF motion is pulsatile, and there is substantial evidence that hyperdynamic choroid plexus pulsations are necessary and sufficient for ventricular dilation in communicating hydrocephalus. We have developed a model of intracranial pulsations based on the analogy between the pulsatile motion of electrons in an electrical circuit and the pulsatile motion of blood and CSF in the cranium. Increased impedance to the flow of CSF pulsations in the subarachnoid space redistributes the flow of pulsations into the ventricular CSF and into the capillary and venous circulation. The salient features of communicating hydrocephalus, such as ventricular dilation, intracranial pressure waves, narrowing of the CSF-venous pressure gradient, diminished cerebral blood flow, elevated resistive index and malabsorption of CSF, emerge naturally from the model. We propose that communicating hydrocephalus is the result of a redistribution of CSF pulsations in the cranium.