Minimally invasive neurosurgery: Anesthetic implications

Abstract

late to new anesthettc challen~,es could be restated as New surgical procedures demand new anesthetic techniques. Neurosurgery has come a long way from the days of Harvey Cushing and Walter Dandy. Cushing was the pioneer of modern neurosurgery and, in the words of Sir William Osler, ° he opened a new chapter in the field of surgery. Cushing followed the principles of brain imaging, but it was based on his knowledge of neurophysiology and the patient's clinical features. Today, the scope of the available techniques in neuroimaging is vast. Apart from computed tomography (CT) and magnetic resonance imaging (MRI), there are other imaging modalities, such as magnetic resonance spectroscopy, magnetic resonance angiography, single photon emission contrast tomography, and positron emission tomography, to name a few. These techniques, besides providing precise neuroanatomical visualization of intracranial lesions, also have functional imaging capabilities, which give us physiological information about cerebral blood flow/metabolism, outline functional areas like the speech center and motor center and, in chronic pain patients, make it possible to visualize hyperactivity of the pain center in the thalamus, thus differentiating the psychological component from the somatic component of pain. Simultaneously, the field of endoscopy has come a long way, with the availability of video endoscopes and miniature cameras. Tools for endoscopic surgery have permitted surgical access to lesions previously considered inaccessible because of their location. Therefore, minimally invasive neurosurgery is the fulfillment of a long-felt need to develop surgical techniques with minimum potential for damage to the normal brain and a sequel to various technological innovations. The principle of primum nor nocire (do no harm), although important in medicine as a whole, has always been the guiding philosophy in neurosurgery. Preserving the integrity of normal tissue while maximizing the resection of a brain tumor is more effectively possible with the combination of available imaging techniques and a minimally invasive approach (endoscopic surgery). The availability of open MRI systems 2 allows real-time imaging intraoperatively, adding more precision to tumor localization and resection. Besides this, modern imaging technology is also being used for nonsurgical approaches to some of the central nervous system disease states, such as Parkinsonism, chronic pain, acoustic neurinoma, and arteriovenous malformation (AVM). This discussion will focus on 3 aspects of minimally invasive neurosurgery--endoscopic neurosurgery, brain imaging, and gamma knife surgery. NEUROENDOSCOPY History