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Intraoperative Brain Mapping
Source: 2000 May;:77-105.
Author: Toga AW, Ojemann GA, Cannestra AF.
Abstract:
A variety of specialized techniques have been developed to identify functionally important brain areas during neurosurgical operations. Some of these methods provide perspectives on functional localization similar to those derived with techniques used outside the operating room: intraoperative electrical stimulation mapping identifies those brain areas whose function is necessary for a particular behavior at a point in time, by interrupting local cerebral activity and interfering with the behavior. Behavioral changes after brain lesions, intraarterial amobarbital perfusion, in vivo tomographic methods and measurements of electrical activity provide similar data in the extraoperative setting. Intraoperative optical imaging of intrinsic signals identifies brain areas with altered vascular and metabolic activity during a behavior, physiological alterations that are thought to reflect changes in neuronal activity. Imaging of blood flow and oxygen extraction changes by PET or fMRI provide somewhat similar data in the extraoperative setting. The intraoperative setting also provides opportunities for the direct recording of physiologic correlates of behavior, in the electrocorticogram (ECoG) or of neuronal activity directly with microelectrodes. In general, intraoperative techniques provide greater local anatomic resolution than the analagous extraoperative techniques. However, such measurements are made over a more restricted area of brain, in special patient populations that come to neurosurgical procedures, as well as the time constraints, nature and level of anesthesia (local or general) and other requirements of the operating room environment. Many of these techniques were developed to reduce the morbidity of neurosurgical operations by identifying those areas where resections were likely to lead to functional deficits, areas that can then be avoided by the surgeon. The value of a technique in providing this information is thus an important clinical consideration, and is not necessarily the same for all methods. There is also considerable interest in relating extraoperative imaging to the intraoperative setting. This includes both methods for projecting preoperative structural imaging on to the surgical field and relating preoperative functional imaging. However, it does not necessarily follow that sites with changes in blood flow or oxygen extraction on preoperative PET or fMRI will identify sites that the surgeon must spare to avoid a functional deficit. That relation must be established empirically for each technique. This chapter reviews the specialized techniques and their application for functional localization used in the operating room, methods for relating preoperative imaging to the surgical field, and the relation between them.
Source: 2000 May;:77-105.
Author: Toga AW, Ojemann GA, Cannestra AF.
Abstract:
A variety of specialized techniques have been developed to identify functionally important brain areas during neurosurgical operations. Some of these methods provide perspectives on functional localization similar to those derived with techniques used outside the operating room: intraoperative electrical stimulation mapping identifies those brain areas whose function is necessary for a particular behavior at a point in time, by interrupting local cerebral activity and interfering with the behavior. Behavioral changes after brain lesions, intraarterial amobarbital perfusion, in vivo tomographic methods and measurements of electrical activity provide similar data in the extraoperative setting. Intraoperative optical imaging of intrinsic signals identifies brain areas with altered vascular and metabolic activity during a behavior, physiological alterations that are thought to reflect changes in neuronal activity. Imaging of blood flow and oxygen extraction changes by PET or fMRI provide somewhat similar data in the extraoperative setting. The intraoperative setting also provides opportunities for the direct recording of physiologic correlates of behavior, in the electrocorticogram (ECoG) or of neuronal activity directly with microelectrodes. In general, intraoperative techniques provide greater local anatomic resolution than the analagous extraoperative techniques. However, such measurements are made over a more restricted area of brain, in special patient populations that come to neurosurgical procedures, as well as the time constraints, nature and level of anesthesia (local or general) and other requirements of the operating room environment. Many of these techniques were developed to reduce the morbidity of neurosurgical operations by identifying those areas where resections were likely to lead to functional deficits, areas that can then be avoided by the surgeon. The value of a technique in providing this information is thus an important clinical consideration, and is not necessarily the same for all methods. There is also considerable interest in relating extraoperative imaging to the intraoperative setting. This includes both methods for projecting preoperative structural imaging on to the surgical field and relating preoperative functional imaging. However, it does not necessarily follow that sites with changes in blood flow or oxygen extraction on preoperative PET or fMRI will identify sites that the surgeon must spare to avoid a functional deficit. That relation must be established empirically for each technique. This chapter reviews the specialized techniques and their application for functional localization used in the operating room, methods for relating preoperative imaging to the surgical field, and the relation between them.