Stereotactic surgery

Thanks to anatomical and neurophysiological studies conducted over the past 100 years, the brain sections for planning and execution of movements and processing of perceptions such as seeing, hearing, touch, smell, and the pain are known. These are located in well-defined portions of the brain mantle (cortex) and in low-lying small switching cores, which are connected by paths with the appropriate areas of the cortex or the spinal cord. The idea of functional stereotactic is to selectively disable certain small switching cores or connecting tracks, and thereby influence - within a very small space and with low injury - very effectively the movements or the pain processing. The position of these switching cores and webs is known from specific anatomical atlases and can be determined in magnetic resonance images of the patient. Since the structures which have to reached are very small, ranging from the size of a bean to a rice grain, a very accurate calculation and mechanically extremely precise insertion of the probe to the desired destination point is necessary. Great importance is also attached to the intraoperative control. This is done by repeated verification of the electrode position in X-ray images, also by registering the cell discharge with microelectrodes and by observing the irritation caused by electrical stimulation of the microelectrode tip. The stereotactic method was developed 70 years ago for the treatment of functional disorders and applied successfully worldwide in the meantime on more than 100 000 patients. Originally a small lesion was set at the target point. For about 20 years non-destructive and reversible stimulation methods are preferred with implanted electrodes, due to fewer side effects. Because the target points for the lesion and for stimulation are the same, it must be assumed that the stimulation suppresses the activity or transmission of the pulses during the irritation. The calculation has since evolved from invasive methods with puncture and contrast filling of the ventricles towards noninvasive CT / MR procedures on computer design stations.