3-DIMENSIONAL COMPUTER-ASSISTED STEREOTAXIC-GUIDED MICRONEUROSURGERY COMBINED WITH CORTICAL MAPPING OF THE MOTOR AREA BY DIRECT ELECTROSTIMULATION

TIM (Zeppelin Chirurgische Instrumente GmbH, 82 049 Pullach, Germany) is a tomographic imaging system which enables surgeons to visualize th e pathologic lesions three dimensionally in relationship to the surrou nding structures. The distance and the angle between the pathologic le sion and the anatomical and/or bony landmarks as well as the volume of the mass lesion can be measured. Therefore an accurate localization o f the lesion is possible with this technique. It is very applicable fo r planning of surgery on skull base tumors. The surgical procedure for small and well-defined, intrinsic pathologic deep-seated brain lesion s, however, becomes much easier by using the stereotactic techniques o f this system. The target point and the direction brain-surface-to-les ion can be determined within seconds. Before the aiming probe is inser ted to the target, the cortical motor area is mapped by direct electri cal stimulation. The approach can be varied depending on the results o f these neurophysiologic investigations of the brain surface. The diss ection is made along the aiming probe up to the target point. Because of the fixation of the brain with the needle, a brain shifting due to the dissection as well as to CSF release is diminished. Forty patients with deep-seated intracerebral lesions were operated on during a 13 m onths period by these combined techniques in our service. Using this t echnique, we never made a negative exploration. In all but three patie nts, total removal of the mass lesion was achieved. Permanent neurolog ical deficits were observed in two patients only. In our opinion, this combined imaging and neurophysiological technique is easy to perform, and of major benefit for the patients due to its accuracy and is pref erable in comparison with other single computer localizer techniques w ithout neurophysiological monitoring.