Different methods for anatomical targeting

Several procedures are used in the different neurosurgical centers in order to perform stereotactic surgery for movement disorders. At the moment no procedure can really be considered superior to the other. We contribute with our experience of targeting method.

Ten patients were selected, in accordance to the guidelines for the treatment of Parkinson disease, and operated by several methods including pallidotomy, bilateral insertion of chronic deep brain electrodes within the internal pallidum and in the subthalamic nucleus (18 procedures).

in each patient an MR scan was performed the day before surgery. Scans were performed axially parallel to the intercommissural line. The operating day a contrast CT scan was performed under stereotactic conditions.

after digitalization of the MRI images, it was possible to visualize the surgical target and to relate it to parenchimal and vascular anatomic structures readable at the CT examination. The CT scan obtained was confronted with the MR previously performed, the geometrical relation between the different parenchimal and vascular structures and the selected targets were obtained. Stereotactic coordinates were obtained on the CT examination.

It was possible to calculate the position of the subthalamic nucleus and of the internal pallidum on the CT scan, not only relating to the intercommissural line, but considering also the neurovascular structures displayed both on the MRI and the CT scans.

The technique that our group presents consist in an integration between information derived from the CT and the MR techniques, so that we can benefit from the advantages of both methods and overcome the disadvantages.