[Subthalamic nucleus targeting and spatial variability]

The effectiveness of anatomic localization of the subthalamic nucleus (EAL) was assessed and the mapping method is described here. The symmetry of contralateral nuclei (SCN) was analyzed on 11 parkinsonian patients submitted to bilateral subthalamotomy with ablative lesioning.

To assess EAL the percentage so much of first trajectory (p1) as the total of trajectories (pt) that hit the target and the rest of subthalamic nucleus average distance (d) was calculated. The anatomic localization error (epsilon) is determined as a difference between first trajectory coordinates with those of medial determined nucleus point, through electrophysiological data as to the statistical significance of this error. SCN is analyzed by contrasting equality hypothesis at the nucleus maximum height alongside a trajectory, average electrophysiological position center and spatial distribution of all intranuclear recordings found in each hemisphere in all patients.

The pi, pt and d obtained values were 86.36%, 86.13% and 1.41 +/- 1.01 mm respectively. The epsilon value was greater in anteroposterior direction of 1.11 +/- 0.83 mm without statistical significance. The average number of recorded trajectories for the first procedure was 6.45 and 6 for the second. The asymmetry of contralateral nucleus was not significant.

An indirect method with CT brain images and a new electrophysiological mapping method with a multiunitary recording for first and second nucleus is safe enough and it yields a high effectiveness in anatomofunctional nucleus localization. The nucleus of a same patient are symmetrical. There is little space variability among patient non related to the differences in the intercommissural distance.