Hypofractionated conformal stereotactic radiotherapy may be an important alternative to single-fraction radiotherapy in patients with large AVMs or AVMs located in eloquent areas, because it allows the administration of a higher radiation dose than is possible to deliver in single-fraction radiosurgery. With our technique of hypofractionated conformal stereotactic radiotherapy, the rate of obliterating AVMs was comparable to that of single-dose radiosurgery, although the volumes of the irradiated AVMs in our study were larger than those reported previously.

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Thalamic, pallidal, and hypothalamic targets were determined in 16 patients by a stereotactic computerized tomography (CT) study using a noninvasive technique with Laitinen's Stereoadapter. At surgery, the Stereoadapter was remounted to the head and the stereotactic CT coordinates were transferred to the Stereoguide without radiography. Air ventriculography was then carried out. The positions of the anterior and posterior commissures (AC and PC), the length of the intercommissural (IC) line, the width of the third ventricle, and the stereotactic coordinates of the target were measured on the ventriculograms and compared to the stereotactic CT measurements. The study showed that the width of the third ventricle was significantly larger on the ventriculograms than on the stereotactic CT scans, whereas the length of the IC line was not significantly different. The differences in the coordinates of the target and of the AC and PC were statistically significant only for the anteroposterior (y) coordinate. Both commissures as well as the surgical target lay, on average, 1.0 mm more anteriorly on the ventriculograms than on the stereotactic CT study. It is concluded that air ventriculography may cause slight anterior displacement of the midbrain structures. The surgical coordinates of the targets based on the stereotactic CT study with the Stereoadapter were on average as accurate as those obtained with ventriculography; therefore, ventriculography may become superfluous in functional stereotaxis.

Twenty-five patients underwent 33 stereotactic procedures on the thalamus for the treatment of persistent pain of benign or malignant origin. There were 19 ablative and 14 stimulation procedures. The thalamic targets were the centrum medianum (CM), the pulvinar, the nucleus ventralis posteromedialis and/or the nucleus ventralis posterolater-alis. Ablative surgery was successful in 52.6% of the procedures, and chronic stimulation in 66%. Stimulation in the ventroposterior group of the thalamus was most effective for peripheral deafferentation pain while ablative stereotaxis on the CM may be more appropriate for patients with central pain or cancer pain.

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