• Mehmet Tatli and Marc Sindou.
• Department of Stereotactic and Functional Neurosurgery, Hôpital Neurologique Pierre Wertheimer, University of Lyon, Lyon, France. tatli.mehmet@gmail.com
• Neurosurgery. 2008 Jul 1;63(1 Suppl 1):ONS129-37; discussion ONS137-8.

ObjectiveThe correct positioning of the electrode is of prime importance for effectiveness and selectivity of percutaneous trigeminal radiofrequency thermorhizotomy (RF-TR) for the treatment of trigeminal neuralgia (TN). The aim of our study was to establish some anatomoradiological landmarks for the purpose of accurate placement of the electrode tip in RF-TR.MethodsOf 1000 patients who underwent RF-TR, 100 were retrospective and randomly selected and divided into study groups according to postoperative hypoesthesia in the trigeminal nerve divisions. The patients' petroclival angle, petroelectrodal angle, electrode tip, and the petroelectrodal angle/petroclival angle ratio were calculated on lateral cranial x-rays. These measurements were then correlated with the topography of hypoesthesia obtained by the RF-TR to define the anatomoradiological x-ray landmarks corresponding to the divisions of the trigeminal root. The postoperative hypoesthesia groups were correlated with their respective preoperative pain topography to check the accuracy of the thermolesion. In addition, the intraoperatively evoked paresthesia responses and the side effects were evaluated. The results were analyzed using a paired-samples Student's t test, the chi test, and one-way analysis of variance, followed by Bonferroni and Tamhane post hoc tests.ResultsAll study groups were comparable with respect to age, sex, side effects, electrode tip location, side of TN, and values of petroclival angle. The lowest values of petroelectrodal angle/orbitomeatal electrodal angle and petroelectrodal angle/ petroclival angle were detected in patients with V3 TN, whereas the greatest values were in patients who had TN in all branches of the trigeminal nerve. The greatest height of the electrode was in patients who had TN in all branches, whereas the least height was in patients with V3 TN. When the results were compared with each other, the mean differences were found to be statistically significant between V3 TN patients and the other groups with different P values. There was no statistical difference between the postoperative hypoesthesia data and the preoperative pain topography, which demonstrated evidence of the accuracy of the thermolesion in our series.ConclusionOur data suggest that the determination of the presented landmarks allows customization to individual patient anatomy and may help the surgeon achieve a more selective effect with a variety of percutaneous procedures for each branch of the trigeminal root.

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