The deep brain stimulation of the pedunculopontine tegmental nucleus

Objective. The aim of the present study was to describe the surgical and clinical outcomes of the implantation and stimulation of the pedunculopontine tegmental nucleus in humans. Materials and Methods. Fourteen patients affected by movement disorders (12 Parkinson's disease and 2 progressive supranuclear palsy) underwent surgery for bilateral or monolateral implantation of stimulating electrodes in the pedunculopontine tegmental nucleus. The correct placement of electrodes was established and verified by combining angio-CT scans with magnetic resonance imaging. Intraoperative and postoperative evaluations were made to assess the clinical effectiveness of stimulation according to different Unified Parkinson's Disease Rating Scale items and neurophysiologic parameters. Results. No major complications occurred following the insertion of electrodes into the pedunculopontine tegmental nucleus. Neuroimaging showed that the electrode contacts were always correctly placed below the ponto-mesencephalic line. Stimulation of the pedunculopontine tegmental nucleus improved gait, posture, and speech, and modulated reflexes integrated at spinal or pontine levels. Conclusions. The surgical targeting of the pedunculopontine tegmental nucleus requires a careful adaptation of the traditional stereotactic approaches owing to the high variability of brainstem anatomy from one patient to another. The insertion of the leads in the pedunculopontine tegmental nucleus as well as their activation did not appear to induce serious adverse effects. The correct positioning of stimulating electrodes in pontine structures such as the pedunculopontine nucleus may be ascertained not only through neuroimaging techniques but also through clinical neurophysiology. The evolution of the surgical planning that we have developed emphasizes the limited value of single-unit recordings to identify the pedunculopontine tegmental nucleus and highlights the opportunities offered by functional evaluations of neurophysiologic parameters. As far as the clinical efficacy is concerned, our data suggest a promising outcome for simultaneous implantations of different basal ganglia nuclei in Parkinsonian and in progressive supranuclear palsy patients as well.