The nucleus tegmenti pedunculopontine (PPTg) is a new target for deep brain stimulation (DBS) in Parkinson's disease (PD), in particular for ameliorating postural abnormalities and gait disturbances. The objective of the study is to describe the pre-operative planning, the surgical procedures and results of the DBS of PPTg in humans. Thirteen patients were considered. The surgical approach evolved from the traditional 'indirect' method based on stereotactic ventriculography (5 patients) to a more recent 'direct' method, based on both a digital elaboration of axial stereotactic CT scan and on the 'direct' visual 3D representation of the PPTg (8 patients). No major complication occurred. The direct approach allowed to eliminate the major sources of variability caused by the use of the traditional stereotactic approach. The DBS of PPTg induced a significant amelioration of the following clinical symptoms: gait disturbances, freezing on, speech and arising from the chair. These symptoms are usually not improved by levodopa treatment. The implantation of PPTg proved safe and effective in the treatment of levodopa resistant PD patients. The classic determination of stereotactic coordinates, through a proportional system based on ventriculography, utilising as landmark the CA-CP line and the top of the thalamus, and stereotactic atlases, can hardly be applied to brainstem surgery. The 'direct' method, based on both a digital elaboration of axial stereotactic CT scan and, on the 'direct' visualisation of brainstem borders as well as on the 3D representation of the PPTg, permits a better adaptation to individual anatomic features.

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The application of deep brain stimulation (DBS) to the pedunculopontine tegmental nucleus (PPTg) has required profound modifications of classic neurosurgical techniques and of the criteria for evaluation of clinical results. This review analyzes a novel method of targeting the PPTg, based on angio-computerized tomography (angio-CT) scans and the tridimensional reconstruction of nuclei and cerebral vessels, and considers the advantages of applying these methods in comparison to the more traditional approach based on reference points obtained through the evaluation of the bicommessural line. Validation of the results obtained following unilateral PPTg DBS through neurophysiological recordings and objective measurements of functional parameters suggests that the PPTg may be considered as an initial target for the treatment of motor symptoms in selected patients affected by idiopathic Parkinson's disease (PD), which, if required, could be followed by DBS of other target areas. Moreover, on the basis of the observations derived from stimulating the PPTg, the potential utility attributed up to date to intraoperative neurophysiological recordings for identifying neurosurgical targets should be revisited, and the need for changes in the intraoperative management of patients has arisen from the body of evidence accumulated over recent years. The results obtained by different groups following PPTg DBS in parkinsonian patients are not uniform, most likely due to a cautious acceptance of this methodology, the experience progressively acquired, the criteria for patient selection and to subtle differences in target location. Although the role of PPTg in PD and/or in other pathologies remains to be clarified, pursuing the traditional approach on classical basal ganglia targets may limit the perspective of DBS based on multiple implantations.

The region of the pedunculopontine tegmental nucleus (PPTg) has been proposed as a novel target for deep brain stimulation (DBS) to treat levodopa resistant symptoms in motor disorders. Recently, the anatomical organization of the brainstem has been revised and four new distinct structures have been represented in the ventrolateral pontine tegmentum area in which the PPTg was previously identified. Given this anatomical reassessment, and considering the increasing of our experience, in this paper we revisit the value of DBS applied to that area. The reappraisal of clinical outcomes in the light of this revisitation may also help to understand the consequences of DBS applied to structures located in the ventrolateral pontine tegmentum, apart from the PPTg. The implantation of 39 leads in 32 patients suffering from Parkinson's disease (PD, 27 patients) and progressive supranuclear palsy (PSP, four patients) allowed us to reach two major conclusions. The first is that the results of the advancement of our technique in brainstem DBS matches the revision of brainstem anatomy. The second is that anatomical and functional aspects of our findings may help to explain how DBS acts when applied in the brainstem and to identify the differences when it is applied either in the brainstem or in the subthalamic nucleus. Finally, in this paper we discuss how the loss of neurons in brainstem nuclei occurring in both PD and PSP, the results of intraoperative recording of somatosensory evoked potentials, and the improvement of postural control during DBS point toward the potential role of ascending sensory pathways and/or other structures in mediating the effects of DBS applied in the ventrolateral pontine tegmentum region.