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This issue is dedicated to a potential new target for the treatment of movement disorders, the pedunculopontine tegmental nucleus (PPTg), or, more simply, the pedunculopontine nucleus, that some authors abbreviate as PPN. We provide an overview of the field as an introduction to the general reader, beginning with the clinical experience to date of Mazzone and co-workers in Rome, some basic questions that need to be addressed, and potential future directions required in order to ensure that the potential benefits of this work are realized. [ABSTRACT FROM AUTHOR]

In Parkinson's disease (PD), the effects of deep brain stimulation of the pedunculopontine nucleus (PPTg-DBS) on gait has been object of international debate. Some evidence demonstrated that, in the late swing-early stance phase of gait cycle, a reduced surface electromyographic activation (sEMG) of tibialis anterior (TA) is linked to the striatal dopamine deficiency in PD patients. In the present study we report preliminary results on the effect of PPTg-DBS on electromyographic patterns during gait in individual PD patients. To evaluate the sEMG amplitude of TA, the root mean square (RMS) of the TA burst in late swing-early stance phase (RMS-A) was normalized as a percent of the RMS of the TA burst in late stance-early swing (RMS-B). We studied three male patients in the following conditions: on PPTg-DBS/on l-dopa, on PPTg-DBS/off l-dopa, off PPTg-DBS/on l-dopa, off PPTg-DBS/off l-dopa. For each assessment the UPDRS III was filled in. We observed no difference between on PPTg-DBS/off l-dopa and off PPTg-DBS/off l-dopa in UPDRS III scores. In off PPTg-DBS/off l-dopa, patient A (right implant) showed absence of the right and left RMSA, respectively, in 80% and 83% of gait cycles. Patient B (right implant) showed absence of the right RMS-A in 86% of cycles. RMS-A of the patient C (left implant) was bilaterally normal. In on PPTg- DBS/off l-dopa, no patient showed reduced RMS-A. Although the very low number of subjects we evaluated, our observations suggest that PPTg plays a role in modulating TA activation pattern during the steady state of gait. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]