Introduction: Postural instability (PI) and freezing of gait (FOG), common in advanced Parkinson’s disease are insufficiently addressed by pharmacotherapy and deep brain stimulation of standard sites subthalamic nucleus, globus pallidum and thalamus. Recent reports have identified pedunculopontine nucleus, a structure with unclear borders as a promising DBS target to address PI/FOG in PD. Both motor and non-motor benefits have been reported with PPN DBS, however side effects have also been documented, due to inadvertent stimulation of neighboring anatomical structures.

Methods: We performed a literature review to determine effects from PPN DBS, analyzing stimulation parameters and anatomical coordinates, that were most effective.

Results: Bilateral PPN stimulation at low frequency stimulation caused significant improvement in motor scores, Hoehn and Yahr score, UPDRS scores 18-30 (gait and posture subitems) and reduction in freezing episodes/falls. Improved attention, with improvement in pre-programming reflexes and improved mood & sleep were also reported. There was NO improvement in step length deficits and rarely improvement in other motor components i.e. bradykinesia, rigidity and tremors. Unilateral PPN DBS had less satisfactory results compared to bilateral PPN stimulation. Side effects included contralateral paresthesia, frequently accompanied by gaze abnormalities, which could be controlled by adjusting voltage. Rarely long lasting and irreversible side effects including urinary incontinence, infection, bleeding were reported.

Conclusions: Electrode placed in caudal/ mid PPN with low frequency (25-35 Hz) stimulation, pulse width 60 ms (60-90 ms) and voltage below threshold to induce paresthesia and/or oscillopsia (<2 V) are suitable. Intraoperative monitoring of eye movements can be an additional tool to help determine accurate location of the electrode.

Patient Care: We present literature review and analysis of reports describing DBS of novel structure PPN. Our review presents comprehensive educational information of how PPN DBS addresses symptoms of advanced PD, and identifies surgical details necessary for best outcome without inadvertent side effects.

Learning Objectives: 1) Benefits and side effects of PPN DBS reviewed 2) Technical details including stimulation parameters and anatomical coordinates most effective, when stimulating PPN described. 3) Basic anatomy of PPN and nearby structures shown in diagram

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