The Clinical Effects of Deep Brain Stimulation of the Pedunculopontine Tegmental Nucleus in Movement Disorders May Not Be Related to the Anatomical Target, Leads Location, and Setup of Electrical Stimulation

BACKGROUND: The pedunculopontine tegmental nucleus (PPTg) is a novel target for deep brain stimulation (DBS) in movement disorders. OBJECTIVE: To clarify the relationships between the individual anatomic variations of the brainstem, the site in which the PPTg DBS is applied, and the clinical outcome in a relatively large number of patients affected by Parkinson disease or progressive supranuclear palsy. METHODS: Magnetic resonance images have been used to evaluate brainstem anatomy and the relationships between lead position and specific brainstem landmarks. All data were matched on atlas representations of the PPTg and were correlated with Unified Parkinson Disease Rating Scale III (UPDRS III), subitems 27 to 30 of UPDRS III and the Hoehn and Yahr evaluations. RESULTS: A high variance of brainstem parameters was evident, affecting the relationships between the position of the nucleus and lead contacts. According to the contacts giving the best clinical outcome, patients could be distinguished between those who required the use of 2 adjacent contacts and those who required stimulation through 2 nonadjacent contacts. Furthermore, in the former group the target coordinates were more lateral and deeper compared with the latter group. CONCLUSION: Individual PPTg-DBS planning is required to overcome the inconsistencies linked to the high variability in the brainstem anatomy of patients. The lack of correlations between lead position, contact setup, and clinical outcome indicate that the benefits of PPTg DBS may not be strictly linked to the site of stimulation within the PPTg area, and may not depend upon the neurons still surviving in this region in Parkinson disease or progressive supranuclear palsy.