Objective: While deep brain stimulation (DBS) of the subthalamic nucleus (STN) alleviates Parkinson”s Disease(PD) related motor symptoms, to date PD dementia (PDD) patients are excluded from this highly effectivetreatment since dementia is an accepted contraindication.

Background: The DEMPARK study is an ongoing doubleblind, sham-controlled phase-1b study at our institution that aims to provide proof of safety of combined STN and Nucleus basalis of Meynert (NBM) DBS in PDD patients and its impact on cognition as an exploratory endpoint. Here we focus on surgical aspects of the implantation strategy.

Method: Patients received asleep STN and NBM DBS including micro-recording and test stimulation. Indirect targeting of the NBM considered landmarks such as convergence of the optic tract and the temporal crus of the anterior commissure and the level inferior to the external pallidum. Fusion of post-op CT to pre-op MRI and clinical protocols served for analysis of adverse events and sequels, of lead sites and trajectory angles in relation to planning.

Results: Combined STN & NBM implantation was carried out in 7 patients (Ø65.4 years, pre-op: MMST22.6, UPDRS On/Off 48.6/19.6, UPDRS Stim-On/Med off 32.2). Any penetration of the ventricles or the caudate nucleus as well as crossing or disturbance of trajectories could be avoided. By MER nospecific NBM discharge pattern was identified nor did NBM test stimulation provide special motor effects.Planned NBM coordinates relative to AC-PC-midpoint were 24.4 mm lateral, 6.8 mm anterior and 6.4 mm inferior to the midpoint. Definite lead sites for the designated active contact were identified at 24.9 mmlateral, 7.6 mm anterior and 5.0 mm inferior to the midpoint. Sequels included brain shift in one patient, prolonged post-surgical ICU care in pulmonary infection in one and transient delirium in 4 patients.

Conclusion: Combined STN/NBM implantation was conducted without surgical sequels such as hemorrhage or infection. Of notice, more than half of the patients developed a postoperative confusion state. Currently it remains uncertain whether this is to be attributed to rather long anesthesia in pre-demented patients or related to a stun effect in the STN or NBM. In view of the high incidence of post-surgical confusion states, only careful long-term analysis will reveal their complete resolution and possible response to NBM stimulation as well whether the risks are outweighed by the benefits of this concept.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/combined-stn-and-nbm-dbs-in-pd-and-mild-to-moderate-parkinsons-dementia/