Intermittent NBM stimulation paired with STN DBS produced cognitive gains in Parkinson’s disease
Cognitive decline often enters Parkinson’s disease early, long before many patients or clinicians expect it to become clinically dominant. In this Stanford feasibility study, a small group of patients with Parkinson’s disease and cognitive impairment underwent a combined neuromodulation strategy designed to treat both motor and cognitive disease biology at the same time: continuous subthalamic nucleus (STN) deep brain stimulation for motor symptoms and intermittent stimulation of the nucleus basalis of Meynert (NBM) for cognition.
The rationale is biologically grounded. The NBM is a major cortical cholinergic hub, and its lateral efferent fiber bundle degenerates early in Parkinson’s disease. When that cholinergic network erodes, attention, executive function, and cognitive-motor integration can weaken in ways that standard dopaminergic therapy does not address well. Intermittent stimulation of this pathway is intended to restore activity in cortical circuits that are especially vulnerable to cholinergic loss.
Five patients were enrolled as part of an ongoing clinical trial under an Investigational Device Exemption. Every participant had Parkinson’s disease with cognitive impairment and had already been approved for STN DBS. The study used two surgical strategies for reaching the NBM target. Three participants underwent a “vertical” trajectory, with two leads placed in the STN and two additional leads placed in the anterior portion of the NBM through the same burr hole on each side. Two other participants underwent a “lateral trajectory,” in which the NBM leads were placed along the lateral efferent bundle using a small twist craniostomy behind the ear.
The surgery itself is only half the story. Precision programming determined whether the biologic concept could be translated into a usable clinical intervention.
An automated programming algorithm, DBS Illumina 3D™ from Boston Scientific, guided NBM lead programming based on volume of tissue activated modeling. The investigational Chronos software delivered continuous high-frequency DBS to the STN around the clock and intermittent patterned DBS to the NBM for one hour per day. Every participant was programmed successfully, and no adverse effects emerged during programming.
Cognitive change after six months was the central clinical signal
At six months, all five participants showed clinically meaningful improvement on a neuropsychological assessment battery. Motor benefit from STN DBS also appeared as expected. The cognitive result is the more unusual finding, because it suggests that intermittent stimulation of a cholinergic target may influence symptoms that have traditionally been considered difficult to modify with surgery.
A small case series cannot define durability, responder phenotypes, or comparative efficacy, but the direction of effect matters. Cognitive impairment in Parkinson’s disease often reflects disruption in distributed cortical networks rather than a single focal lesion, which is one reason neuromodulation strategies have struggled to move beyond motor endpoints. By targeting the NBM, investigators are working directly on a neurotransmitter system tied to cortical attention and executive control. The clinical logic is straightforward: if cholinergic drive is part of the deficit, patterned stimulation may help stabilize the network enough to improve day-to-day cognition.
The finding also fits the design of the intervention. Continuous stimulation was reserved for the STN, where motor benefits are well established, while intermittent patterned stimulation was used for the NBM, presumably to avoid overstimulation of a cholinergic system that may respond better to pulsatile engagement than constant drive. The use of two anatomical routes to the same therapeutic goal is particularly notable. A standard vertical approach and a novel lateral approach both achieved accurate placement, suggesting that surgeons may have more than one viable pathway for reaching the intended circuit.
Surgical feasibility and device programming were accomplished without reported adverse effects
The procedural results are clinically important because cognitive targets in deep brain stimulation add complexity to an already demanding operation. Two NBM leads were added to the usual STN DBS procedure, yet all leads were successfully and accurately placed. That matters for future scalability, because a therapy can only advance if the implantation burden remains tolerable in real-world surgical practice.
The lateral trajectory deserves particular attention. A small twist craniostomy behind the ear to reach the NBM lateral efferent bundle suggests a potentially less invasive or more anatomically tailored route than a purely vertical approach through the standard burr hole. Whether that route will prove superior for efficacy, safety, or technical reproducibility remains unknown, but the concept broadens the surgical toolbox for targeting a basal forebrain structure that has not been routinely approached in Parkinson’s disease surgery.
Equally important, all participants were programmed successfully with the DBS Illumina 3D™ algorithm without adverse effects. In practical terms, that means the device and software workflow supported individualized targeting without immediate tolerability problems. In a first-in-human or early feasibility context, the absence of programming-related adverse effects is not a trivial detail; it is the difference between a therapy that can be explored further and one that stops at proof of concept.
Why the NBM target changes the Parkinson’s DBS conversation
Standard STN DBS has earned its place by improving tremor, rigidity, bradykinesia, and other motor symptoms. Cognitive symptoms have remained a more stubborn frontier. The NBM offers a different mechanistic angle because it sits within the cholinergic circuitry that supports cortical alertness, attention, and higher-order processing. Degeneration of that system in Parkinson’s disease plausibly contributes to the cognitive and cognitive-motor impairments that many patients experience early in the course of illness.
Intermittent stimulation may be especially relevant here. Cholinergic circuits are not simply on or off; they regulate the gain of cortical processing. A patterned pulse train delivered for a limited time each day may be enough to nudge network function without forcing constant activation. The study’s design reflects that biological hypothesis rather than treating the NBM as a generic add-on target.
The combined strategy also suggests a future in which Parkinson’s DBS becomes more circuit-specific and symptom-specific. Motor circuitry and cognitive circuitry do not fail in identical ways, so a single target is unlikely to solve both problems. This feasibility study points to a model in which one implanted system addresses motor disability while a second target is layered on to address cognition.
Early promise, narrow evidence
The strength of the study lies in its procedural feasibility and the consistency of the cognitive signal across a very small cohort. The limitation is equally clear: five patients cannot establish efficacy, cannot define which cognitive domains improved most, and cannot determine how durable the benefit will be beyond the six-month window. Preprint status also matters, because the findings have not yet been certified by peer review.
The investigators have opened an important path, but the next questions are more demanding than the first. Larger controlled studies will need to determine whether the cognitive benefit persists, whether the vertical and lateral trajectories differ in response, and whether intermittent NBM stimulation can meaningfully change the trajectory of cognitive decline rather than simply improving test performance over a short interval. For now, the most defensible conclusion is narrower and concrete: combined STN and intermittent NBM DBS was feasible, well tolerated in this small cohort, and associated with clinically meaningful cognitive improvement at six months.