Helps w/ motor symptoms only - does NOT address any dementia/psychosis symptoms.
If we could get this kind of treatment early it might alleviate the need for dementia treatment.
That being said, from DBS clinical series - we know the technology helps w/ limb rigidity, bradykinesia and tremor. It helps initially with gait but sometimes the gait declines despite DBS and meds, say, roughly a decade after implant (even as the upper limb symptoms stay well treated).
He decided early on to never get this treatment and I feel sad to this day that he couldn't have lived a happier last few years.
movement/neuroplasticity/physical stimulation absolutely helps - hence PT, exercise classes, etc have being an important part of treatment
My point is, though - the onset of decline in gait ability typical of Parkinson's patients, is a sign of a decline of cognitive ability because the ability to perform gait and all the inherent brain commands associated with gait, is very much a cognitive function as much as it is motor.
One can argue that good DBS therapy by helping keep patients active and engaged does, at least indirectly, help cognition in that sense. BUT - it is consider not to directly treat Parkinson's dementia if a patient is unfortunate enough to come down with that aspect of disease. i.e. it's not like we can switch the device on or fiddle around w/ the programming and the patient's cognition directly improves from the brain stimulation itself.
The actual clinical results so far shows that the gizmo with recording is not necessarily worse than DBS devices that don't have recording ability. I don't know if they published those results in a paper yet, but it was shown in poster form at MDS congress in Philly.
That being said, there are also reasons at the moment (better imaging support/stimulation programming abilities) to sometimes choose a competitor device over Medtronic (namely Boston Scientific)
Better DSP/ML techniques might make this more effective, but uh...the Parkinson's research community has never been known to be great at math...just saying
And while it’s something if it doesn’t help with dementia it seems like it’s not addressing whatever is the root cause of dopamine deficiency
The stimulators seem to affect the signaling in that circuit (they are targeted by the implanting neurosurgeon to specific nodes in that circuit as best as targeting surgical technology allows) that seem to restore the ability to move well. Exactly why, no one knows. It's just a dumb signal at around 1-4 milliamps at 130-180 hz at those specific spots but presumptively it corrects some aberrant behavior in the whole network. It was observed in the '00s that recordings taken during or right after surgery often showed a strong peak at ~13-35 hz (give or take, but roughtly around 20 hz) during the disease state, and that's what Medtronic has been trying to target w/ these devices.
Of note - there actually isn't a system-wide dopamine "deficiency" - dopamine in general is fine for most of the body, it's just that the particular part of the brain that is affected happens to use dopamine as its signaling neurotransmitter so it's deficient in just that connection within the network.
Dementia is theorized to happen when the abnormal brain process spreads to other parts of the brain other than the substantia nigra (see the Braak hypothesis)