Gait impairment and Freezing of gait (FOG), lead to falls, injury (even death), loss of independent living, and are common in neurodegenerative diseases such as Parkinson?s Disease (PD), affecting over 7 million people worldwide. The incidence of neurodegenerative diseases increases with age and as the population lives longer, the societal consequences of FOG, will be very significant. Gait impairment and FOG have a partial response to medication and subthalamic nucleus (STN) open loop deep brain stimulation (olDBS), which cannot adjust therapy in response to underlying brain signals or motor symptoms such as FOG. One reason is that FOG may respond to different parameters of DBS, such as lower frequency, than that needed for tremor and most patients do not tolerate 60 Hz DBS for long periods of time. Emerging technology using sensing neurostimulators and Bluetooth enabled wearable sensors has allowed research into closed loop or adaptive (a)DBS using neural or behavioral control variables. FOG is episodic and usually occurs in predictable environments, so it is well suited for ?on demand? aDBS. ADBS, responding to markers of gait impairment and intermittent FOG, with changes in DBS intensity or frequency, could then prevent FOG, falls and injury, while still treating other motor signs of PD. From over four years of research and regulatory experience in an academic-industry collaboration with Medtronic, we have provided design inputs for the next generation aDBS devices, and have determined that aDBS for tremor and bradykinesia is safe and tolerable in the largest freely-moving PD cohort implanted with a Medtronic investigative neurostimulation/sensing system (Activa PC+S-Nexus D/D3/E). We have discovered neural and behavioral markers of gait impairment and FOG using synchronized neural and kinematic recordings during gait tasks that elicit FOG. Our research findings and the technological advances embedded in the Medtronic Summit RC+S-system now enable the next step: the first clinical studies of lateralized, independent, bilateral STN aDBS control algorithms for FOG in PD, driven by subject-specific neural (Aim 1) or behavioral (Aim 2) control variables, and in response to medication (Aim 3). The project will translate stepwise in a ?bench to bedside? manner, testing aDBS during the stepping in place (SIP) task, where the subject is in a harness and steps in place on dual force-plates. Then aDBS will be tested during the forward walking Turning and Barrier Course, which mimics environments known to trigger FOG in the real world, and then how aDBS responds to subject-specific doses of medication, while freely moving. The outcome of these experiments will provide critical next-steps for safety and feasibility of testing aDBS for gait impairment and FOG in the subject?s home environment, and on their normal medication. Patient safety, tolerability, adverse effects, gait parameters, and the number and duration of freezing episodes (FEs), during no DBS, olDBS, aDBS and a control, intermittent (i)olDBS will provide inputs for future devices and novel algorithms applicable to NaDBS or KaDBS for gait impairment and FOG in other neurological diseases.
Gait impairment and freezing of gait (FOG) poses a severe complication in Parkinson?s disease and other neurological disorders, and leads to falls, injury, and a loss of independent living, but is difficult to measure and treat. Adaptive deep brain stimulation (aDBS) that responds to subject-specific neurobiomechanical features could be an effective treatment for FOG to restore normal gait to PD freezers and reduce adverse side effects associated with other commonly used treatments. Our research along with the advances in sensing neurostimulator technology enables the first clinical studies of bilateral STN aDBS for FOG in PD and will lay the groundwork for the development and improvement of neuromodulation therapy for gait impairment in a wide range of neurological disorders.
