Vestibular Neurostimulation for Parkinson's Disease: A Novel Device-Aided Non-Invasive Therapeutic Option

Abstract

Dopaminergic replacement therapy remains the mainstay of symptomatic treatment for Parkinson's disease (PD), but many unmet needs and gaps remain. Device-based treatments or device-aided non-oral therapies are typically used in the advanced stages of PD, ranging from stereotactic deep brain stimulation to levodopa or apomorphine infusion therapies. But there are concerns associated with these late-stage therapies due to a number of procedural, hardware, or long-term treatment-related side effects of these treatments, and their limited nonmotor benefit in PD. Therefore, there is an urgent unmet need for low-risk adjuvants or standalone therapies which can address the range of burdensome motor and nonmotor symptoms that occur in PD. Recent studies suggest that non-invasive neurostimulation of the vestibular system may be able to address these gaps through the stimulation of the vestibular brainstem sensory network which extensively innervates brain regions, regulating both motor and a range of nonmotor functions. Therapeutic non-invasive vestibular stimulation is a relatively modern concept that may potentially improve a broad range of motor and nonmotor symptoms of PD, even at early stages of the disease. Here, we review previous studies supporting the therapeutic potential of vestibular stimulation for the treatment of PD and discuss ongoing clinical trials and potential areas for future investigations.

Keywords: Parkinson’s disease; caloric vestibular stimulation; galvanic vestibular stimulation; non-invasive neuromodulation; sensory neuromodulation; vestibular system.

Figure 1

A schematic view showing the mechanism of action of CVS and projections of the vestibular nuclei to brain regions implicated in PD and/or migraine. The action potential firing rates of the vestibulochoclear nerves are increased by the warming of the left ear and decreased by cooling of the right ear by means of the tvCVS solid-state device. These nerves innervate the vestibular nuclei in the brainstem that send both direct and indirect excitatory afferents to a number of brainstem nuclei implicated in migraine pathology. The vestibular nuclei also show extensive polysynaptic connectivity with numerous structures in the midbrain and forebrain affected in PD and migraine pathology. The orientation of the brain has been turned 90° to show connectivity in a sagittal cross-section. Modified figure from (Black and Rogers 2020 [14]).

Figure 2

Time-varying caloric vestibular stimulation (tvCVS) treatment delivery. Image shows a participant lying on an incline wedge pillow while undergoing treatment with a solid-state tvCVS headset device.