## 1 Introduction  
Deep brain stimulation (DBS) is an established therapy for people with levodopa-responsive Parkinson's Disease (PD) whose symptoms are not adequately controlled by medication alone [1]. Many people with PD with DBS use a monopolar configuration [2], in which the implanted pulse generator, typically implanted in a sub-pectoral position, is positive (anode) and one of the four lead contacts, implanted in the target brain area and connected to the implanted pulse generator via an insulated extension wire, is negative (cathode). The implanted pulse generator produces continuous electrical stimulation (with individualised voltage, pulse width, and frequency stimulation parameters) to achieve optimal symptom control. Whilst this is a very successful therapy for advanced PD,the electromagnetic fields generated during stimulation create significant signal artifacts that can limit the interpretation of neurophysiological studies such as electroencephalography, electromyography, magnetoencephalography and vestibular evoked myogenic potentials (VEMPs) [3]. VEMPs are commonly used in the neuro-otological test battery during the assessment of dizziness and imbalance. They specifically measure vestibular otolith organ function and their brainstem reflex pathways [4; 5]. There is significant research interest in using VEMPs assessment to improve our understanding of neurodegenerative processes in people with PD due to the known post-mortem morphological changes in brainstem vestibular nuclei [6], suspected central vestibular reflex pathway dysfunction, as well as the significantly increased prevalence of postural instability and falls in people with PD, particularly in those with advanced disease [7]. See [PERSON] (2018) for a review [8]. There has also been research interest in using VEMPs to differentiate between neurodegenerative disorders such as PD and multisystem atrophy [9]. VEMPs represent short-latency vestibular-dependent brainstem reflexes evoked by an air-conducted stimulus (ACS), e.g., sounds; via bone-conducted vibration (BCV); or by galvanic stimulation. Cervical VEMPs (cVEMPs) are a biphasic inhibitory reflex (approximately 100 to 300 \(\mu\)V) measured via surface electrodes on the tonically activated ipsilateral sternocleidomastoid muscle, with early peaks at approximately 13 and 23 ms (known as p13 and n23) post-stimulus. They are predominantly used as a measure of ipsilateral saccular function via the inferior portion of the vestibular nerve [10]. Ocular VEMPs (oVEMP) are recorded from the contralateral inferior oblique extra-ocular muscles with a small excitatory (5-10 \(\mu\)V) early reflex peak at approximately 10 ms and a negative peak at 15 ms (known as n10 and p15, respectively). oVEMPs are used clinically to measure utricular function via the superior portion of the vestibular nerve [4]. Previously, obtaining VEMP recordings using most commercial VEMP recording systems has been impossible in patients with monopolar DBS due to the overwhelming signal noise produced by the implanted pulse generator swamping the input signal detected by surface electrodes. A study by [PERSON] et al. (2012) investigated the effects of DBS and L-Dopa on cVEMP amplitudes in people with PD [3]. To manage monopolar DBS signal artifacts, these researchers either switched off the DBS device or adjusted the stimulation parameters to a bipolar mode, where they increased the stimulation voltage by 30% based on an established neurological conversion algorithm. However, it is known that switching off the DBS device can, in some participants, result in an almost immediate worsening of tremors (within 5 min) and subsequent worsening of rigidity and bradykinesia (over 15-60 min) [11]. These re-emerging movement artifacts can have an impact on background electromyographic (EMG) readings during VEMP testing, further obscuring the accurate interpretation of results. Adjusting the stimulation to bipolar mode and increasing the stimulation requires specific knowledge of the DBS device and its settings.