INVEST: Refining, evaluating, and implementing an INtegrated VEStibular physiotherapy and cognitive-behavioural Treatment for people with persistent dizziness

Research question Can physiotherapists be effectively trained to deliver a psychologically informed vestibular rehabilitation intervention (INVEST) and does INVEST lead to significant improvements in symptoms and disability for patients with Persistent Postural-Perceptual Dizziness (PPPD) compared to current treatment? Background Persistent Postural Perceptual Dizziness (PPPD) is a functional neuro-vestibular disorder (1). It causes dizziness and imbalance that is present for most of the time, but exacerbated by upright posture, active or passive movement, and exposure to moving or complex visual stimuli (2). Around 4% of the population experience chronic dizziness (3), and PPPD is now recognised as the single most common vestibular syndrome (4), accounting for up to 20% of patients in balance clinics (5). There are no randomised controlled trials (RCTs) demonstrating effectiveness for PPPD treatment (6, 7). During my NIHR Clinical Doctoral Research Fellowship, I developed a psychologically informed physiotherapy intervention called 'INVEST', integrating the most promising exercise and behavioural interventions adapted for PPPD. I then conducted a feasibility RCT (n=40) which showed high levels of acceptability, recruitment, and retention and promising reductions in dizziness burden when compared to current gold standard physiotherapy. However, the implementation of INVEST requires a skilled therapist trained in this approach. Feedback from patients also suggested that there were ways to optimise the intervention and patient manual. Aims and objectives To further refine and optimise INVEST and investigate whether physiotherapists can be successfully trained to deliver it, and whether this intervention leads to significant improvements in symptoms and disability for patients with PPPD. Methods & Timelines for delivery Stage 1 (years 1-2): 1) Work with people with PPPD (including seldom heard minoritized groups) and healthcare professionals to refine and optimise the INVEST manual, including videos. 2) Develop a therapist manual with input from physiotherapists 3) Develop and deliver a therapist training package, testing competency and fidelity (n=8). A nested qualitative study will be conducted post-intervention to explore the views of therapists and factors involved in developing competence and any barriers to implementation. Stage 2 (years 3-5): RCT comparing INVEST to standardised treatment-as-usual vestibular rehabilitation therapy (VRT). 152 people with PPPD will be randomised by an independent clinical trials unit to receive eight sessions of either INVEST or VRT. Measures will be collected at baseline, 4- and 8-months post randomisation. The primary outcome will be dizziness related burden (Dizziness Handicap Inventory). I will also measure symptom severity, and other secondary outcomes will include balance, perception, and a range of psychological process variables. The examiner and statistician will be blinded to group allocation. Process analysis will also look at mediators and moderators of treatment outcome. Anticipated impact and dissemination This will be an important step forward in the development of effective treatments for PPPD. The process analysis will also enhance understanding of PPPD and test the theoretical model. The dissemination of the trial results through publication in high-impact journals, press releases, and presentation at conferences will help to raise awareness of PPPD and the potential of INVEST as a treatment option among clinicians and patients.