Background
Traumatic brain injury (TBI) is the leading cause of long-term disability in working age adults. Recent studies show that most acute TBI patients demonstrate vestibular features of dizziness and imbalance, often from combined peripheral and central vestibular dysfunction. Effective treatment for vestibular impairments post-TBI is important given its significant adverse impact upon quality of life and employment prospects. The most frequent peripheral vestibular disorder in acute TBI is benign paroxysmal positional vertigo (BPPV), affecting approximately half of acute cases. Although there is effective treatment for idiopathic BPPV, there are no high quality clinical data for post-TBI BPPV regarding its prevalence, natural history, which treatment is most effective and when is the best time to treat. In particular, observational studies suggest post-TBI BPPV may be recurrent indicating that hyperacute treatment of BPPV may be futile. Given the potential hurdles and the lack of accurate post-TBI BPPV data, the current study was designed to provide information regarding the feasibility and the optimal design of future large-scale prospective treatment studies that would compare different interventions and their timing for post-TBI BPPV.

Method
A multi-centre randomised mixed methods feasibility study design was employed. We aim to recruit approximately 75 acute TBI patients across a range of clinical severities, from three major trauma centres in London. Patients will be randomised to one of three treatment arms: (1) therapist-led manoeuvres; (2) patient-led exercises; and (3) advice. Participants will be re-assessed by blinded outcome assessors at 4 and 12 weeks. Acceptability of the intervention will be obtained by patient interviews at the end of their treatment, and therapist interviews at the end of the study. Primary outcomes relate to feasibility parameters including recruitment and retention rates, adverse events, and intervention fidelity. We will also aim to provide a more accurate estimate of the prevalence of BPPV in TBI cases on the trauma ward.

Discussion
The multi-centre nature of our feasibility study will inform the design of a future prospective treatment trial of BPPV in acute TBI. Important parameters we will obtain from this study, key for designing a future prospective treatment study, include estimating the prevalence of BPPV in TBI patients admitted to UK major trauma wards, and elucidating both patient and care-provider barriers, in delivering BPPV treatment.