ICF: A novel diagnostic for vestibular dysfunction

Vertigo and dizziness are among the commonest clinical symptoms, with a prevalence of ~17% in the general population, rising to 39% in those over 80 yrs. A clinician may suspect vestibular deficits, referring the patient for caloric irrigation, currently the most common vestibular diagnostic. This involves hot/cold water flushed into the ear, which activates the fluid of the semicircular canals. However, it is rated as one of the least comfortable audiological procedures by patients. It has numerous health contraindications including excess earwax, eardrum damage, uncontrolled heart disease and mental illness. Hence, there is a need for a better-tolerated, more convenient and patient-friendly test of vestibular function. We have recently developed a novel vestibular diagnostic called Electrical Vestibular Stimulation (EVS). EVS involves small painless currents (typically 5mA) applied to the mastoid processes behind the ears. In a person with intact vestibular function this activates the vestibular nerve, evoking an eye movement which can be readily recorded by a video camera. EVS has previously been used to study balance function in a variety of vulnerable groups, including stroke patients and the elderly. It is quicker to perform and better tolerated than Calorics. Furthermore, it potentially offers a greater wealth of diagnostic information since it stimulates a greater proportion of the peripheral vestibular system than Calorics. The main obstacles in bringing EVS to clinic are currently: a) clinical validation in for peripheral vestibular pathologies, and b) integration into convenient clinically-ready test equipment. This project will address both issues. We will directly compare EVS with caloric irrigation in patients who have been diagnosed with peripheral vestibular dysfunction. We will also apply the video Head Impulse Test (vHIT), another common diagnostic test, for comparison. The aim is to show that EVS is at least as effective as Caloric and vHIT, while being more convenient and patient-friendly. We will work directly with Interacoustics, a leading global developer of balance diagnostics, to develop a commercially-available version of the EVS test.

Caloric irrigation is the most commonly used test of vestibular function but suffers practical limitations due to its invasive nature and numerous health contraindications. We have developed a more convenient and well-tolerated non-invasive test which measures the ocular torsion response to Electrical Vestibular Stimulation (EVS). This is a simple seated test in which the eye movement response to small current applied to the mastoid processes is measured in darkness using an infrared camera. We have established the proof of principle that EVS can detect vestibular paresis and that it compares well to caloric irrigation in its ability to diagnose vestibular asymmetry. In this project we will perform a direct comparison of EVS, caloric irrigation and the video Head Impulse Test (vHIT), a more recently developed test of peripheral vestibular function, in two patient groups: Vestibular Schwannoma (VS) and Ménière's disease. VS presents a relatively well-defined peripheral vestibular dysfunction which will enable us to validate EVS against the other tests. Ménière's disease is often difficult to diagnose, and EVS will offer useful additional diagnostic information not offered by Caloric or vHIT. Test results will be dichotomised into normal versus pathological for all three tests, and then statistically compared to determine parity among tests. This project will allow us to demonstrate parity between EVS and Calorics/vHIT as well as aiding differential diagnosis. We will also initiate commercial integration of EVS into existing diagnostic equipment from Interacoustics. Ultimately, EVS has the potential to provide a faster, cheaper and less invasive diagnostic than existing tests.