Dizziness Due to Visual Stimuli in Patients With Concussion and Other Causes of Dizziness: Examination of Balance Behaviour

Overview

This research project aims to measure how balance is affected by special visual stimulation. Dizziness caused by complex moving visual patterns, known as optokinetic stimulation, is usually called visually induced dizziness (VID). The study includes patients with persistent symptoms after a concussion and those with non-traumatic dizziness. Healthy participants serve as a control group for the comparison of balance and symptom responses. The optokinetic stimulation is done using either a physical rotating disk or a virtual reality (VR) headset. The visual effects are created by bright moving dots. During the stimulation, these patterns move in a specific manner and directions while the subject's balance is recorded. Symptoms such as dizziness, headache, and nausea are also documented. The goal of this project is to improve objective diagnosis of VID. By comparing patients and healthy subjects, the study aim to assess the severity of the disorder. It is also assumed that using different visual stimuli during the balance assessment will offer more sensitive and accurate results. In the long term, this innovative assessment method shall support clinicians to establish the diagnosis of VID, and improve the treatment and management of patients with VID.

Sport-related concussion (SRC) refers to traumatic head injuries caused by direct biomechanical forces to the head, neck or body during physical activity. Due to very heterogeneous clinical patterns in concussed patients including multiple clinical profiles and subtypes, standardised diagnosis for SRC is still in scope of research. Thus, diagnostic procedures are currently based on clinical examination and subjective complaints using questionnaires, while objective assessments supporting a diagnosis for concussed patients are lacking. Only some functional limitations are recorded via objective methods, but no quantification and no diagnosis are possible. Common questionnaires to assess VID in concussed patients and for vestibular disorders are the visual vertigo analogue scale (VVAS), and the situational vertigo questionnaire (SVQ), though there exist more. The dizziness handicap inventory (DHI) is used to classify the general aspect of dizziness. Other methods to support VID diagnosis have been developed including subjective visual vertical assessment or balance screenings with optokinetic stimulation. Such objective findings are essential for a reliable diagnosis supporting subjective complaints. However, determined parameters and observed pathologies vary among studies and thus, a classification via objective assessments in VID patients is still in scope of research. Nevertheless, symptom assessment is still considered as one of the best and reliable method to support diagnosis and success in treatment. Outcomes of previously discussed and used questionnaires to assess VID rely on patients' compliance. Subjective evaluations on dizziness are challenging for patients and may therefore diverge from objective measurements. In addition, questionnaires do not explicitly distinguish between vertigo and dizziness. Moreover, self-reported symptoms showed moderate correlation to objective findings. This highlights the importance of realising objective methods such as balance assessments. Some objective assessments to identify VID, and to discriminate among patient groups and healthy subjects have been introduced. But most of the studies investigating VID examined a broad variety of vestibular disorders, rarely including concussion. Concerning balance assessment combined with optokinetic stimulation, several studies found significant differences among control groups and patients with vestibular disorders and dizziness, but findings varied across calculated parameters. Overall, mean deviations on sway path tended to be more predictive than lean sway, and significant effects are supposed to be in stimulated planes. Additionally for path length, there exists two quotients representing the balance response ratio between eyes open and eyes closed (Romberg quotient), and the ratio between eyes open and optokinetic stimulation (optokinetic quotient), which both showed significant effects comparing healthy subjects and visual vertigo patients. However, parameters evaluated from velocity were often in favour compared to path length. Furthermore, prolonged exposure to optokinetic stimulation triggered symptoms in patients with visual vestibular mismatch but not in control subjects, supporting the hypotheses of symptom exacerbation by visual motion. Regarding defined triggers for VID, one could assume that triggers are based on an individual level and therefore include various visual motion conditions such as complex, large-field or moving elements in order to conflict one's sensory integration. Given those multidimensional conditions for an assessment, the use of VR environments for this project benefits a broad and flexible range in VID assessment. Regarding the mentioned studies, one could assume that balance evaluation on multiple optokinetic stimuli and comparison to reference values based on healthy subjects has the potential to increase the sensitivity of the balance screening for VID subjects, and in particular concussed patients. This project aims to generate greater reliability using a more differentiated balance assessment with optokinetic stimulation. Findings are assumed to help identifying potential VID on a more individual basis and support accurate classification.