Misperception of Visual Verticality Measured with a Virtual Reality Device in Patients with Fibromyalgia Syndrome: A Cross-Sectional Study

Abstract

The objective of this study was to analyze the perception of visual verticality (VV) in subjects with Fibromyalgia Syndrome (FMS) and to correlate this with the symptoms of the disease and balance capacity. A cross-sectional study including 54 patients (51 female) was conducted. The evaluation of visual verticality was carried out with a virtual reality device by calculating the Mean Absolute Error (MAE) of degrees deviation in two tests: the Subjective Visual Vertical (SVV) test for the contribution of the vestibular system to the perception of verticality and the Rod and Frame test (RFT) for the contribution of the visual system. In total, 16 subjects (29.6%) presented good VV perception, 6 subjects (11.1%) presented an exclusive alteration of the SVV test, 19 subjects (35.2%) presented an exclusive alteration of the RFT and 13 subjects (24.1%) showed alteration in the two tests. The MAE in the SVV test showed medium correlations with several variables such as the Fibromyalgia Impact Questionnaire (FIQ) (Rho = 0.399, p = 0.003), the Pain Catastrophizing Scale (PCS) (Rho = 0.417, p = 0.002), the Dizziness Handicap Inventory (DHI) (Rho = 0.376, p = 0.005), and the Activities-Specific Balance Confidence Scale (ABC-16) (Rho = −0.367, p = 0.006). The MAE in the RFT showed medium correlations with the Instability Support Reduced (Rho = 0.327, p = 0.016) and Instability Gait Eyes Open (Rho = 0.312, p = 0.022) subscales of the JAEN (Joined Assessment of Equilibrium and Neuro-motor) Scale. Conclusions: Around 70% of the subjects with FMS showed some alteration in the perception of VV; 60% of these patients presented visual system dependence. The SVV test correlates with the impact and health status of FMS, and the RFT correlates with the alteration in the dynamic balance.