2-dimensional Versus 3-dimensional Virtual Reality Game Training in Individuals With Benign Paroxysmal Positional Vertigo: A Randomized Controlled Study

The vestibular, visual, and somatosensory systems are all important in maintaining posture. Multiple structures of the central nervous system process and integrate afferents from these systems. The vestibular system is crucial for maintaining static and dynamic posture and balance. The vestibular system consists of two structures, peripheral and central. The peripheral vestibular system is located within the petrous bone and consists of the semicircular canals, utricle, and saccule in the inner ear that are sensitive to head movements. The semicircular canals consist of three parts: anterior, posterior and lateral semicircular canals. The semicircular canals, which are filled with a viscous fluid called endolymph, are located at right angles to each other and help to perceive the angular movements of the head. It transmits information about the peripheral vestibular system and head movements to the central systems via the vestibular nerve. In this way, it provides regulation of head, body, extremities and eye movements.

BPPV (Benign Paroxysmal Positional Vertigo) is a condition that affects the inner ear and is caused by semicircular canal dysfunction. Because the otoliths are placed in the semicircular canal and can impair their free movement, the anatomical placement of the canals is critical. BPPV is one of the most frequent peripheral vestibular illnesses with a prevalence of 20-40%. The first pathogenetic element is canalolithiasis, defined as the dissociation of the otoconia from the otolytic membrane and its free movement in the endolymph, which is seen in 80% of the patients. Cupulolithiasis is the occurrence of dizziness (vertigo) and nystagmus specific to the affected canal due to calcium carbonate crystals adhering to the canal. Because of its anatomical location, posterior semicircular canal BPPV is observed 80-90% of the time, lateral semicircular canal BPPV is seen 10-20% of the time, and anterior semicircular canal BPPV is less prevalent. BPPV often is treated with particle repositioning maneuvers once the involved canal is identified. These maneuvers are supposed to move otoconia particles out of the affected canal and back into the vestibule, where they dissolve.

Vestibular rehabilitation is another non-pharmacological intervention for BPPV. Vestibular rehabilitation can enhance general balance function, including gait, gaze, and postural stability, physical mobility, and function with activities of daily living, by integrating proprioceptive, visual, and residual vestibular function. Vestibular rehabilitation utilizes central neuroplasticity mechanisms to improve visuo-vestibular interactions and restore static and dynamic postural stability in situations where sensory input is conflicting. Vestibular rehabilitation includes adaptation, habituation, and substitution exercises. The adaptation exercises are based on the vestibular system's ability to change the magnitude of the vestibulo-ocular reflex (VOR) in response to a specific stimulus (head movement). Habituation exercises, in contrast to adaptation exercises, are based on the notion that frequent exposure to provoking stimuli such as head movements will reduce motion-provoked symptoms. Substitution exercises combine vision and somatosensory cues with vestibular cues to improve gaze and postural stability by enhancing central programming. Maneuvers are shown to be more successful than vestibular rehabilitation in the short term, although combining the two is useful for long-term functional recovery in BPPV. However, there is insufficient evidence to distinguish between different types of vestibular rehabilitation.

The positive impact of vestibular rehabilitation on balance is based on mechanisms related to the central nervous system's neural plasticity, and its goals are to promote visual stabilization, improve vestibular-visual interaction during head movements, thereby improving the standing and dynamic postural stability in conditions that produce conflicting sensory information, and decrease sensitivity to head movements. However, numerous aspects have been identified as having a detrimental impact on the outcome of vestibular rehabilitation, including poor exercise execution, the necessity for active efforts, and the patients' desire. Given the drawbacks associated with the time-consuming, repetitive, monotonous, and non-challenging aspects of vestibular rehabilitation, more efficient and cost-effective types of treatments were proposed as a potential alternative. Currently, virtual reality (VR) applications, can be outfitted with real-time simulations, interactive functions, and game features to allow for more motivated vestibular rehabilitation.

Many studies suggest that engaging virtual reality components can contribute to successful outcomes. It is claimed that it allows visual-vestibular interaction with a large number of visual stimuli, resulting in an optimal environment for better VR performance. It is suggested that this is due to the activation of target-oriented attention and the brain's neural network and that VR applications using eye-tracking algorithms and 'glasses' can be effective. In most of the studies, 2-dimensional systems (e.g. Nintendo Wii, Play station) has been used for the treatment of patients with BPPV. However, due to their proximity to the eye, head-mounted displays (3D VR gaming) may offer high-resolution images which make the users feel like they are a part of the computer-created environment. 3D technologies have been debated about their negative effects such as discomfort, visual fatigue, dizziness, headache, disorientation, motion sickness, which are indicative of VIMS (visually induced motion sickness). The most accepted explanation for VIMS is the classical conflict theory based on the mismatch between the visual, the proprioceptive, and the vestibular stimuli.