Rotational chair testing in patients with unilateral peripheral vestibular disorders

Abstract

Abstract The aim of the study was to evaluate the rotational chair (RC) sinusoidal harmonic acceleration (SHA) test and the rotational velocity step (RVS) test in patients with unilateral peripheral vestibular disorders. This study was retrospective in nature. It was conducted in a clinical tertiary care vestibular function test center. A total of 119 patients (63 men and 56 women) with documented unilateral peripheral vestibular lesions were evaluated with bithermal binaural caloric and sinusoidal and step velocity RC tests. Clinical, caloric, and RC tests were carried out. The study group was selected by including patients with a clinical diagnosis suggestive of peripheral vestibular lesions and with documented unilateral caloric weakness matching the clinical diagnosis, and by excluding patients with a clinical diagnosis suggestive of a peripheral vestibular lesion but not documented by unilateral caloric weakness, as well as patients with incomplete tests or uninterpretable data (due to poor recordings or eye movement artifacts). Caloric testing was performed using an infrared video-oculographic system and a Brookler-Grams closed-loop irrigation unit with standard bithermal irrigations of 30 and 44°C for 45 s each in the following order: L30°C, R30°C, R44°C, and L44°C. The RC testing paradigms used in this study were the rotational SHA test and the RVS test. When patients were classified on the basis of etiology, the most common cause of dizziness in the study group was found to be Mιniθre’s disease (34.9%), followed by vestibular neuritis (31.1%). Seventy-two patients in the study group demonstrated right caloric weakness and 47 patients demonstrated left caloric weakness, whereas only 18 of 119 patients demonstrated directional preponderance. When the RC SHA test parameters (gain, phase, and symmetry) in the study group were compared with the manufacturer’s normal values, statistically significant difference was seen in vestibulo-ocular reflex (VOR) gain at low frequencies (0.01-0.08 Hz), in VOR phase at all frequencies, and in VOR symmetry at low frequencies (0.01-0.04 Hz). In summary, despite the encouraging results of the discriminating power of caloric testing, it should be emphasized that RC testing has its own unique capabilities, such as the following: (i) it is a physiologic stimulus whose frequency and amplitude can be varied precisely; (ii) the stimulus is unrelated to physical features of the external ear or temporal bone; (iii) it is useful in children who may not tolerate caloric testing; and (iv) it is very useful in assessing patients receiving vestibulotoxic drugs. Multiple stimuli of varying intensities can be applied to the vestibular system within a relatively short period of time.