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Vestibular stimulation causes postural unsteadiness accompanied by a sensation of tilt. The mechanism of the sensation of tilt needs to be assessed by accurate calculation of the rotational axis of torsional eye position under various vestibular stimulations. Twenty-two healthy subjects participated in the study. Thirteen subjects underwent bilateral vestibular stimulation by on-axis yaw rotation under various head positions, and eighteen subjects underwent unilateral vestibular stimulation by caloric irrigation under various head positions. Listing's Plane was plotted for the eye movement data obtained by three-dimensional video-oculography. The offset of Listing's Plane showed sustained deviation of torsional eye position that was more prominent in head positions that stimulated lateral semicircular canals more than vertical semicircular canals. There was a less prominent and directionally reversed offset in head positions that stimulated vertical canals more than lateral semicircular canals. The sustained torsional eye position was validated by accurate assessment using Listing's Plane. The mechanism behind the deviation may be due to a combination of multiple anatomical components within the vestibular apparatus, with potentially stronger influence from lateral semicircular canals. [ABSTRACT FROM AUTHOR]

Purpose:To identify the tests and tools used to evaluate vestibulo-ocular reflex (VOR) function after traumatic brain injury (TBI) in all age groups and across TBI severity. Methods: An electronic search was conducted to include relevant peer-reviewed literature published up to November 2019. Studies included those done with humans, of all ages, and had assessments of oculomotor and/or vestibulo-ocular function in TBI. Results: Of the articles selected (N = 48), 50% were published in 2018/2019. A majority targeted mild TBI, with equal focus on non-computerized versus computerized measures of VOR. Computerized assessment tools used were videonystagmography, dynamic visual acuity/gaze stability, rotary chair, and caloric irrigation. Non-computerized tests included the head thrust, dynamic visual acuity, gaze stability, head shaking nystagmus, rotary chair tests and the vestibular/oculomotor screening tool. High variability in administration protocols were identified. Namely: testing environment, distances/positioning/equipment used, active/passive state, procedures, rotation frequencies, and variables observed. Conclusions: There is a rapid growth of literature incorporating VOR tests in mild TBI but moderate and severe TBI continues to be under-represented. Determining how to pair a clinical test with a computerized tool and developing standardized protocols when administering tests will help in developing an optimal battery assessing the VOR in TBI. [ABSTRACT FROM AUTHOR]

Objective: To investigate whether the use of mental tasking, when compared to no mental task, affects measurement of nystagmus response with regard to gain, phase & symmetry, and artefact when utilising video-oculography (VOG) as the measurement technique in rotary chair testing (RCT). Design: A within-subject repeated-measures design was utilised. Study samples: Seventeen (17) healthy adults were evaluated (age 22–25 years). Each participant underwent slow harmonic acceleration (SHA) testing for 0.01, 0.02, 0.04, 0.08, and 0.16 Hz using RCT at two separate counterbalanced visits. At one visit mental tasking was utilised while the other visit did not utilise mental tasking. The following outcomes were measured for each visit: gain, phase, symmetry, and artefact. Results: No significant difference between the tasking conditions with regard to gain, phase, symmetry, or artefact. Significant frequency affects were noted, as expected, for gain, phase, and artefact. Analysis of individual subject data did, however, describe significant effects of tasking with regard to gain, phase, symmetry, and artefact. Conclusion: These results suggest that the use of mental tasking during RCT using VOG had no significant group effect on SHA gain, phase, symmetry, and artefact. However, individual subject effects were observed indicating variability in the effects of mental tasking during RCT. [ABSTRACT FROM AUTHOR]