DSpace Collection:
https://hdl.handle.net/10171/18980
2024-03-29T00:01:30ZRelevance of artifact removal and number of stimuli for video head impulse test examination
https://hdl.handle.net/10171/68803
Title: Relevance of artifact removal and number of stimuli for video head impulse test examination
Abstract: Objective: To evaluate the effect of artifacts on the impulse and response recordings with the video head impulse test (VHIT) and determine how many stimuli are necessary for obtaining acceptably efficient
measurements.
Methods: One hundred fifty patients were examined using VHIT and
their registries searched for artifacts. We compared several variations
of the dataset. The first variation used only samples without artifacts,
the second used all samples (with and without artifacts), and the rest
used only samples with each type of artifact. We calculated the relative
efficiency (RE) of evaluating an increasingly large number of samples (3
to 19 per side) when compared with the complete sample (20 impulses
per side).
Results: Overshoot was associated with significantly higher speed
(p = 0.005), higher duration (p < 0.001) and lower amplitude of the
impulses (p = 0.002), and consequent higher saccades’ latency (p =
0.035) and lower amplitude (p = 0.025). Loss of track was associated
with lower gain (p = 0.035). Blink was associated with a higher number
of saccades (p < 0.001), and wrong way was associated with lower saccade latency (p = 0.012). The coefficient of quartile deviation escalated
as the number of artifacts of any type rose, indicating an increment of
variability. Overshoot increased the probability of the impulse to lay on
the outlier range for gain and peak speed. Blink did so for the number
of saccades, and wrong way for the saccade amplitude and speed. RE
reached a tolerable level of 1.1 at 7 to 10 impulses for all measurements
except the PR score.
Conclusions: Our results suggest the necessity of removing artifacts
after collecting VHIT samples to improve the accuracy and precision of
results. Ten impulses are sufficient for achieving acceptable RE for all
measurements except the PR score.2020-01-01T00:00:00ZVisual performance and perception as a target of saccadic strategies in patients with unilateral vestibular loss
https://hdl.handle.net/10171/68801
Title: Visual performance and perception as a target of saccadic strategies in patients with unilateral vestibular loss
Abstract: Objectives: To evaluate the ability of saccadic strategies developed during vestibular compensation to reduce the effect of an impaired vestibulo-ocular reflex (VOR) on a retinal smear and image motion sensation.
Design: Twenty patients with unilateral vestibular loss were examined
with a video head impulse test before and after vestibular rehabilitation
(VR) with the use of gaze stabilization and refixation saccades training. Head and eye velocity functions were processed to infer the retinal
eccentricity, and through its correlation with visual acuity (VA), several
measurements are proposed to evaluate the influence of VR on saccades
behavior and visual performance. To isolate the effect of saccades on the
findings and avoid bias because of gain differences, only patients whose
VOR gain values remained unchanged after VR were included.
Results: Improved contribution of covert saccades and reduction of
overt saccades latency were measured after VR. We found significant differences when assessing both the interval less than 70% VA (50.25ms),
which is considered the limit of a moderate low vision, and less than
50% VA (39.515ms), which is the limit for severe low vision. Time
to recover a VA of 75% (near normal) was reduced in all the patients
(median: 56.472ms).
Conclusion: Despite the absence of VOR gain improvement, patients
with unilateral vestibular loss are able to develop saccadic strategies that
allow the shortening of the interval of retinal smear and image motion.
The proposed measurements might be of use to evaluate VR outcomes
and visually induced impairment.2018-01-01T00:00:00ZA new and faster method to assess vestibular compensation: A cross-sectional study
https://hdl.handle.net/10171/68800
Title: A new and faster method to assess vestibular compensation: A cross-sectional study
Abstract: Objectives/Hypothesis: Characterize the state of vestibular compensation of subjects diagnosed with acute unilateral
vestibulopathy (AUV) of peripheral origin according to the temporal organization pattern of the refixation saccades (Perez and
Rey (PR) score).
Study Design: Retrospective cross-sectional study using previously collected clinical data from a tertiary referral center.
Methods: Following the vestibular compensation criteria defined by Eisenman, we used the video head impulse test as
the main vestibular function test and compared the results with other traditional tests: rotatory chair test (ROT), caloric test,
videonystagmography, clinical situation (CLIN), and the Dizziness Handicap Inventory (DHI) questionnaire from 28 subjects
(17 men, 11 women), average age 60.21 years, who were in a compensated and noncompensated vestibular situation. We used
the PR score to measure the differences between the study groups. A cluster was developed to define a cutoff point that objec-
tively distinguishes the vestibular compensation status.
Results: Significant differences in the PR score were found in the state of vestibular compensation in the ROT test
(P = .01), DHI (P = .04), and CLIN (P = .023). The vestibular compensation criteria that groups the original variables (PR-
CLUSTER) cutoff point was 55 (P = .019).
Conclusions: The PR score is a measure of temporal organization of the refixation saccades that enables us to distinguish
clearly and objectively the vestibular situation of subjects with AUV. We suggest its clinical application.
Key Words: Vestibulo-ocular reflex, refixation saccades, unilateral vestibular loss, dizziness, rehabilitation.
Level of Evidence: NA2020-01-01T00:00:00ZClassification of vestibular signs and examination techniques: Nystagmus and nystagmus-like movements
https://hdl.handle.net/10171/68799
Title: Classification of vestibular signs and examination techniques: Nystagmus and nystagmus-like movements
Abstract: This paper presents a classification and definitions for types of nystagmus and other oscillatory eye movements
relevant to evaluation of patients with vestibular and neurological disorders, formulated by the Classification Committee of
the Bar´ any Society, to facilitate identification and communication for research and clinical care. Terminology surrounding the ´
numerous attributes and influencing factors necessary to characterize nystagmus are outlined and defined. The classification
first organizes the complex nomenclature of nystagmus around phenomenology, while also considering knowledge of anatomy,
pathophysiology, and etiology. Nystagmus is distinguished from various other nystagmus-like movements including saccadic
intrusions and oscillations.2019-01-01T00:00:00Z