Sensory substitution in bilateral vestibular a-reflexic patients (original) (raw)
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Frontiers in Systems Neuroscience, 2021
Introduction: The unilateral vestibular syndrome results in postural, oculomotor, perceptive, and cognitive symptoms. This study was designed to investigate the role of vestibular signals in body orientation representation, which remains poorly considered in vestibular patients.Methods: The subjective straight ahead (SSA) was investigated using a method disentangling translation and rotation components of error. Participants were required to align a rod with their body midline in the horizontal plane. Patients with right vestibular neurotomy (RVN; n =8) or left vestibular neurotomy (LVN; n = 13) or vestibular schwannoma resection were compared with 12 healthy controls. Patients were tested the day before surgery and during the recovery period, 7 days and 2 months after the surgery.Results: Before and after unilateral vestibular neurotomy, i.e., in the chronic phases, patients showed a rightward translation bias of their SSA, without rotation bias, whatever the side of the vestibular...
Patients with bilateral vestibular loss (BVL) of both central and peripheral origin experience multiple problems with balance and posture control, movement, and abnormal gait. Wicab, Inc. has developed the BrainPort™ balance device to transmit head position/orientation information normally provided by the vestibular system to the brain through a substitute sensory channel: tactile sensation of the tongue. Head-orientation data (artificially sensed) serves as the input signal for the BrainPort balance device to control the movement of a small pattern of stimulation on the tongue that relates to head position in real-time. With training, the brain learns to appropriately interpret the information from the device and utilize it to function as it would with data from a normal-functioning natural sense. In a total of 40 subjects trained with the BrainPort, 18 have been tested using standardized quantitative measurements of the treatment effects. A specialized set of exercises, testing, and training procedures has been developed that may serve as the course of intensive physical therapy with the BrainPort balance device. Our results demonstrate consistent positive and statistically significant balance rehabilitation effects independent of aging and etiology of balance deficit. risk of falling, driving a car, moving in a crowd, reading a book, or watching TV.
Dissociating Vestibular and Somatosensory Contributions to Spatial Orientation
Journal of neurophysiology, 2016
Inferring object orientation in the surroundings heavily depends on our internal sense of direction of gravity. Previous research showed that this sense is based on the integration of multiple information sources, including visual, vestibular (otolithic) and somatosensory signals. The individual noise characteristics and contributions of these sensors can be studied using spatial orientation tasks, such as the subjective visual vertical (SVV) task. A recent study reported that patients with complete bilateral vestibular loss perform similar as healthy controls on these tasks, from which it was conjectured that the noise levels of both otoliths and body somatosensors are roll-tilt dependent. Here, we tested this hypothesis in ten healthy human subjects by roll-tilting the head relative to the body to dissociate tilt-angle dependencies of otolith and somatosensory noise. Using a psychometric approach, we measured bias and variability in perceived orientation of a briefly flashed line ...
Balance deficits increase the risk of falls and compromise quality of life. This single group, interventional study assesses a computerized vestibular retraining protocol in patients with objectively determined unilateral peripheral vestibular deficits. Participants received twelve twice-weekly sessions of vestibular retraining guided by an interactive display. Objective posturography tests and questionnaires were administered before and after retraining. We enrolled 13 participants (5 females and 8 males) with a median age of 51 years (range 18 to 67). After retraining, the median change in sensory organization test (SOT) composite scores was 8.8 (95% CI, 0.6 to 19.1). The SOT visual (median change of 0.12 [-0.09 to 0.30]) and vestibular (0.10 [-0.06 to 0.25]) ratios improved but there was no change in the somatosensory or visual preference ratios. Participants with moderate-to-severe disability at baseline (n=7), as measured by Dizziness Handicap Inventory, had a larger magnitude ...
Psychophysical Evaluation of Sensory Reweighting in Bilateral Vestibulopathy
Frontiers in Neurology, 2018
Perception of spatial orientation is thought to rely on the brain's integration of visual, vestibular, proprioceptive, and somatosensory signals, as well as internal beliefs. When one of these signals breaks down, such as the vestibular signal in bilateral vestibulopathy, patients start compensating by relying more on the remaining cues. How these signals are reweighted in this integration process is difficult to establish, since they cannot be measured in isolation during natural tasks, are inherently noisy, and can be ambiguous or in conflict. Here, we review our recent work, combining experimental psychophysics with a reverse engineering approach, based on Bayesian inference principles, to quantify sensory noise levels and optimal (re)weighting at the individual subject level, in both patients with bilateral vestibular deficits and healthy controls. We show that these patients reweight the remaining sensory information, relying more on visual and other nonvestibular information than healthy controls in the perception of spatial orientation. This quantification approach could improve diagnostics and prognostics of multisensory integration deficits in vestibular patients, and contribute to an evaluation of rehabilitation therapies directed toward specific training programs.
Vestibular dysfunction of either central or peripheral origin can significantly affect balance, posture, and gait. We conducted a pilot study to test the effectiveness of training with the BrainPort balance device in subjects with a balance dysfunction due to peripheral or central vestibular loss. The BrainPort balance device transmits information about the patient's head position via electrotactile stimulation of the tongue. Head position data is sensed by an accelerometer and displayed on the tongue as a pattern of stimulation. This pattern of stimulation moves forward, backward, and laterally on the tongue in direct response to head movements. Users of the device were trained to use this stimulation to adjust their position in order to maintain their balance. Twenty-eight subjects with peripheral or central vestibular loss were trained with the BrainPort balance device and tested using the following standardized quantitative measurements of the treatment effects: Computerized Dynamic Posturography (CDP) using the Sensory Organization Test (SOT), Dynamic Gait Index (DGI), Activities-specific Balance Confidence Scale (ABC), and Dizziness Handicap Inventory (DHI). All subjects had chronic balance problems and all but one had previously participated in vestibular rehabilitation therapy. The scores on the clinical tests upon entry into the study were compared to their scores following training with the BrainPort balance device. Our results exhibit consistent positive and statistically significant improvements in balance, posture and gait. These results exceed what could normally be achieved in three to five days of traditional balance training alone. Since this was not a controlled study, we are unable to distinguish the degree to which these improvements are attributable to training with the BrainPort balance device versus the balance exercises performed by all subjects as a part of the BrainPort training sessions. Nonetheless, after training with the BrainPort balance device, all subjects demonstrated significant improvements in performance beyond what might be expected from conventional vestibular rehabilitation therapy.
Changes of visual vertical perception: A long-term sign of unilateral and bilateral vestibular loss
Neuropsychologia, 2007
This study investigates how unilateral and bilateral vestibular deafferentation modifies visual vertical perception in the presence of dynamic and static visual cues. We tested 40 Menière's patients before and after (from 1 week to 1 year) a curative unilateral vestibular neurotomy (UVN), and 4 patients with bilateral vestibular loss. Patients' performances were compared with those of 24 healthy subjects. The perception of the dynamic visual vertical (DVV) was investigated during optokinetic stimulations around the line of sight at various angular velocities. The static visual vertical (SVV) was recorded with a stationary visual pattern. In the acute stage after UVN, Menière's patients exhibited drastic impairment of DVV, which was tilted towards the lesioned side, whatever the direction of the optokinetic stimulation. In addition, the SVV was systematically tilted towards the lesioned side. The optokinetic-induced tilt of the vertical was asymmetrically organized around the new SVV with a significant decrease for contralesional stimulations and no change for ipsilesional stimulations, whatever the postoperative time. The SVV regained normal values 1 year postoperatively. For the patients with bilateral vestibular loss, the optokinetic-induced tilt of the visual vertical was drastically increased and symmetrically organized around an unmodified SVV aligned with the gravitational vertical. This study constitutes the first description of the recovery time-course of DVV perception after unilateral vestibular loss. Data reveal a long-term impairment of the DVV perception after unilateral vestibular loss, suggesting an asymmetrical processing of visual information and a permanent increased weight of dynamic visual cues after bilateral vestibular loss.
Current concepts and future approaches to vestibular rehabilitation
Journal of neurology, 2016
Over the last decades methods of vestibular rehabilitation to enhance adaptation to vestibular loss, habituation to changing sensory conditions, and sensory reweighting in the compensation process have been developed. However, the use of these techniques still depends to a large part on the educational background of the therapist. Individualized assessment of deficits and specific therapeutic programs for different disorders are sparse. Currently, vestibular rehabilitation is often used in an unspecific way in dizzy patients irrespective of the clinical findings. When predicting the future of vestibular rehabilitation, it is tempting to foretell advances in technology for assessment and treatment only, but the current intense exchange between clinicians and basic scientists also predicts advances in truly understanding the complex interactions between the peripheral senses and central adaptation mechanisms. More research is needed to develop reliable techniques to measure sensory de...
Otology & Neurotology, 2017
Background: Patients with an acute unilateral peripheral vestibular deficit (aUPVD), presumed to be caused by vestibular neuritis, show asymmetrical vestibular ocular reflexes (VORs) that improve over time. Questions arise regarding how much of the VOR improvement is due to peripheral recovery or central compensation, and whether differences in peripheral recovery influence balance control outcomes. Methods: Thirty patients were examined at aUPVD onset and 3, 6, and 13 weeks later with four different VOR tests: caloric tests; rotating (ROT) chair tests performed in yaw with angular accelerations of 5 and 20 degrees/s 2 ; and video head impulse tests (vHIT) in the yaw plane. ROT and vHIT responses and balance control of 11 patients who had a caloric canal paresis (CP) more than 90% at aUPVD onset and no CP recovery (no-CPR) at 13 weeks in caloric tests were compared with those of 19 patients with CP recovery (CPR) to less than 30%, on average. Balance control was measured with a gyroscope system (SwayStar) recording trunk sway during stance and gait tasks. Results: ROT and vHIT asymmetries of no-CPR and CPR patients reduced over time. The reduction was less at 13 weeks (36.2% vs. 83.5% on average) for the no-CPR patients. The no-CPR group asymmetries at 13 weeks were greater than those of CPR patients who had normal asymmetries. The greater asymmetries were caused by weaker deficit side responses which remained deficient in no-CPR patients at 13 weeks. Contra-deficit side vHIT and ROT responses remained normal. For all balance tests, sway was slightly greater for no-CPR compared with CPR patients at aUPVD onset and 3 weeks later. At 13 weeks, only sway during walking eyes closed was greater for the no-CPR group. A combination of 5 degrees/s 2 ROT and balance tests could predict at onset (90% accuracy) which patients would have no-CPR at 13 weeks. Conclusions: These results indicate that for ROT and vHIT tests, central compensation is observed in CPR and no-CPR patients. It acts primarily by increasing deficit side responses. Central compensation provides approximately 60% of the VOR improvement for CPR patients. The rest of the improvement is due to peripheral recovery which appears necessary to reduce VOR asymmetry to normal at 13 weeks on average. Balance control improvement is more rapid than that of the VOR and marginally affected by the lack of peripheral recovery. Both VOR and balance control measures at onset provide indicators of future peripheral recovery. For these reasons VOR and balance control needs to be tested at aUPVD onset and at 13 weeks.