Journal of Vestibular Research-Equilibrium & Orientation最新文献

Background: During a simulated coordinated turn in a gondola centrifuge, experienced pilots show a substantial inter-individual variability in visual measures of perceived roll tilt. Because of the centrifuge's small radius, the pattern of stimuli to the semicircular canals during acceleration of the centrifuge differs in certain respects from that of an aircraft entering a turn.

Objective: To explore whether these differences may be of significance for the pilot's roll- plane orientation and whether individual characteristics revealed in the centrifuge correspond to those during real flight.

Method: 8 fixed-wing air-force pilots were tested in a centrifuge and a high-performance aircraft. The centrifuge was accelerated to 2 G (gondola inclination 60°) within 10 s. The duration at 2 G was 6 minutes. Similar profiles were created in the aircraft. The subjective visual horizontal (SVH) was measured using an adjustable luminous line in darkness. Each pilot was tested on three occasions: centrifuge (2 runs), aircraft (2 turns), centrifuge (2 runs). For each 2-G exposure, initial and final SVH values were established via curve fitting.

Result: Despite a large inter-individual variability (±SD), group means were similar in the aircraft (initial: 43.0±20.6°; final: 22.5±14.8°) and centrifuge (initial: 40.6±17.0°; final: 20.5±16.0°). Further, individual peculiarities in response patterns were similar in the two conditions. For both the initial and final SVH tilt there was a high correlation between centrifuge and aircraft.

Conclusion: The correspondence between conditions suggests that the centrifuge is an adequate means for demonstrating the fundamental motion pattern of coordinated flight and also for establishing the individual pilot's ability to perceive an aircraft's roll attitude.Findings are discussed in connection with vestibular learning and the possibility of underlying differences between pilots in the keenness for semicircular canal and somatosensory cues.

Background: Rafael Lorente de Nó was a neuroscientist that worked alongside two of the giants of Medicine, the Nobel Prize winners Cajal and Bárány.

Objective: To describe the contributions of Lorente de Nó to vestibular neuroscience.

Methods: Detailed review of the publications of Lorente de Nó and analysis of the archives from Junta para Ampliación de Estudios e Investigaciones Científicas at Residencia de Estudiantes (Madrid, Spain), Casa de Salud Valdecilla at Hospital Universitario Marqués de Valdecilla (Santander, Spain), Becker Medical Library at Washington University (St. Louis, MO, USA), Rockefeller Archive Center (Sleepy Hollow, New York, NY, USA), Archivo Fernando de Castro (Madrid, Spain), Biblioteca Nacional de España (Madrid, Spain) and Legado Cajal at Instituto Cajal (Madrid, Spain). Most of this material is unpublished and includes over a hundred letters to or from Lorente.

Results: Lorente de Nó made a substantial contribution to our understanding of the vestibular system. Amongst these, he meticulously detailed the course of the vestibular nerve and its central projections. He described the vestibulo-ocular reflex as the consequence of an integration of the various nuclei and connections across the vestibular system, rather than a simple three-neuron arc. He also highlighted the role of the reticular formation in the generation of the fast phase of the nystagmus.

Conclusions: Lorente de Nó was a pioneer of modern neuro-otology, having made outstanding contributions to vestibular neuroscience, forging novel discoveries that still burn true today.

Background: During near-viewing, the vestibulo-ocular reflex (VOR) response/gain increases to compensate for the relatively larger translation of the eyes with respect to the target.

Objective: To review vergence-mediated gain increase (VMGI) testing methods stimuli and responses (latency and amplitude), peripheral/central pathways and clinical relevance.

Methods: The authors discuss publications listed in PUBMED since 1980 in the light of their own studies.

Results: The VMGI can be measured during rotational, linear and combined head accelerations. It has short-latency, non-compensatory amplitude, and relies on irregularly discharging peripheral afferents and their pathways. It is driven by a combination of perception, visual-context and internal modelling.

Conclusions: Currently, there are technical barriers that hinder VMGI measurement in the clinic. However, the VMGI may have diagnostic value, especially with regards to measuring otolith function. The VMGI also may have potential value in rehabilitation by providing insight about a patient's lesion and how to best tailor a rehabilitation program for them, that potentially includes VOR adaptation training during near-viewing.

Introduction: No reliable biometric measurement of vestibular involvement with migraine is currently available.

Objective: Measures of autonomic nervous system and postural responses could serve as quantifiable indicators of vestibular involvement with migraine.

Methods: A convenience sample of 22 young healthy adults (34±9 years old) and 23 young adults (34±8 years old) diagnosed with vestibular migraine (VM) participated. A rod and frame test and clinical outcome measures of dizziness and mobility were administered. Participants stood on foam while viewing two dynamic virtual environments. Trunk acceleration in three planes and electrodermal activity (EDA) were assessed with wearable sensors. Linear mixed models were used to examine magnitude and smoothness of trunk acceleration and tonic and phasic EDA. A Welch's t-test and associations between measures were assessed with a Pearson Correlation Coefficient. Effect sizes of group mean differences were calculated using Cohen's d.

Results: Visual dependence was present in 83% of the VM population. Individuals with VM exhibited lower baseline EDA (t(4.17) = -7.2, p = 0.001) and greater normalized trunk accelerations in the vertical (t(42.5) = 2.861, p = 0.006) and medial (t(46.6) = 2.65, p = 0.01) planes than healthy participants. Tonic EDA activity increased significantly across the period of the trial (F (1,417) = 23.31, p = 0.001) in the VM group. Significant associations appeared between vertical trunk acceleration and EDA, Dizziness Handicap Inventory, and Activities of Balance Confidence tools.

Conclusions: Higher tonic EDA activity in healthy adults results in more accurate postural reactions. Results support the supposition that EDA activity and postural acceleration are significantly different between VM and healthy individuals when accommodating for postural instability and visual-vestibular conflict.

Background: Vestibular rehabilitation therapy (VRT) is effective for most patients with dizziness and imbalance. Home exercise programs are widely used. It is unknown, however, how specific the instructions for exercises have to be.

Objective: To evaluate the effects of expert assessment and instructions in a booklet-based home VRT program for patients with chronic dizziness.

Methods: Randomized controlled study on 74 participants with disabling dizziness for >3 months. All study participants received a booklet-based VRT for training at home. Participants were prescribed 20 minutes of exercise, twice a day. The intervention group (n = 37) received specific instructions (expert physiotherapist). The control group (n = 37) practiced without specific instructions. Primary outcome was the total score of the Dizziness Handicap Inventory (DHI-G). All outcomes were assessed at baseline, after 4 weeks, and at follow up 4 weeks later.

Results: Both groups improved (DHI-G 43.94±18.89 at inclusion to 33.06±19.67 at follow-up in controls and 42.82±16.60 to 22.65±19.12 in the intervention group). The intervention group, however, improved more (p = 0.014).

Conclusions: We show a significant effect of expert physiotherapy guidance in home-based VRT. This strengthens the role of the physiotherapist in VRT: Tailored, personalized instructions are needed to get the best effect of VRT.

Background: Motorist Disorientation Syndrome (MDS) is a term used to describe patients who primarily experience symptoms of dizziness/disorientation whilst in a motor car [21]. There is uncertainty about the relevance of vestibular dysfunction and whether this disorder could instead be a visually induced dizziness (VV) or part of a functional disorder similar to Persistent postural perceptual dizziness (PPPD).

Objective: We present the largest case-series to date of patients whose main complaint is of illusions of movement of self/vehicle when driving, characterising features of this group.

Methods: 18 subjects underwent detailed clinical assessment including validated questionnaires. A subset of patients underwent vestibular function testing.

Results: Mean onset age was 42 years, with no gender preponderance. Mean symptom duration was 6.39 years and was significantly longer in women. 50% reported moderate or severe handicap. Vestibular abnormalities were found in 60% of subjects tested. There was no significant difference in VSS total score between those with MDS and vestibular migraine (p = 0.154) with both having higher scores than healthy controls (p = 0.002, 0.000 respectively).

Conclusions: MDS represents consistent symptoms, with high symptom burden, comparable to vestibular migraine. Vestibular deficits were not a consistent feature and similarities to VV and PPPD exist.

Background: Acceleration and changes in acceleration (jerk) stimulate vestibular otolith afferents. Bone-conducted (BC) vibration applied to the skull accelerates the head and produces short latency reflexes termed vestibular evoked myogenic potentials (VEMPs).

Objective: To determine the magnitude, variability and symmetry in head acceleration/jerk during VEMP recordings and investigate the relationship between head acceleration/jerk and VEMP properties.

Methods: 3D head accelerometery (sagittal, interaural and vertical axes) was recorded bilaterally in thirty-two healthy subjects during cervical (cVEMP) and ocular (oVEMP) recordings. BC 500 Hz sinusoidal tones were applied to the midline forehead using a positive polarity stimulus.

Results: The direction of induced acceleration/jerk was predominately backward, outward and downward on either side of the head during cVEMP and oVEMP recordings.Overall, acceleration/jerk was larger in the sagittal and interaural axes and peaked earlier in the interaural axis bilaterally. Acceleration was more symmetric in the sagittal and interaural axes whereas jerk symmetry did not differ between axes. Regression models did not show a systematic relationship between acceleration/jerk and either VEMP reflex.

Conclusions: The pattern of skull acceleration/jerk was relatively consistent between the two sides of the head and across subjects, but there were differences in magnitude, leading to inter-side and inter-subject variability.