Visual Vertigo, Motion Sickness, and Disorientation in Vehicles.

Environmental circumstances that result in ambiguity or conflict with the patterns of sensory stimulation may adversely affect the vestibular system. The effect of this conflict in sensory information may be dizziness, a sense of imbalance, nausea, and motion sickness sometimes even to seemingly minor daily head movement activities. In some, it is not only exposure to motion but also the observation of objects in motion around them such as in supermarket aisles or other places with visual commotion; this can lead to dizziness, nausea, or a feeling of motion sickness that is referred to as visual vertigo. All people with normal vestibular function can be made to experience motion sickness, although individual susceptibility varies widely and is at least partially heritable. Motorists learn to interpret sensory stimuli in the context of the car stabilized by its suspension and guided by steering. A type of motorist's disorientation occurs in some individuals who develop a heightened awareness of perceptions of motion in the automobile that makes them feel as though they may be rolling over on corners and as though they are veering on open highways or in streaming traffic. This article discusses the putative mechanisms, consequences and approach to managing patients with visual vertigo, motion sickness, and motorist's disorientation syndrome in the context of chronic dizziness and motion sensitivity.

Effects of prochlorperazine on normal vestibular ocular and perceptual responses: a randomised, double-blind, crossover, placebo-controlled study.

BACKGROUND: The present study investigated whether prochlorperazine affects vestibulo-ocular reflex (VOR) and vestibulo-perceptual function. METHODS: We studied 12 healthy naïve subjects 3 h after a single dose of oral prochlorperazine 5 mg in a randomised, placebo-controlled, double-blind, crossover study in healthy young subjects. Two rotational tests in yaw were used: (1) a threshold task investigating perceptual motion detection and nystagmic thresholds (acceleration steps of 0.5°/s(2)) and (2) suprathreshold responses to velocity steps of 90°/s in which vestibulo-ocular and vestibuloperceptual time constants of decay, as well as VOR gain, were measured. RESULTS: Prochlorperazine had no effect upon any measure of nystagmic or perceptual vestibular function compared to placebo. This lack of effects on vestibular-mediated motion perception suggests that the drug is likely to act more as an anti-emetic than as an antivertiginous agent.

Factors influencing clinical outcome in vestibular neuritis - A focussed review and reanalysis of prospective data.

Following vestibular neuritis (VN), long term prognosis is not dependent on the magnitude of the residual peripheral function as measured with either caloric or the video head-impulse test. Rather, recovery is determined by a combination of visuo-vestibular (visual dependence), psychological (anxiety) and vestibular perceptual factors. Our recent research in healthy individuals has also revealed a strong association between the degree of lateralisation of vestibulo-cortical processing and gating of vestibular signals, anxiety and visual dependence. In the context of several functional brain changes occurring in the interaction between visual, vestibular and emotional cortices, which underpin the aforementioned psycho-physiological features in patients with VN, we re-examined our previously published findings focusing on additional factors impacting long term clinical outcome and function. These included: (i) the role of concomitant neuro-otological dysfunction (i.e. migraine and benign paroxysmal positional vertigo (BPPV)) and (ii) the degree to which brain lateralisation of vestibulo-cortical processing influences gating of vestibular function in the acute stage. We found that migraine and BPPV interfere with symptomatic recovery following VN. That is, dizziness handicap at short-term recovery stage was significantly predicted by migraine (r = 0.523, n = 28, p = .002), BPPV (r = 0.658, n = 31, p < .001) and acute visual dependency (r = 0.504, n = 28, p = .003). Moreover, dizziness handicap in the long-term recovery stage continued to be predicted by migraine (r = 0.640, n = 22, p = .001), BPPV (r = 0.626, n = 24, p = .001) and acute visual dependency (r = 0.667, n = 22, p < .001). Furthermore, surrogate measures of vestibulo-cortical lateralisation were predictive of the amount of cortical suppression exerted over vestibular thresholds. That is, in right-sided VN patients, we observed a positive correlation between visual dependence and acute ipsilesional oculomotor thresholds (R2 0.497; p < .001), but not contralateral thresholds (R2 0.017: p > .05). In left-sided VN patients, we observed a negative correlation between visual dependence and ipsilesional oculomotor thresholds (R2 0.459; p < .001), but not for contralateral thresholds (R2 0.013; p > .05). To surmise, our findings illustrate that in VN, neuro-otological co-morbidities retard recovery, and that measures of the peripheral vestibular system are an aggregate of residual function and cortically mediated gating of vestibular input.

[18F]2-fluoro-2-deoxy-D-glucose positron emission tomography (FDG PET) as a diagnostic tool for neurofibromatosis 1 (NF1) associated malignant peripheral nerve sheath tumours (MPNSTs): a long-term clinical study.

BACKGROUND: Malignant peripheral nerve sheath tumours (MPNSTs) are difficult to detect in neurofibromatosis 1 (NF1) individuals. The purpose was to evaluate [(18)F]2-fluoro-2-deoxy-D-glucose positron emission tomography (FDG PET) and PET computed tomography (CT) as a diagnostic tool for MPNST in NF1 patients with symptomatic plexiform neurofibromas and to verify the diagnosis by pathology and clinical follow-up. PATIENTS AND METHODS: NF1 individuals with symptomatic plexiform neurofibromas underwent clinical evaluation and magnetic resonance imaging. Qualitative FDG PET and PET CT associated with semi-quantitative maximum standard uptake value (SUVmax) assessed possible malignant change. Excision/biopsy verified the diagnosis when possible and clinical follow-up was undertaken in all patients. RESULTS: In all, 116 lesions were detected in 105 patients aged 5-71 years, including 80 plexiform neurofibromas, five atypical neurofibromas, 29 MPNST and two other cancers. Biopsy confirmed the findings in 59 tumours and no MPNST was diagnosed on clinical follow-up of 23 lesions diagnosed as benign on FDG PET and PET CT. FDG PET and PET CT diagnosed NF1-associated tumours with a sensitivity of 0.89 [95% confidence interval (CI) 0.76-0.96] and a specificity of 0.95 (CI 0.88-0.98), but the SUVmax level did not predict tumour grade. CONCLUSION: FDG PET and PET CT is a sensitive and specific diagnostic tool for NF1-associated MPNST. Other PET tracers will be required to solve the problem of predicting tumour grade.

Motion sickness.

Over 2000 years ago the Greek physician Hippocrates wrote, "sailing on the sea proves that motion disorders the body." Indeed, the word "nausea" derives from the Greek root word naus, hence "nautical," meaning a ship. The primary signs and symptoms of motion sickness are nausea and vomiting. Motion sickness can be provoked by a wide variety of transport environments, including land, sea, air, and space. The recent introduction of new visual technologies may expose more of the population to visually induced motion sickness. This chapter describes the signs and symptoms of motion sickness and different types of provocative stimuli. The "how" of motion sickness (i.e., the mechanism) is generally accepted to involve sensory conflict, for which the evidence is reviewed. New observations concern the identification of putative "sensory conflict" neurons and the underlying brain mechanisms. But what reason or purpose does motion sickness serve, if any? This is the "why" of motion sickness, which is analyzed from both evolutionary and nonfunctional maladaptive theoretic perspectives. Individual differences in susceptibility are great in the normal population and predictors are reviewed. Motion sickness susceptibility also varies dramatically between special groups of patients, including those with different types of vestibular disease and in migraineurs. Finally, the efficacy and relative advantages and disadvantages of various behavioral and pharmacologic countermeasures are evaluated.

Effects of transcutaneous electrical nerve stimulation and aspirin on late somatosensory evoked potentials in normal subjects.

The effects on late somatosensory evoked potentials (SEPs) of transcutaneous nerve stimulation (TENS) and aspirin (600 mg), compared with placebo, were studied in 32 young, healthy male and female volunteers. SEPs were produced by electrical stimulation of the median nerve at moderate, non-painful, intensities. There was a reduction in the peak-to-peak amplitude of the late components N1P2 (N1 latency: 100-160 msec; P2 latency: 160-260 msec) of the SEP in all groups over time. TENS but not aspirin produced further significant changes compared with placebo, including a fall in N1P2 amplitude, an increase in N1 latency, and a decrease in the total excursion of the SEP between 25 and 450 msec after stimulus onset.

Motion sickness susceptibility questionnaire revised and its relationship to other forms of sickness.

The Reason and Brand Motion Sickness Susceptibility Questionnaire (MSSQ) has remained unchanged for a quarter of a century. The primary aims of this investigation were to improve the design of the MSSQ, simplify scoring, produce new adult reference norms, and analyse motion validity data. We also considered the relationship of sickness from other nonmotion causes to the MSSQ. Norms and percentiles for a sample of 148 subjects were almost identical to the original version of this instrument. Reliability of the whole scale gave a Cronbach's standardised item alpha of 0.86, the correlation between Part A (child) and Part B (adult) was r = 0.65 (p < 0.001), and test-retest reliability may be assumed to be better than 0.8. Predictive validity of the MSSQ for motion sickness tolerance using laboratory motion devices averaged r = 0.45. Correlation between MSSQ and other sources of nausea and vomiting in the last 12 months, excluding motion sickness itself, was r = 0.3 (p < 0.001), migraine was the most important contributor to this relationship. In patients (n = 101) undergoing chemotherapy, there were significant correlations between MSSQ and chemotherapy-induced nausea and vomiting. Migraine also appeared as a predictor of chemotherapy-induced sickness. It was concluded that the revised MSSQ can be used as a direct replacement of the original version. The relationship between motion sickness susceptibility and other causes of sickness, including migraine and chemotherapy, points to the involvement of the vestibular system in the response to nonmotion emetogenic stimuli. Alternatively, this relationship may reflect individual differences in excitability of the postulated final common emetic pathway.

Seasonality, social zeitgebers and mood variability in entrainment of mood. Implications for seasonal affective disorder.

BACKGROUND: Seasonal variations in mood (seasonality) appear to be entrained to light, a physical zeitgeber. We hypothesised that people high in seasonality may be responsive to a range of zeitgebers, because of greater mood variability. We investigated whether the moods of people high in seasonality were more strongly entrained to the calendar week, a social zeitgeber, and whether any such effect was dependent on variability of mood. METHODS: 53 participants (14 male, 39 female; overall mean age=30) completed a daily mood report, over 56 consecutive days. Participants also completed the Seasonality Score Index (SSI) of the Seasonal Pattern Assessment Questionnaire. Each participant's time series of daily mood was analysed by spectral analysis to quantify the strength of their weekly mood cycle. RESULTS: Participants with high SSI scores (> or =11) had significantly stronger weekly mood cycles than those with low SSI scores (<11), and significantly greater variability in mood. Covarying for mood variability reduced the difference between high and low SSI groups in mean strength of weekly mood cycle to non-significance. LIMITATIONS: The time series of moods obtained was relatively short, and moods among high seasonal participants may have been affected by seasonal weather variability. CONCLUSIONS: People high in seasonality appear to be more responsive to external zeitgebers, and this could be linked to their greater variability in mood. The integration of research on mood variability with research on SAD appears to be warranted.

Time-course of effects of oral cinnarizine and hyoscine on task performance.

Investigations into antimotion sickness drugs fall into two main categories: efficacy ('benefits') and side-effects ('costs'). This study was of the second type. Oral cinnarizine (30 mg: normal dose; and 75 mg: 2.5 x normal dose) and placebo, were investigated using a battery of automated mental, motor, physiological and other tests in twelve young healthy male volunteers. The higher cinnarizine dose level was chosen to exaggerate effects and make it easier to track them. Oral hyoscine (1.2 mg: 2 x normal dose) was employed as a positive internal control. Side-effects were almost exclusively due to hyoscine whereas cinnarizine was almost free of significant effects even at the higher dose of 75 mg. Hyoscine impaired performance 1-3 hours postdrug, whereas the effects of cinnarizine occurred approximately 5-7 hours postdrug. This paralleled the slower time-course for the protective action of cinnarizine against motion sickness noted in earlier studies. These results, taken in conjunction with previous trials, suggest that oral cinnarizine would seem less likely than hyoscine to produce unwanted decrements in performance.

Effects of acupuncture and transcutaneous electrical nerve stimulation on cold-induced pain in normal subjects.

The effects of acupuncture, transcutaneous electrical nerve stimulation (TENS) at high (100 Hz) and low (8 Hz) frequency and placebo on pain induced by cold immersion of the hand were studied in 46 young healthy male and female volunteers. Acupuncture produced significant elevations of pain threshold, while 100 Hz TENS or placebo had no effect. Eight Hertz TENS produced elevation of pain threshold with significant variation in response between individuals. There was some evidence that the L scale score of the Eysenck Personality Questionnaire predicted analgesic outcome for 8 Hz TENS. No significant relationship was found between baseline pain threshold or tolerance and personality variables.

Effects of cigarette smoking on resting EEG, visual evoked potentials and photic driving.

The effects of smoking a cigarette (1.3 mg nicotine delivery) versus sham smoking were studied using EEG, visual evoked potentials (VEP), photic driving (PD) and heart rate (HR) in thirty young healthy male and female habitual cigarette smokers. Heart rate (HR) and exhaled carbon monoxide (CO) level were significantly increased by real as opposed to sham smoking. Real versus sham smoking significantly increased relative power in the beta bands, reduced alpha and theta activity to a small but significant extent, but had no effect on delta activity. Dominant EEG alpha frequency was significantly increased by real as opposed to sham smoking. Smoking produced no significant mean change in PD or VEP. However, correlational analysis indicated that variables such as basal CO level, residual butt filter nicotine, basal electrocortical response level and personality, predicted to varying degrees the magnitude and direction of the effect of smoking on VEP, PD and EEG.

Objective and subjective time courses of recovery from motion sickness assessed by repeated motion challenges.

The aim of this study was to determine whether the time course of recovery of tolerance, as assessed objectively by rechallenge with motion, paralleled the subjective recovery from motion sickness. Subjects (n = 20) were exposed to 5 pairs of nauseogenic motion challenges in which the time interval between the end of the first and the start of the second of each pair ranged from 15 min to 2 h. The cross-coupled motion challenge had an incrementing profile of rotational velocity from 4 degrees to 92 degrees.s-1 in steps of 4 degrees.s-1 every 30 s, with 8 head movements per 30 s, of approximately 45 degrees, and was continued to the point of moderate nausea. Objective loss of tolerance decreased from 15 min to 60 min after the first challenge, but increased again at 2 h. By contrast, most individuals reported subjective recovery by 15 min to 30 min. It was concluded that there is an underlying effect of motion sickness that sensitizes the response to subsequent motion for a period of at least 2 h. This underlying objective effect can occur in the absence of subjective symptoms, has a slower time course than the subjective recovery from symptoms, and appears to be non-monotonic.

Phasic skin conductance activity and motion sickness.

Sweating is commonly associated with motion sickness. Previous studies have attempted to relate sweating or the associated electrodermal activity to the degree of motion sickness symptoms. This study was aimed at improving methodology by study of 1) recording site--palmar finger versus forehead; and 2) signal analysis--tonic skin conductance level (SCL) versus phasic skin conductance responses (SCRs). Eleven subjects were exposed to a cross-coupled motion challenge, produced by repeated head movements (16 per minute) during rotation around the Earth vertical axis in which rotational velocity was incremented on a staircase profile from 3 degrees to 99 degrees.s-1 to an end point of moderate nausea. Six subjects underwent additional control conditions of rotation only and head movements only. A group of 12 subjects underwent sessions of vertical and horizontal sinusoidal linear motion through the head z-axis at 0.3 Hz, 1.8 ms-2 rms. Sweating responses were recorded in a further three subjects by mass spectrometry for water vapor from the skin using a dry N2 gas flow method. Phasic skin conductance activity at the forehead site provided the best correlate of motion sickness onset and recovery. Other combinations of signal analysis or recording site were less useful.

Perceptual scaling of whole-body low frequency linear oscillatory motion.

Evidence that Z-axis oscillation in the Earth-vertical plane is more provocative of motion sickness than the equivalent imposed oscillation acting in the Earth-horizontal raises the possibility that horizontal oscillation is perceived as less intense than equivalent vertical oscillation. In Experiment 1, subjects (n = 8) were oscillated through their head Z-axis in both the Earth-vertical and horizontal planes. In Experiment 2, another group (n = 10) were oscillated through their head Y-axis in the Earth-horizontal. Stimuli were 5 cycles of motion at 0.3 Hz ranging in 3.5 dB intervals from 0.19 to 2.15 m.s-2 (Expt. 1) and from 0.1 to 3.98 m.s-2 (Expt. 2). Perceptual scaling of intensity against acceleration was similar irrespective of direction of oscillation in the Earth-plane or head-body axis. Displacement tended to be overestimated, this being most marked for the lower acceleration levels in the horizontal condition. Results supported the notion that Stevens' Power Law exponents decrease as a function of increasing stimulus range. Differences in perception of oscillation intensity and displacement do not seem to explain the markedly greater nauseogenic potential of vertical oscillation.

Psychometric evaluation of divers performing a series of heliox non-saturation dives.

Psychometric performance of 12 divers was evaluated throughout a series of 60-72-m in-water heliox non-saturation ('bounce') dives using a repeated-measures, within-subject design. Assessments were made onboard a dive tender, using a portable computerized battery within 30 min of the diver leaving the water, 2 h later, and on rest days. No significant decrement in performance was demonstrated either post-dive or throughout the series. Ten controls showed no alteration in performance due to environmental factors such as ship motion. The consistency of the results confirmed the suitability of this system for monitoring cognitive function during a series of potentially hazardous dives.

Effect of sickness severity on habituation to repeated motion challenges in aircrew referred for airsickness treatment.

The aim of this study was to determine whether varying the predetermined malaise level at which provocative motion challenges were stopped would affect the habituation rate. At the rate of 2 per day, 21 motion challenges were delivered, stopping either at initial symptoms or at moderate nausea, on a cross-over design randomized between subjects (n = 20). The cross-coupled motion challenge had an incrementing profile of rotational velocity from 2-90 degrees.s-1 in steps of 2 degrees.s-1 every 30 s, with 8 head movements per 30 s, of approximately 45 degrees. The number of head movements tolerated before the onset of nausea increased over the 21 challenges, but the effects of the treatment variation on habituation were not significant. The number of motion challenges, rather than the severity of malaise level achieved, was the more important factor determining habituation.

Effect of frequency of horizontal linear oscillation on motion sickness and somatogravic illusion.

BACKGROUND: Low frequency linear (translational) oscillation is an important stimulus in provoking motion sickness in a variety of modes of transport. HYPOTHESIS: Lower frequencies of horizontal linear oscillation would be more nauseogenic. The somatogravic illusion (SGI) would be affected by frequency. METHODS: Subjects (n = 12) were exposed to horizontal sinusoidal motion (3.6 m.s-2 peak) at three different frequencies (0.205 Hz, 0.350 Hz, 0.500 Hz) at one week intervals, with order randomized between subjects. Subjects were seated in the upright position, with motion through the X head body axis. RESULTS: The mean (+/- S.D.) motion exposure time required to produce moderate nausea decreased significantly (p < 0.01) towards the lower frequency: 24.4 +/- 19.3 min. at 0.500 Hz, 12.0 +/- 9.5 min. at 0.350 Hz, 7.8 +/- 6.2 min. at 0.205 Hz. The linear fit of time (t) to nausea with frequency was -7.4 dB/octave. This was equivalent to a -3.7 dB/octave decrease of nauseogenic potential with increasing frequency, if t1/2 were to be used as in the standard "motion dose" models. The SGI was reported by 5/12 subjects (mean illusory tilting angles 16.2 degrees forward, 14.3 degrees back) but there was no relationship between SGI and motion frequency or motion sickness. CONCLUSIONS: Horizontal motion with subjects seated upright was more nauseogenic than would be predicted by mathematical models based on vertical oscillation, and the relationship of frequency to nauseogenicity for horizontal motion was significantly less steep than that previously reported for vertical motion.

A comparison of the nauseogenic potential of low-frequency vertical versus horizontal linear oscillation.

The aim of this study was to compare the nauseogenic potential of low-frequency linear motion in the Earth-vertical versus the Earth-horizontal plane, delivered through the same Z-axis of the head and body. Twelve subjects were challenged with linear motion (0.3 Hz, 1.8 ms-2 rms) through the same head and body Z-axis in the Earth-vertical (sitting upright) versus horizontal (lying on the back), while either performing a continuous visual search task or with their eyes closed. Each subject completed the four conditions on a Latin square design with sessions spaced 1 week apart at the same time of day. Vertical motion was clearly more provocative than horizontal motion, and nauseogenicity of motion was exacerbated by a visual search task. Motion sickness impaired performance of the search task. Motion Sickness Susceptibility Questionnaire (MSSQ) scores correlated with individual susceptibility to the motion challenge. Mean sickness ratings for vertical motion showed some correspondence with those predicted by mathematical models of motion sickness dose response relationships.

Scopolamine blood levels following buccal versus ingested tablets.

Speed of absorption and elimination of an antimotion sickness drug sets limits on the protection afforded. The aim of this experiment was to determine whether a well proven antimotion sickness drug--scopolamine (hyoscine)--could be absorbed more rapidly from buccal tablets than from the standard issue ingested tablets. Plasma scopolamine levels were measured using a radioreceptor assay of repeated blood samples from 10 volunteers, each of whom took buccal and standard ingested tablets (both 0.6 mg scopolamine hydrobromide) on two different occasions, and from a further 8 volunteers following ingestion of a pharmacy-prepared scopolamine capsule (0.6 mg scopolamine hydrobromide). There was no statistically significant speed advantage for the buccal tablet (mean time to peak levels approx 50 min). Individual variation in the speed of scopolamine absorption and rate of elimination (mean half-life approx 170 min) was great. This may account for failure of motion sickness protection in some individuals.

The effects of motion direction, body axis, and posture on motion sickness induced by low frequency linear oscillation.

BACKGROUND: A recent experiment demonstrated that low frequency linear oscillation through the Z-axis of the body was more nauseogenic when applied in the vertical direction, with subjects seated upright, than in the horizontal direction, with subjects supine. HYPOTHESIS: The nauseogenicity of low frequency linear oscillatory motion is dependent on direction of motion with respect to the gravity vector, orientation of body axis with respect to motion, and body posture. METHODS: The following conditions were compared: A) seated upright, with horizontal motion, X-axis; B) seated upright, with vertical motion, Z-axis; and C) supine, with vertical motion, X-axis. Sinusoidal motion at 0.35 Hz, 3.6 m.s-2 peak was used in all conditions. Two experiments were performed. In Experiment 1 subjects (n = 28) were exposed to conditions A and B. In Experiment 2 subjects (n = 12) were exposed to conditions A, B and C. RESULTS: Horizontal motion (condition A) was found to be twice as nauseogenic (p < 0.05 to p < 0.0001) as vertical motion (condition B), but there was no difference in nauseogenicity between upright and supine postures for vertical motion (condition B vs. C). Mean motion exposure times to achieve moderate nausea were: Experiment 1: A) 9.0 min.; B) 22.4 min.; Experiment 2: A) 15.3 min.; B) 27.1 min.; C) 22.5 min. CONCLUSIONS: These results, taken together with those of the previous experiment, suggest that upright vs. supine body posture and stimulation through X- vs. Z-axis, both enhance the nauseogenicity of low frequency linear oscillation, these effects are additive, but that motion direction with respect to the gravity vector (horizontal vs. vertical) is a less important factor.