Background: Migraine is a common disorder most typically presenting as headache and often associated with vertigo and motion sickness. It is a genetically complex condition with multiple genes ultimately contributing to the predisposition and development of this episodic neurological disorder. We identified a large American family of 29 individuals of which 17 members suffered from at least one of these disorders, migraine, vertigo, or motion sickness. Many of these individuals suffered from several simultaneously. We hypothesized that vertigo and motion sickness may involve genes that are independent to those directly contributing to migraine susceptibility. Methods: Genome-wide linkage analysis performed using 400 microsatellite repeat markers spaced at 10 cM throughout the genome. The members of this family were phenotyped for each condition, migraine, vertigo, and motion sickness and analyzed separately. Statistical analysis was performed using two-point and multipoint linkage analysis employing a number of models including autosomal recessive or dominant patterns of inheritance with high and low genetic penetrance. Results: We identified a novel locus for migraine, 9q13-q22 (maximum two-point logarithm of odds [LOD] score-2.51). In addition, there are suggestive LOD scores that localize to different chromosomes for each phenotype; vertigo (chromosome 18, LOD score of 1.82) and motion sickness (chromosome 4, LOD score of 2.09). Conclusions: Our analysis supports our hypothesis that the migraine-associated vertigo and motion sickness may involve distinct susceptibility genes.

Objectives: This is an evaluation of the efficacy of metoclopramide (MTCP) or diphenhydramine (DPH) to relieve symptoms of motion sickness in patients being transported via ambulance in a mountainous setting.

Methods: This is a prospective, randomized, double-blinded, placebo-controlled study of patients transported by ambulance in the Sierra Nevada mountains of Fresno County. Consenting patients who met the inclusion criteria were asked to rate their motion sickness every five minutes using a visual analog scale (VAS) during transport. If motion sickness occurred, they were randomized to receive MTCP (20 mg IV), DPH (50 mg IV), or placebo (normal saline), and remaining symptoms were recorded every five minutes. If signs and symptoms of motion sickness persisted after 15 minutes, a rescue dose of MTCP was offered.

Results: Twenty-six patients were enrolled in the study. Twenty-two (84.6%) developed motion sickness and were randomized to MTCP, DPH, or placebo. Eight patients received MTCP, seven received DPH, and seven received placebo. The MTCP group showed a statistically significant decrease in the mean VAS score at 15 minutes compared to the DPH and placebo groups. There was no significant difference in the decrease in VAS score between the placebo and the DPH group. Twelve out of 22 patients requested a rescue dose of MTCP after 15 minutes. At 25 minutes, there was no significant difference in the VAS score between the three groups.

Conclusion: During ambulance transport in a mountainous setting, the administration of MTCP is superior to both DPH and placebo in the treatment of motion sickness. Diphenhydramine is not superior to placebo.

The P50 potential is a midlatency auditory evoked response which is sleep state-dependent, habituates rapidly and is blocked by the muscarinic cholinergic antagonist scopolamine. It is thought to be generated, at least in part, by ascending projections of the reticular activating system. The amplitude of the P50 potential can be used as a measure of level of arousal, while the degree of habituation to repetitive stimulation can be used as a measure of sensory gating. We studied these processes in three conditions which show sleep-wake cycle dysregulation and attentional disturbance, but differ greatly in their etiology, depression, Huntington’s disease and rotation-induced motion sickness. Subjects with depression and rotation-induced motion sickness showed significant decreases in the habituation of the second of paired evoked responses, while Huntington’s disease subjects showed decreased amplitude as well as decreases in the habituation of the second P50 potential. This waveform may represent the manifestation of pre-attentional processes, and may become a useful measure for monitoring the severity, progression and/or remission of disorders which affect these processes.

We evaluated the effects of two laboratory stressors (speech preparation and isometric handgrip) on gastric myoelectrical and autonomic cardiac activity, and the extent to which autonomic responses to these stressors and somatization predict reports of motion sickness during exposure to a rotating optokinetic drum. Both stressors prompted a decrease in preejection period (PEP) and respiratory sinus arrhythmia (RSA), and an increase in a dysrhythmic pattern of gastric myoelectrical activity, termed gastric tachyarrhythmia. Stressor-induced decreases in RSA and higher somatization scores predicted increased reports of motion sickness during drum rotation. These results demonstrate that laboratory stressors concurrently affect gastric myoelectrical activity and autonomic control of the heart, and that stressor-induced decreases in RSA and higher levels of somatization predict motion sickness susceptibility.

The post-operative anti-emetic efficacy of 4 and 8 mg of ondansetron in adult patients with and without a previous history of motion sickness (PHMS) was assessed by meta-analysis. MEDLINE and EMBASE databases were searched for randomized placebo-controlled trials evaluating the anti-emetic effectiveness of ondansetron in a 24-h period. In the 49 studies found, a further selection was with respect to those studies that noted the patient's previous history of motion sickness. Twelve trials involving 2122 patients; 446 previous history of motion sickness(+)patients and 1676 previous history of motion sickness(−) patients met the selection criteria. The dose of 4 mg ondansetron was 71.5% more effective in previous history of motion sickness(+) than in previous history of motion sickness(−) patients. For the 8 mg dose, the odds ratios (95% CI) were: previous history of motion sickness(+)=3.11 (1.40–6.93) and previous history of motion sickness(−)=2.08 (1.35–3.21). The calculated number needed to treat was also more favourable in previous history of motion sickness(+) patients for both doses of ondansetron,demonstrating a higher effectiveness in this subgroup of patients.

Low frequency oscillatory motion (0·05 to 0·5 Hz) experienced in ships and road vehicles is known to cause motion sickness in humans and some predictive models are available. There have been very few studies of the incidence of motion sickness in pigs and none which has attempted to identify the frequencies of motion of transporters which are likely to be implicated. In this study, the vibration and motion characteristics of a commercial pig transporter were measured while seven individually penned 40-kg pigs were transported for short (100 min) journeys and 80-kg pigs penned in groups of 12 or 13 were transported for longer (4·5 h) journeys. Direct behavioural observations were made of individual pigs for symptoms of travel sickness (sniffing, foaming at the mouth, chomping, and retching or vomiting). A comparison was then made between the incidence of travel sickness in pigs and that expected in humans given the measured vehicle vibration characteristics. The low frequencies of motion measured on the transporter (0·01 to 0·2 Hz) were well within the range implicated in human motion sickness with considerable power in the longitudinal and lateral axes but little in the vertical axis. On both short and long journeys pigs exhibited symptoms of travel sickness. The likely incidence of travel sickness on the short journeys predicted by the human model was 24 to 31% which corresponds to approximately two of the seven 40-kg pigs becoming travel sick. The numbers observed were generally lower than this although the same pigs were transported twice each day for 2 days and this may have therefore reflected the effects of habituation. The incidence of travel sickness on the long journeys predicted by the human model was 34%. During these journeys which involved four groups of 80-kg pigs which were not repeatedly transported, 26% of pigs vomited or retched (13 out of 50) while 50% showed advanced symptoms of foaming and chomping. These results are not inconsistent with the human model which should form the basis offurther research.

Seventy-nine pairs of same-sex twins were examined at the age of three years at a municipal clinic and their mothers were interviewed to assess the twins' current and past behaviours. The zygosity was determined after the interview by fingerprints and/or bloodtyping in the majority of cases. The following significant differences in concordance between monozygotic and dizygotic twins were found: 1) fear of strangers during observation at the clinic; 2) marked fear of strangers in the first year of life; 3) whether or not the child was startled by sudden noises during infancy; 4) whether or not the child was able to sleep alone at three years without a parent sitting nearby; 5) susceptibility to motion sickness; 6) nocturnal enuresis; 7) short attention span or restlessness during the test.

A sample of 119 pairs of twins, together with their 87 siblings and 100 pairs of parents, were examined with respect to susceptibility to the motion sickness syndrome. Children were found to exhibit resistance to the syndrome below two years of age, and females were more susceptible than males. The incidence appeared to be highest in families with both parents affected. Concordance rates were much higher in MZ (100%) than in DZ pairs (27.6%). Genetic effects are likely, but cultural factors should not be ignored.