Visual vertigo and motion sickness is different between persistent postural-perceptual dizziness and vestibular migraine.

INTRODUCTION: Persistent postural-perceptual dizziness (PPPD) and vestibular migraine (VM) share symptoms of visual vertigo and motion sickness that can be confusing for clinicians to distinguish. We compare the severity of these symptoms and dynamic subjective visual vertical (dSVV) in these two common vestibular conditions. METHOD: Twenty-nine patients with PPPD, 37 with VM, and 29 controls were surveyed for subjective symptoms using the visual vertigo analogue scale (VVAS) and motion sickness susceptibility questionnaire during childhood (MSA) and the past 10 years (MSB). dSVV is a measure of visual dependence measures perception of verticality against a rotating background (5 deg./s). RESULTS: VVAS revealed contextual differences for dizziness between those with PPPD and VM. Ratings of visual vertigo were most severe in PPPD, less in VM, and mild in controls (VVAS PPPD 27.1, VM 11.2, control 4.6, p < 0.001). MSA was more severe in VM than in PPPD or control (12.8 vs 7.6 vs 8.5, p = 0.01). MSB was more severe in VM than controls (MSB score 12.9 VS 8.1 p = 0.009) but was not different than PPPD (MSB score 10.0, p = 0.10). dSVV alignment was similar among the three groups (p = 0.83). Both VM and PPPD groups had greater simulator sickness than controls after completing the dSVV. CONCLUSIONS: Patients with PPPD report more visual vertigo than those with VM, but a history of motion sickness as a child is more common in VM. Additionally, the environmental context that induces visual vertigo is different between PPPD and VM.

One simple question detects motion sickness susceptibility in migraine patients.

OBJECTIVE: To find out if motion sickness susceptibility (MSS) of vestibular migraine (VM) patients and migraine only (MO) patients can be reliably detected with a single simple question: "Can you read while travelling in a car without getting motion sick?". METHOD: Ninety-two definite VM and 58 MO patients and 74 healthy control (HC) subjects were asked about their MSS and about being able to read while riding in a car without becoming motion sick. A Motion Sickness Susceptibility Questionnaire (MSSQ-Short) including childhood (MSA), adulthood (MSB) and total (MST) parts was also administered to all participants. ROC curves of MSSQ-Short were prepared for "not being able to read in a car" as the gold standard. RESULTS: Mean MSA scores were significantly higher in both VM and MO patients than in HCs (p < 0.001), but their scores were not significantly different (p = 0.171). Mean MSB and MST scores were significantly higher in VM than in MO patients (p < 0.001) and both VM and MO patients had significantly higher scores than HCs (p < 0.001). MSA scores were significantly higher than MSB scores in MO patients (p < 0.001). All sections of the questionnaire were associated with high area-under-curve values for MSS detected by the question about being able to read in a car without becoming motion sick. CONCLUSION: We propose that all migraine patients could have the same level of MSS in childhood but MO patients are able to compensate over years, but VM patients are not. A quick way to determine MSS is to ask about the ability to read without becoming motion sickness while riding a car.

Calcitonin gene-related peptide receptor antagonism reduces motion sickness indicators in mouse migraine models.

BACKGROUND: Migraine and vestibular migraine are disorders associated with a heightened motion sensitivity that provoke symptoms of motion-induced nausea and motion sickness. VM affects ∼3% of adults in the USA and affects three-fold more women than men. Triptans (selective serotonin receptor agonists) relieve migraine pain but lack efficacy for vertigo. Murine models of photophobia and allodynia have used injections of calcitonin gene-related peptide (CGRP) or other migraine triggers, such as sodium nitroprusside (SNP), to induce migraine sensitivities in mice to touch and light. Yet, there is limited research on whether these triggers affect motion-induced nausea in mice, and whether migraine blockers can reduce these migraine symptoms. We hypothesized that systemic delivery of CGRP or SNP will increase motion sickness susceptibility and motion-induced nausea in mouse models, and that migraine blockers can block these changes induced by systemically delivered CGRP or SNP. METHODS: We investigated two measures of motion sickness assessment [motion sickness index (MSI) scoring and motion-induced thermoregulation] after intraperitoneal injections of either CGRP or SNP in C57BL/6J mice. The drugs olcegepant, sumatriptan and rizatriptan were used to assess the efficacy of migraine blockers. RESULTS: MSI measures were confounded by CGRP's effect on gastric distress. However, analysis of tail vasodilatations as a surrogate for motion-induced nausea was robust for both migraine triggers. Only olcegepant treatment rescued tail vasodilatations. CONCLUSIONS: These preclinical findings support the use of small molecule CGRP receptor antagonists for the treatment of motion-induced nausea of migraine, and show that triptan therapeutics are ineffective against motion-induced nausea of migraine.Trial Registration: Not Applicable.

Postdischarge Nausea and Vomiting and Co-occurring Symptoms in Women Following Breast Cancer Surgery.

PURPOSE: The purpose of this study was to investigate the influence of potential co-occurring symptoms, including fatigue, sleep disturbance, anxiety, depressive symptoms, and pain, on the incidence of postdischarge nausea (PDN) measured two days following discharge to home after surgery for breast cancer. DESIGN: This study used a prospective, cross-sectional, observational design. METHODS: The sample was 334 women aged 27 to 88 years of age. Demographic data were collected from the patient and the medical record before surgery. Symptom data were collected 48 hours following surgery using the Patient Reported Outcome Measurement System (PROMIS) and numerical nausea and pain scales. FINDINGS: Eighty-five (25.4%) of study participants reported some nausea two days after discharge. Study participants who experienced PDN frequently described that it occurred after they left the hospital to drive home following their surgery. Unadjusted odds ratios showed the presence of co-occurring symptoms of anxiety, fatigue, sleep disturbance, and pain were all significantly associated with the presence of nausea 48 hours following surgery. Other significant factors associated with (PDN) were history of motion sickness, history of pregnancy-induced nausea, use of opioids, and type of surgery. CONCLUSIONS: Same-day surgery nurses providing postoperative education for women following surgery for breast cancer should explain to patients that nausea may occur after they are discharged, especially those with known motion sickness. In addition, patients should be informed that other symptoms, especially fatigue, sleep disturbance, and anxiety, may co-occur.

Vestibular migraine, demographic and clinical features of 415 patients: A multicenter study.

OBJECTIVE: To evaluate demographic and clinical features of vestibular migraine (VM) patients METHODS: Four hundred fifteen patients with VM were evaluated by using a structured questionnaire in addition to clinical examination. RESULTS: The mean age of headache and vertigo onset was 25 years and 39 years, respectively. In 12.3%, benign paroxysmal positional vertigo (BPPV) was detected during the interictal period. Ten percent had hearing loss on audiometry, in 8.7% it was one-sided low-frequency sensory-neural hearing loss below 2000 Hz and the history was typical for Meniere's disease (MD) in addition to VM. Tinnitus was present in 94.4%, aural fullness in 83.4%, nausea in 72.2% and vomiting in 30.5% of patients with VM/MD. The prevalence of these symptoms was higher in patients with VM/MD than in pure VM. Median attack severity determined by visual analog scale measured in centimeters from 0 to 10 was 8 for headache and 7 for vertigo for the whole group. Severe headache was significantly correlated with age of ≤ 43 years (OR: 6.831, 95% CI: [4.10-11.63]; p < 0.001) and severe vertigo was significantly correlated with age ≥ 41 years (OR: 7.073, 95% CI: [4.55-10.98]; p < 0.001). Motion sickness was revealed from past medical history in 51.8%. Family history of migraine was present in 72.5% and the age of onset of both migraine headaches (p = 0.008) and vertigo attacks (p = 0.004) was lower in these patients. CONCLUSION: Younger patients suffered more severe headache attacks whereas vertigo attack severity was higher in the elderly. BPPV and MD were commonly associated with VM and VM/MD was accompanied by aural and autonomic features more frequently than pure VM. Previous history of motion sickness was detected in more than half of the whole group. Family history of migraine was associated with younger onset of migraine headaches and vertigo attacks.

Clinical characteristics of definite vestibular migraine diagnosed according to criteria jointly formulated by the Bárány Society and the International Headache Society.

OBJECTIVE: To investigate the clinical features of patients with definite vestibular migraine (dVM). METHODS: A total of 91 patients with vestibular symptoms accompanied by migraines/migraine-like symptoms were enrolled and diagnosed according to the criteria of the Bárány Society and the International Headache Society. Baseline data were collected. Videonystagmography and immune-related laboratory tests were performed. RESULTS: Among the 91 patients, 62 (68.1%) had dVM (11 men, 51 women). Among dVM patients, migraine occurred earlier than vestibular symptoms in 42 (67.7%) patients. Spontaneous vertigo occurred in 41 (66.1%) patients. Induced vertigo occurred in 21 (33.9%) patients. Motion sickness occurred in 33 (53.2%) patients. Central oculomotor dysfunction was observed in 11 (17.7%) patients. Caloric test revealed unilateral horizontal semicircular canal dysfunction in 12 (19.4%) patients. Severe intolerance during the test occurred in 44 (71.0%) patients with dVM. 12 (19.4%) patients showed abnormal immune-related indicators. CONCLUSION: dVM is more common in women. The onset of migraine precedes that of vestibular symptoms, which are often accompanied by photophobia and phonophobia. Motion sickness and severe caloric test intolerance can contribute to the diagnosis of dVM. Immunological indicators are abnormal in some patients with dVM, dVM may be secondary or an accompanying disorder, but the causal relationship needs further investigation. LEVEL OF EVIDENCE: IV.

Sopite Syndrome Identified in a Student Naval Aviator.

BACKGROUND: Sopite syndrome is a poorly understood symptom complex characterized by drowsiness and lethargy relating to motion sickness. Though often occurring in conjunction with the classic symptomatology of motion sickness, the literature suggests that sopite syndrome is a separate entity that may occur independently of the feelings of nausea characteristic of traditional motion sickness. Additionally, the syndrome can last long after symptoms of nausea have subsided and can be debilitating to some patients. Due to the frequent concomitance of sopite syndrome and the classic symptoms of motion sickness, the syndrome may frequently go unidentified and there is a paucity of data recording its exact incidence in the available literature. CASE REPORT: In this study, we report a case of sopite syndrome identified in a 23-yr-old student naval aviator who was ultimately unable to overcome his symptoms and adapt to the dynamic environment of flight. DISCUSSION: This process is particularly relevant to student aviators and others involved in transportation settings where the existence of even mild performance challenges may create the potential for operational hazards. Because the training of aviators and flight officers is historically one of the most expensive investments undertaken by the Department of the Navy each year, documenting unique manifestations of this common problem and addressing them early in the training pipeline may help reduce the time and financial burden associated with student naval aviator attrition in the later stages of training.Gemender MS, Sholes PC, Haight SP. Sopite syndrome identified in a student naval aviator. Aerosp Med Hum Perform. 2018; 89(9):848-850.

Effects of visual flow direction on signs and symptoms of cybersickness.

Our objective was to assess the influence of visual flow direction on physiological changes and symptoms elicited by cybersickness. Twelve healthy subjects (6 male and 6 female) were exposed to a 15-min virtual ride on a rollercoaster on two different days in a counterbalanced manner, such half of participants were facing forward during the first ride while another half was facing backward. Forehead skin conductance, heart rate and HRV parameters (SDRR, RMSSD) were collected as objective measures; subjective symptoms were assessed with the Motion Sickness Assessment Questioner immediately after exposure. We found that while nausea ratings at which participants terminated the experiment did not differ between forward/backward rides, the mean ride tolerance time was significantly longer during reverse ride compared to forward ride (6.1±0.4 vs 5.0±0.5 min, respectively, p = 0.01, η2 = 0.45). Analysis of HRV parameters revealed significant reduction in both RMSSD (p = 0.02, t = 2.62, η2 = 0.43) and SDRR (p = 0.01, t = 2.90, η2 = 0.45) in the forward ride; no such changes were found in the backward ride. We also found that amplitude of phasic changes in forehead skin conductance increased significantly in both ride directions. This increase however was significantly lower (p<0.05) in backward ride when compared to the forward ride. When assessed immediately post-ride, subjects reported significantly lower (p = 0.04) subjective symptom intensity after the reverse ride compared to the forward ride. We conclude that the direction of visual flow has a significant effect on the symptoms reported by the subjects and on the physiological changes during cybersickness.

Review of Issues and Challenges of Practicing Emergency Medicine Above 30,000-Feet Altitude: 2 Anonymized Cases.

We present 2 anonymized cases to identify issues and challenges associated with long-haul in-flight medical emergencies. The first case involved a middle-aged man with a history of carditis on a systemic steroid who developed vomiting and rigor. Four physicians, including a pediatric intensivist, responded to the emergency call. In the second case, a pediatric trainee who was the only onboard medical personnel was summoned for help when a middle-aged man developed acute shortness of breath while traveling on a commercial flight. The cases illustrate the challenges and issues on the critical decisions of diagnosis, resuscitation, and whether the flight had to be returned or diverted. An extensive literature search is made to summarize the evidence available for these decisions and challenges. Epidemiology and outcomes associated with these medical emergencies are reviewed. In-flight medical emergencies are not rare. Physicians of all disciplines should be prepared to deal with these emergencies and make sensible decisions when equipment and resources are likely to be limited.

Alpha-9 nicotinic acetylcholine receptors mediate hypothermic responses elicited by provocative motion in mice.

Hypothermic responses accompany motion sickness in humans and can be elicited by provocative motion in rats. We aimed to determine the potential role in these responses of the efferent cholinergic vestibular innervation. To this end, we used knockout (KO) mice lacking α9 cholinoreceptor subunit predominantly expressed in the vestibular hair cells and CBA strain as a wild-type (WT) control. In WT mice, circular horizontal motion (1Hz, 4cm radius, 20min) caused rapid and dramatic falls in core body temperature and surface head temperature associated with a transient rise in the tail temperature; these responses were substantially attenuated in KO mice; changes were (WT vs. KO): for the core body temperature-5.2±0.3 vs. -2.9±0.3°C; for the head skin temperature-3.3±0.2 vs. -1.7±0.2°C; for the tail skin temperature+3.9±1.1 vs+1.1±1.2°C. There was a close correlation in the time course of cooling the body and the surface of the head. KO mice also required 25% more time to complete a balance test. We conclude: i) that the integrity of cholinergic efferent vestibular system is essential for the full expression of motion-induced hypothermia in mice, and that the role of this system is likely facilitatory; ii) that the system is involvement in control of balance, but the involvement is not major; iii) that in mice, motion-induced body cooling is mediated via increased heat flow through vasodilated tail vasculature and (likely) via reduced thermogenesis. Our results support the idea that hypothermia is a biological correlate of a nausea-like state in animals.

An Analysis of Behavioral and Genetic Risk Factors for Chemotherapy-Induced Nausea and Vomiting in Japanese Subjects.

There are individual differences in the frequency of chemotherapy-induced nausea and vomiting (CINV) in cancer patients. We investigated the individual variability in susceptibility to CINV with focus on both behavioral factors and genetic factors in Japanese cancer patients. We performed a prospective study to investigate the association between patient attributes (backgrounds and habits as well as gene polymorphisms) and anorexia, nausea, or vomiting in 55 Japanese cancer patients undergoing chemotherapy at Nagoya University Hospital. We found that gender (female), use of non-steroidal anti-inflammatory drugs, susceptibility to motion sickness, and anxiety were associated with the frequency of CINV. Gene polymorphisms of rs1076560 (dopamine D2 receptor gene), rs6766410 (serotonin 5-HT3C receptor gene) and rs4680 (catechol-O-methyltransferase gene) were also associated. Our data suggest that these attributes may thus be risk factors for CINV. Our results provide novel information that can be used to predict the incidence of CINV in Japanese patients undergoing chemotherapy; this can help provide a substantial improvement in supportive care for patients with different types of cancer.

2000 CDC or 2007 WHO – What is the most sensitive anthropometric reference for determination of overweight and cardio-metabolic risk in children aged 6–10 years?

Objective To compare the two anthropometric standards for screening of overweight and cardio-metabolic risk in 6–10-year-old children.Subjects and methods This cross-sectional study included 175 subjects attending the Referral Center for the Treatment of Children and Adolescents in Campos, Rio de Janeiro. They were classified according to CDC and WHO BMI z scores as normal-weight (z-score > –1 and < 1), overweight (z-score ≥ 1 and < 2) or obese (z-score ≥ 2). Sensitivities and specificities in predicting systolic (SBP), diastolic (DBP) blood pressure and homeostatic model assessment insulin resistance index (HOMA-IR) alterations were calculated.Results There was a major difference in 11 children who rated overweight by the CDC but were reclassified as obese by the WHO. Their mean z-scores for SBP (1.71 ± 1.54), DBP (2.64 ± 1.83) and HOMA-IR (1.84 ± 0.98) were higher than those classified as overweight by both references (SBP = 0.49 ± 1.34, p < 0.023, DBP = 1.45 ± 0.97, p < 0.04 and HOMA = 1.24 ± 0.67, p < 0.04), but were similar to those classified as obese by both criteria (SBP = 1.25 ± 2.04, p = 0.60, DBP = 1.94 ± 1.19, p = 0.50 and HOMA = 2.09 ± 1.12, p = 0.76).Conclusion the 2007 WHO reference was the most sensitive in screening for overweight and alterations in blood pressure and HOMA-IR in 6–10-year-old children. Arch Endocrinol Metab. 2015;59(3):220-5.

Combining sudomotor nerve impulse estimation with fMRI to investigate the central sympathetic response to nausea.

The skin conductance (SC) signal is one of the most important non-invasive indirect measures of autonomic outflow. Several mathematical models have been proposed in the literature to characterize specific SC features. In this work, we present a method for the estimation of central control of sudomotor nerve impulse (SMI) function using SC. The method is based on a differential formulation decomposed into two first order differential equations. We validate our estimation framework by applying it on an experimental protocol where eleven motion sickness-prone subjects were exposed to a nauseogenic visual stimulus while SC and fMRI signals were recorded. Our results show an expected significant increase in the mean amplitude of SMI peaks during the highest reported nausea, as well as a decreasing trend during recovery, which was not evident for skin conductance level. Importantly, SMI/fMRI analysis found a negative association between SMI and fMRI signal in orbitofrontal, dorsolateral prefrontal, and posterior insula cortices, consistent with previous studies correlating brain fMRI and microneurographic signals.

Vertigo in childhood: a retrospective series of 100 children.

OBJECTIVE: Evaluation and management of vertigo in children vary between institutions and medical specialties. The aim of this study is to describe the characteristics of vertigo in children presenting to a pediatric neurology referral center and to investigate the relationship between vertigo and migraine. STUDY DESIGN: Patients <18 years old presenting with vertigo to Hacettepe University Ihsan Dogramaci Children's Hospital Neurology Unit between January 1996-January 2012 were included (n = 100). Data were obtained from patient files and phone interviews. RESULTS: Mean age was 7.5 years. The most common etiological groups were benign paroxysmal vertigo of childhood (BPVC) (39%), psychogenic vertigo (21%), epileptic vertigo (15%), and migraine-associated vertigo (MAV) (11%). BPVC was the most common diagnosis in children ≤5 years of age while psychogenic vertigo prevailed in children >5 years. Staring episodes characterized epileptic vertigo patients (p = 0.021) while headache was more often described by MAV patients (p < 0.001). Vertigo attacks >5 min were uncommon in BPVC patients compared to others (p = 0.013). Twenty percent of BPVC patients contacted through phone interviews were experiencing migraine type headaches that started at a median age of 7.5 years. An algorithm for evaluation of children with vertigo was formed based on data obtained from this study and the literature. When this algorithm was applied to 100 cases of this series, 88 (88%) were correctly diagnosed. CONCLUSION: While most vertigo cases in children can be diagnosed accurately by a detailed medical history, physical and neurological examination, a standard algorithm can help with the correct classification.

The effect of mild motion sickness and sopite syndrome on multitasking cognitive performance.

OBJECTIVE: In this study, we investigated the effects of mild motion sickness and sopite syndrome on multitasking cognitive performance. BACKGROUND: Despite knowledge on general motion sickness, little is known about the effect of motion sickness and sopite syndrome on multitasking cognitive performance. Specifically, there is a gap in existing knowledge in the gray area of mild motion sickness. METHOD: Fifty-one healthy individuals performed a multitasking battery. Three independent groups of participants were exposed to two experimental sessions. Two groups received motion only in the first or the second session, whereas the control group did not receive motion. Measurements of motion sickness, sopite syndrome, alertness, and performance were collected during the experiment RESULTS: Only during the second session, motion sickness and sopite syndrome had a significant negative association with cognitive performance. Significant performance differences between symptomatic and asymptomatic participants in the second session were identified in composite (9.43%), memory (31.7%), and arithmetic (14.7%) task scores. The results suggest that performance retention between sessions was not affected by mild motion sickness. CONCLUSION: Multitasking cognitive performance declined even when motion sickness and soporific symptoms were mild. The results also show an order effect. We postulate that the differential effect of session on the association between symptomatology and multitasking performance may be related to the attentional resources allocated to performing the multiple tasks. Results suggest an inverse relationship between motion sickness effects on performance and the cognitive effort focused on performing a task. APPLICATION: Even mild motion sickness has potential implications for multitasking operational performance.

Sopite syndrome: a revised definition.

In 1976, Graybiel and Knepton proposed the term "sopite syndrome" to describe a symptom complex centering on drowsiness and lethargy related to motion sickness. However, existing descriptions and definitions of sopite syndrome have limitations in fully conveying the appropriate information to the reader. Our objective is to propose a revised definition providing a more adequate conceptual framework for research. The proposed definition of sopite syndrome addresses the nonspecificity of soporific symptoms, the health state of the individuals, and the existence of a motion stimulus.

Thermoregulatory correlates of nausea in rats and musk shrews.

Nausea is a prominent symptom and major cause of complaint for patients receiving anticancer chemo- or radiation therapy. The arsenal of anti-nausea drugs is limited, and their efficacy is questionable. Currently, the development of new compounds with anti-nausea activity is hampered by the lack of physiological correlates of nausea. Physiological correlates are needed because common laboratory rodents lack the vomiting reflex. Furthermore, nausea does not always lead to vomiting. Here, we report the results of studies conducted in four research centers to investigate whether nausea is associated with any specific thermoregulatory symptoms. Two species were studied: the laboratory rat, which has no vomiting reflex, and the house musk shrew (Suncus murinus), which does have a vomiting reflex. In rats, motion sickness was induced by rotating them in their individual cages in the horizontal plane (0.75 Hz, 40 min) and confirmed by reduced food consumption at the onset of dark (active) phase. In 100% of rats tested at three centers, post-rotational sickness was associated with marked (~1.5°C) hypothermia, which was associated with a short-lasting tail-skin vasodilation (skin temperature increased by ~4°C). Pretreatment with ondansetron, a serotonin 5-HT3 receptor antagonist, which is used to treat nausea in patients in chemo- or radiation therapy, attenuated hypothermia by ~30%. In shrews, motion sickness was induced by a cyclical back-and-forth motion (4 cm, 1 Hz, 15 min) and confirmed by the presence of retching and vomiting. In this model, sickness was also accompanied by marked hypothermia (~2°C). Like in rats, the hypothermic response was preceded by transient tail-skin vasodilation. In conclusion, motion sickness is accompanied by hypothermia that involves both autonomic and thermoeffector mechanisms: tail-skin vasodilation and possibly reduction of the interscapular brown adipose tissue activity. These thermoregulatory symptoms may serve as physiological correlates of nausea.

Long-lasting adverse effects after short-term low-dose treatment with metoclopramide for vomiting.

Metoclopramide is commonly used to treat vomiting caused by seasickness and acute gastroenteritis on cruise ships and serious adverse effects have not been reported from use at sea. We report severe long-lasting adverse effects in a young female seafarer following short-term, low-dose use of metoclopramide. During rough seas a 25-year-old female musician on a cruise vessel presented with nausea and vomiting. She was given intramuscular metoclopramide 10 mg and diphenhydramine 25 mg. Vomiting stopped after the injections, but she felt tired, confused and dizzy. She then had been taking metoclopramide 5-10 mg a day, but stopped after a total per oral dose of 30 mg as she developed disturbing symptoms that she related to the medication, including dizziness, anxiety, fatigue, depression and involuntary movements (twitches, jerks, ticks, and tremors of the eyelids, tongue, neck, fingers, arms and legs). Neurological examination, blood tests, electrocardiography and magnetic resonance imaging of the brain were all normal. Although gradually reduced in strength and frequency, the adverse effects were very disturbing for about 10 months, but at 13 months she was almost fully recovered. For many years numerous vomiting sea travellers have been successfully treated with a single parenteral 10 mg dose of metoclopramide. There are no obvious reasons why our previously healthy patient experienced such serious and long-lasting side effects after low-dose, short-term metoclopramide administration. Until more is known, metoclopramide should be reserved for debilitating cases - and only be given after other remedies have been tried and found ineffective.

Musk shrews selectively bred for motion sickness display increased anesthesia-induced vomiting.

Susceptibility to motion sickness is a predictor of postoperative nausea and vomiting, and studies in humans suggest that genetic factors determine sensitivity to motion sickness. The aim of the current study was to determine if a preclinical model could be selectively bred for motion-induced emesis and to assess a potential relationship to anesthesia-induced emesis. Musk shrews were tested for motion-induced emesis using a shaker plate (10min, 1Hz, and 4cm of lateral displacement). Animals were rank ordered for motion-induced emesis and selectively bred to produce high and low response strains. Shrews were also tested with nicotine (5mg/kg, sc), copper sulfate (CuSO4; 120mg/kg, ig), and isoflurane anesthesia (10min; 3%) to measure responses to a panel of emetic stimuli. High response strain shrews demonstrated significantly more emetic episodes to motion exposure compared to low response strain animals in the F1 and F2 generations. In F2 animals, there were no significant differences in total emetic responses or emetic latency between strains after nicotine injection or CuSO4 gavage. However, isoflurane exposure stimulated more emesis in F1 and F2 high versus low strain animals, which suggests a relationship between vestibular- and inhalational anesthesia-induced emesis. Overall, these results indicate genetic determinants of motion sickness in a preclinical model and a potential common mechanism for motion sickness and inhalational anesthesia-induced emesis. Future work may include genetic mapping of potential "emetic sensitivity genes" to develop novel therapies or diagnostics for patients with high risk of nausea and vomiting.