Orna Spitzer

The effects of dimenhydrinate, cinnarizine and transdermal scopolamine on performance

We assessed the influence of dimenhydrinate, cinnarizine and transdermal scopolamine on the ability to perform simulated naval crew tasks. The effect of single doses of dimenhydrinate, 100 mg, cinnarizine, 50 mg, and one transdermal scopolamine patch on psychomotor performance was evaluated using a double-blind, placebo-controlled, randomized, crossover design in three separate studies. A total of 60 young naval crew (20 for dimenhydrinate, 15 for cinnarizine and 25 for transdermal scopolamine) underwent a battery of computerized and paper and pencil performance tests, and filled out a questionnaire on side-effects and well-being self-assessment. Dimenhydrinate significantly impaired decision reaction time and auditory digit span. Most of the subjects who took dimenhydrinate also reported a subjective decrease in well-being and general performance abilities. Cinnarizine and transdermal scopolamine did not affect performance abilities. Cinnarizine was free of significant side-effects. Dry mouth was the only significant side-effect of transdermal scopolamine. These findings could be explained by the well-known sedative properties of dimenhydrinate and not by a specific effect on any particular cognitive or motor function. Our results suggest that dimenhydrinate, 100 mg, adversely affects psychomotor function, whereas single doses of cinnarizine, 50 mg, and transdermal scopolamine appear to be free of side-effects on performance and seem to be a preferable anti-seasickness drug for use by a naval crew.

Inner Ear Decompression Sickness in Sport Compressed-Air Diving

Objective We report our experience over the past 12 years with recreational diving‐related inner ear decompression sickness (IEDCS).

Diving-related inner ear injuries

Diving-related inner ear barotrauma (IEB) and inner ear decompression sickness (IEDS) most often result in permanent severe cochleovestibular deficits, unless immediate diagnosis is reached and the correct treatment is commenced early. Nine cases of sport-diving-induced inner ear injuries that were referred to the Israeli Naval Hyperbaric Institute between October 1987 and September 1989 are presented with regard to evaluation, treatment, and follow-up. The diagnosis was IEB in five divers and IEDS in four. Explorative tympanotomy was carried out with remarkable results in two patients with IEB, while the remaining three were relieved by bed rest alone. Three of the four IEDS patients were recompressed according to the extended US Navy Table 6 with good short-term results. The role of complete otoneurological evaluation in the decision-making process leading to the correct diagnosis and treatment is emphasized.

Alterations in R-R variability associated with experimental motion sickness

Motion sickness is a complex integration of responses from multiple physiological systems. Whether the changes that occur during the time course of motion sickness are mediated by the sympathetic or parasympathetic systems is still controversial. The present study evaluates alterations in R-R variability during experimental motion sickness in motion sick and non-motion sick subjects. Ten motion sick subjects and 7 non-motion sick subjects participated in the study. Power spectrum analysis of R-R variation was conducted for all subjects 10 min before a brief vestibular disorientation test (BVDT), for 5-10 min of the test, and 10 min after the test. Subjects were also asked to report their symptoms during the test. The motion sick group showed a significant reduction in the power spectrum density of the R-R interval at the mid and high frequencies during the BVDT test period (BVDT), in comparison with the rest period (Rest). These changes probably indicate a decrease in parasympathetic activity during the time course of motion sickness. The non-motion sick group did not show significant differences at any of the frequencies during BVDT. Power spectrum analysis of the R-R interval provides an objective measure of the autonomic response to experimental motion sickness.

Computerized Dynamic Posturography and Seasickness Susceptibility

Objective/Hypothesis: The neural mismatch theory emphasizes the role of conflicting multimodal sensory interactions in producing both motion sickness and the rearrangement process that finally leads to habituation to the adverse motion conditions. If this theory is, indeed, correct, the patterns of the response to the integrated signal from simultaneous multisensory stimulation, characterized by unusual relationships between the senses responsible for spatial orientation, should differ according to motion sickness susceptibility. Computerized dynamic posturography (CDP) provides the opportunity to simultaneously change the interactions between visual, somatosensory, and vestibular inputs, thus giving an indication of the relative importance of these senses in maintaining balance. The objective was to investigate balance strategies in naval crew members with differing susceptibility to sea conditions using CDP.

Vestibular Findings Associated with Chronic Noise Induced Hearing Impairment

Histological and functional derangements of the vestibular system have been reported in laboratory animals exposed to high levels of noise. However, clinical series describe contradictory results with regard to vestibular disturbances in industrial workers and military personnel suffering from noise induced hearing loss (NIHL). The purpose of the present study was to evaluate vestibular function in a group of subjects with documented NIHL, employing electronystagmography (ENG) and the smooth harmonic acceleration (SHA) test. Subjects were 22 men suffering from NIHL and 21 matched controls. Significantly lower vestibulo-ocular reflex gain (p = 0.05), and a tendency towards decreased caloric responses were found in the study group. No differences in the incidence of vertigo symptoms, spontaneous, positional and positioning nystagmus, directional preponderance and canal paresis in the ENG, or the SHA test phase and asymmetry parameters were observed between the groups. These results demonstrated a symmetrical centrally compensated decrease in the vestibular end organ response which is associated with the symmetrical hearing loss measured in the study group. Statistically significant correlations were found between the average hearing loss, the decrement in the average vestibulo-ocular reflex gain (p = 0.01), and ENG caloric lateralization (p = 0.02). These correlations might indicate a single mechanism for both cochlear and vestibular noise-induced injury. The results imply subclinical, well compensated malfunction of the vestibular system associated with NIHL.

Vestibulo-Ocular Reflex as a Parameter of Seasickness Susceptibility

The vestibulo-ocular reflex (VOR) is known to be modulated in response to changing vestibular and optokinetic stimuli. The purpose of this study was to investigate possible relationships between VOR and future susceptibility and habituation to seasickness. Thirty candidates for future maritime service were exposed to a series of yaw axis smooth harmonic accelerations before and after 6 months of regular sailing, and their VOR gain and phase responses were recorded. Seasickness severity was estimated after 1 and 6 months of service by a questionnaire. We conclude that VOR gain at 0.01 Hz may serve as a physiologic correlate helping to predict seasickness susceptibility, and that the increase in phase lead at 0.02 Hz may mark the habituation process to sea conditions.

Cinnarizine in the prophylaxis of seasickness: laboratory vestibular evaluation and sea study.

Cinnarizine was evaluated for the prevention of seasickness in a laboratory and sea study. The effects of 25 mg cinnarizine on the vestibulo‐ocular reflex were investigated in 13 subjects. Significant reduction of the gain in response to sinusoidal oscillations at 0.02, 0.08, and 0.16 Hz (p < 0.05) and increased phase lead at 0.16 Hz (p < 0.01) were observed. The effect of 25 and 50 mg cinnarizine on seasickness severity was examined in 95 subjects during a voyage in rough seas. Seasickness symptoms were improved in 69% of the subjects by 50 mg cinnarizine versus 35% and 31% in the groups receiving 25 mg cinnarizine and placebo (p < 0.05 and p < 0.01, respectively). The percentage of vomiting protection provided by 50 mg cinnarizine was 63% (p < 0.05). We conclude that 50 mg cinnarizine is an effective drug for the prevention of seasickness. The reduction in vestibular sensitivity observed even after administration of 25 mg cinnarizine may explain the potency of cinnarizine in the prevention of seasickness.

THE VESTIBULO-OCULAR REFLEX AND SEASICKNESS SUSCEPTIBILITY

VOR parameters were compared in subjects at the extremes of the seasickness susceptibility scale. Thirty-nine subjects highly susceptible to seasickness and 30 nonsusceptible subjects participated in the study. The VOR was evaluated by the Sinusoidal Harmonic Acceleration (SHA) test at frequencies of 0.01, 0.02, 0.04, 0.08, and 0.16 Hz. In subjects susceptible to seasickness, VOR gain was significantly higher at 0.02 and 0.04 Hz, and phase lead was significantly lower at 0.01, 0.02, 0.04, and 0.08 Hz, than in nonsusceptible subjects. Our findings are in agreement with the notion that the vestibular response will be more intense in subjects susceptible to motion sickness. The present results support the contention that a natural insusceptibility, or increased resistance to seasickness produced by adaptive responses to repeated sea exposures, may be reflected by lower VOR gain and higher phase lead.

Vestibulo-ocular reflex in migraine patients: the effect of sodium valproate.

SYNOPSIS