Th.--Sci.--Bordeaux 1, 1983. N°: 769. / Contient des articles.

This study reports the occurrence of daily rings in the otoliths of Oncorhynchus nerka fry and examines their relationship to growth. In experiment 1, sockeye salmon fry were collected from the Fulton River spawning channel at Babine Lake, British Columbia in May 1978. The fish were reared for 26 days in enclosures in the spawning channel and were sampled every seven to ten days. Sagittae were removed from 25 fish from each sample, and the growth rings in one otolith from each fish were counted. A regression of the number of rings on the number of days since capture showed that these rings are, on average, formed daily, beginning at the time of emergence. A number of possible technical and biological causes of variation in ring counts within and between samples are considered. In Experiment 2, sockeye salmon fry were reared in the laboratory from fertilized eggs taken in the fall of 1978 at the Weaver Creek spawning channel near Mission, British Columbia. A random sample of 64 of these fry was marked to enable identification of individuals. Each individual was weighed initially on June 6 or 8, again on July 6, and surviving fish were weighed a third time on July 20. After a final weighing, sagittae were removed and a standard otolith radius was determined by counting back the appropriate number of daily rings which corresponded to each weight. The regression of £n otolith radius on £n fish weight was linear, and had an R2 of 0.92, which demonstrates a relationship between the mean width of a daily ring in sockeye salmon fry sagittae, and a mean daily change in the weight of the fry. Using this regression line, we back-calculated the previous weight of the individual fish from the corresponding otolith radius and a latter fish weight and otolith radius and found the errors to be relatively small — in the order of 15 per cent. / Science, Faculty of / Zoology, Department of / Graduate

Cervical vestibular evoked myogenic potential (cVEMP) testing is widely used in the assessment of vestibular disorders in clinical practice (Welgampola & Colebatch, 2003). Ocular vestibular evoked myogenic potentials (oVEMPs) are similar to the cervical VEMPs in that the vestibular system is also stimulated by a loud sound. The difference is that the response is measured on the inferior oblique muscle of the eye as opposed to the sternocleidomastoid muscle (SCM) of the neck (Chihara, Iwasaki, Ushio, & Murofushi, 2007). The current study compares the standard cervical VEMP to the ocular VEMP in both control subjects and participants with “clinically certain” Ménière’s disease. By investigating cervical VEMPs in comparison to ocular VEMPs we aimed to improve the ability to stage and diagnose Ménière’s disease using the ocular VEMP. 22 control participants and 19 participants with confirmed unilateral Ménière’s disease took part in the study. The peak latency and amplitudes of the ocular and cervical VEMP tests were recorded and analysed. In addition, the background electromyographic (EMG) activity of both the inferior oblique and sternocleidomastoid muscles was recorded throughout testing. A questionnaire was also distributed to all participants to compare the relative difficulty of the VEMP tests. Statistical analysis using the paired t-test, standard t-test and the one-way ANOVA on ranks test was applied to determine a difference between the control and patient groups for both the ocular and cervical VEMP tests. Overall, the threshold and IAD ratio measures did not produce any significant results when sound was presented to the affected ear for the cervical and ocular VEMP tests. A significant reduction in amplitude of the VEMPs from the Ménière’s groups was found compared to the control groups for the ocular the cervical VEMPs. Overall, an increase in P2 and N3 latency of the ocular VEMP response in Ménière’s patients was determined. Results from the questionnaire suggest that the ocular VEMP test was more tolerable to the cervical VEMP test in this current study. Furthermore, statistical analyses revealed no significant differences in EMG level between the control and Ménière’s group for both the ocular and cervical VEMP data. Overall, results suggest that both the cervical and ocular VEMP tests provide information regarding the integrity of the saccule, owing to the abnormal VEMP findings in the participants with Ménière’s disease. In addition, this study provides evidence that the ocular VEMP is as useful a tool in diagnosing Ménière’s disease as the cervical VEMP.

Cervical vestibular evoked myogenic potential (cVEMP) testing is widely used in the assessment of vestibular disorders in clinical practice (Welgampola & Colebatch, 2003). Ocular vestibular evoked myogenic potentials (oVEMPs) are similar to the cervical VEMPs in that the vestibular system is also stimulated by a loud sound. The difference is that the response is measured on the inferior oblique muscle of the eye as opposed to the sternocleidomastoid muscle (SCM) of the neck (Chihara, Iwasaki, Ushio, & Murofushi, 2007). The current study compares the standard cervical VEMP to the ocular VEMP in both control subjects and participants with “clinically certain” Ménière’s disease. By investigating cervical VEMPs in comparison to ocular VEMPs we aimed to improve the ability to stage and diagnose Ménière’s disease using the ocular VEMP. 22 control participants and 19 participants with confirmed unilateral Ménière’s disease took part in the study. The peak latency and amplitudes of the ocular and cervical VEMP tests were recorded and analysed. In addition, the background electromyographic (EMG) activity of both the inferior oblique and sternocleidomastoid muscles was recorded throughout testing. A questionnaire was also distributed to all participants to compare the relative difficulty of the VEMP tests. Statistical analysis using the paired t-test, standard t-test and the one-way ANOVA on ranks test was applied to determine a difference between the control and patient groups for both the ocular and cervical VEMP tests. Overall, the threshold and IAD ratio measures did not produce any significant results when sound was presented to the affected ear for the cervical and ocular VEMP tests. A significant reduction in amplitude of the VEMPs from the Ménière’s groups was found compared to the control groups for the ocular the cervical VEMPs. Overall, an increase in P2 and N3 latency of the ocular VEMP response in Ménière’s patients was determined. Results from the questionnaire suggest that the ocular VEMP test was more tolerable to the cervical VEMP test in this current study. Furthermore, statistical analyses revealed no significant differences in EMG level between the control and Ménière’s group for both the ocular and cervical VEMP data. Overall, results suggest that both the cervical and ocular VEMP tests provide information regarding the integrity of the saccule, owing to the abnormal VEMP findings in the participants with Ménière’s disease. In addition, this study provides evidence that the ocular VEMP is as useful a tool in diagnosing Ménière’s disease as the cervical VEMP.

Thesis (Ph. D.) -- University of Texas Southwestern Medical Center at Dallas, 2005. / Vita. Bibliography: 197-219.

Vestibular evoked myogenic potentials (VEMP) are short latency electromyograms (EMG) evoked by high-level acoustic stimuli and recorded from surface electrodes over the tonically contracted sternocleidomastoid (SCM) muscle and are presumed to originate in the saccule. The present experiments examined the effects of click and tone-burst level and stimulus frequency on the latency, amplitude, and threshold of the VEMP in subjects with normal hearing sensitivity and no history of vestibular disease. VEMPs were recorded in all subjects using 100 dB nHL click stimuli. Most subjects had VEMPs present at 500, 750, and 1000 Hz, and few subjects had VEMPs present at 2000 Hz. The response amplitude of the VEMP increased with click and tone-burst level, whereas VEMP latency was not influenced by the stimulus level. The largest tone-burst-evoked VEMPs and lowest thresholds were obtained at 500 and 750 Hz. VEMP latency was independent of stimulus frequency when tone-burst duration was held constant.

Vestibular-evoked myogenic potentials (VEMPs) are proposed as a reliable test to supplement the current vestibular test battery by providing diagnostic information about saccular and/or inferior vestibular nerve function. VEMPs are short-latency electromyograms (EMGs) evoked by high-level acoustic stimuli and recorded from surface electrodes over the tonically contracted sternocleidomastoid muscle. VEMP amplitude is influenced by the EMG level, which must be controlled. This study examined the ability of subjects to achieve the EMG target levels over a range of target levels typically used during VEMP recordings. In addition, the influence of target EMG level on the latency and amplitude of the click- and tone-evoked VEMP was examined. The VEMP amplitude increased as a function of EMG target level, and the latency remained constant. EMG target levels ranging from 30 microV to 50 microV are suggested for clinical application of the VEMP.

Background: The otoliths act as gravito-inertial force sensors and contribute to the perception of spatial orientation. The perception of gravitational vertical can be assessed by asking a subject to adjust a light bar to the vertical. Prior to clinical use of the SVV (subjective visual vertical) test, normative data and test-retest reliability must be established. Purpose: To obtain normative data and d etermine the test-retest reliability for the SVV test performed in static and dynamic test conditions. Research Design: A descriptive design was used to obtain normative data. Study Sample: Twenty-four young adults with no history of neurological disease, middle-ear pathology, open or closed head injury, cervical injury, or audiovestibular disorder participated in the study. Data Collection and Analysis: The SVV angle was measured in the static position and in three dynamic conditions: (1) on-axis clockwise (CW) rotation, (2) off-axis CW rotation of right ear, and (3) off-axis CW rotation of left ear. Results: In young healthy individuals, the SVV was Conclusions: The normative data obtained in this study may be useful in identifying patients with chronic utricular dysfunction. We recommend the use of difference angles (on-axis SVV ‐ off-axis SVV) to remove baseline bias and decrease the variability of the SVV angles for the off-axis conditions.

Despite our understanding of the impact of noise-induced damage to the auditory system, much less is known about the impact of noise exposure on the vestibular system. In this article, we review the anatomical, physiological, and functional evidence for noise-induced damage to peripheral and central vestibular structures. Morphological studies in several animal models have demonstrated cellular damage throughout the peripheral vestibular system and particularly in the otolith organs; however, there is a paucity of data on the effect of noise exposure on human vestibular end organs. Physiological studies have corroborated morphological studies by demonstrating disruption across vestibular pathways with otolith-mediated pathways impacted more than semicircular canal-mediated pathways. Similar to the temporary threshold shifts observed in the auditory system, physiological studies in animals have suggested a capacity for recovery following noise-induced vestibular damage. Human studies have demonstrated that diminished sacculo-collic responses are related to the severity of noise-induced hearing loss, and dose-dependent vestibular deficits following noise exposure have been corroborated in animal models. Further work is needed to better understand the physiological and functional consequences of noise-induced vestibular impairment in animals and humans.

Young adults are more likely to suffer blast injury and traumatic brain injury (TBI) than other age groups. This article reviews the literature on the vestibular consequences of blast exposure and TBI and concussion. In addition, the vestibular test findings obtained from 31 veterans with a history of blast exposure and/or mild TBI are presented. The authors discuss loss of horizontal semicircular canal function and postural instability related to head injury. Preliminary data suggest the novel theory that otolith organs are uniquely vulnerable to head injury and blast exposure.