PubMed · 632676
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
L W Pratt, A L Giroux. 1978. Electronystagmography.. https://pubmed.ncbi.nlm.nih.gov/632676/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
In the present study, all the nystagmus reactions following the rotatory test are represented graphically after being split up into successive time intervals of 5 seconds each. The range of reactions is illustrated by comparing healthy subjects with patients with acute lesions of the vestibular system. It has been shown that during the rotatory test no signs of habituation were to be seen. The use of the parameter "fast phase velocity" (FPV) of the nystagmus to analyze the nystagmus reactions did not prove meaningful. In particular the findings in patients with acute vestibular lesions show that the nystagmus reactions following rotatory stimuli of appropriate intensity increase only to a limited extent. When interpreting the results, the influence of spontaneous nystagmus which usually underlies acute vestibular disease, is discussed in detail.
In this study, on the basis of the graphics showing the time course of the nystagmus reactions following rotatory stimuli (Part I), some practical proposals are made on how the nystagmus responses following the rotatory test can be routinely analysed more quickly. The recommendations are oriented to the requirement that the selection of defined 30-second-intervals during the per- and postrotatory phase for the nystagmus analysis should reflect the total reaction in healthy subjects as well as in patients with acute vestibular lesions in a representative manner. It is also shown that reducing the analysis intervals to only 15 seconds or selecting unfavourable segments, can lead to an unacceptable falsification of the results.
To clarify the existence of the vertical component during a caloric nystagmus and the existence of a second phase of the nystagmus, 194 induced incidents of a caloric nystagmus in 29 normal subjects have been analyzed. Each nystagmus episode was recorded by using ENG and an infra-red video camera. The caloric stimuli were given by pouring 5 ml of water at 20 degrees C into the ear at an ear-up position. After irrigation, each subject then assumed a supine or a prone position, with the head bent 30 degrees forward in either position. All recordings contained vertical components that depended on the supine or prone head position and not on the side of the stimulated ear, i.e., an up-beating nystagmus resulted in the supine position and a down-beating nystagmus in the prone position. Further, the vertical component was far stronger in the prone position. In contrast, the horizontal component had larger velocities and was of longer duration in the supine position than in the prone position. When the first phase of the caloric nystagmus ended, the body position was changed 90 degrees, i.e., to a sitting position or a right-ear-down or left-ear-down position. All trials showed a horizontal component during the secondary phase when the head assumed the sitting position. As for the ear-down positions, only when the irrigated ear was moved upwards from the prone position during the secondary phase, an up-beating vertical nystagmus resulted in almost all the trials. These findings suggest that a caloric nystagmus may originate not only from the lateral semicircular canal but also from the vertical canals, and the second phase of a caloric nystagmus may be strongly influenced by the otolithic organs.